Odor of gear oil

[craig-o]

On my way home last week (~50 miles, mostly highway, no stop-and-go), I noticed a VERY strong smell that I associate with gear oil as soon as I exited the car. There's nothing on the garage floor, although I haven't lifted it up and crawled around underneath, yet. The other interesting thing is that the smell seems to be most noticable around the base of the windshield, not the rear of the car as I would expect if it was differential fluid dripping on a hot exhaust.

I drove it again yesterday with the top down on the freeway, and got occasional whiffs of the same smell while traveling at 70+MPH.

I have a 2001 6-speed convertible with just over 100k miles. I've owned it since new, commute about 100 miles/day and do 2-3 HPDE days per year. I do most of my own maintenance. I changed both the transmission and differential fluids at 68k miles as PM (but that was > 2 years ago.)

If I'm going to lift it and crawl underneath, it would help to know what I'm looking for. Is there anything under the hood that contains gear oil? Anything that smells like gear oil when it burns/leaks onto something hot like an exhaust? Any ideas?

[aquaholic]

i know of no other fluid that stinks like gear oil. it has a very distinct odor. my only guess would be melting wiring or melting plastic.

[dgrant3830]

I agree too that gear oil is a distinctive smell. But Mobil 1 doesn't smell like normal oil either, at least to me. Check the bottom of the exhaust just before the cats and see if anything has dripped down onto them. If so, start with the oil pressure sender and see if there is any oil coming out of the connector which is a common failure. Unfortunately, you are going to have to get the car up on jacks and get under there to locate it.

[c4c5specialist]

HI there,
It would be suggested to check the rear mufflers for any fluid being blown onto them from the differential area.
Allthebest, c4c5

[craig-o]

Originally Posted by c4c5specialist

HI there,
It would be suggested to check the rear mufflers for any fluid being blown onto them from the differential area.
Allthebest, c4c5

I checked that out last night - the differential is clean and dry (OK relatively clean, it does have 100,000 miles on it afterall.)

A friend suggested that it may be the clutch slave cyllinder leaking. He claims to have personal experience with this on his 2002. He said that the brake fluid leaking onto the pressure plate burned and it smelled like gear oil. I'd be OK with that as a possibility, except that this smell seems to come after long freeway driving, when the pressure plate shouldn't be hot (unless it's slipping.)

Thoughts on this possibility of brake fluid burning causing this?

[c4c5specialist]

HI there,
Anything is possible.
However, you would see it as residue on the inspection cover of the flywheel.
Take a look and see what you have.
Allthebest, c4c5

[craig-o]

I'm still trying to solve this mystery. It went away for a while, but now it's back, and is most noticable around the top of the rear wheel wells.

I jacked the car up last night and looked all around. Here's what I found:
1. No residue on the flywheel cover.
2. There's some residue (but nothing wet, just grimey) around the power steerting reservoir - and no smell, even when just driven 50 miles.
3. Some residue on the block below the valve covers - again nothing wet, just grimey - also no smell.
4. No residue on the exhaust, from the manifolds all the way back to the exhaust tips.
5. Some residue on the bottom of the transmission - looks like road grime, no leaks from any seals, and nothing that seems wet.
6. Some residue on the bottom and sides of the differential - again, this looks like road grime, nothing wet, and certainly nothing dripping on to a hot exhaust.
7. No fluids on the garage floor.

The smell is definitely getting worse, so I intend to clean all this grime with simple green over the weekend. What am I missing?!

[c4c5specialist]

HI there,
Try to take out the fill plug and tell us ifyou hear air rushing IN OR OUT of the differential.
Allthebest, c4c5

[craig-o]

Sounds like a slight vacuum, with a little air rushing in (for about 2 seconds.) I also felt around for the vent on the top of the differential (after I removed the fill plug) and the vent appears to be free.

[jss812]

Check the bottom side of the exhaust pipe where it goes over the cv joints. Also, check the cv joints at the differential. And the top of the spring under the cv joint.

My differential output shaft seals went bad and that's where the oil slung to.

I guess the most oil I found was on the cv joint at the differential. Just reach up there and wipe across it with your finger.