Vauxhall Corsa 1.4 2010

[Technician]

That was part of the problem though, one hose hot and the other cold and the hoses going hard as the temperature rised. Misleading me to think of a pressure rise before the coolant blow out the cap and boiled.

[Technician]

Well do we want the good news or the bad?

Customer came back this afternoon and said that the car has been okay since collection on the 04th November, however, the car is now broken down in Manchester and the customer showed me a picture of the reservoir hose going to the engine, which has split!

I'm sure if we read back I had concerns about head gasket failure at some point and wondered about the hoses becoming hard due to increases in working pressure!

The car is coming back Monday and the boss is away on holiday for a week. Huray

[Technician]

So the car came back today. I've carried out further engine cranking tests using the WPS500x and engine idle running tests froma cold engine. Nothing stood out as far as I've seen to now, however, just letting the engine run at idle and installing a temperature gauge in the cooling system, it has now been established that at 90 degrees coolant temperature that the coolant starts to boil. Observing the scope trace, the voltage rises and the waveform goes erractic up and down as the coolant boils. The final pressure looking at me on the scope reached approx 6 bar. I said previously the hoses were going hard to the touch when compressed. Tomorrow I'll do some more in cylinder testing to see which cylinder is at fault. I find this difficult to believe that it would be a cylinder head gasket failure! I think I said some time back that I thought the cause could be a fracture in the cylinder head or dry liner(s)? This will be an interesting one to find, and one I'll enjoy now the boss is away for a week. I'll up date when I've found the cause.

To be continued...

[Technician]

This type of cooling system fault is quite tricky to pin down to a specific component. I did a few in-cylinder WPS tests and was not confident that I was seeing a problem. One member on here believed that I'd not got a cylinder head gasket leak, and I didn't think the engine had a cylinder head gasket leak either. So I carried on with the testing and although I could see there was a problem from the engine behaviour, tests were not to me anyway showing a conclusive result. I compared all cranking tests with engine running tests from the WPS and I didn't think I was seeing anything out the ordinary. The last time the Corsa was in from the date of the last post, I thought I'll spend some time now the boss is away and see what I find?

The results...

I started with a cold engine cranking test using the WPS500x. I compared all four cylinders and didn't think I was seeing anything obvious. I then moved onto engine idle tests using the WPS500x and a visual inspection of each cylinder and they looked the same! I then repeated the cylinder tests by inserting a spark plug into each adjacent cylinder when the WPS500x was used. I didn't think I was noticing anything out the ordinary. While these tests were being carried out I had a temperature gauge in the cooling system reservoir measuring coolant temperature. Now in the North West of England I'm at about sea level and not up Mount Everest, therefore I should not be seeing the coolant in the reservoir boiling at a coolant temperature of about 40 degrees C, but I was and we filmed it.

Previously to these tests on other days I'd notice during engine warm up that the cooling system hoses would go hard to the touch when depressed. This only occurrs when cylinder pressure is escaping into the coolant jackets some how, but how! On this last ocassion the coolant hoses did not go hard, but was sucked into themselves. Clearly now the engine cylinder(s) were drawing coolant from the cooling system into the cylinder(s), the evidence now clearly showing this. The WPS500x cooling system test at idle only showed nothing for quite a long time, but then as the coolant started to boil the pressure in the cooling system did rise up to about 6 bar. This is a lot, which did not occur at the same time as the hoses collapsing inwards.

While the cooling system was reacting this way I did another WPS test of each cylinder at idle but again I was not seeing anything obvious! It was only at some time later that I thought about using the rulers to measure the exhaust pocket and intake pocket to see if a measured amount of difference were present, because visually I was not seeing anything obvious!

Now thesedays what should manifold vacuum read on a good engine? 20 - 22 inches of Hg? I'll need to go back on the other pc and look at the files, but I'm sure I saw vacuum readings as low as 17" Hg. Each cylinder was different ranging up to about 19" Hg. This occurred obviously across all four cylinders, therefore, given no other evidence I could see suggested any other type of fault, such as a fracture in any one off cylinder, it does appear then that when the engine was warming up that the shape of the cylinder head face was not sealing against the cylinder head gasket and therefore allowing leaks to occur. I was not afforded the opportunity to remove the cylinder head to visually inspect the head gasket, but over the years I've seen many head gaskets removed for leaking that were actually not blown or damaged around the sealing rings.

I'll upload the Pico files when I'm back at work on my works pc where they are stored. I'd value other views on this. Others might seen something in the pico files I'm missing?

[Technician]

Files attach;

I wonder!! I read somewhere some time back about another brand pressure transducer that did not see engine vacuum? I have only just thought about this! looking at the engine cranking waveforms there is very little showing on the exhaust pockets but absolutely nothing showing on the intake vacuum pockets. Knowing now that cylinder leakage is present (no doubt) I wonder what a engine cranking waveform should look like on a known good Corsa engine of this code? A14XER