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I have a 1986 911 Carrera Turbo that has been sitting in the garage for 10+ years. I've been working on getting it back to its prime again.
After a few small replacements, everything is running well. However, exhaust starts to come through the defrost vents. After talking to a few guys, it sounds like I need to replace my heat exchangers.
Since the heat exchangers can be pricey, I wanted to explore all other potential causes first.
Probably heat exchangers, or more precisely, a leak in the exhaust pipe. You may be able to repair them. The clamshells have to be drilled out, taken off, and the exhaust welded shut.
Since the heat exchangers can be pricey, I wanted to explore all other potential causes first.
Any thoughts or comments are greatly appreciated!
If you can smell exhaust fumes coming through the vents... then there is a crack in your headers that is leaking into the heater vents.
You should check to make sure your vents are closing properly if you don't have your heater fans turned on.
Otherwise, it sounds like you'll have to replace the heat exchangers/headers
Are we sure it's exhaust and not just heat? It could be the flapper boxes are sticking open just a bit letting the hot air from the heat exchangers to enter the car. Of course, if you are moving down the road and are definitely breathing exhaust, then ya, time to look inside the exchangers. If it's just sticky flappers then you may be able to get away with new return springs or adjusting the cables. I finally just backdated my flapper boxes and called it a day.
Regardless of flapper boxes sticking or not sticking exhaust should not becoming in.
But what I find interesting is that the inner has corrupted before the outer in the exchanger
My exchangers practically rotted right off the car. Yet the inner was rock solid.
But I think your mechanic may be right. Did he happen to take any pictures ?
Also used exchangers are plentiful and can be in good shape.
I'm not familiar with the turbo so check that forum. They may be able to send you to a good source for used ones.
If the car has been sitting for a long time, are you sure that you haven't had any oil leak into the exchangers? If you have, then it could be oil smoke. I expect oil smoke would be more likely to linger than exhaust.
^^^^ Much more likely. Does it mark it's spot? If it is dripping there is a good chance it's the "triangle of death" and oil is hitting the passenger side exchanger.
If the car has sat for a long time, then you may have oil inside the exhaust pipe, not just in the exchangers. In that case, it will smoke like hell and you'll smell exhaust anyway.
I think SC exchangers will fit, but have a thinner flange, so you may need to do some thread chasing on the exhuast studs if you find them used.
Check the oil lines that supply the Cam towers. There's a short rubber piece that will degrade overtime and see boil. This can leak down, get on the heat exchangers and simulate an exhaust smell when they get hot. Get a big enough we can get smoke to boot.
If they seem wet or there is oil in the area on the sheet metal replace them. You have to take up the distributor and air-conditioning but it's doable in the car.
If the car has sat for a long time, then you may have oil inside the exhaust pipe, not just in the exchangers. In that case, it will smoke like hell and you'll smell exhaust anyway.
I think SC exchangers will fit, but have a thinner flange, so you may need to do some thread chasing on the exhuast studs if you find them used.
78 -79 thin flange 80-83 I believe went to thick flange exchangers.
Thank you for all your help! I do believe everyone's right and this is from oil dripping on the passenger heat exchanger. It has left a spot under the car. I wondered if the leak could be from the oil cooler right above it?
@n8kruger I will check the oil lines that supply the cam towers.
@theiceman I took a few pictures and attached them below. (Don't have a lift, so not the greatest).
Going to keep pursing this and will keep everyone updated! I apologize for the late response, been a busy last month.
I'm not sure if it's the dreaded triangle of death. Usually those leaks hit the cross pipe. That could be the oil cooler o-rings. And this is a CIS car? Oil pressure light switch might need a partial engine drop to reach.
Edit: OK nevermind. This is a 3.2 easy peasy to reach. Might just pull the airbox, the airflow sensor, and stick your head in there sideways, and look down on the top of the motor with a strong flashlight. If you see oil there, then you know what it is.
05-24-2017, 10:39 PM
Exhaust coming through window defroster 911 Turbo
They may have aged out.