Fumes From Heater

[JohnnyO]

I have a ‘71T targa with an unverified 55,000 miles on the original 2.2L MFI engine, complete with oil leaks. The car is originally from California and now in Canada. With the fall days getting cooler I love to take the top off and crank up the heat for a Sunday drive. Trouble is I am getting noxious fumes into the car. Excepting this was probably caused by rusting heat exchangers I took it into my mechanic. He came back to me saying the HE seemed fine. The test was blocking off the exhaust, the engine immediately stalled indicating there were no perforations in the exhaust. He is thinking that the oil leaks are bad enough to seep into the heat exchangers and that the fumes are actually burnt oil. So now he’s suggesting an engine tear down to redo all the seals. And then while we have the engine open, we might as well replace any worn parts. With costs for all this in the $5000-$6000 range I am wanting to make sure I am heading in the right direction. I truly believe my mechanic is honest and have been recommended to him from a couple of different early 911 owners. Any feedback on my situation would be great appreciated.

[Mr9146]

Here's the general answer:

Exhaust fumes are one thing ... oil fumes are another. Can your nose tell the difference?

The exhaust fumes would be due to cracked or rusted-through pipes inside the heater boxes themselves (you wouldn't be able to see the cracks but you'd surely smell the exhuast). I had the same problem with a set of 914-6 factory heater boxes that I had ... I had to drive with the windows open if I wanted to run the heater. The solution - replace the boxes.

The smell of burning oil would be - as your mechanic said - due to the oil leaking onto and, in the worst case, filling up the heater boxes. Nine times out of ten this is accompanied by oil smoke from the engine grill and the wheel wells after the car is parked once it's been run a while. The only solution would be to FIRST, fix the leaks. Then, get the exhaust good and hot a couple of times and let the oil that's in 'em burn off. If that doesn't fix your situation, time to replace the boxes.

[kenikh]

To know burning oil is to know 911. Usually you can burn it off after a long drive, but it sounds like you don't have the luxury. One other thing: if the MFI pump is sloppy and dumping fuel into the oil, that will smell something awful burning off of the HEs.

[JohnnyO]

Thanks guys. I am 'pretty' sure the fumes are exhaust and not oil burning. My next step is to go ahead and have my mechanic replace the original heat exchangers with SSI's from Pelican Parts. Apparently they are welded together rather than crimped providing a better seal. So even if there are leaks the SSI's won't allow oil to seep in as much. I'll revisit the oil leaks in due time. Wish me luck.

Fingers crossed,
JohnnyO

[ret9191]

Before you replace the heat exchangers try drilling a hole up front in in when the engine is hot at the lowest point. Jack up the car and see if oil drains out. If so when the engine is cold spray brake clean up in the hole and let it drain. Most likely the oil is from the cam seal/ MFI pump seal. Thanks Ron PS If you can see the oil burning from the heat exchanger just behind were the exhaust pipes com out on the left exchanger it s the cam seal.