[mark e]

Following up on another thread about cooling here , I thought I'd share my write up of using an Electric Water Pump as a replacement for the mechanical one on my 9000. Parts of it may well be relevant for other models too.

OK, here’s the full story…

Since fitting the Abbott intercooler last year, I noticed a significant increase in coolant temperature on hotter summer days. Because mine is a MY93, the gauge reads real temperature, unlike later ones which will stay pretty much level once warmed up until temps rise a lot. The reason for this temperature increase is that in order to achieve a good temperature drop whilst being very free flowing, the Abbott intercooler must have to increase the cooling fin are which will in turn further restrict the flow of air to the radiator.

I know that 9000's, especially when tuned, can run hot and after noting the info in the CCC article about the Abbott 9000 about the mechanical water pump cavitating at higher revs, I decided the "easy" way forward was to use an electric water pump (EWP) rather than look at trying to improve air flow. There are essentially two options for installation- as a boost to your existing pump or as a replacement. I decided on the latter.

To replace your existing mechanical pump, you use an EWP controller and remove the mechanical thermostat. In its place you insert a temperature sensor that feeds the EWP controller. Basically, as things heat up in the block, the controller increases the speed of the pump. You can set whether you want the system to run cooler (more power) or warmer (more economy).

The recomended location for the EWP is in the bottom hose of the radiator that feeds in to the water pump. It's a complete pig to fit in there on a 9000, believe me. You also have to get two straight flange adaptors ratehr than one staright and one right angle that come with the kit. I'll post a pic later...

You then have the option of either removing the mechanical impeller from the pump or using a shorter belt to bypass the pulley. I chose the former and ordered a new water pump from ECP that I then removed the impeller from with an angle grinder (messy but effective!).

Once in, and leaks sorted, all seemed to be OK, but I was pulling air in as noted. The pump could be seen to have a varying voltage applied to it according to engine temp. Bear in mind though that this was a month or so back when ambient temps were a lot lower.

I did have a problem with lack of flow to the heater matrix, which their info did say might happen. To counteract this, I ordered a smaller booster pump and fitted it to the circuit.

The problem, however, with this, was that it's flow rate was so high that it increased overall temps as it was clearly preventing the main flow from the bigger pump getting in to the block effectively. No problem, thinks I, I'll just reduce the voltage to it. Except that unlike the bigger pump, which runs from about 2 to 13.5V, the motor isn't really designed for this and although I achieved a partial reduction, it wasn't enough.

All this became apparent in the last day or so leading up to the track day at Goodwood, and even without the smaller pump running temps were still higher than before so on the way down I decided the thing to do was put in a bypass switch to feed 12V directly to the pump. Fortunately, Halfords were still open at 7.30pm and I managed to grab a handful of suitable bodgery. Unfortunately I didn't have a multimeter and the following morning at about 6.50am managed to make an incorrect assumption about the controller wiring that resulted in a spark and a dead controller

.

Meanwhile, whilst down at Abbott the other week I asked them what could be done, and had teh following very useful advice which I intend to put to use soon...

1. Use a raditor from an automatic- apparently they're a bit more efficient

2. Drill holes in the wheel arch liners to let the heat out (Mark A, do you have the pic?)

3. Remove the seal from the aquarium and pack up the rear of the bonnet with 5mm spacers.

4. For track days, remove the mesh grille which is fairy restrictive.

So, after a lengthy (and costly) period, I've come to the conclusion that an EWP doesn't really work on a 9000 for a variety of reasons, and I shall revert to the mechanical pump and use the EWP as a booster to maintain a high flow for track days. I will probably also wire it in with a run on timer/stat for everyday use to help eliminate heat soak.

 

[markcanderson]

Indeedy do.. will post the pic when I get home from work tonight

 

[sgould]

Another few random thoughts while they're in my mind.

Increasing air flow is a good idea.

If you put the EWP in the top hose you will reduce pressure in the mechanical water pump and could increase the risk of cavitation. Cavitation is in effect localised low pressure boiling, it's not air-entrainment.

Bear in mind that you are trying to remove energy from the system as heat. The heat out of the rad is a function of both water flow and temperature drop. The water system is closed, so increasing water flow will also increase the outlet temp from the rad and hence the inlet temp to the engine. There will be an optimal rate somewhere. The airflow is an open system so the more the merrier, up to a point.

If things are marginal make sure that the rad is matt black and not exposed copper. Make sure the air passages are really free (no muck, no bent fins). Would a total loss water spray on the outside of the rad help in reducing effective air temp by evaporation?

Final point (for now

)with the current system by removing the impeller of the original pump you have no turbulence or whatever at that point as designed and tested by the engine designers. Is the flow through the engine block following the original flow pattern? Could be a bit directional, say, only running down one side of the bores? Bit of a long shot, but if you're collecting air somewhere....?

 

[Mark B]

Mark E,

A couple of thoughts:

1) The seal on the aquarium is there to prevent hot air reaching the cabin air intake so that a: the cabin does not over heat, and b: so that noxious fumes (exhaust leak?) do not enter the cabin. So if you are going to remove it, make sure you've no exhaust leaks!!

2) I really struggle to understand how the set up as described could possibly be an improvement on the original design. In particular, the fact that the thermostat has been removed. The stat shuts off the water flow around the block and to the heater when things get really hot, forcing all the flow through the rad. Surely removing the stat means that some coolant flows through the rad and some recirculates around the block (or does something else that it wasn't intended to, like stop flow to the heater).

In addition to the new intercooler possibly causing a reduction in air flow, the other problem is that it will cause an increase in the temperature of the air reaching the radiator. Furthermore, as the ambient air temp increases, the air conditioning radiator will start to put out heat, increasing the air temp still further, so you may well have a compound problem.

A couple of things that might help:

The standard cooling fan is shrouded to ensure that it operates efficiently. Unfortunately, this shrouding also covers quite a lot of radiator area around the fan. I am assuming that your hot running is whilst on the move, not sitting in traffic, in which case either remove the shroud and find another way of supporting the fan, or drill a lot of holes in the area of the shroud that obstructs the radiator. I estimate that the shroud obstructs 10-20% of the radiator area.

Clutching at straws here, but you could try using one of the "water wetting" agents which may improve the rate of heat transfer from the block to the coolant, and more importantly from the coolant to the radiator fins. Demon Tweeks list one in their catalogue.

It may also be worth noting that in warm climates, the 9000 was fitted with two cooling fans, the second being in front of the air con radiator. I suspect this was primarily to keep the air con happy, but who knows? Obviously this would not help if your overheating occurs at speed, indeed it would make matters worse at speed as the motor body forms an air flow restriction.

I think that in going back to the standard pump and thermostat setup, and using the EWP as a booster, you are moving in the correct direction. Increasing the radiator power, and increasing the airflow by removing restrictions should be the other areas to concentrate on.

By the way, my car's automatic, so if any of the above doesn't apply to yours, then apologies.

 

[Mark B]

Why didn't I think of it earlier?

What you really need is a nice louvred bonnet...

 

[mark e]

Mark,

Good thoughts, there. I especially like the idea about doing something about the shroud around the fan- perhaps even replacing it with a Pacet unit as they have very little shroud and are fixed throught the rad.

Anyway, to complete the discussion on your points:

1. Removing the seal- I was only going to take out the top section that seals it against the bonnet, wheich, combined with the packing, should provide a useful flow.

2. I have come to the conclusion that EWP doesn't work in my case- in other instances it may- certainly it makes more thermodynamic sense to have the spped of the pump and hence your cooling capacity defined by the cooling need, not engine speed. On the way home tonight, I turned off the smaller pump, clamped down the small hose and had the EWP flat out- result? At a steady 70, temp gauge sitting at about 9 o clock, which I reckon is a tocuh higher than it would have been with the regular set up. I think the stat must play a key role in ensuring correct diversion of flow.

And yes, there is a compound problem!

I've used water wetter before and is is effective- I just hadn't got round to putting any in yet whilst I still had leak problems (£15 a pop IIRC).

I've had a couple of small fans fitted to the front for a while now which run in parallel with the main fan but I can also turn them on independently. I've found they help a lot around town with both the AC and reducing heat soak in the intercooler when, say, you've been queueing at a junction for a minute or so before needing

to get out into traffic.

I'll update once I've got through the next round of knuckle scraping...

[edit]
Oh yes, louvred bonnet. I have thought about it

, but it really will be a last resort... Bubbles ain't no rice girl!!!

 

[markcanderson]

 

[Eric van Spelde]

Anything to save weight, eh?

 

[sgould]

One thing has occurred to me. The comment about the heater being less effective. Does this mean that the repositioning of the pump has reversed the flow through the heater?

If so, the heater will not only be taking the"cold" water from the radiator it will be on a by-pass loop around the engine, rather than acting as a second cooling radiator. In which case your extra pump is trying to reverse this flow and act against the main pump

 

[mark e]

Originally posted by sgould:
If you put the EWP in the top hose you will reduce pressure in the mechanical water pump and could increase the risk of cavitation. Cavitation is in effect localised low pressure boiling, it's not air-entrainment.[/b]

I'm not sure I follow this... If I put the EWP anywhere in the circuit, it will have the basic effect of increasing the pressure on the inlet to the mech pump and decreasing the pressure at the outlet. Cavitation as I understand it is caused basically by too small an impeller trying to shift too much water (overcoming a pressure differential) thus if I reduce the pressure differential across the pump that should surely reduce cavitation?

Bear in mind that you are trying to remove energy from the system as heat. The heat out of the rad is a function of both water flow and temperature drop. The water system is closed, so increasing water flow will also increase the outlet temp from the rad and hence the inlet temp to the engine. There will be an optimal rate somewhere. The airflow is an open system so the more the merrier, up to a point.[/b]

Heat extraction is down to the product of the specific heat capacity of the liquid (kj/kg) and the rate at which it flows (kg/min) with the temperature differential chucked in there somewhere.

So, without getting too much in to the theory, if we think of a high capacity domestic boiler, you need to have a high throughput of liquid to avoid kettling (localised boiling). Up to a point, governed by the ability of the raditor to dissipate heat, increasing flow rate will improve the cooling as you have a greater effective mass per minute of heat soak passing through. Beyond that point, any further increase in flow rate will not improve cooling but will minimise the likelihood of localised hot spots, which is good news in high performance engines. Of course, if you take it to extremes, then resultant turbulence will actually decrease the cooling ablity.

If you increase the flow rate in to any heater, you will reduce the differential across it. In car terms this will mean a higher inlet temp but more crucially a lower outlet temp.

Would a total loss water spray on the outside of the rad help in reducing effective air temp by evaporation?[/b]

Yes. This is acutally a technique used on some intercoolers (Mitsu Evo IIRC) to reduce inlet air temps and I see no reason (aprt from it using a lot of water

) why it shouldn't work on a water-to air heat exchanger (aka radiator).

Final point (for now        )with the current system by removing the impeller of the original pump you have no turbulence or whatever at that point as designed and tested by the engine designers. Is the flow through the engine block following the original flow pattern?  Could be a bit directional, say, only running down one side of the bores? Bit of a long shot, but if you're collecting air somewhere....?[/b]

Absolutely. I think this is the core of my problems. I also think that having no thermostat is likewise messing things up. On paper the EWP has more than enough pumping capability to keep temps down... practice is another matter though.


What I will try next is the other mods to enhanc eair flow over the rad plus re-installing the mech water pump and stat, leaving the EWP in place in the bottom hose. That may just sort out the air suction problem. If not, I will next try to tee in the small pipe in to the pipe from the expansion tank to the water pump just below the tank.

If that fails, I shall move the EWP to the top hose...

Hopefully I'll get it sorted by June 30th

 

[mark e]

Just a separate post to say thanks guys for the really useful debate we've had here- it's certainly given me a lot more insight in to engine cooling

 

[sgould]

We managed to post at the same time. I'll try and put my thoughts among your comments below.

______________________________________________________
If I put the EWP anywhere in the circuit, it will have the basic effect of increasing the pressure on the inlet to the mech pump and decreasing the pressure at the outlet.
______________________________________________________
All a pump can do is produce a pressure differential between its inlet and its outlet. The highest pressure in a system is at the outlet to the pump. Pressure will reduce from there around the system as a result of friction, turbulence and section changes until it gets back to the pump suction (inlet). If there are a lot of losses the inlet could reduce in pressure to below normal atmospheric.


_______________________________________________________
Cavitation as I understand it is caused basically by too small an impeller trying to shift too much water (overcoming a pressure differential) thus if I reduce the pressure differential across the pump that should surely reduce cavitation?
_______________________________________________________
This is a bit more difficult to explain. If you remember in physics lessons, the barometer experiment where you can sustain a mercury column of around 30 inches. If the tube is any longer you get a vacuum above the top of the mercury. If you do the same with a column of water the max height is about 34 feet (1bar). When you spin an impeller you are increasing the pressure in front of the vanes and producing low pressure (suction) behind them. In certain circumstances this low pressure falls below atmospheric and the water gets to the same condition as it would at the top of the 34 ft water column - it can't remain liquid and forms a vapour. In effect it boils at low temperature in much the same way that mountaineers find the boiling point of water is reduced at high altitude as the pressure reduces. If your elec pump is in the top hose you could be reducing the absolute pressure in the block and pump which will increase the risk of boiling in the block and cavitation in the mech pump.


_________________________________________________________
So, without getting too much in to the theory, if we think of a high capacity domestic boiler, you need to have a high throughput of liquid to avoid kettling (localised boiling). Up to a point, governed by the ability of the raditor to dissipate heat, increasing flow rate will improve the cooling as you have a greater effective mass per minute of heat soak passing through. Beyond that point, any further increase in flow rate will not improve cooling but will minimise the likelihood of localised hot spots, which is good news in high performance engines.
________________________________________________________
Yes. I agree, up to a point the faster the flow the better.


__________________________________________________________
On paper the EWP has more than enough pumping capability to keep temps down...
__________________________________________________________
But only if the radiator is adequate at max pump output.


______________________________________________________
If that fails, I shall move the EWP to the top hose...
________________________________________________________
This will not solve the problem (if I guessed right earlier) of the heater flow by-passing the engine. If this is the case then I think this is the main cause of your problem.

Good luck. I'll have to look at a 9000 engine bay now and check what I've been saying and guessing

 

[mark e]

Originally posted by sgould:
[qb]One thing has occurred to me.  The comment about the heater being less effective.  Does this mean that the repositioning of the pump has reversed the flow through the heater?

If so, the heater will not only be taking the"cold" water from the radiator it will be on a by-pass loop around the engine, rather than acting as a second cooling radiator.  In which case your extra pump is trying to reverse this flow and act against the main pump    [/qb][/b]

From what I've been able to gather, the flow to the heater matrix relies on the thermostat being in place, I'm guessing providing some sort of pressure diversion valve. This is in line with the description of it's operation being that under high coolant temperatures as it opens furterh the coolant flow goes predominantly to the raditor rather than the heater matrix which may not be receiving any cooling air flow. By removing it, I've effectively taken out the pressure diversion and all the flow goes to the radiator.

I made sure that the extra pump was in the "flow" pipe to the matrix and pumping the coolant in the same direction that it would normally flow with the stat in place.

Thanks again for the other info... my understanding of cooling systems is growing further. Now all I need to do is sort out the

properly (that's another story

)

 

[sgould]

I really need to show some sketches to explain.

But it would be interesting to see what happens to your cooling if you clamp off the heater circuit. Always provided you don't clamp off anything else at the same time - like the link to the header tank or the turbo cooling.

 

[Mark B]

Mark E,

I wonder if we need to consider the basics of the cooling system in order better to define the correct areas to spend your money on.

(This description is generic, I am not fully familiar with Saab plumbing, cooling of the turbo etc) When the engine is cold, the coolant flows up and along the block/head to the thermostat, which is closed. Some coolant then flows through the heater back to the pump, whilst most flows down a bypass return hose to the pump. The coolant is cycled internally in this way until it reaches the thermostat's opening temperature (about 90C). At this point, the thermostat opens slightly to allow a small amount of coolant to pass through the radiator. Under normal usage (moderate constant speed and reasonable ambient temperatures), the amount of coolant directed to the radiator is small, the vast majority is fed back to the bottom of the engine block via the bypass hose and the heater. As power requirements increase (higher speed, uphill sections etc), the thermostat opens a little further, diverting more flow to the radiator. It should be noted that in these part load conditions, increasing the size of the radiator makes no difference as the temperature is controlled by the thermostat. When the coolant temperature reaches the level at which the thermostat is fully open (about 105C), the bypass hose is shut off by the circular plate on the bottom of the thermostat, and all the flow is directed to the radiator. Also in a Saab, unlike any other manufacturer that I am familiar with, the thermostat shuts off the flow to the heater, ensuring that all the coolant is directed to the radiator. This is logical as you are highly unlikely to want the heater on in conditions that cause the engine to run hot. I do not have the figures to hand, but typically the cooling fan will turn on (low speed) at a temperature below the thermostat's fully open temperature. The point I am trying to make is that, until the engine is running seriously warm (105 or so), the temperature is controlled entirely by the thermostat, and radiator size does not matter, nor does pumping speed matter much.

The other thing to consider is that the cooling system should have been designed to allow the car to run at maximum speed in a warm climate, i.e. producing 225 bhp at 150 mph with at least 30C ambient. At 75 mph you only need 1/4 of maximum power to push the car along (drag being proportional to the square of velocity), so 55bhp or so. At 1/4 power you still have 1/2 of the cooling air velocity. You can see therefore that no condition in normal driving should tax the cooling system. The worst cooling condition normally encountered is a long steep incline with the car loaded, in high summer (think Alpine passes, four people plus luggage). It is for these conditions that Saab fit a two speed fan, the second stage coming on only when the thermostat is fully open.

I presume that you only have an overheating problem on track days, when in your modified car, you are producing power in excess of the original maximum output for a significant proportion of the time, and the average speed of the cooling air is not that high.

So the first question is:

Are you running at temperatures continuously in excess of the thermostat's fully open temperature? If not, the very first thing you should do is get a thermostat with a lower temperature range. Saab may even specify such a device for warmer climates than ours. Perhaps one of our American or Australian chums could comment. If not, take your stat out and go to Halfords/your local purveyor of parts, and get one that is physically exactly the same (check the stroke length to ensure the footplate can close off the bypass and heater flow) but with a lower operating range.

Only if this proves insufficient to maintain the desired temperature should you consider spending money on anything else.

If it is insufficient, then you should look at all the things previously discussed, i.e. bigger radiator, higher fluid flow rates, greater air flow.

One point that has been puzzling me a bit is the issue of cavitation. I presume that you are running a 50% antifreeze mixture, as I believe this will reduce the pressure at which cavitation or low temperature boiling occurs. One thing that you might wish to consider to reduce cavitation is to increase the pressure at which the cooling sytems runs, during normal operation. Obviously the cooling system maximum pressure is governed by the pressure cap (I don't know off hand what that pressure is), but during normal operation the pressure is lower. You could increase the normal running pressure by adding something like a tyre valve at a suitable point (the expansion tank or the small hose would be good), and then inflating the system when cold to perhaps half or three quarters of the cap pressure rating. If the system gets really hot, it would "blow off" some air, and the pressure would be low once it had cooled, so you might need to inflate it each time before serious use. Obviously this would only help if cavitation is a serious problem. Perhaps you could enlighten us as to what evidence you have for this.

Apologies if I have been stating the obvious and rambling on a bit, but I thought it would be best to get back to basics and start from there. I have bitter personal experience of similar problems some years ago. After a lot of wasted time/effort/money, I discovered that the previous owner had fitted an old fashioned thermostat that did not have the circular foot plate, so when the thermostat was fully open, the bypass was not being closed off, hence only part of the flow was being directed to the radiator rather than all off it.

 

[Mark B]

Quote from Mark E

From what I've been able to gather, the flow to the heater matrix relies on the thermostat being in place, I'm guessing providing some sort of pressure diversion valve. This is in line with the description of it's operation being that under high coolant temperatures as it opens furterh the coolant flow goes predominantly to the raditor rather than the heater matrix which may not be receiving any cooling air flow. By removing it, I've effectively taken out the pressure diversion and all the flow goes to the radiator.[/b]

Mark,

I think you are barking up the wrong tree slightly. The standard pump in its original location is at the centre of three possible coolant paths, 1) from the top of the engine, through the heater, to the bottom of the engine, 2) from the top of the engine, through a bypass hose (or internal bypass channel) to the bottom of the engine, 3) from the top of the engine, through the radiator to the bottom of the engine.

I will ignore the turbo cooling circuit and anything else like that.

In normal usage, engine warm but not seriously hot, the coolant flows down all these routes. When cold, there is no flow to the radiator, when very hot there is only flow to the radiator.

Putting an electric pump in the radiator circuit only cannot possibly provide adequate replacement for the standard pump. I'm not sure, but I suspect that some of the electric pump's flow may well go up the bypass route (i.e. in reverse) instead of up the engine, and cycle back to the top of the radiator as cold water. If this is the case, it's no wonder you are overheating. I suspect that most electric pump systems are intended for race engines which do not have heaters, bypass circuits and so on, just a simple radiator feed. In this case you could control engine temp with pump speed.

If you want to discuss this, send me a PM and I'll give you my phone number.

 

[sgould]

I think Mark B and I are of one mind here. If you keep the EWP you will need some replumbing at the very least.

Was the car overheating in normal driving with the standard pump? Or just on the track days?

 

[mark e]

Fantastic stuff again Mark!

To pick up on a couple of points...

I wasn't actually overheating; I was just running very hot. I first noticed it on a circa 32 deg day when pushing it up an incline and the temp needle was within a few mm of the red zone- certainly significantly past the point that the fan would have cut in. Bearing in mind the relatively low gearing of the 2.3T 9000 (3000rpm= approx 90mph) I knew that I wasn't going to have maximum coolant flow at normal cruising speeds, and wanted to improve it.

One of the killers of heads/gaskets on preformance enhanced engines is localised heating/hotspots, and the best way to avoid this is to get as much coolant flowing past as possible. Bearing in mind that I was already running warm, the temperature increase required to produce localised boiling would have been quite low.

I already have the 82 deg C stat fitted.

The pump only has two "hoses" connected to it (rad return & expansion tank) but is connected ot the block by a further two stubs that seal with O rings. I guess these two are the other coolant paths.

As I said, I wanted to do something primarily to increase the coolant flow rate to avoid hotspots and from reading the sales info, reckoned the EWP would be a good bet, primarily because, as I've said before, of the ability to control coolant flow regardless of engine speed. It's clear that it has not worked in my case, for a number of reasons that I am sure cannot be unique to the design of the 9000. I feel there has been a degree of misrepresentation in the selling of the product and I shall be taking it up with the suppliers.

Basically, I've made a costly mistake due to a lack of understanding of how the coolant system works on my part, and marketing info that is only part of the story- the theory as far as it goes with the EWP is sound; it just doesn't go far enough IMO for a typical engine.

I think the key elements where their theory falls down are:

a) the fact that there are multiple circuits returning to the mechanical pump chamber and thus an inline replacement at some other point cannot function properly and
B) the assumption that the thermostat simply acts as an inline temperature dependent flow regulator in a single circuit.

So, I'll look on the bright side- I do now have tried and tested solution with the recommendations from Abbott and I've also hopefully stopped someone else from making the same mistake...

 

[billj]

Originally posted by Mark E:
[qb]I do now have  tried and tested solution with the recommendations from Abbott and I've also hopefully stopped someone else from making the same mistake...  

 [/qb][/b]

He who never made a mistake, never made anything...

The great thing about a forum like this is that adventurous people can break new ground and the whole community benefits from the result. If you'd found that the EWP was the solution to 9000 cooling problems, a number of us would probably have followed suit. As it is, anyone with cooling problems on a tuned 9000 will be able to avoid an unsuccessful and potentially costly scenario. This approach spreads the cost of learning over a number of people, rather than each person having to learn individually (and perhaps at great expense).

 

[Mark B]

He who never made a mistake, never made anything...[/b]

I quite agree!