Steam/Vapour from exhaust in older cars
Discussion
I'm getting lots of steam from my 1996 525i's exhaust, and I'm not sure how much I should expect. It's a pretty continuous little cloud all the way to work (7 miles/20 minutes). Temp gauge normal (warms up to 90 then stays there), no other symptoms, MPG 23+ town 29+ on a run, recently serviced, no condensation under rocker cover etc etc. Presumably this is either normal or my car is overfuelling?
The other cars I see doing this tend to be large-ish petrol engined cars which are 15+ years old.
The other cars I see doing this tend to be large-ish petrol engined cars which are 15+ years old.
With those engines and their aluminium bits I'd be very tempted to get it looked at, or at least compression tested.
I had similar symptoms on my E34 and then I had lots (i.e. head gasket failure symptons), I just dumped a bottle of K-weld into the coolant. Which did "fix" it for a bit.
But then it failed again, and upon pulling it apart revealed that the problem wasn't the head gasket, but the head itself had cracked
I had similar symptoms on my E34 and then I had lots (i.e. head gasket failure symptons), I just dumped a bottle of K-weld into the coolant. Which did "fix" it for a bit.
But then it failed again, and upon pulling it apart revealed that the problem wasn't the head gasket, but the head itself had cracked
I've noticed the same on my car (4.2ltr V8 2001) too, so watching this with interest.
I've always put it down to it being such a large lump of an engine it creates more exhuast gases which are hotter than the ambient which when the get out of the pipe condensates like steam from a Kettle.
Sometimes it can look really quite bad, the other night I was leaving a gig at the NIA and I actually switched the engine off in the traffic jam.
I've always put it down to it being such a large lump of an engine it creates more exhuast gases which are hotter than the ambient which when the get out of the pipe condensates like steam from a Kettle.
Sometimes it can look really quite bad, the other night I was leaving a gig at the NIA and I actually switched the engine off in the traffic jam.
Sounds normal, water is a byproduct of combustion. On stop start journeys the exhaust is cool enough for it to be condensing out as it comes out the back. Big engine not working very hard. If you ran high speed for a minute it would not be so visible, but would increase again when stopped at lights etc.
wombat172a said:
With those engines and their aluminium bits I'd be very tempted to get it looked at, or at least compression tested.
Yep I'm aware that these engines have a reputation for cracked heads/head gaskets so that's part of the reason why this is concerning me. I have been keeping a close eye on it for weeks and not a drop of coolant has been lost. The engine is fantastically smooth to boot. My instinct, and that of my dad (who was/is a skilled mechanic) is that the engine is okay.So why ask? well, if it's over-fuelling and replacing the ECU water temperature sensor or lambda sensor would fix it, then I'd like to do so before it kills my cat and/or costs me unneccessary fuel money.
HustleRussell said:
Yep I'm aware that these engines have a reputation for cracked heads/head gaskets so that's part of the reason why this is concerning me. I have been keeping a close eye on it for weeks and not a drop of coolant has been lost. The engine is fantastically smooth to boot. My instinct, and that of my dad (who was/is a skilled mechanic) is that the engine is okay.
So why ask? well, if it's over-fuelling and replacing the ECU water temperature sensor or lambda sensor would fix it, then I'd like to do so before it kills my cat and/or costs me unneccessary fuel money.
Overfueling shouldn't result in steam though, should it? Overfueling = black smoke as far as I'm aware.So why ask? well, if it's over-fuelling and replacing the ECU water temperature sensor or lambda sensor would fix it, then I'd like to do so before it kills my cat and/or costs me unneccessary fuel money.
A certain amount of water vapour is a natural by-product of hydrocarbon combustion (that's where the hydrogen bit goes). The colder it gets, the more likely that water is to condense enough to be visible as it leaves the exhaust and hits the ambient air.
I'd just keep an eye on the coolant and oil levels and colours and leave it, unless you have a compression tester handy.
I'd just keep an eye on the coolant and oil levels and colours and leave it, unless you have a compression tester handy.
NISaxoVTR said:
Sometimes when I'm walking to work these cold mornings I get steam comming from the front of my face, I've been to the doctors about it but I can never seem to reproduce the problem in the warm waiting room .
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DonnyMac said:
Has it only started happening since you've had frost on the windscreen?
I've only had the car since July, this is my first winter with it. With my previous cars the steam stopped once the engine was up to temp and it'd boiled off all of the condensate in the engine/exhaust system.In answer to your question, I noticed it happening some time ago when temps were still up at ten degrees or so.
It's no different to seeing your own breath this time of year. Hot air condenses in cold air very visibly, sometimes as steam.
Also, exhaust systems are massive moisture traps. As it warms up, any trapped water heats up and turns to steam.
If your head gasket was gone, you'd know about it
Also, exhaust systems are massive moisture traps. As it warms up, any trapped water heats up and turns to steam.
If your head gasket was gone, you'd know about it
ImDesigner said:
Seriously?
7 miles barely warms my car up in the mornings. Take the car for a proper run, get it warm and watch your condensation disappear.
I drove Surrey > Cambrideshire > Leicestershire > Surrey last Friday with a trailer on the back. The car does get used for longer runs.7 miles barely warms my car up in the mornings. Take the car for a proper run, get it warm and watch your condensation disappear.
The water temp is up at 92 degrees by the half-way point of my commute.
Thanks everybody for the hydrogen = combustion by-product information, However I'm still unsure why the newer cars seem to do it less?
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