Blown head gasket after 900 miles. Any reasons?

[Paul Kelley]

As reported recently, I have had my engine rebuilt and all was going well until yesterday. Noticed temperature gauge creeping up slightly and then buzzer on header tank. Water loss for sure but nothing leaking out, luckily near home so left overnight and did checks today and found tell-tale creamy white oil and some white smoke from exhausts. All points to a blown head gasket (could it be anything else?). The engine has been professionally rebuilt by trusted mechanic of many years. The head gaskets are the extra-thick Payen copy type and were given a final torque down at about 650 miles. The car has been running in until then and was still being used moderately. What could be the possible causes? Is the wording Payen 'copy' a clue - anyone else had this problem? Your thoughts appreciated, as ever.
Paul

[DJT]

If no water has blown out of the expansion/header tank, then it could be inlet manifold gaskets. Head gasket failure would usually result in over pressuring of the cooling system. That is how it manifested itself on my car after which, I fitted the BGA gaskets in 2014.

[jbuckl]

Pressure test the system.
Because of the head / manifold fight (sequence) I always use wellseal to allow the parts to shuffle before final tighten.
Have seen a few gaskets that don’t stand a chance of lasting long due to unsuitable shape.
Thought bga / payen copies were ok.
the cometic ones seem steep, but maybe worth it? Didn’t try them yet

[Paul Kelley]

Thanks both. No signs of water blowing out of header tank so will do the pressure testing and keep fingers crossed it's the inlet manifold gasket - which was also the better quality version!

[jbuckl]

To clarify the wellseal I use on the head gaskets.
pu sealer for manifold.

[flying farmer]

Hopefully its the inlet manifold gaskets.

If you do have to pull the heads then check the block for warping at the back of both cylinder banks. My first Stag came with a history file that included 3 sets of head gaskets in 15000 miles.
There was nothing wrong with the heads, both block decks were warped and needed 8 thou skimming off to true them up, no problems in the 10 years since.

Obviously this is a total engine strip down to fix so lets hope its the manifold gaskets!

Neil

[KOY 23]

The OP mentions mayonnaise, where was that? if in HT, surely that rules out inlet manifold? Apart from heads the only other places where oil and water are close are the transfer housings and water pump O rings?

[Paul Kelley]

Thanks Neil and Koy. Good point about the block and here's hoping, likewise re the pump and housings. The oil in the sump (dipstick oil) is clear, cream foam is at the filler cap, water level drops but doesn't seem to be under excess pressure but is going somewhere internally. I'm away next week on short break in Scotland - which should have been in the Stag - so have now left it with the mechanic who stripped and rebuilt it to investigate further. I'll report back when we know more. Thanks again for the feedback.

[Goldstar]

My £5 is on inlet manifold gaskets or condensation.

[Paul Kelley]

I'll take either. But condensation wouldn't explain the significant water loss...

[Paul Kelley]

UPDATE: I feel I should apologise for my first real onset of Stag paranoia! My suspected blown gasket turned out to be a leak from the radiator, easily repaired, plus condensation. A case of 1 + 1 = 3, as the coincidence of water loss with no visible leak plus condensation looked like water and oil mixing. So, a very good result but still a bit of a mystery as to the cause of condensation. One theory is the temperature difference on the outside of the timing chain cover. Any other ideas for causes of condensation? As always, thanks for the various replies and I'll just go back to watching the temperature gauge to manage my paranoia.

[NeilR]

How often do you run it ?.
Too many short runs / running up to temp in the garage will cause excess condesation to build up.
Noticed that on mine during winter months, none at all evident during summer months when it gets more use / regular use.

[taroz]

Hi Paul, could it be that the cork gasket on the oil filler cap is missing or damaged? Tariq

[Paul Kelley]

I run it pretty regularly NeilR, every few days and even during the winter when I can. New oil cap and cork gasket fitted very recently Tariq. Thanks both for the ideas but looks like it's something else.

[jbuckl]

The original expansion bottle on a mk 2 often allows pressure out at the brass crimp.
the new replacements can also allow pressure out when the cap doesn’t seal & it often doesn’t.
this appears to be one reason why some owners end up fitting a header tank instead.
It’s worth having a pressure test kit to check for pressure leaks imho.
ebay sellers offer them at about £38