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Sudden catastrophic smoke leak

zcacogp

Active member
Chaps,

Sometimes I hate my S2.

Two weeks ago, on the way back from church on Sunday morning, it started leaking oil all over the known universe. That was the subject of this thread here:

http://www.porscheclubgbforum.com/tm.asp?m=745679&mpage=1&key=catastrophic&#745679

... and everyone was very helpful and it's now fixed. Thank you.

This morning, on the way to church, it managed to start leaking smoke - from under the dashboard and under the rear edge of the bonnet. It started when we arrived and parked up. Not huge clouds, but fairly thick wisps. And a nasty acrid burning-electrics smell to go with it. Wipers weren't on, neither was the heater fan nor the lights. In fact, no ancillary electrics were turned on. The missis (predictably) had kittens.

I turned everything off and the smoke stopped. A couple of hours later I started it up again, and the smoke started again - although only for a short while. We got home (about 10 minutes driving) and it didn't happen again, although there was no explanation for it stopping.

Immediate guess was the heater fan; it's fairly heavy electrics and in the right bit of the car (under the scuttle). I've removed the heater motor cover and the motor itself and there is no sign of anything wrong; various bits smell acrid but not very acrid. I have run the motor up on the bench and it smells faintly acrid, but that could be residual smell from earlier - I'm not convinced either way. It seems to run fine. There is nothing else that seems to be amiss.

So, in short, what else is there in this part of the world that can cause this sort of thing? It started with no clear reason, and stopped equally unexpectedly. I still have the scuttle contents in pieces (having hoovered up a large quantity of fine-quality compost that had accumulated there) and will have a better look tomorrow, but all suggestions of areas to have a look at are welcome.

Thanks for reading.


Oli.
 
Just a few guesses from your description:

If the smoke is coming into the cabin from the heater vents but the heater motor itself seems okay, I'd guess the fan is drawing the smoke in from it's inlets, which are either side of the motor unit under the bonnet.

On the passenger side the fusebox has plenty of stuff that could let the smoke out but should have a watertight seal under the lid (check this seal for damage). On the drivers side you have a battery positive terminal (under a blue plastic screw cover) which could have been surrounded by crud, and probably the alarm siren.

Also check the big rubber seal between the engine bay & heater; the smoke could be coming from the loom that sits under the inlet manifold, but I'd expect more smoke to leak from the sides of the bonnet if the source were in the engine bay.

Check all the electric accessories in the car, check for blown fuses. I once had a heavy footed passenger who managed to kick something under the dash. I hear an electrical 'pop' at the time but everything worked until the next time I used the ABS & it failed.

Good luck!
 
Hi Oli,

The heater resistor pack gets hot... could something have stuck to it, or maybe a resistor burnt out? There is a seal that runs along the scuttle under the bonnet, so I don't think the smoke could come from the engine?

Rob
 
Chaps,

Thanks for the reply.

Malc, the driver's side seemed smellier than the passenger side, and the smoke seemed to be coming more from that end of the world. The fat seal between the engine and the heater gubbins is in good nick and the smell was very definitely 'electrical'. Good point about the battery terminal; I'll have a better look at that tomorrow. There doesn't seem to be anything amiss with the fuse/relay box. Once I had the fan system out and tested, I did run the car up and turned everything electrical on and everything seemed fine. The fan didn't work, for obvious reasons ... [&:]

Rob, hey, thanks. Resistor pack - that's an interesting idea. Where is it? The fan was off when the smell started and hence the resistors shouldn't have been doing anything (and hence cold) but it's possible that one has blown. I guess the only way to test this is with the fan back in the car, which will hopefully be tomorrow. Thanks for the suggestion. As above, I don't think the smoke was engine-related. (Although I did have the fire extinguisher in my hand when I opened the bonnet! [:eek:])


Oli.
 
Thinking about this overnight & if the heater fan wasn't on maybe the source is under the dash & the smoke was getting to the bonnet via the heater?

If a device or component were faulty I guess it would blow the fuse & no smoke would escape, but a bad earth & short circuit (ie earth contact is rusted/corroded, electricity takes the path of least resistance through something else that consequently overheats).

Under the drivers side dash the biggest current load is through the ignition switch I think, it all uses relays though so I can't really suggest a particular thing to look for.

Hope this is of some use!
 
Oli,
Remember that the heater fan is always on at a slow speed and therefore the heater resistances are being used AND the resistances are on the drivers side under the plastic cover.

Mike
White 2.7 automatic
 
Chaps,

Thanks for the answers. I've now cleaned up the blower box (top and bottom) and run the fan on the bench for a good 10 minutes or more. All was well so I reinstalled it, after having put a little grease on the bushes for the flaps and some light lube on the flap actuator mechanisms. They now move freely - much better than before.

It all seems to work. No more smoke. There is the faint trace of the acrid electrical smell, but I think this is historic; it will take time to go away. Everything electrical seems to work and I'm not sure what caused the smoke and smell. Which is annoying - I don't have a diagnosis!

One thing I have noticed is that the two flaps at either end of the heater fan box don't move (although they are free to do so - they move well when pushed but spring back to 'open'.) I think this is the topic of another thread so I'll post one up ...

Thanks for your input and suggestions. I am none the wiser with this one but will keep my fingers crossed.


Oli.
 
sorry to hear about your cars ongoing problems Oli.

Its a bit worrying that you haven't found the source of the burning smell yet.

It occurred to me that it might be a good idea to fit one of those battery cut-off switches on your battery, just in case it returns .[;)] I think I would mount the switch somewhere in the rear hatch/seat area where it was accessable from within the cab .
It would probably be a good mod for all of us to do given how inaccessible the battery is in a well in the back under the carpet.
http://www.ebay.co.uk/itm/UNIVERSAL...arts_Vehicles_CarParts_SM&hash=item23287c8df9
 
Nick,

Thanks for your message. Yes, I have failed to diagnose it, but I am (fairly) satisfied that the problem has gone away, at least for now. I have driven the car a few times since re-assembling it and it doesn't smoke any more (and the nasty smell has cleared too).

I do like the idea of the battery cut-off switch though. That's a stroke of genius - I'll order one pronto. Thanks.


Oli.
 

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