I recently bought a 2008 Saab 9-5 wagon with roughly 50,000 miles on it.
The issue is that when I turn on the heater, after about ten minutes of driving, the cabin begins to smell like a poorly-ventilated auto repair shop.
The weird thing is that I am able to stop the smell by turning on the defroster. Switching back to the heater brings the smell back.
I don’t smell it when both the heater and the defroster are off, and I haven’t checked to see what happens when I turn on the AC.
The mechanics at the used Saab dealer who sold me the car are pretty experienced, but can’t solve the problem.
They first thought that it might be a grease deposit on the engine block that smells when it heats up, or that there is something dripping onto the engine block and burning, but cleaning the underside of the engine didn’t make the smell go away (and doesn’t explain why the smell goes away when the defroster is on).
We did discover that there is a leak in the reservoir for the windshield wiper fluid.
The mechanics at my local Saab dealer haven’t ever heard of such a problem.
Any ideas about what is going on?
(or any ideas about where to find help)
You more than likely have an exhaust leak at the header. The fumes are being carried into the cabin. I would be looking for exhaust leaks in or very near the engine bay…oil leaks onto the exhaust can also contribute nicely.
When you turn on the defroster…the cabin closes its vent from outside air and goes into recirc mode and usually engage the Air conditioning (or does the defrost open the vent, i forget). At any rate…what I would be most suspicious of are exhaust manifold leaks or where the exhaust meets the downpipe…there is a rather large gasket at the downpipe. There is also an exhaust manifold gasket on the cylinder head. If you have a Turbo…again…exhaust leaks. I dont know the smell you mean…but it may lean towards the Hot or burning oil smell… This points to valve cover gasket…leaking down onto the exhaust. Anywhere oil can come into contact with the hot exhaust is an area to look at. You problem description supports the smell is coming from the engine bay…esp where the vent intake location happens to be on the cowl.
The cabin vent system draws its air from the cowl area of the car… base of the windshield, right under the windshield wipers. So…any engine bay smells will easily make the journey into the cabin.
Look for exhaust leaks at the engine…near the engine or exhaust manifold etc… Oil leaking onto hot exhaust…these sorts of things… You should be able to find it. Nothing uncommon really. Happens a lot.
Reseting your 08 may help but make sure the blend doors are moving as they tend to break the little arms that connect the doors to the motor or you might have a jammed blend door actuator that is overheating when it can’t move the door.
To test for an exhaust leak, stuff a raw potato in the exhaust while the car is idling. If there is a leak it will hiss loudly so you can trace it. If all is tight, the engine will slow and stop. To remove the potato, aim it in a safe direction, restart the engine and rev the throttle. It will come shooting out the back like a cannon. You might have a leak, but you just had a little laugh as well.