Steamy exhaust ??
Discussion
Burning a gallon of petrol or diesel produces - amongst other things - a large quantity of water.
This is visible as steam from the exhaust on cold/cool days & the liquid that drips from the tailpipe.
A lot of it condenses inside the cold engine & inside the cold exhaust.
If the engine & exhaust don't get hot enough to boil it off it will appear as mayo in the oil filler cap & is the main reason why cars that only do short journeys go through exhaust systems faster than those used for long journeys.
If you aren't losing any coolant then it's entirely normal.
This is visible as steam from the exhaust on cold/cool days & the liquid that drips from the tailpipe.
A lot of it condenses inside the cold engine & inside the cold exhaust.
If the engine & exhaust don't get hot enough to boil it off it will appear as mayo in the oil filler cap & is the main reason why cars that only do short journeys go through exhaust systems faster than those used for long journeys.
If you aren't losing any coolant then it's entirely normal.
Pistoner said:
Thank you!
I will check my coolant levels.
I do 25 miles a day so not a huge amount that’s why I chose the petrol engine.
Wouldn’t Mayo on the oil cap be a head gasket ??
No.I will check my coolant levels.
I do 25 miles a day so not a huge amount that’s why I chose the petrol engine.
Wouldn’t Mayo on the oil cap be a head gasket ??
If you aren't losing any coolant then you don't have HGF - at least not as far as a coolant leak is concerned.
As I've said many times before I wonder how many have had their trousers pulled down for unnecessary work by the unscrupulous claiming that mayo is a surefire indicator of HGF.
Pistoner said:
Wouldn’t Mayo on the oil cap be a head gasket ??
It could be. As already mentioned it could also be condensation due to short journeys and the engine not getting properly not.The Mayo is water mixed with oil so all it tells you is there is some water in the oil, it doesn’t tell you where the water came from.
Pistoner said:
Wouldn’t Mayo on the oil cap be a head gasket ??
It's normal and common to have condensation inside the oil filler. There's no reason to assume that's a problem unless you have some other symptoms.Head gasket failure will often lead to combustion gases or oil in the cooling system. If you see contamination in the coolant, that's a sign of trouble.
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In quite large quantities too - burn one gallon of petrol, you get about two gallons of water from combustion (the extra is the bound oxygen from the air) - delivered as vapour
Given that steam at 100degC is c 1300x the volume of the water that generated it - you soon see why,at idle,on the right kind of cool humid or cold day - you can see gallumphing amounts of water vapour out of the exhaust- that diminishes once the whole exhaust system gets warm enough.
Nothing to worry about. And if the car is new to you, good idea to keep half an eye on coolant and oil levels anyway -over the first 3-6000miles, say,after which you'll get a feel that watershouldnt need attention, and oil, probably not much at all. ATB
Given that steam at 100degC is c 1300x the volume of the water that generated it - you soon see why,at idle,on the right kind of cool humid or cold day - you can see gallumphing amounts of water vapour out of the exhaust- that diminishes once the whole exhaust system gets warm enough.
Nothing to worry about. And if the car is new to you, good idea to keep half an eye on coolant and oil levels anyway -over the first 3-6000miles, say,after which you'll get a feel that watershouldnt need attention, and oil, probably not much at all. ATB
Huff said:
In quite large quantities too - burn one gallon of petrol, you get about two gallons of water from combustion (the extra is the bound oxygen from the air) - delivered as vapour
Given that steam at 100degC is c 1300x the volume of the water that generated it - you soon see why,at idle,on the right kind of cool humid or cold day - you can see gallumphing amounts of water vapour out of the exhaust- that diminishes once the whole exhaust system gets warm enough.
Nothing to worry about. And if the car is new to you, good idea to keep half an eye on coolant and oil levels anyway -over the first 3-6000miles, say,after which you'll get a feel that watershouldnt need attention, and oil, probably not much at all. ATB
Thank you ! It is new to me 2 weeks old ! 2018 Audi A4 saloon. Given that steam at 100degC is c 1300x the volume of the water that generated it - you soon see why,at idle,on the right kind of cool humid or cold day - you can see gallumphing amounts of water vapour out of the exhaust- that diminishes once the whole exhaust system gets warm enough.
Nothing to worry about. And if the car is new to you, good idea to keep half an eye on coolant and oil levels anyway -over the first 3-6000miles, say,after which you'll get a feel that watershouldnt need attention, and oil, probably not much at all. ATB
Short journeys I find it shows more water obviously where the engine isn’t warm enough to clear it. Is this common on both fuel types or just petrol? Never noticed it before on my 2015 diesel.
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