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Discussion Starter · #1 ·
After a week of troubleshooting everything relating to ignition and timing and lots of searching the BBs for clues, I suspected a valve problem. So, next was a compression test. Something tells me that 3 cylinders with 133-150 psi compression and one with zero isn't good. Not sure where I go from here... Other than a stuck or burnt valve, any ideas why I'd have no compression in #2? #1 and #3 are OK and there's no evidence of a head gasket failure. I suppose the piston could be holed but, it doesn't seem like it. Again, above 2000 rpm the engine 'seems' OK. Is it possible that the valve comes unstuck at higher RPMs?
Any idea what a head + valve job will run me?

Rod.
'89 9000T; 235,000 km
 

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I don't know how much help I can be but as someone who had a similar problem I'll throw in my 2 cents. I don't think you will be able to really know what the culprit is until you pull the head. If you do it yourself, regardless if it's a valve or piston, I would go ahead and hone the cylinders and install a new ring set at least. And you might as well look for anything else you could do since your that far in. As far as price on a head work-up mine cost $250 but I'm in the US.

If you have someone else do it I can't help you on a price. Whatever shop you take it to will probably send the head out anyway and tack on their fee to that and to the parts so you might save some bucks by just paying them to pull it and reinstall it. That way you can take the head to the head shop and buy the parts yourself, avoiding the shop mark-up.

Well, that's my 2 cents.
 

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Just one maybe silly advice: before removing the head, when cam cover removed, check that there is clearance between cams and hydraulic lifters (or tappets, or whatever you call them) when the valve is supposed to be closed.

It's possible for them to get stuck in the fully extended position, maybe for non quality oil or negleted oil changes, so the valve can't close fully. Mine did, but the engine still run fine. Maybe your lifter(s) is stuck in a more extended position.

Just a thought, hope this helps.
 

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If a valve is leaking, it can "come right" at higher RPM. I think this is purely because at those speeds the air, being a viscous fluid, doesn't have time to completely leak out past the valve and you get enough compression for combustion to take place. Years ago, my girlfriend's Metro had two leaking exhaust valves. It hardly idled at all, but with a bit of
, it would take off as if there was nothing amiss.
 

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Yes BillJ, I agree. Since the compression test is run at low rpm (a bit under normal idle speed), it would reveal a leaking valve.

It's a quick check he can do without "for free", since he's already removing the head off.

Are you sure your engineering degree isn't mechanical? Sometimes your competence and your familiarity with all this stuff make me think so... I'm in the mechanical field, and my knowledge of your field (informatic, isn't it?) is light years behind yours in mine...
 

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had some experience of this ....
I had an exhaust valve go with no real explanation why
there was a semi circle chunk out of one of them

I just replaced the valve and spring and it seems ok so far
On head refurbishing its going to cost you a bag of sand at least
Abbott will refurb and port and fit for this price which I think is a really grt value
for a couple o hundred quid extra you can get a big valve conversion as well
my head off and replace valve all in was about 300
 

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Discussion Starter · #9 ·
Thanks for the advice everyone. This is the first time I've come up against this so I'm grateful for any and all advice. I've some experience with DIY (used to drive a TR6) but I haven't tackled anything like this before.

Financial circumstances being as they are, if I can fix this myself, that's my preferred route. From the info in the Haynes manual, it 'seems' relatively straight-forward...

So, to confirm what valve problem is, it seems my options are either to pull the cam cover and explore further, or to have a leak down test done. Since I can do the first myself, that's what I'd like to do -- especially if it can be fixed without pulling the head. Could it be a worn camshaft lobe or a failed camshaft follower?
TIA,
Rod.
 

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I had this exact problem on my 900, the valves were burnt in that cylinder. I've reground all the valves, ensuring they aren't oval and I'm goona throw the head back on when I get round to it. I wouldn't bother honing the cyls either unless there is any sign of damage, mine at 177k is like new.
 

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I wouldn't bother honing the cyls either unless there is any sign of damage, mine at 177k is like new.[/b]
I agree, Neil, it's not necesary to hone or to add new rings but if you're doing the work yourself and you've already got the head off, it's a cheap enough time-killer while you wait on the head. Granted, it is a bit more work but with a willing buddy it's not too bad.
 

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Discussion Starter · #12 ·
Stefano,
You mentioned that I should check for the clearance between the cams and the lifters (followers). I took the cover off tonight and didn't see any noticable clearance -- how much should there be?
I'd hoped that a broken valve spring might be the reason for zero compression, but no such luck.
Thanks,
Rod.
 

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No clearance needed, it's just that the lifters surfaces have to be able to go down a bit, maybe a couple of millimetres, when depressed. If applying pressure on the lifter, on the side of the cam, when the cam is up and the valve is closed of course, implies the opening of the valve, then the lifter is bad. Viceversa, if applying pressure on the lifter causes it going down for a couple of mm then becomung harder because the valve spring starts to compress, this well this is a evidence of a good lifter.

I hope I've beeen clear, if somebody got it right and can explain it better then I did, please do it, really.

Hope this helps.
 

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Discussion Starter · #14 ·
Thanks again Stefano. I haven't pulled the cams off yet to check further. If a lifter is the problem.

Here's another question...
Each cavity where the lifters (followers) are is filled with oil. This engine has the internal oil supply for the lifters (ie, no external pipes). Should the lifters be in this oil bath or is there a leak somewhere? I can't tell from the Haynes manual.

Thanks,
Rod.
 

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With just the cam cover removed you can turn the engine by hand (in gear and push it forward and back a bit - unless it's an auto). Watch the 8 followers go down and make sure that they all come back up to the same level. If one stays low you have a sticking valve. If they all come back up properly you most likely have a burnt or broken valve.

You can check which ones are fully up by the "rule of nine". Number the followers 1 to 8. When 1 is down 8 is up (1+8=9). When 2 is down 7 is up (2+7=9) etc.

As far as oil goes. it should be everywhere under the cam cover.
 

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Discussion Starter · #16 ·
Thanks for the quick reply and for the "rules". I know that it's the #2 cylinder that's got the problem as it has zero compression. The others are pretty much in spec. Still not sure yet if I've got a problem with the intake or exhaust side though.

About the rule of nine -- any idea how it runs with a 16V?

Glad to know that I don't have an oil leak as well
.
Thanks,
Rod.
 

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Sgould,
in my car all the followers did come back in the upper pos, all at the same level, but some of them didn't retract fuly, do the valve couldn't come up enough to close. You couldn't tell the differences between a bad or a good follower just looking at it, you had to put a finger on it (with camshafts still in place) and see if it was possible to depress them a bit without compressing the valve spring, just the little follower's spring (very weak force). When the engine runs, part of all the oil that is inder the cam cover penetrates in the follower and keeps it extended the right amount to clear all the play between cam and valve. But if it's sticking, it extends too much (or better: it can't retract, so as the valve seat wears, it doesn't let the valve come up to meet the seat) and you can feelthe valve spring is preloaded (valve partially open) when touching the uppper face of the follower.

You're welcome, Rod. Sorry I coulnd't make you realize the test I was proposing was possible to do without removing camshafts.

One last thing: the engine has to have been sitting for a couple of days before doing this test. But I think this is not a matter in your case.
 

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Discussion Starter · #18 ·
Maybe, there is still hope! Thanks Stefano -- I haven't pulled the cams yet as I expected to have to take the head off after checking today to see if the followers moved when the cam rotated -- which they do. I will try your test tomorrow to see if followers themselves might be bad. How much should it compress -- I assume that it's on the order of a few mm.

Rod.
 

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Discussion Starter · #20 ·
Should the intake and exhaust followers have the same amount of movement? All of my intake side followers have the 2-3 mm play before hitting the resistance of the valve spring. Only one of the 8 on the exhaust side has any movement and it's maybe 1 mm. Does this sound normal?

Rod.
 
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