Exhaust smell when heater on

86Carrera · 12:35 AM

I noticed a few months ago that when I have the heater on I smell exhaust.

When I took it to the mechanic for an oil change he said it was probably oil leaks (it's probably oil you're smelling not exhaust) but it's always leaked a little before and no smell.

Now I'm thinking it might be a broken head stud. I searched head stud symptoms but didn't see anything about the exhaust smell. Is that one of the symptoms?

Under part throttle acceleration I think I hear a rattling / popping sound and that's making me concerned.

Car is 1986 Carrera with about 145K miles.

If it's head studs do you have any recommendations for a really good mechanic to fix it? What will be the approximate cost assuming no major work besides that?

Rob G · 11-16-2009, 09:02 PM

Not 100% sure but it might be a bad exhaust manifold. I could see if the exhaust manifold had a hole in it the heat exchanger might be sucking the exhaust into the car. Just be very careful about driving with this issue. NOT HEATHY FOR YOU.

Rob G

vulcan300 · 11-16-2009, 09:05 PM

You may want to check the condition of the fabric hoses connected to the baffle boxes. Holes in these hoses may be the cause of your issue.

RNajarian · RNajarian's Garage

Lots of good mechanics in LA Area. My money is on TRE. Dave is very thorough. I bet he's seen this sort of thing all the time. CO is pretty nasty. Make sure if you drive the car your windows are down.

jwernquist · 11-16-2009, 10:34 PM

I would agree with another poster, check your heat hoses. Its pretty easy to also check for leaks, start the car go under feel around the cat connections(Without touching) and feel around the cat to muffler flange, see if there is and exhaust coming out. If there is then check the hose closest to the leak. If you can't find or see anything then bring it do Dave at TRE.

mhunter · 11-16-2009, 10:44 PM

I have a 1971 targa and have the same problem. Everytime I turn on the heater it gets warm but it always smells a little toxic. I'm going to check those hoses first. Thanks.

Mh

86Carrera · 11:00 PM

Thanks a lot guys I'm going to check those hoses tomorrow.

twistoffat · 11-16-2009, 11:28 PM

It sounds definitely like the heat exchanger. Have the originals ever been changed. If not they should be overdue. Even in a dry climate they are prone to degeneration.

86Carrera · 12:26 AM

Quote:

Originally Posted by twistoffat

It sounds definitely like the heat exchanger. Have the originals ever been changed. If not they should be overdue. Even in a dry climate they are prone to degeneration.

No it's got the original heat exchangers in it, I didn't know that they wore out! I have 145K miles on the car.

If anyone else has had to replace the exchangers what was the concern? Exhaust smell in the heater? Were there any noises? And, of course... how much does it cost to replace them? I need the heat but can't deal with the exhaust smell let alone the CO poisoning. Thanks.

twistoffat · 12:12 AM

Its usually the smell that you descibe. The heat exchanges are an integral part of the heating system wrapping themselves around the exhaust and channeling the warm air through the heating ducts. Because of the heat etc they are prone to wear over time and they get holes which lead to the engine smell being sucked though the heating ducts. After 145k the originals should definiotely be due for a change. The bad news is they are expensive but get a decent set and they should last you another 50k. My car spent 24 years in a dry climate had only 50k miles and they had to be changed
Our host sells them for 1165$

86Carrera · 11-17-2009, 12:32 AM

Twist and everyone I think the exhaust sounds a little different as well. Then I convinced myself I had broken head studs -- even though they were fine 2 years ago when checked -- and so the sound sounded like popping but it may have been my imagination... unless a bad heat exchanger makes similar sounds.

For the rest of you who had to replace were there any other symptoms besides the exhaust smell in the heat?

86Carrera · 11-17-2009, 12:39 AM

I forgot to add that when the heater is on there is no exhaust smell until I start accelerating.

twistoffat · 11-17-2009, 12:41 AM

Taken from 101 projects

" If two studs break on the same head, then it’s definitely time for an immediate rebuild. In addition, if you can hear an exhaust popping noise when accelerating, it’s time to rebuild. Driving the car with an exhaust leak can cause the head and cylinder to vibrate and knock against each other. If this problem is left unresolved, then the exhaust leak can end up damaging the head and the piston. In general, if you have an exhaust leak at the junction between the head and the cylinder, it’s best not to drive the car."