I have a 1994 S500L (W140) I often notice that after I force the transmission to do a red-line shift there is a funky smell, most noticeable outside the vehicle. Does anyone know if this smell is hinting at something going wrong. The engine temperature is always normal, My only concern is there could be a problem with the transmission, I don't know what burning transmission fluid smells like but I would describe my smell as something "funky" not like hot plastic or oil. Also what is the correct procedure for checking the trans fluid level, I have heard something about the car has to be either hot or cold and in a certain gear when the level is checked. Any ideas are appreciated even if it is just reassurance that "funky" smells are normal operation.

I presume your "funky" smell is coming from the catalytic convertor. it is either burning off carbon that doesn't get hot enough to burn at normal conditions or you have enough hydrocarbons getting into the cat to change the chemical activity. Also under full load oxides of nitrogen are heavily produced. This is refered to as NOx where x can be equal to 2 or 3, giving either NO, NO2 or NO3 (not sure if there is a NO). One of the two smells terrible. The other doesn't. NO3 is a few water droplets short of being Nitric Acid.

Another likely possibility is that your exhaust is getting any of a number of lubricants leaked onto it. They just accumulate untill you get them hot enough by such driving to start them burning.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

In my 99 S420, I had the same funky smell. Turned out my O2 sensors + MAF ruined the cats by making the car run rich. The excess fuel ends up showing its presence by giving the potent sulfur "rotten egg" smell. Twenty hour job according to my service advisor.
Parts needed:
MAF
2 O2 Sensors
2 Catalytic Converters-$2500 a peice, Special Order parts
Maybe Parts if sh?t happens
Resonator
Muffler $1495

Another cause could be faulty plugs, wires, distributor or even the fuel injection system.
It is not a normal smell at all. I have heard of V12s on this board that were running rich and ended up needing new engines. Once you redline you are pushing alot of fuel that has to be burned in a very short time.

royaiii,

Bet ya didn't know about fastlane with their price of $800 for cats, did ya?

Just had the engine wiring harnes and MAF replaced so I'll just cross my fingers that nothing is wrong. It's not so much of a rotten egg smell but more of a toast smell, I think i'll ignore this problem as it only happens at red-line shifts. Ignorance is bliss!!!