Hey Guys,

I recently got a CLS55 a couple months ago and have recently noticed a strange smell coming from the engine compartment. It's not a strong smell but it's noticeable after parking the vehicle in the garage. It smells like a mixture of burning rubber / plastic and appears to be coming from the passenger side near the SBC unit behind the headlamp housing.

The only mods I've done to the car so far are changing the parking lights to LED bulbs and the HID conversion on the fogs. I don't use my fogs much and the car emits this smell without them being on. Anyone experience a similar smell?

 

I had something similar happen to my W210, it turned out to be a plastic bag sticking and melting to the exhaust under the car.

 

Thanks for the reply Cheeze but I looked underneath and didn't see any remnants of any plastic bag. I'm wondering if it may have anything to do with the swap in the low beam bulbs and / or parking bulbs. I've noticed something curious in the parking bulbs. The plastic chip material that the LED diodes sit on has started to turn a dark brown color whereas before it was white. Perhaps the soldering points corroded from handling the bulb chips (sweat from my finger tips) when i attempted the install. I'll check after my morning commute when my parking bulbs aren't on to see if I get the burning smell.

 

I had to happen to me on an old e class. very very annoying.

 

A plastic bag stuck to the exhaust on my wife's car, and I can still smell the burning plastic more than two years later. It won't go away.

 

As others have said, something plastic may have gotten stuck on to your exhaust, and what you're smelling may be the reminiscence of that matter. You don't have to physically see a plastic hanging from below, to experience this. Although this may not be 100% your problem, it is a good start. I would get underneath the car and examine the entire exhaust system from the manifolds all the way to the tips. Be sure to do so when the vehicle is cool so you can feel around the pipes for anything stuck or burned on. If you do find something, you can use a steel brush to remove it. If it's really burned on, you may need to use a metal gasket scraper or trowel like tool to remove the bulk of the matter.

If you don't find anything on the exhaust system, don't forget to check in and around the lower half of the engine and transmission. You also want to keep an eye out for anything loose, or hanging that may be rubbing on a hot surface. Although not as common, don't forget to check your plug wires too. Split, cracked, or arching wires can also emit a burning rubber/plastic like smell.

Last but not least, and this is more so on the worse case scenario option, you have an electrical issue somewhere. Diagnosing this may be a little more difficult but you can start by checking any visible ground and harness connections to make certain everything is tight and secure. Check both the front and rear battery connections. If there's any corrosion present, clean it up or replace the battery. Look for any ripped, scorn, or damaged wires.

You mentioned you had performed some minor lighting mods, and although I doubt they're the cause, I would pull them off and see if you still have the smell. It may be a little bit of work, but hey at least it'll ease your mind and possibly eliminate their involvement. If you do notice the smell goes away after you go back to stock configuration, then you need to examine the aftermarket lighting equipment very carefully. It could be they're heating up due to a faulty connection, an on board resistor, or from simply poor quality / craftsmanship. Some aftermarket HID kits are infamous for burn-out's due to the use of extremely poor low grade wiring. Not saying that's your problem, but it is something to consider.

Anyhow, good luck with your findings... Let us know how things go!

 

Thanks for all your responses guys. Ducati-G thanks for your through feedback. I couldn't really detect the smell this morning when I got to work. I drove the whole way keeping my lights in the off position. Since it's dark by the time I leave work I'll check when I get home to see if I can detect the smell. If I smell it in the evening and not in the morning I can probably conclude that the source is the parking lights or the led chips themselves and will remove them as you suggest and revert back to stock (these parking light bulbs were such a pain in the *** to get in!!). I don't have a lift, jack or stands so I'll have the dealer check my undercarriage for any sneaky plastic bags that may have gotten stuck to the exhaust. Will keep the thread posted when I can pin down the source.

 

is your car lacking power. Ive seen the relays stick on the secondary coolant circulation pump and literally burn up. smoke and all. but once it burns up the pump is no more and the supercharger doesnt kick in, so if your supercharger still works i would say its not the pump that burned up

 

I think it's safe to say that my supercharger is functioning. Haven't noticed a drop in power as of yet. I have plans to take it in to the dealer next week when this storm lets up. I'll be sure to have them look at the relays. Thanks MBTech.

 

Hey Guys - thanks for all your input. I got word from the dealer today that the source of the smell was indeed some foreign object that got stuck to the exhaust. Most likely a plastic bag. They also noticed a valve cover that was leaking oil so I'm glad I brought it in. Thanks again guys!