Car smokes on start up every morning, then it clears up. The issue of exhaust smoke is quite common and it’s very hard to tell sometimes or pinpoint the actual problem. It can be nothing to worry about or it can be a big problem.
It all depends on how old the engine is, the colour of the smoke and whether its present when idling or under load or heavy acceleration and it also depends on whether the engine has run too hot or not before.
First of all, we’d want to determine what colour the smoke is. Usually it’s either white or blue and you also need to make sure that the smoke you are seeing isn’t actually steam. Steam is common on colder days or when we have a wet spell, it’s caused by condensation. Black smoke is usually running on too rich a mixture and we won’t really look into that at this time.
We’d need to answer a few questions so we get to the bottom of the problem. Is the smoke whitish or blue? Is there a white milky residue on the ceiling of your oil cap? Is your radiator clean with clear coolant? Is the engine oil clean or frothy?
If the smoke is whitish, it’s possible that your engine is burning coolant. What it means is that there possibly is an internal leak, possibly a cylinder-head gasket leak.
What happens is that when the head gasket has a leak, coolant seeps into the combustion chambers when the car is not running — in this case overnight as your car smokes in the morning. The cooling system is pressurised and when there is a leak the coolant leaks into the combustion chambers so when you start up your engine that coolant burns passing out the white smoke.
You would notice a considerable loss of coolant if this is the case. If you constantly need to add coolant in your radiator then that possibly the problem. Usual causes are engine overheating from running car with no coolant or perhaps a faulty fan or thermostat.
You may also want to check the oil cap for any milky residue. Remove the oil cap and check if the inside has any white milky residue. If so, it still points to the head gasket having a leak. You may want to park your car and attend to it before it’s too late. Coolant or water mixing with oil is just as good as food poisoning to the human body. Your engine will take quite a beating if oil mixes with coolant so your urgent attention would be needed.
In the event that the radiator also has a milky kind of coolant, it points to an even worse head gasket leak. Since you didn’t mention overheating I take it it hasn’t reached this point as yet but if you keep driving it without sorting out the problem then more problems worse than the smoke you see will arise.
Moving onto the next likely issue, if the smoke is blue in colour we’d then need a different set of questions to answer so that we get to the bottom of the problem. Is the smoke on start-up only? That question has been answered and we do know that the smoke goes after start-up.
Does the smoke come back under load, when the car is now moving does it still smoke? If it just smokes when idling on start-up and the smoke is blue then worn valve stem seals could be the culprit. You would need to check and be sure that the smoke isn’t present when the engine has warmed up to ascertain that its valve seals.
Worn valve seals will let oil drip into the combustion chamber and when you start your car up, that oil burns and consequently the puff of blue smoke.
This is not a problem that requires immediate attention, it may not cause other bigger problems like that of mixing oil and coolant. You would just need to monitor your oil level overtime though. If it bothers you that much as it would bother me, a cylinder head job would be in order.
Normally, smoke from worn valve seals is apparent on start-up and when engine warms up it goes away. It may not always be so easy to tell if indeed its valve seals that are worn out, but the simplest way to tell is by checking if the engine smokes with no load and under load.
If your engine just smokes on start up with no load then it’s probably the valve seals, if it smokes with load, then you might also have worn out rings as well.
Ultimately you will need to do a compression test to ascertain if the compression is good then the valve stem seals are bad and the rings are still okay. I hope that helps your case.
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