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Crankcase pressure?


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Triumph Spitfire 1500 - 1979

Car starts fine and runs ok but on start up there is a huge amount of white billowing smoke from the exhaust. It calms down a bit as it warms up.

I've just run compression test on all four - no problems - all identical at 10.5 psi.

I noticed however, if I take the oil filler cap off while the engine is running it stalls - the revs drop right off.  I didn't think this should happen???  Seems to be a lot of pressure inside the rocker box.


Any thoughts?



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The engine will stall if you take the oil filler cap off as it's letting air into the carbs through the breather pipes.

The smoke on start up can be condensation, maybe a rich mixture or worn valve guides. If it goes when the engine as warmed up it sounds more likely to be condensation which on a cold day is not abnormal. There is just a chance that the head gasket has gone letting coolant into the combustion chambers, but that would show up as a constant lose of coolant. 


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Hello Pete,

If you run a servo on the car, then that will certainly give plenty of white smoke if the diaphragm is knackered as the brake fluid is sucked in to the engine; however that would be a constant sight when driving after brake application.

Ideally, to check the head gasket it will be worth taking the rad cap off from cold - start the engine and see if there are any bubbles coming to the rad neck within ten seconds or so - if yes then the head gasket is on its way out.



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if its on start up then its head gasket letting coolant into a cylinder bet if you remove the rad cap after stopping . next day start up will be less smokey

before long you may start to notice coolant levels dropping without any leaks .

all due to coolant pressure oozing a few droplets into a cylinder overnight .

take a sniff does it smell of oil /  rubber or gylcol antifreeze ????


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Looking at those pics and if starting from cold, it could be an over-rich mixture on top of what the choke is adding.

I still say you should check for rad bubbles on start up; this really is a case of process via elimination rather than guesswork.

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