Discussion
When my car starts even from cold there is no smoke whatsoever, then as soon as I drive it there is some white smoke (sometime a fair bit), even at idle whilst sat in traffic. As it gets warmer it gradually goes away. Also when I start it from cold the oil pressure can get pretty damn high and close to the end of the gauge whilst driving but this again gradually subsides as the car warms up. Why would the car not make smoke whilst sat still just after starting, then make smoke when I drive it off and make smoke whilst sat still after I've set off? Is it related to the oil pressure at all? Is it anything to worry about?
It is probably not smoke, it is (water) condensate. Exhaust gases contain a certain amount of water vapour and when you stop your engine the exhaust fills with air. The air is heated up by the hot exhaust and the humidity increases. As the exhaust cools down (overnight) the water vapour in the air inside the exhaust condenses out. When you start your car again the next day the condensed water vapourises and is carried out of the exhaust. You may occasionally notice water actually dripping from the end of the tailpipe soon after a cold start. This is all perfectly normal.
Mild steel exhaust systems tend to rust from the inside out on petrol-engined cars because of the inherent water vapour. Diesel engines have less water vapour in their exhaust fumes and the exhaust systems therefore tend to last longer.
Your oil pressure drops as the engine warms up because the oil becomes less viscous at it heats up. This is also normal.
The white "smoke" should all but disappear when the engine is fully up to normal working temperature and the exhaust system has heated up and purged all of the collected condensate.
Mild steel exhaust systems tend to rust from the inside out on petrol-engined cars because of the inherent water vapour. Diesel engines have less water vapour in their exhaust fumes and the exhaust systems therefore tend to last longer.
Your oil pressure drops as the engine warms up because the oil becomes less viscous at it heats up. This is also normal.
The white "smoke" should all but disappear when the engine is fully up to normal working temperature and the exhaust system has heated up and purged all of the collected condensate.
Edited by ronime on Monday 5th March 15:15
Thankyou. Is it normal for this to last up to half an hour after the car has started? Also it does it if the car gets driven then left to cool for say a few hours. The head gasket is fine. And no signs of it failing anytime soon which is why it confused me. The exhaust system is stainless steel, so that maybe makes a difference?
If you have been doing only short journeys recently then it is possible that the exhaust is not fully purged. A good non-stop blast on the motorway for an hour might help. If the coolant is not disappearing then you should have no head gasket worries as you have already surmised. If the ambient temperatures improve as we head towards Easter then you should find that the white smoke issue becomes less apparent.
Edited by ronime on Monday 5th March 15:19
My mazda 1.8 eunos would start white smoking after about 30 second from start up . For about 4 mins . It was quite alot of smoke . Lots of white smoke . We did a pressure test they were all even . It lost no water used none . WE WAITED TO IT SMOKES TURNED OFF THEN TOOK OUT THE SPARK PLUG S. WE FOUND OUT IT WAS A INJECTOR WAS DUMPING FUEL ON ONE PISTON . NO SMOKE SINCE . GREAT
Gassing Station | Mazda MX5/Roadster/Miata | Top of Page | What's New | My Stuff