1.8CVH running very cool

I've seen this happen when there is an airlock in the system. Usually, if you let it warm up to fan cut-in temp with the expansion tank cap off, it will eventually push the air out.

Of course, with a non-working t'stat, it's going to take forever to get that hot!

Chris

It's not randomly going up and down like an air lock. You could set your watch by it. Did get warm enough yesterday. I'd say stat is unreliable more than permanently open. Or may have been because it was a very warm afternoon and I'd been holding it in 2nd at 30 for ten minutes.

Anyway, its not a problem, just wondered if anyone had actual experience of seeing this on a 1.8 CVH.

Mark

that is symptomatic of an air lock, but if it continues indefinitely then it would imply that air getting in, often through a head gasket leak. first check the little breather hose that goes to the top of the expansion bottle, take it off, with the engine running hot water should flow out of it steadily (hold it over the open top of the bottle) if none comes out then check where it goes onto the engine for a blockage. If it comes out ok then check that the passage way in the top of the bottle is clear. Normally this pipe will let out any air from the system rather than it be forced up through the larger pipe to the bottom of the expansion tank.

Yep all flowing well out that pipe. No need to remove it as can see it flowing out with the expansion tank cap off.

I not investigating this or trying to fix it as its done it for the last 3 years and car works well enough, just curious if anyone else had it.

Mark

Sussed it, it is getting to near boiling point, water rises, thermostat opens, cool comes in and level drops. With a new stat and good antifreeze in it will probably stay near enough level.

Good therory. Could well be. Only snag is that its been doing it for a few years, but only been running cold recently. Could well be the thermostat on way out for a few years perhaps? I only do 3000 miles a year in that car. Certainly sounds a good possibility to me.

Cheers Mark

My neighbour has a philosophy about that sort of thing: 'Let it develop' If it isn't causing a problem then just ignore it, but bear it in mind.

Yep, me too. I ignore most things until they become serious or really should do something about it. I have not done a thing to that 20 year old Sierra in the three years I've had it as it has been working perfectly. Oh I did change the oil and put two wipers blades on it, but that is all. The very cold temp gauge reading drew my attention as can't leave it like as at the very least my mpg will go up. If its cheap to sort out that will be great. If not, I'll run the engine into the ground. Always interesting to see how long these things last. Most of the time, I never find out as the fault lasts to the end of the car's life. As the cars I used are in the 15-25 year old range, I tend to drive them with care. Trying not to give it any revs at start up until the oil reaches the top of the engine and if possible not starting it in very cold conditions. All that sudden change from minus temps to engine temp must hassen a head gasket failure with the block and head expanding at different rates. Once warm it is driven properly and sometimes hard.

I'll let you know if the stat change alters the water surging.

Mark