Hi,

On my '91 F150, I have noticed that when I run the blower fan (it only works on High) I get exhaust fumes inside the cab, especially when it's sitting still. If I have the blower fan shut off, it's not as noticable. With winter coming, I will be having it sitting, warming up, while I scrape the windows. Last time I had to do this, the whole cab filled up and I could barely breathe until I could get the window down. Please help!

 

I'd guess you have a leak somewhere in on of the heating lines, if it only works on high

 

The heater blower motor has a resistor block thats held by two screws on the heater box under the hood. That controls your lower fan speeds. You can get them at most part stores. Exhaust fumes in the cabin are serious so investigate your exhaust system, cab floor and firewall for leaks. The AIR and EGR systems can also cause leaks.
Regards
rikard

 

Sounds to me like you got an exhaust leak under the hood. or the exhaust ends under the cab, instead of goin out under the bed or out from under the truck.

 

the air injection tube or air check valve at back of engine next to firewall may be leaking. i have that, am trying to get rusted parts off, but it puts fumes into cab when i run the blower. its in a location where you cant see the parts very easily but you might be able to see fumes coming out from the engine compartment, especially if its colder outside.

 

Hmm, might have to check my '89 for that, as I to have exhaust smell inside the cab when I run my heater, especially on high.

No holes in the cab, heck it doesn't even have rust!



But my exhaust dumps right behind the cab though.

 

Could just be a leaf or some other debris burning off the blower resistor.

I've certainly had smoke and strange smells because of that.

Be sure to get the correct replacement (depending on A/C or not) the plugs are different.

 

Great ideas! Thanks!

When I had the upper intake manifold gasket replaced, the guy that did it forgot to push the valve on the back of the engine (he said it was the PCV valve, but Barryf says it's the air check valve). It was letting smoke out, but he pushed it back in all the way and it doesn't smoke anymore. Could it still be bad?

 

Could well be a leaky Thermactor check valve, or the pipe between the heads is loose or rotted out,