My temperature gauge was reading very high this morning, fortunately on a short journey so I was able to get the car home before it boiled over. On checking there was a lot of pressure in the expansion tank when I undid the cap, and the fan had not cut in.
Thermostat stuck shut or something more worrying?
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Was the coolant at its normal level? If not, then it might be worth getting a sniff test done to see if there are any hydro-carbons present in the cooling system.
IIRC, the thermostat on this engine is behind the cambelt and therefore not easy to access and change.
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What was the outside temperature, sub-zero?
What's the state of your anti-freeze?
I'll let you fill in the gaps.
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The car's with my local indie who did a test on the header tank and he reckons the head gasket is ok so that's a relief.
He reckons either thermostat or water pump. The coolant was changed a month ago.
Last edited by: Robin Regal on Wed 23 Nov 11 at 14:35
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>> The car's with my local indie who did a test on the header tank and
>> he reckons the head gasket is ok so that's a relief.
>>
>> He reckons either thermostat or water pump. The coolant was changed a month ago.
>>
The thing that comes to my mind, is an airlock.
Who did the coolant change?
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The coolant change was done by the garage who now have the car, a very reliable and efficient outfit. It is actually nearer two months (and over 2k) since it was changed and no problems since.
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Not sure why a stuck-closed thermostat or failed waterpump wouldn't trip the fan when the head temperature turns up to cook.
What about the switch for the fan or the fan itself?
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The fan thermostat is mounted on the radiator.
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>> The coolant change was done by the garage who now have the car, a very
>> reliable and efficient outfit. It is actually nearer two months (and over 2k) since it
>> was changed and no problems since.
>>
OK... I believe your car has a heater valve. (Im not 100% sure it has, but they are listed on some factors websites)
Did the problem occur after a cold snap? (ie have you put the heating on?)
IMHO there may have been some air in the heater matrix, that then moved into the cooling circuit..
On some cars it is a hellish job to clear air blocks, Im not trying to slag off your indy, just making suggestions........
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>> The thing that comes to my mind, is an airlock.
Very unusual on this or any Vauxhall engine, from my experience, and reading Vauxhall forums. Any air in the system will end up in the header tank as that's the only place it can go, making it a self bleeding system.
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>> On checking there was a lot of pressure in the expansion tank when I undid the cap
There's supposed to be after a run. If you can slowly remove the cap (covering it with a rag) without clouds and clouds of steam billowing out, then it's OK.
I had the same "overheating" problem on my Escort of the same vintage. It turned out to be a defective temperature gauge sender unit - there was nothing wrong with the cooling system at all. An AA patrolman proved this to me by pointing his infra-red thermometer at all of the different coolant hoses in turn with the engine running, showing them all to be between 65 - 85 degrees C.
What I would do Robin Regal is run the engine outside your house to see if the fan cuts in. If it does, then you know the fan thermostat is working fine.
The fan thermostat generally triggers at a slightly higher temperature than the main thermostat (95 degrees as opposed to 88 degrees), therefore as long as the fan doesn't cut in then you know the engine's running below 95 degrees, therefore the main thermostat is also working and your problem is the temperature gauge sender like mine was.
I could have replaced mine, but I don't like disturbing cooling system connections as antifreeze will "hunt" for any imperfect joins to leak out of, so I just ignored the gauge and kept an ear out for the fan. Ran it for another year like that.
EDIT: Swiss Tony's on the right track with his air lock theory. Best way to clear that is to take the expansion tank cap off and repeatedly squeeze/fondle all the coolant hoses you can get to. Replace cap, warm up engine, repeat a few times. Try not to burn yourself :)
Last edited by: Dave_TDCi on Wed 23 Nov 11 at 21:14
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>> EDIT: Swiss Tony's on the right track with his air lock theory. Best way to
>> clear that is to take the expansion tank cap off and repeatedly squeeze/fondle all the
>> coolant hoses you can get to. Replace cap, warm up engine, repeat a few times.
>> Try not to burn yourself :)
>>
Thanks Dave.... may I just add, be careful of moving parts - not just the hot bits!
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Thanks for the replies, the car is with the garage now so I'll find out what's wrong tomorrow. I don't think it's an air lock as I have used it early mornings and late nights during a couple of cold snaps with the heater on since the coolant change and it's behaved itself perfectly.
Checking round the interweb these are apparantly prone to shearing the inpeller off the water pump and more than a few people have had stuck thermostats, which I hope it is as it's the cheapest option.
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Garage phoned Mrs RR, water pump and thermostat replaced.
Didn't have time to go there to day so I'll speak to them when I pick it up in the morning.
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Vauxhall Astra F - 97 1.4 Engine overheating - VxFan
