Do I have a leaking cylinder head gasket?
 

Hello all,

My expansion tank sometimes (a few months) drops below its minimum mark causing the car to display an out of collant error message.

I have performed a pressure test and the system seems to be holding.

I do not see any white vapour coming from the exhaust.

What I have noticed is that after filling to the max mark, it usually behaves nicely again; however, sometimes after driving I find that the expansion tank is nearly full.


I tried to perform a CO2 test after removing half a liter of collant from the expansion tank; however, the tank became full and the coolant ran into my tester contaminating the test fluid before it had a chance to reach running temperature. T

I get hot air inside the car when I want it, and the top and bottom radiator hoses are both hot once the engine is at running temperature, so I think the thermostat is working OK.


I intend to drain more coolant before trying again this weekend in the hopes that my tester will have the chance to see if these is CO2 coming out of the coolant, as well as perform a compression test.

I would also like to perform a leakdown test; however, I have been unable to find one for diesel engines.


Am I on the right track or have I missed something blatantly obvious?

Back in the good old, bad of days of motoring a LONG time ago. When ever I had car with a cylinder head problem, it was always accompanied by overheating followed by performance issues. Does your car do that?

A compression test of the cylinders usually confirmed it, but not sure how you would do that easily on a diesel.

Just my experience, but I am sure someone will be able to help more.

Good luck and keep us informed?

No performance issues nor overheating.

I would flush the coolant and monitor, maybe it has got trapped air for it to rise again.

I am having similar issues but mine just disappears, performance was fine and held pressure fine, mine is the headgasket though so hopefully yours isn't that.

Cheers

Silly me forgot to measure my glow plugs before buying a compression tester, as I need an M8 adapter but my test kit only starts at M10. :-( I am hoping the manufacturer has an M8 adapter that will work with it.


The good news
When checking it the other day when cold, it was below the minimum mark, and when I took the expansion cap off it rose to half way between min & max. I then started the car and allowed it to idle until it reached running temperature with the cap still off after topping it up to the max line. The level in the tank only started to rise a little each time I squeezed the top and bottom hoses.

I have just checked it this morning after it had been driven, and the level was half way between min and max, and then rose to just under the return port after removing the cap. I then attached my CO2 tester and ran the car at running temperature for over five minutes. This time the expansion tank level did not rie, and the test fluid remained blue, so it would seem that I do not have CO2 in my coolant.

I still intend to perform a compression test once I get an adapter.


Observations
Although the top hose is hot, the bottom one seems to be cold (I mistakenly stated earlier that both hoses were hot). Is this normal or could my thermostat be stuck in the open position?

Also, with the fans on max and the AC turned to max heat, the driver side of my LHD car gets good heat and good air speed; however, the passenger side gets less heat and little air speed. Does this indicate that my dust and pollen filter needs changing or do I have an AC problem?

Finally got to perform the compression test, and all cylinders report 25 bar.

As they are all the same pressure, this would indicate they are all good; however, as I do not know what the actual pressure should be I cannot tell if 25 bar is truly good or not.

25 is a good reading for a diesel engine its abt 365 psi

Check for any radiator hoses bulging or feeling soft when cold.

Opening the rad cap (expansion tank cap, same thing) when cold and immediately having a higher level sounds like its under pressure and then you release the pressure and the expanded hose somewhere contracts.

Just a theory, mind

Could it be the tank cap itself?

This could well be a possible cause as I believe that the cap is supposed to be designed to release pressure once it rises above 1.5 bar; however, from what I can remember, the system held pressure when it introduced to 2 bar.

I will need to perform the pressure test again to confirm this though.

If the cap is supposed to release pressure, but doesnt, what part of the cap should be performing this action?