V6 heads gasket roulette

[flamingm0]

I have a Mondeo V6. Two and a half years ago the waterpump failed and it overheated. Was apparently ok after a new pump. 18 months later the coolant system was presurrising up and the cap was leaking and sure enough it had nicely blown head gaskets which were replaced for a princely sum. Now just under a year later I can get slight hissing from the pressure cap (which had been replaced) and chemical testing reveals hydrocarbons in the coolant (I assume this was refreshed during the HG work). The garage that did the HG work said that they straight-edged the heads and as ok decided not to skim. I guess this means maybe the overheating was not that severe? They have also said they would be surprised if it's the gaskets again after less than a year and 15k so they reckon a cracked head is most likely. This seems odd if heads were not warped.

If the heads are warped then horrible cost would be incurred to get the thing road worthy again. If it's the gaskets then all is covered by the warranty. Bit of a risk to find out then! What are the opinions of folks in the know out there? Is the garage avoiding the warranty work or would I be stupid to get them to strip it down? Thanks for any input!

[dern]

Any garage worth their salt would have pressure tested the heads looking for cracks imo. Did they not do this? If they did then the cracks probably would have developed since then and can't really be attributed to the work they did. If they didn't pressure test the heads then you still have to prove that the cracks existed when they rebuilt which would be difficult especially as some time and some miles has passed since the job was done.

The first thing I would do would be to replace the cap. Our leaked with only 40k miles on it and hissed as the engine was running because the cooling system is under pressure. My next step would be to flush the cooling system completely and retest just in case the system wasn't completely flushed last time and the traces you are getting are from the last head gasket failure.

Mark

>> Edited by dern on Tuesday 5th April 16:56

[flamingm0]

Thanks Mark. They made a call not to test the heads as they were apparently not warped and didn't need skimming. The current hissing is very slight and only seems to come on when it's ragged hard. The coolant level hasn't actually dropped. I do wonder if the chemical test failure was due to left over residue or it not being flushed properly. I do remember thinking the coolant wasn't very clean looking when it came back. Would be nice if it is ok afterall.

Do you know how sensitive hydrocarbon chemical tests for coolant are? Would a residue lining the system be enough to contaminate a fresh fill if not thoroughly flushed?

[dern]

flamingm0 said:

Thanks Mark. They made a call not to test the heads as they were apparently not warped and didn't need skimming. The current hissing is very slight and only seems to come on when it's ragged hard. The coolant level hasn't actually dropped. I do wonder if the chemical test failure was due to left over residue or it not being flushed properly. I do remember thinking the coolant wasn't very clean looking when it came back. Would be nice if it is ok afterall. Do you know how sensitive hydrocarbon chemical tests for coolant are? Would a residue lining the system be enough to contaminate a fresh fill if not thoroughly flushed?

I wouldn't be surprised if they were pretty sensitive as normally the combustion and cooling systems should be entirely seperate so I imagine a positive result would be "some" but I'd check this. Having had a few cooling systems apart I imagine it would take sticking a hose in one end and running it through for a while to get rid of all the old coolant as no matter how well you drain stuff there's always some coolant ready to drop on the hall carpet just as your wife catches you taking a short cut to the shed through the house

Assuming you don't have any contamination of the oil or any overheating it's got to be worth flushing the whole system out and then redoing the test. If you're happy doing this yourself then you can buy the testing kit from here <a href="http://www.premiertools.co.uk/item2322.htm">www.premiertools.co.uk/item2322.htm</a> for 23 quid and then you just need antifreeze and a hose... probably cost you quite a bit less than getting a garage to do it for you.

Regards,

Mark

>> Edited by dern on Tuesday 5th April 18:16

[nighthawk]

You WILL get a hissing noise from ANY pressurised cooling system which uses an expansion tank and the engine has been run to temperature.

On older systems without the tank, you'll just get boiling hot collant up your arm!


Is the vehicle showing signs of overheating?

bubbling noises heard in the system (sounds like a kettle at boil)

is it forcing the coolant up through the pressure relief valve within the expansion tank cap?

is the gauge higher than normal when under load?

In the past i've found testing for HC within the cooling system to be very unreliable.

From a warranty point of view, it would be very difficult to prove that the gasket failed due to a manufacturing defect, and the age and mileage of the repair would suggest that poor workmaship can not be claimed also, if this job is done wrong...you know about it from the off.

I don't think the dealer has told you anything but the honest situation, if the heads were cracked when the original overheating occured, you'd have had problems long before now.
They say they assessed the face of the heads with a straight edge and they were fine, this in itself is good as FMC do not recommend the heads to be skimmed!!!

[flamingm0]

That looks a handy product, I did indeed pay more than £23 for the last test!

The hissing is from the pressure release in the expansion tank cap. There are no signs of overheating, the gauge is stable and there's been no oil contamination. The is only a small amount of condensed vapour leaking out with the hissing, the level is not bubbling above the max mark. Interestingly there is a "drainage channel" round the base of the neck and down the side of the bottle which does suggest that some minor leakage from the cap is expected by design.

I guess the garage wouldn't have put forward the possibilty of contamination from previous coolant as this would mean they hadn't fully flushed it. Tho admission of this would be better for them than a possible strip down under warranty I'd have thought. Ah well, maybe they just assumed it was flushed ok.

All interesting stuff, thank you! I think some flushing is in order and then I'll see what's what from there.

[kevinday]

Don't forget to remove the thermostat before you flush it. Buy a new one for replacement rather than reuse the old one, or, at least a new gasket.

[flamingm0]

Ahh yes, good point. Otherwise the full system won't get flushed! Thanks.

[flamingm0]

Out of interest I did call my garage and asked if the coolant hadn't been been fully flushed whether the HG test could register a false positive. He said no, even if the system was running on all the old coolant it wouldn't fail of the there was no exhaust gas leakage. They tested by attaching a unit containing some sort of test substance over the top of the coolant bottle neck (not dipped in the coolant itself) which then turns a certain colour if gases are coming off the coolant. Kind of makes sense I guess. If there was no leak and just old coolant then I wouldn't expect gases to be actively rising. Does this sound feasible?

[dern]

flamingm0 said:

Out of interest I did call my garage and asked if the coolant hadn't been been fully flushed whether the HG test could register a false positive. He said no, even if the system was running on all the old coolant it wouldn't fail of the there was no exhaust gas leakage. They tested by attaching a unit containing some sort of test substance over the top of the coolant bottle neck (not dipped in the coolant itself) which then turns a certain colour if gases are coming off the coolant. Kind of makes sense I guess. If there was no leak and just old coolant then I wouldn't expect gases to be actively rising. Does this sound feasible?

No idea I'm afraid. If you trust the garage then I'd go with what they say or get a second opinion.

Good luck,

Mark

[nighthawk]

"The hissing is from the pressure release in the expansion tank cap. There are no signs of overheating, the gauge is stable and there's been no oil contamination. The is only a small amount of condensed vapour leaking out with the hissing, the level is not bubbling above the max mark."

And there lies all you need to know my friend

Ignore it and have some fun