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pritesh24

white smoke from engine bay???

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A bit of a weird one, Saturday eve I took a 40mile journey mostly motorway, had ac on for most of the journey for the first time in a while, I was running a little late so was heavy with the right foot, as i got to my intended car park and was going around looking for a space I see white smoke coming from under the hood at the windscreen wiper area and a bit coming through the air vents. Had a burnt electric smell inside the cabin as well. looked under the hood and it had dissipated by then.

Had the same journey on the way back home but little less heavy with the right foot and everything seemed fine, no smoke.

Went on a 16 mile A road journey yesterday and came back again all seemed fine but was not too confident in giving it the beans,

Oil is at a good level, coolant seems fine. There is a small bit of fresh oil on the ATF only cap and the 25nm cap with the arrow. Although I don't think its that causing the white smoke.

After a journey the bit to the right of the windscreen washer filler cap is really warm when you put your head over it, its like opening an oven door.

 

Also dunno if this is related but a few days ago I realised my foot fans (down arrow) and windscreen vent fans (up arrow) only blow hot air even if its the coldest setting with the AC on. Only the centre fans with the straight arrow blow the correct air temperature and AC .Not sure if that is related to the problem or a separate one.

 

Does anyone have any idea what might have caused the white smoke and if I should be worried?

Edited by pritesh24

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It could be your A/C had blown off its gas due to your AUX fan not working and when you slowed down driving in the car park there’s  not been enough airflow over the condenser and there fore the gas decided to exit the system to save the compressor from exploding.... 

 

so I’d say it’s your Aux fan that’s at fault and has caused the “white smoke” AKA R134a ;) 

I’d start there :) 

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Ahh you legend will mention this to my indy when I call him tomorrow morning. 

 

If I go out and turn the car on should the aux fan (assuming it's the big one at the front) start spinning straight away?

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No the Aux fan should be the smaller one there’s no need to turn the car on just turn it with your hand, if you can then it might be ok? But then you need to turn the car on to let it get warm enough to activate the aux and see if it comes on or not? 

IIRC there’s 2 different types of Aux fans for the E39? Both controlled differently 

there will be someone along with better technical knowledge than myself. 

 

When I had this exact same issue it was my Aux fan that was knackered, I had access to unlimited supply of R134a so just regassed my system ;) as I only used my E39 on the odd occasion I never bothered replacing the Aux fan. But my air con was always ice cold! ;) 

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The hot air problem probably stems from a failure of the water valve which sits in the passenger side of the engine bay and controls the supply of hot water to the heater matrix.When the solenoids fail or the valves stick in the open position the supply of hot water is not cut off when it should be. I had the same problem and fitted a used unit off EBay ( around £25) which sorted the problem. If you do a search you will find stuff on this.

 

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I would check valve cover gasket above the exhaust manifold . especially at the back towards the firewall - all dry or oily?

 

If not the gasket you may also have an airline crack in the valve cover itself. Airline crack is visible with the cover off and inspected against the light. Competent ABS welder can fix it easily. 

 

What happens is oil dripping on the exhaust manifold hence the smoke.

 

If you notice more smoke when the car is pointing uphill (low speed or stationary) that's most likely the cause.

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Sorry just saw this. Will check the valve cover gasket tomorrow morning. Its been booked into the specialist for the 25th. 

I ran the car yesterday and turned the ac on and the small fan at the front wasn't spinning. 

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25 minutes ago, pritesh24 said:

Sorry just saw this. Will check the valve cover gasket tomorrow morning. Its been booked into the specialist for the 25th. 

I ran the car yesterday and turned the ac on and the small fan at the front wasn't spinning. 

Was the A/C working cold or not? 

I’d still put my money on my first diagnosis ;) 

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Yeh it was cold out of the centre vents. The feet vents and the ones under the glass still blow hot which probably is that water valve Steve mentioned. 

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1 hour ago, pritesh24 said:

Yeh it was cold out of the centre vents. The feet vents and the ones under the glass still blow hot which probably is that water valve Steve mentioned. 

Ok 

then it could be something else? 

If your air con is blowing ice cold on the bits it can then I doubt it’s the gas that what caused your mist? 

Yeah, I’d say the valves are the culprit. 

 

Dunno what the mist was/is? Has it happened again at all? 

Is all the fluid level in the car still ok? 

 

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2 hours ago, pritesh24 said:

Yeh it was cold out of the centre vents. The feet vents and the ones under the glass still blow hot which probably is that water valve Steve mentioned. 

 

Had exactly this on mine recently, turned out to be the fogging sensor behind the rear view mirror.

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Ahh another thing that can cause it. Is this easy to replace might just try it n see if it works if not will be that water valve. 

Lol my indy gonna be happy when I give him the list of things to check. 

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Hasnt happened again yoko, but I haven't been driving with the aircon since. That day I let it run and turned aircon on and smaller fan at the front didn't come on, I still thing if aircon is on its gotta spin so think your initial theory is right. I think the hot air is another issue either the water valve or fogging sensor. 

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Just got back from a 30min drive bits of it were spirited. Anyways when I got home left the car on went out to the front and small aux fan still wasn't running turned the ac on as well and checked at the front again nothing. 

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The ac when turned on made the cold air from the centre vents even cooler, like super cold. Again it only works for centre vents (top and foot vents still blow hot air). 

 

The nozzles under the hood lining seem fine, is there a way to test them? I got a 1hr drive back later I think I will try n recreate it and turn the ac on when on the motorway. It was this sort of heat that day it happened as well. So the while smoke should reappear when I get home and slow down. 

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Tried to create the incident after a motorway run with the ac on. Left the car running on the driveway but no white smoke, then turned the ac on and left it for a bit nothing. Fan at the front was still not showing no signs of movement. 

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