Hi all
I've mentioned this problem on another thread, but it probably warrants being covered seperately.
I have a high-miled Mk2 Gti 8v that has recently had a temeperature sender replaced to cure an idling problem. The car now idles well, but upon collecting from the garage the expansion bottle was empty. I filled this and thought no more of it. However, my girlfriend uses the car a lot and she told me that she has had to fill the expansion bottle repeatedly. I contacted the garage who replaced my temperature sender and suggested that I'd look for a split pipe and would get back to them if there were any further problems.
Whilst running the engine up to operating temperature during checking I noticed a bit of steam/vapour escaping the expansion bottle, and then suddently a lot of of water rushed up the bottle and came out in quite a jet from the expansion bottle. There are two slot/hole things on the back of the expansion bottle that I assumed were vents or relief valves, and it is from these that the water came. It took less than 10 seconds to drain the expansion bottle. Apparently there aren't any vents on the bottle, so it looks like a split somewhere within these slot/holes. This has now happened a few times, and tneds to occur when the engine is switched off after a reasonable length journey.
The current thinking us that the thermostat is shot and (obviously) so is the expansion bottle. this doesn't explain why the water was ejected so forcefully. The head gasket has been mentioned, but I've heard that there are usually tell-tale signs in terms of the water becoming contaminated etc., whereas the water ejected from the expansion bottle was clear water (I didn't have any coolant at the time). steve-o suggested that it could be an airlock, which makes some sense. As mentioned before, it really only seems to happen when the engine is stopped (or the car is stationary for a while).
Does anyone else have any ideas? I am trying to get the garage to check it out and make good any problems caused by the temperature sender, however it's not clear how much liability they'd accept.
All advice gratefully received.
Matt
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If your temp gauge is telling you all is well then I am afraid the head gasket is away. Contamination of the water only happens if oil is laking across the gasket and or water in the oil. Go to the gargae and get them to sniff the air in the header bottle for emmissions and this will identify whether the combustion gases are pressurising the system. Come back for more help if required but from what you say i's the gasket. Regards Peter
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Thanks for comments Peter
I'm a little confused as to how the gasket has gone, I was under the impression there has to be a failure in the cooling system somewhere for it to happen. As stated earlier, these problems have only occured since the temperature sender was replaced, hence I would suggest that an error on their behalf is the cause of any subsequent problems with the cooling system, however I can't really see the garage involved accepting responsibility.
I'm going to try to find out if there is an air lock somewhere, and see if the garage will perform a pressure test to find out if the gasket is gone.
I can't believe it, a simple replacement electrical device takes out the head gasket. It's nenver easy.
Matt
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Golfs are not prone to air locks and if you temp gauge is normal and the fan is not cutting in before the headdere blows then is is the gasket. I look after several of these and been there a few times. Get the bottle sniffed for combustion gasses and you have your answer my friend. Do it very soon as the longer you run with a minor seep the more damage you will do to the head and the deeper the skim will ber required. If you want to do tests. Warm the car up with the cap released then when warm close the cap and hold the engine at 3000 rpm for 2 minutes if the temp is still in the normal range then qweeze the top hose to see if it pressurized. if so slowly and carefully relase the cap, be carefull and you will see the water level rise due to air in the sytem decompessing and displacing water. The other test is to remove the plugs bring each piston uo to a few degrees before TDC and shine a light in to see if the piston has been steam jet washed a sure sign of a gasket away. Come Back. Regards Peter.
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Hi all
I feel a bit foolish admittin gthis, but it turned out to be the tank cap. I had checke dit, but not closely enough. the 'vents' that the water came shooting out of are in fact a neat design feature that allows water to be directed through the cap, down the outside of the bottle and away from the mechanic's face in the event of cap seal failure. Unfortunately, not one reference to this appeared in my Haynes manual and it did not seem to crop up on forums (in respect of being the specific cause of this problem, although quite a few mentioned that the cap seals are reasonably prone to failing).
Apologies for the wate of your time, at least it was something minor, although perhaps something that I should have picked a bit sooner. In mitigation, of everyone I approached in garages or in spares retailers only one garage was aware of this recirculation through the cap and outer sleeve of the expanion tank.
As a somewhat pessimistic footnote, I am still 'treading on eggshells' with the car as I have solved problems many times in the past only for them to reappear, so I don't consider this quite closed. All is OK for now though.
Thanks for all of your comments.
Matt
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Going down the replies, I thought expansion bottle cap. Happened on an old SAAB of mine. Sometimes difficult to see as the rubber looks OK, but isn't. Remember all systems are pressurised. If it can't, the water may boil and woosh out. Sometimes antifreeze stains on the bottle neck are a giveaway.
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