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Discussion Starter · #1 ·
I have a 2000 9-5 with 3.0 V6 petrol engine. Recently It has been overheating and I do not know why.

First incident:
Drive about 25 minutes to a local park. sitting in the park looking at a map with the engine at idle (no air conditioning) for about 10 minutes. It is then that I notice white smoke coming from under the hood. Temp guage is right in the middle as usual. I shut it off and jump out and open the hood to see that about one quart of coolant on the ground beneath the car and it spraying all over the engine through the coolant reservoir cap. I wait a while, fill it with water, and remove the coolant cap so there is no pressure, crank the interior heater and make it home without incident.

The following week I drove the car to work and back (~10 miles each way) without the reservoir cap on. It is not too long of a drive, but engine does get to normal temp according to temp guage. Without the cap there is no incident, and the coolant level does not change (no fluid left on asphault in parking lot).

I decide maybe it was just a freak thing, so I put cap back on one day and drive ~30 minutes. Driving on freeway when the "fill coolant" comes on, instantly pull over and pop the hood. The water (because I had used water to refill before) is boiling up inside the reservior tank and spraying everywhere. Again I lose about a quart of water on the ground. Fill with water and remove cap and was able to get home.

No check engine light. If it is water pump I think it would be more drastic than an occasional overheating. Maybe a pinhole leak would cause me to lose fluid over a long period of time when system is pressurized, and overheat the little remaining fluid? Not sure if thermostat could be bad? I understand the cap controls pressure regulation, maybe a bad cap?

Any help would be greatly appreciated. I must say that I love my 9-5 but I would not have it if it weren't for you folks!
 

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Sounds like a head gasket
However , start with the basics and rul them out
could be a split header tank or persihed cap/cap seal.
could be a loose pipe.
Has it got the correct coolant mix/ratio? just water will boil earlier/lower temp than coolant.
Water pump failed/failing?
Failed thermostat - the usually fail in the open position though but not unheard of
Rad silted up

Get a sniff test done, don't let it boil up. This will tell you if the h/g has gone. Remember the h/g blowin is a symptom of another problem in 99% of cases, it goes and or the head warps due to excessive/localised heat build up - usually from the above list of mine.
 

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Discussion Starter · #3 ·
update:

Went to local Midas, they did a coolant system pressure check = couldn't find any leaking, then they did a block test to see if head gasket was bad = no leak found their either. Mechanical said water pump is working (i agree because i've driven it this way for over a week) and thermostat seems to be working because it gets to normal temp about right and engine doesnt seem to be overheating. His only suggestion was a new reservior cap($9 at autozone in stock!) Just put that on and I will see how she does!


Thanks for the suggestions!
 

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Hey guys, I am new here and have a similar problem with my 9-5 V6: when driving in the city, coolant occasionally starts to boil over and is sprayed all over the engine compartment through the cap. Before the incident, the temperature gauge, however, does not leave the normal range and the car runs great. No oil in coolant and no coolant in oil. I wait some time, fill it up again, put on the cap and continue driving carefully. Yesterday, after the last time it boiled over, I drove it home for 30 miles on the highway going about 60mph and nothing happened. Coolant level is perfectly fine today. Also, when driving outside of the city and the outside temperature is low, I can't even reproduce the problem, not even if I drive it and afterwards let it idle for an hour in the garage.
The only thing I've noticed is that the fans never start working. Could that maybe be the root of the problem? What do you think, folks?
(Sorry for my English, I am from Austria, English is not my language.)
 
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