2001, 1.2, 16V, Corsa C coolant / heater issues.

Short journeys will not heat the exhaust system and exhaust gas will condense inside it.

My experience of GM engines is a 1.2L 16v Chevy. The cooling system has no bleed points. All the coolant flow circuits self bleed as they route though the header tank.

Was the heater temp control set on heat? Set to fully cold many have a tap that shuts off flow though the matrix.

Does the heater blow hot air?

How long has it taken to use 1L of coolant?

Has anyone re-tensioned the cam belt? Moving the water pump / belt tensioner is a common source of leaks on this engine.

Sludge / mayo only forms if the head gasket is blown at both an oilway and coolant channel. If it continues to use coolant without any noticeable leak do a compression test or coolant exhaust gas test.

Understood and as I've not checked behind any vehicle I've just started (in the cold) lately, and especially one that hasn't been on a run in a while, I logged it my head but wasn't immediately 'worried' by the dribbling water and water vapour I saw, especially as I wasn't seeing any other symptoms and the engine seemed to be running freely?

I don't believe this one has either Peter.

Similar here then. There is a fairly small diameter hose that comes off the top of the waterpump and back to the header tank and that was flowing water ok.

Yes and I swung it down to cold and back to hot.

Ok.

Not hot, only warm Peter.

Good question. I noticed there was some missing when topping up her washer bottle the other day but that was a good couple of months (possibly a lot more) but probably not that many miles.

Cam chain on this one Peter. ;-)

Understood. It had a leaky water pump a while back and a new pump thermostat and belt fitted at that time. The belt feels tight and the pump pulley rotating and no visible leaks in that area. I assume the impeller hasn't dropped of as the bypass is flowing fairly well and the water circulating across the rad when the stat opens (and electric fan came on / off fairly smartly).

Whilst I will do both (I have a compression tester and a mate has a coolant tester set that we went to use previously but couldn't get any pressure because of the water *pouring* out of the water pump seal! ) is it possible there are two issues, a head gasket (cracked head / block) and / or the matrix blocked? As I said, one side of the matrix (hoses though bulkhead) felt pretty hot whilst the other was pretty cold. Now I'd understand that if the heater was on hot and the blower on full (assuming a clear / efficient matrix) but with no fan and the engine fan cutting in (and even me holding the engine at ~3k) the cold side of the matrix stayed that way.

If I can get the hoses off the matrix I can fwd and reverse flush it with a hosepipe and go from there?

Just the sort of job I want to be doing in this weather ... ;-)

Cheers, T i m

It does now! I pulled the hoses from the engine side of the matrix and flushed it both way with a garden hose. Initially, it took a bit of effort to get water moving and then as I started flushing each way it ran dirty and then ran clear. Once it ran clear both ways I hooked it all back up, topped up the coolant and left it to warm up. 'Now' the heater out gets as host (nearly) as quickly as the in so we have flow again. A test drive showed the heater working very well even with the blower off. ;-)

My next question is would you think it would be a good idea to use a flushing solution to clear it further, now I know I've got it flowing in general?

Ok, so while it was hot I gave it a coolant pressure test and it seemed to hold 15psi for quite a while (5 mins)? I'm not sure if any slight pressure drop I did observe was down to the system cooling down or a fine leak somewhere so I'll do it again once it's cold.

At least it did seem to hold some pressure for some time so it's nothing split or hanging off etc.

Cheers, T i m

A head gasket leaks because of the very high combustion chamber pressures, it only needs a tiny,tiny leak to be a problem, unless the leak is severe it may well not show up by pressurising the coolant, you just cannot put enough pressure in safely to get it to blow back in to the cylinder.

Having the pressure tester connected up while the engine starts 'can' show up as an immediate pressure rise.

The only real test is the 'block test' using a fluid which reacts with combustion gas byproducts and changes colour, a sucker device sucks air from above the coolant and passes it through the liquid. (about 20 ? quid for the kit which does many tests)

Understood.

And such a problem could be combustion pressures:

... breaking though the head gasket into the fresh air causing (possible loss of (measurable)) compression on that cylinder and possibly exhaust blowing noise?.

... breaking into the oil passage and pressurising the crankcase, possibly blowing oil out of any breather and a loss of compression and power.

... breaking into a waterway and pressurising the cooling system, bursting a hose or blowing off water from the expansion tank (and loss of compression / power etc).

... breaking into another cylinder causing a loss of compression and power (not sure how you would detect it other than low compression on those cylinders)?

Then you get the other leaks / cracks that join the water jacket to crankcase / outside world etc.

Understood. Do such leaks ever carbon themselves up?

Good point. I didn't like to test that at the time because it wasn't my kit.

Interesting. So that would potentially highlight an issue that wouldn't be detectable using a std compression tester (general wear variations by swamp any loss values)?

With the expansion tank brimmed after refilling and with the cap left off it slowly expelled water as it warmed up. There was the odd air bubble but nothing major. If I squeezed the top hose I could work a bit more of the overfill out. Revving the engine a bit caused the level to raise a bit and when it dropped back to tickover the level also lowered.

What about chemically flushing the system though MrC? Is it worthwhile and if so is there a 'go to' brand / variant that you would recommend please? Someone mentioned Wynn's Cooling System Flush? Is it likely to do more harm than good or should I go for the gas leak test first?

Cheers, T i m

Head gasket faults do not self heal. I would not recommend any flushing solutions, there are too many different combinations of metals to be safe IMO. By all means flush and refill a few times with water, but get antifreeze (which has inhibitor) back in as soon as possible. The only likely cause of the heater matrix getting gunked up is either rotting debris from the inside of the cooling system (often a result of HG leakage) or someone has put in an anti-leak formula, which has sludged up in the tiny waterways of the heater matrix.

Definitely get a block test kit (they are on ebay) and put your mind at rest or at least know for sure what you are facing.

Ok, so I ran that today and I think it shows we do have a problem:

So, is it worth giving one of the leak sealants a go? I mean, if it gives the car another couple of thousand miles that could be worth it?

Failing that ... (and considering daughter likes the car, it's otherwise pretty clean and she would like to see it get to 200,000 miles (currently nearer that than I first mentioned) even if it costs her a few quid), would it be a second hand engine or get the head off and see if we just have a blown gasket or something worse first?

I spoke to a pretty experienced d-i-y mechanic mate the other day and he has used a Bars 'Head Gasket Fix' type product and it worked till he finally scrapped the vehicle (a few thousand miles and several years later). Given this seems to be a fairly slight leak and the car starts and runs ok ...

Don't get me wrong, we would both rather do a 'proper repair' but the chances are (because it's twin cam and cam chain) it's not going to be a cheap as if it was the Kent engine in the kitcar. ;-)

Cheers, T i m

I had expected that. You are on your own there. Mostly, on modern cars hg failure means the end of the car, fixing it properly is probably uneconomic even if your labour is free.

K-seal is the only stuff that has any sort of reputation as to working, let us know if it does.

Understood.

Ok, I'll check that out and report back etc.

Cheers, T i m