Finally figure out why i smell exhaust with the heat on

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Topic author
candymancan
Posts: 3652
Joined: Tue Mar 22, 2016 11:32 pm

Finally figure out why i smell exhaust with the heat on

Post by candymancan »

Clearly i have a exhaust leak somewhere now probly the exhaust manifolds.. But for 2 years every winter my heat woukd just blow exhaust into the cabin... I made a thread about this and you guys said it was from the fresh air intake by the hood but the a.c didnt stink.

Opened the hood and eith the heater on i felt around that box with the heater core and blower motor and i guess there is a foam seal between the two. i could feel air rushing into it so the heater core is sucking air from the engine bay.

Im not sure if they sell these gaskets ? So i just got some spray foam and sprayed around the gasket under neeth and behind was kinda tricky so i just sprayed until it leaked from thr bottom and come up the top.. Overkill but the back is impossible to reach.

Let it harden and turned my heat on and no more exhaust smell. Thank god.

Anyone know if they sell these gaskets for the heatercore.blower motor box ?
1998 Jeep Grand Cherokee 5.9L Limited 219k
1998 Jeep Grand Cherokee 4.0 I6 laredo 430k
1990 Jeep Grand Wagoneer 155k
1976 Jeep J10.. 85k(repaired)

1979bettywhite
Posts: 547
Joined: Tue Jul 25, 2017 8:14 am

Re: Finally figure out why i smell exhaust with the heat on

Post by 1979bettywhite »

I don't believe there is a gasket for it. Honestly, it's a pretty easy fix if you pull the heater box. Get some foam insulation roll from the hardware store, pull the old material off, clean up around the inlet and then apply the new foam material around the outside. Should seal up nicely then. I would be a little concerned that the expanding foam would get into places it might should not be inside the heater box and/or the internal parts of the HVAC system. This is what I used for mine to seal it to the firewall:

https://www.homedepot.com/p/Frost-King- ... /100047977

Don't remember if it was that exact size, but it seemed to work pretty well.

SJTD
Posts: 1924
Joined: Tue May 21, 2013 12:02 pm
Location: Lompoc, Sunland or somewhere between

Re: Finally figure out why i smell exhaust with the heat on

Post by SJTD »

A good bead of silly-cone should do it.

Problem is, to replace the gasket you have to drop the evaporator. The spray foam fixed it in place.
Sic friatur crustulum

'84 GW with Nissan SD33T, early Chev NV4500, 300, narrowed Ford reverse 44, narrowed Ford 60, SOA/reversed shackle in fornt, lowered mount/flipped shackle in rear.

Topic author
candymancan
Posts: 3652
Joined: Tue Mar 22, 2016 11:32 pm

Re: Finally figure out why i smell exhaust with the heat on

Post by candymancan »

Silicone cant get on the other side where there is like 1 inch of room between it and the firewall.

There is a foamy gasket look at your heaterbox and the box where thr motor is see that foam gasket.. Turn your blower on full blast and feel around.. I bet a bunch of you have leaks.. May not smell exhaust like i did but still.

The foam is only 1 inch expanding foam and i spray it out the outside of the box around the foam gasket.. there is no way it could get in the blend door or anywhere else lol
1998 Jeep Grand Cherokee 5.9L Limited 219k
1998 Jeep Grand Cherokee 4.0 I6 laredo 430k
1990 Jeep Grand Wagoneer 155k
1976 Jeep J10.. 85k(repaired)
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