Exhaust fumes in cabin

When I open the heat lever on my 72 911E I get serious exhaust fumes/smell in the cabin. I don't mean oil smell, I mean the smell like I was toking on the exhaust pipe. I've checked the outside of the heat exchangers and everything looks solid. Is it possible for these to be rusted out on the inside only? Where else could this be coming from?

Sounds like you diagnosed the problem. Condensation collects in the header pipes when you run the car for short periods of time. This will cause a rust out over time. Look at the bright side - you can now get those SSIs you've always wanted!

i don't know for early cars but on CIS cars if your heater blower motor stops working you can get exhaust fumes into the cabin

The blower motor is always on and when your heater levers are in the off position it dumps the air out the back

jryerson---

Can you explain why having the blower moter off causes exhaust fumes to enter the cabin? The heater blower motor just supplements the amount of air pushed through the heat exchangers by the engine fan. Also, on a car with the auto temp control, the blower motor is off when the heat setting is set to zero.

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Bill Krause
'79 911SC Euro

Kurt,

I had a problem with exhuast fumes coming in the cabin in stop and go traffic and sitting in place. The issue was sloved when I replace the tubes coming of the heat exchanger, they were all splt and sucking fumes into the system. At speed the fumes were obviously sweep away in the slip stream.

Just a thought, Todd

Kurt
The heater fan on the engine should always be on, it helps keep the exchangers cool
listen for it when you turn the ignition on

I know it doesn't make sense that the heater fan blows out the exhaust gas but when my blower motor went out I could smell the exhaust gases coming inside and once my motor was fixed I no longer had the problem


Jeff
78SC

[This message has been edited by jryerson (edited 10-20-2000).]

My heater blower motor, which supplements existing fan pressure, is NOT on all the time. It comes on when you pull on the heater lever, even slightly. With both heater levers pushed all the way down, the fan is OFF. Right now, the fan motor is on my bench. The hole in the engine compartment is taped up very well in the meantime, and this provides heat but not exhaust fumes.

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'83 SC

I believe in 81 they modified the heating system with adding supplemental blower(s) in the front of the car

Before that you have just one fan on the engine that is always running it keeps the heat exchangers from over heating by dumping the hot air out the back, when you pull the red levers up in the cabin the hot air is directed to the interior

[88911coupe]

Just curious...how could having a leak in the hoses that connect the HE's with the heating ducting cause exhaust fumes in the car? Isn't the air being pushed through those hoses under pressure by the engine fan and the auxillary heater fan? Wouldn't that cause heated air to leak OUT of the hoses and into the atmosphere? Or is this one of those tricky fluid dynamic thing's that's way above my ability to understand?

[Rot 911]

Wow, talk about an old post, I think I had only been on here less than a month when I posted this thread back in October 2000. But to answer your question, Buck, if the engine seal was missing around the engine tin and you had oil leaking and causing smoke, said smoke could conceivably get sucked in by the engine fan and then blown into the cabin.

In my case the heat exchangers were rusted out.

[88911coupe]

Now that you mention it, The tin around my engine is not sealed very well since I partially removed it trying to access some things to get at my oil leak. That may be what's causing my exhaust smell. I'm going to give the fibrous tube things a good look to since I think they're pretty ratty IIRC.

[Privateer383]

I am reinstalling the heater system in my 83 SC Targa after it has been out for several years(the HE's were never removed). Is there an easy way to determine the servicability of the HE's BEFORE I hook everything up and test the system? Or, is it necessary to subject oneself to a healthy dose of carbon monoxide to determine servicability?

[Zeke]

I would think you could produce some smoke inside the muffler with incense or something and very lightly pressurize the system watching for smoke coming out of the HE metal. I think I'd use the blow side of a shop vac with a relief built in so as to not blow too hard. Now, one exhaust valve will invariably be open, so be prepared for smoke to come through the motor itself if the stars are aligned right.

[BoxsterGT]

Whenever the heater valves are cracked open even a little bit you are bound to get some fumes into the car.

The engine fan sucks these vapors into the engine shroud & some of it goes up into the cabin.

Its just the nature of the "Air Cooled" beast.

Add the issue of poor seals & loose tin around the motor or oil leaking on or into the htr boxes & more fumes are allowed inside.

Only the water cooled models seem to be free of engine vapors entering the cabin.

Just my 2 cents..........

Len

[Privateer383]

I like the incense idea. Thanks.

[woywitka]

How much heat exchanger related brain damage can I expect from my 911?