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Discussion Starter · #1 ·
had the SID reading a low coolant fluid level at the weekend so duly filled it up. seemed to work fine. however went to use the car the next day and again found the low fluid level. filled it up again and found the car overheating after about 7miles of A road driving.
opened the bonnet to find fluid bubbling out of the expansion tank filler.
There was no over pressure in the hoses and they weren't burning hot nor did the radiator seem particularly hot, although there was some heat in it.
I am hoping it's the thermostat, question is would that cause the bubbling and can the car be run without the thermostat to make sure this is wher the problem lies. The car was never let into the red zone so I'm hopeful I haven't done the head gasket
 

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Hmm..

I'd hope the thermostat is your problem and not a head gasket...

Check your oil to see if its gone mayonaiseish

I assume your coolant is ok.. and not contaminated with oil...

Remove your plugs and check... if one is unusually clean/wet it could be the fact that shes gone on the head gasket and allowing coolant to pass into one/more of the cylinders and steam cleaning it. Usually one of the two middle clyinders. A compression test would prove it for definite.. but the fact your getting bubbles back into the expansion tank is a bit iffy.

Im not sure about the thermostat but running without it shouldnt do any harm Im sure some of the other chaps on hear can confirm if it can done without loosing the water tightness.

Hope that helps.

Michael
 

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Discussion Starter · #3 ·
Thanks Michael, there's nothing in the oil and I couldn't see anything in the coolant although this is now empty again after leaving overnight. I'll check the plugs tonight when I take the thermostat out.

The thing that makes me think it could be the stat or water pump is that the temp was fine for a while and would then rise quite quickly. at first puting into neutral a revving while still rolling did bring the temp back to normal but not for long. There has been no loss of power either.

How long do waterpumps last? the engine is now on 172K
 

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Where abouts was the water bubbling out from the expansion tank, cap or hoses? If the caps letting water through it needs replacing and should cure the water leak. If the thermostat was locked closed, i'd imagine the engine would overheat very quickly, but not use any water from the expansion tank. I'm not sure about Saab's running without a thermostat, i've run an old Cavalier without a stat cos of overheating problems, but it took an eternity to warm up in winter. I'd seek help, either a Saab specialist or even a rad specialist. Can you refill her, let her run and have a look underneath to see if it is the pump thats leaking, at 172K it doesn't owe you much. :eek: Ps pump is run by aux drivebelt, any leak would appear behind the near side headlight area.
 

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Discussion Starter · #5 ·
The water is bubbling up through the hose on the bottom of the expansion tank and escaping out through the cap. I thought the cap was acting as a pressure relief valve venting as the pressure increased due to the temperature rise

I had the car idling yesterday with the cap off the expansion tank the coolant level was fluctuating up and down while bubling. I'm not sure that there is air coming from it as it would if the head gasket was gone, it looks more like the kettle when its boiling. Also when the lid was on there was no pressure in the hoses as can normally be found when the gasket goes, all the hoses can be squeezed between finger and thumb when the engines running.
when running yesterday there were no drips under the car save from below the expansion tank
 

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Discussion Starter · #6 ·
Started the car from cold last night and there was no bubbling in the expansion tank. Took the thermostat off and there were no dodgy deposits to be seen in the block and the thermostat was clean. Dropped it in a container with boiling water no reaction whatso ever so reckoned this was the problem.

Chopped the diaphram out of the centre of the stat and replaced back in the car. filled it with water (temporary messure) and started her up again took a while to warm up but when she did the needles now sitting dead level. took it for a run up some steep slow hills and all seems OK.:D
New stat ordered and will be sorted in a couple of days.:cool:
 

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Nice one!

Always good to know that somethings things are not as serious as they seem to be. A thermostat is something that can be lived with... however replacing the head gasket would be a far more costly affair.

Glad to hear you got it sorted!.

Michael
 
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Just seen this thread. This is what happened when my Thermostat went. It unusually broke in the open position, provided I drove under 30mph the water didnt boil over. It did rather give the symptoms of blown H.G. :roll:
 

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9000Trubble said:
How long do waterpumps last? the engine is now on 172K
My water pump went at about 68K miles. Fortunately it started making a ton of bearing noise prior to any signs of overheating but a week or so before the noise, I got the Low Coolant message.
 
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