Water and steam

[John Mellor]

Hi all, took the 4 out to stretch it's legs and warm up before carb adjustment.  After about 25 mins drive and back in the garage I noticed a few drops of water running from the oil filler cap; removing the cap there was a fair amount of steam drifting out. No mush in the cap and dipstick oil trace was fine, radiator level unchanged. Engine temp almost in middle of gauge

I hope it's just my paranoia but thoughts appreciated

Regards  John Mellor

[RobH]

Depending how you have used the car recently there can be a build up of condensation in the oil - particularly if it has only done short runs and the engine has not become thoroughly warm.  A long run helps to boil that off so it may be that is what you are seeing. 

It takes a surprisingly long time for engine oil to get up to full temperature. 

[Michel Higuet]

20 hours ago, RobH said:

Depending how you have used the car recently there can be a build up of condensation in the oil - particularly if it has only done short runs and the engine has not become thoroughly warm.  A long run helps to boil that off so it may be that is what you are seeing. 

It takes a surprisingly long time for engine oil to get up to full temperature. 

I was surprise too to see white fume at the exhaust last morning, paranoid was creeping until I realise that old cars when morning is cold can show this when the motor is cold, simple condensation mostly not the case with modern cars.

[RobH]

2 hours ago, Michel Higuet said:

simple condensation mostly not the case with modern cars.

It must still be there - whenever you burn petrol you generate water vapour as a by-product.  This becomes visible as steam when it hits something cold - like the early morning air.  The effect wears off as the engine and exhaust warm up to a point where the hot gas disperses before it can condense as a visible cloud.  Perhaps there is less in modern cars with better mixture control and maybe catalytic converters help to warm the gas much sooner.  

I do often see modern cars dribbling water from their exhausts though. 

 

 

Edited November 26, 2023 by RobH
edited for second thoughts!

[Z320]

CnHm + O2 —> H2O + CO2

exotherm reaction = heat

Edited November 26, 2023 by Z320

[john.r.davies]

3 hours ago, RobH said:

It must still be there - whenever you burn petrol you generate water vapour as a by-product.  This becomes visible as steam when it hits something cold - like the early morning air.  The effect wears off as the engine and exhaust warm up to a point where the hot gas disperses before it can condense as a visible cloud.  Perhaps there is less in modern cars with better mixture control and maybe catalytic converters help to warm the gas much sooner.  

I do often see modern cars dribbling water from their exhausts though. 

Me too, Rob!     Converters weigh three or four kilos.   They need to reach about 500C before they work, and until they reach 100C they will condense all the water vapour in the exhaust gas.  They don't leave a white cloud because all the water vapour has condensed out, but the water will pool in the can until greater gas flow pushes it out.  Thus moderns leaving home in the morning widdle all down the road, like a leaky puppy.   

John

[Andy303]

On 11/25/2023 at 6:37 AM, John Mellor said:

Hi all, took the 4 out to stretch it's legs and warm up before carb adjustment.  After about 25 mins drive and back in the garage I noticed a few drops of water running from the oil filler cap; removing the cap there was a fair amount of steam drifting out. No mush in the cap and dipstick oil trace was fine, radiator level unchanged. Engine temp almost in middle of gauge

I hope it's just my paranoia but thoughts appreciated

Regards  John Mellor

John:

Is your oil filler cap the older type with the wire gauze inside? I think that under certain conditions, as found on a misty, moisty late fall morning, that water condensates from the  moisture laden air being drawn into the hot engine and collects inside the cap. It happens even on "moderns" when the PCV system is not working as it should. We had a VW Passat which would collect white goo on the oil filler cap unless the rubber sealing gasket was in perfect condition.

[John Mellor]

Thanks all. I was just surprised that a 25 minute drive, even on a cold day, wasn't enough to have driven off water. The heater was toasty and I assumed, probably wrongly, that oil temp would be toasty as well.