Hi all

I've finally got my Escort cosworth back on the road after 5 years (its a long story). I melted no.3 piston and had the engine rebored and rebuilt but only just getting it back on road. I believe the piston melted due to inadvertedly fitting a standard fuel pump to a chipped car.

Anyway, got it through mot today but was hoping a nice run would have it running sweetly. It didn't. It feels like its misfiring (although it idles ok) and boost gauge will hardly rise above zero. The water tank bubbles slightly at idle (but clears if revved a bit) but once engine is up to temperature the bubbling in the header tank goes crazy once the engine is switched off. It's more like its boiling rather than bubbles you get from a blown headgasket. It continues to bubble (or boil) for several minutes after switch off. It will start and tickover fine first turn of the key, hot or cold. The bubbles in the header tank come out of the top connection (the one that returns from the turbo).

If left idling the car will rise to half way on the temp gauge and maintain around this temp as the fans cut in and out.

Any ideas or any questions?

John

 

have you checked your thermostat,

 

Doesn't sound good, possibly a head gasket issue.
Who did the engine?
Have you replaced any sensors, can you be sure the gauges are reading correctly?
As already stated, what about the thermostat, has that been changed?
it is unlikely to be BOTH, bad guage and thermostat, causing it to overheat, normally you'd have on or the other, TBH it sounds like something more sinister like the HG or other issue.

 

Have you tried bleeding the cooling system as it sounds as you may have an airlock? If it's a fresh engine you shouldn't be wanting to run any major boost to speak of through it yet until it's run in.

Martin

 

I doubt its just a thermostat as that wouldn't cause a misfire and the fans cut in to keep the temp ok. No sensors changed. Only thing done since last run is fuel pump and fuel pipes all changed (they were going rotten). Not put foot hard down to get full boost but under mild acceleration boost should still rise but it gets to just above zero n dont seem to want to do any more. Am thinking it may well be head gasket but it was a new cometic head gasket (the thicker one) so dont see why this would go without car being run. I'm also thinking it might be a blown turbo that boils up the cooling water causing bubbles??? The bubbles all come out of the pipe returning from top of the turbo.

The strange thing is.... the bubbling gets one hell of a lot worse once the engine is switched off....

 

How many heat cycles has it been through, the return from the turbo is where the air should be seen as the system bleeds itself, very effectively as well, this is through here being the highest point, the water gets hotter after switching off as it absorbs the heat in the engine but without being circulated just gets hotter and hotter, after a few 2-3 heat cycles shouldn't have any air left if there though.
Temporarily bypass the water circuit on the turbo and see if the bubbling stops.
tabetha

 

i get bubbling from the turbo in my expansion tank when turned off, after a run. i thaught this was normal...

 

It can be explained by water boiling off.... I've compression checked it today and all cylinders give 165 psi so no problem with valve sticking open etc etc. All plugs were a bit sooty (which i suppose they would be as running in) but no.3 plug was more sooty than the others. When the engine popped it was no.3 that melted. I've borrowed my mates head gasket tester kit (the chemical one where the liquid changes colour) and I'll use that tomorrow. I'm kind of expecting it to fail that test but god knows how a head gasket could go just cos its not been used.

 

It just failed the hydrocarbon test and also boiled out the top of the header tank when i cracked the top off so looking like head gasket or something even worse like a crack in head or block. I don't get it though. Used all new parts and had top of block and head lightly skimmed when the negine was rebuilt. Engine built by mechanic with over 20 years experience but I still end up with problems.

I used a cometic head gasket. Whats peoples thoughts on these? Its a small turbo cos so will only ever be 300bhp max. Am I better off with another type gasket?

 

did you deck the block?

should have used a standard head gasket.

 

iv had problems with cometic head gasket, mine kept bursting coolant hoses (over preshurising) and i had both block and head skimmed too. at 300 bhp group A is fine, i now use a wrc gasket at 2 bar boost done 8k miles now still ok. but my expansion tank bubbles when turned off, i thaught this was just the localised boiling of the coolant on the hot turbo, always ignored it and never used coolant of overheated etc.

 

id concentrait on the missfire and ignor the cooling problem, if it is a problem. ps headgasket gone wouldnt cause missfire unles really badly gone. then you would see white smoke and coolant loss

 

I'm having it checked with the compressed air into the spark plug hole. If the gaskets gone you get bubbles in the cooling system. Will confirm for sure. The misfire is a strange one as it's not like any misfire I've had before. Car feels hesitant to drive a bit like if the timing was out, but its all electronic. I want to get it running something like right, definately without a blown gasket, get a couple thousand miles on the engine and then get it over to Motorsport development for live mapping and make sure everything is spot on. After that I can start having some fun once again. Some work to do first though so it seems.

The block and head were both skimmed as I remember, although it was 5 years ago but I do seem to think both were done.

 

All 4 cylinders held 150psi with no bubbles through to the cooling system indicating head gasket ok. Changed the spark plugs to Denso IK27s and car now runs well but still get bubbling in header tank after switching off. Will keep eye on it and get it ran in. Cant believe spark plugs could make such a difference but I had incorrectly fitted QC59. Thanks for the advice to change to these from Motorsport Developments. I've got a new thermostat to fit yet. I'm not convinced I'm out of the woods yet but a lot happier than yesterday.

 

You will get bubbling in the expansion tank after turn off, it's the turbo boiling the coolant.

 

I'm hoping thats all it is.... will keep an eye on things... I've done about 40 miles tonight and all ok....