Strange Smell

[DSouth]

I'm going to try to be as specific and detailed as I can about this, because it has me a bit concerned.

On Monday I took drove my 73 911 from North Orange County to San Diego for work. All total it was about 90 miles one way. I left at 7:15 AM and arrived by 9 AM. I had the windows up for most of the trip with the ventilation lever open. A completely uneventful drive.

Last night I drove home after spending one night in SD. I left around 7PM and arrived around 9 PM. This time I had the windows up and the ventilation lever closed. An uneventful drive up until I got to Carlsbad CA(about 20 miles into the trip). That is when I noticed a burnt rubber smell. The smell came and went, and I just let it go thinking perhaps it was just another car.

Then it came back. Again very briefly, and went away. This happened 2 - 3 more times, and I decided to pull over to investigate. Stopping in Oceanside I inspected the car with eyes, ears, and nose at a gas station. No rubbery smells around any of the 4 tires, nor did had any of the rubber oil lines come in contact with anything hot or spinning. I then checked under the hood, near the back of the guages. No smells or evidence of melting of fire. Both battery cables looked fine and were not loose. I went back inside the car and sniffed around under the dash and glove box. But nothing stood out.

So I threw a few gallons of gas in the car and hit the road. No rubber smell again for 10-15 miles, until I got to San Clemente, where after climbing the first hill on I5 after El Camino exit the smell returned. Again very briefly, but strong enough to notice. I moved into the slow lane and dropped speed to 65mph(previously I was going 70mph).

After driving @65mph for a few more miles all through San Clemente and all the ups and downs of I5 I thought "load" on the engine from going up hills was not a factor, but all the previous times I had smelled the burning rubber smell coincided with loading the engine as I went up a hill in the road.

I cautiously proceeded to the 133 toll road which I like to take to cut my journey short on my way back to Yorba Linda. I figured the sustained hills off the toll road would be another good test of whether or not "loading" the engine played any roll in causing the burning rubber smell. I made it all the way up to the 91 freeway, without incident. No more burning rubber smell. Until......

I exited the freeway at Weir Canyon/Yorba Linda Blvd. After exiting and stopping for the light, I turned right onto another street and accelerated, after I got up to speed the smell came back again just for a moment. This made me very nervous, so I shut off the headlights. Recalling threads on this forum outlining how the stock headlight setup can be an electrical fire hazard. I made the last few miles of the journey without the headlights on, and the smell did not return, but I also did not do any heavy accelerating either.

When I got home I immediately disconnected both batteries. Just to be safe. But the question remains. What could be causing this seemingly random burning rubber smell? It may be worth noting that this was the first trip I had made with some extra weight in the back seat. I took some luggage, and my tool box. It was also the longest drive I've made at night with the headlights on.

I do not feel comfortable driving the car until I can get this sorted out. I'm hoping that it was maybe just the tire rubbing, but I did not hear anything that would coincide with that occurring. Any thoughts on how to proceed to root cause this?

Thanks!

[Rot 911]

Check your fan belt, could be slipping under load.

[DSouth]

Thanks Kurt. I will. I did some searching of the forum last night and saw this as a possible cause of random burning rubber smells. It's a new belt(I think, the shop that did some work on the car over the summer replaced it), but I'll check it anyway. That would be the nicest solution.

[RWebb]

new belts often need adjustment as they expand under load

[TheGanzman]

Originally Posted by RWebb

new belts often need adjustment as they expand under load

I'll say! Especially after dinner...

[daepp]

You sure it wasn't the hills you were smelling?

Check your belt!

[slw911SC]

Heater vent on one of your pedal rubbers, shoe, mat, or something rubber in the vicinity of a heat source in the cabin?

[DSouth]

Originally Posted by slw911SC

Heater vent on one of your pedal rubbers, shoe, mat, or something rubber in the vicinity of a heat source in the cabin?

Heater was completely off.

[slw911SC]

Rubber line against a heat source underneath ie: engine, exchangers, muffler etc?

[DSouth]

Originally Posted by slw911SC

Rubber line against a heat source underneath ie: engine, exchangers, muffler etc?

I thought this also, I checked under the car when I first pulled over. I did not see anything, but it's difficult to see all of it, without the car up on jack stands, so I'll double check this too.

Question for everyone: Wayne's book lists the deflection spec of the fan belt at between 1/4-1/2 inch. In general, what end of this range do most favor?

[JFairman]

Both fan belts on my car get a bit tighter when the engine gets hot because the entire engine expands, so the distance between the pulleys increases a little bit.
I doubt it's a fan belt. They make screeching noises when they slip anyway.

Are your rear tires rubbing anywhere in your fenders? You said you had more weight in the back.

Maybe something is touching or dripping on your exhaust system or heat exchangers and it smells like burning rubber.

[mca]

Originally Posted by JFairman

They make screeching noises when they slip anyway.

Not true. Mine was too loose at one point and never screeched.

It didn't create any sort of scent. I doubt it is the belt.

[ossiblue]

I know you ''sniffed" around your tires but I'll ask anyway: what size tires and wheels on the rear? Is your car lowered? Did you check the inside lip of the rear wheel wells for signs of rubbing?

[ToddM]

Are you sure something isn't making contact when you accelerate or going up the hill? It may have nothing to do with "load"

For example, my backup lights use to short on metal when accelerating or going up a hill.

[DSouth]

Tire size: 205/60 R15 BFG G-Sport. No flares. I've put a few hundred miles on the car since these tires were put on, and have not smelled anything up until this return trip, so I'm less inclined to think they are rubbing. Since it is so easy, I will remove all 4 wheels though and have a looksi.

I also looked through my recipts from the last service and no belts are listed as parts and just by the looks of it is does not look that new. It seems to have excessive play. I'll do a more through inspection of it tomorrow morning.

ToddM, that's what I was also wondering. I'll need to look around a bit and see if I can find something.

[ToddM]

If you have a wife half as evil as mine, Im sure she'd be more than happy to drive your 911 at speed while you were hanging on outside trying to find the source of the smell

[Joe Bob]

On the Angeles Crest Hwy...there are signs. "Chains Required"......every year I have to add the "Whips Optional".....for some reason CalTrans does an editorial deletion......

[SteveinTO]

Could the smell have been residual ash from the recent fires. I've been smelling it off and on around our house in Thousand Oaks, probably 30 miles away from Sylmar. More kind of a fireplace smell than burning rubber.

Hope it's not intermittent wiring heat. Might check behind dash, in luggage compartment, and in fuse box for any melted wires.

[yo911]

I know what it is. It's gotta be the same smell from Seinfeld's car. Even after washing the darn smell lingered. Even a thief wouldn't steal the car.

[al lkosmal]

I had a very similar occurance recently, except that it was clearly an electrical insulation, burning smell. It came and went, until finally smoke came rolling our from under the dash. I freaked out, stopped and it went away. I drove the final few blocks home and ....nothing. I checked under the dash and under the trunk/heating blower cover, engine compartment and no sign of burnt wiring. Eventually it happened again (smoke). This time I found the burnt wiring under the dash. The blue/black (on my 77S) from the headlight switch and provides 12V, unfused and daisy-chained to all the dash lights and ashtray light. It had shorted to ground, intermittently. Lot's of smoke and stink, but the wire itself showed only minor damage. I'd get out the wiring diagram and check that one out.