Mystery burning smell

[ephantmon]

2004 Sport, 117k miles

Qualitative: Smells like burning rubber, more present from start to 10 mins and seems to go away entirely after 20 mins, more noticeable when sitting still rather than moving

Quantitative: Coolant level and color are fine, temp. gauge never goes above the middle, heat still works fine, no visible smoke or leaking in engine bay, no codes or warning lights

Any guesses? Other symptoms I should look for?

 

[CactusJacked]

Does it smell like burning bacon? Does your Jeep have heated seats?
Seriously tho, is it a burning rubber or burning oil smell?

 

[Kaiser Von Kuhl]

Perhaps it's a worn/ slipping fan belt. On cold starts there might be enough drag to cause slippage and a burning rubber smell without the obvious belt squeal

 

[ephantmon]

Does it smell like burning bacon? Does your Jeep have heated seats?
Seriously tho, is it a burning rubber or burning oil smell?

I wish it was a bacon smell. It's much more rubber-esque in nature. No heated seats either.

Perhaps it's a worn/ slipping fan belt. On cold starts there might be enough drag to cause slippage and a burning rubber smell without the obvious belt squeal

I replaced the fan belt with a Gates EPDM one two years ago, belt tensioner too, could it have worn that quickly?

 

[Porkchop]

Have you checked for a valve cover leak.

 

[Kaiser Von Kuhl]

I replaced the fan belt with a Gates EPDM one two years ago, belt tensioner too, could it have worn that quickly?

Not likely. it's got me stumped, anybody else?

 

[TwoBobsKJ]

Have you checked for a valve cover leak.

X2

I think Pork has your answer right there. ^^^^^

Bob

 

[ephantmon]

Have you checked for a valve cover leak.

No, how do I check?

 

[tommudd]

No, how do I check?

Look at the rear lower corner for leaks
may have to crawl under it and look up from below to see if there are leaks on the exhaust
Don't even have to jack it up
( if you have it lifted ) :emotions33:

 

[jeepguy4276]

Just to throw a few more ideas in. Have you checked to see if anything maybe be rubbing on a tire? Could it be a burnt plastic smell? There could be a wire overheating or shorting. Everything others have posted are great ideas to check as well. I lead more toward a slipping belt if you're sure it's a rubber smell. To me the smell of hot oil is much different than burning rubber. Check for wire that may touch the exhaust system also.

 

[ephantmon]

I lead more toward a slipping belt if you're sure it's a rubber smell. To me the smell of hot oil is much different than burning rubber. Check for wire that may touch the exhaust system also.

Yeah, it's definitely not an oil-based smell (gear, motor, transmission). Could be plastic, but I lean heavily towards rubber. The reason I don't think it's a tire rubbing is that I can smell it when it's been idling for 5 minutes but hasn't been driven yet.

I may have to bite the bullet and have a professional diagnose it. Hopefully after the diagnosis it is something I can fix myself.

 

[jeepguy4276]

I'd check wires and hoses to make sure nothing is touching something hot and the belt to make sure it's not slipping. Does everything work as it should? Check engine lights not on? When you smell it have you popped the hoofd and tried to pinpoint it to front, back, in or out, side)? Had any work done recently? All fluid levels good? Is there anything caught or melted to the exhaust? I had a friend that kept smelling something burnt. She took it in twice to have it looked at. Went to another shop and they saw a large black area on the muffler. Worth a check.

 

[ephantmon]

Update:

Brought it to the dealership, they said they couldn't identify anything that would cause what I was describing. They did note that my valve cover gaskets were starting to leak and that I needed a new water pump.

I replace the water pump myself, but that didn't make the smell go away. The dealership didn't have the gaskets in stock, and I couldn't leave it during the week to get fixed. The smell seems to be located up near the coolant overflow tank. I know that's where there are lines to/from the heater core as well. Does flushing the heater core generally accomplish much? If not, how many hours of labor am I looking at a shop charging me to replace the heater core (I'm clearly not doing it in my driveway)?

 

[TwoBobsKJ]

Update:

Brought it to the dealership, they said they couldn't identify anything that would cause what I was describing. They did note that my valve cover gaskets were starting to leak and that I needed a new water pump.

I replace the water pump myself, but that didn't make the smell go away. The dealership didn't have the gaskets in stock, and I couldn't leave it during the week to get fixed. The smell seems to be located up near the coolant overflow tank. I know that's where there are lines to/from the heater core as well. Does flushing the heater core generally accomplish much? If not, how many hours of labor am I looking at a shop charging me to replace the heater core (I'm clearly not doing it in my driveway)?

If the dealership is telling you the valve cover gaskets are leaking they are agreeing with the consensus here. What you're smelling is the oil burning when it hits the cats. The coolant reservoir sits right above the point where the smoke rises after dripping from the rear of the cylinder head/valve cover gasket.

Time to replace the valve cover gaskets! :waytogo:

Bob

 

[Porkchop]

After replacing the valve cover gasket it my take a little time for the oil to burn off the cat so don't exspect the smell to be instantly gone. This is normal to happen after replacing the VCG in fact you might get a little more on the cat when changing the VCG.

 

[ephantmon]

Time to replace the valve cover gaskets! :waytogo:

Bob

Yeah, it seems so. I would like to do it myself, and think I can, I just really wish the high temperature were 15-20 degrees higher.

Also, the studs for the valve cover are much higher/longer than my sockets can accommodate. Will a deep socket be sufficient? Pass-through socket? Do most people just use wrenches?

 

[TwoBobsKJ]

Yeah, it seems so. I would like to do it myself, and think I can, I just really wish the high temperature were 15-20 degrees higher.

Also, the studs for the valve cover are much higher/longer than my sockets can accommodate. Will a deep socket be sufficient? Pass-through socket? Do most people just use wrenches?

I know what you mean - it is COLD! :icon_eek:

Deep well sockets will work fine to remove the studs/bolts. That's what I used.

Bob

 

[ephantmon]

Finally just bit the bullet and had the garage next to my office fix it today. They allowed me to provide the gaskets myself, so I got out for just under $300 total. It shames me a little that I didn't do it myself, but I'll get by.

I can still smell the burning a little, but according to Porkchop, it may be a couple days until it's entirely burned off. Thanks for all the assistance!