S500 engine discoloration
 

I am purchasing a S500 1996. The engine metal parts, mainly those easily seen beside the big black cover, has a yellowish discoloratiion. I have seen this on some other 500 and 420 engines ofthe same vintage. But others have no discoloration. Is this condition a problem or indication of a problem of any kind. If it is I may want to cancel my purchase. Any reply by tomorrow 7/18 would be greatly appreciated. Thanks.

coating
 

that is the anti corrosion coating put on by mercedes, i wouldn't cancel the purchase based on that alone.

I'm not a mechanic but I do own a '97 S500 with about 100,000 miles. Car runs great and has a slight yellowish discoloration right below the valve covers-right where a small oil leak will show if your valve covers lose their seal. I would guess it's an oil stain if it's in the same area. Your seller probably cleaned the engine prior to putting the car up for sale. If the car passes a pre-purchase inspection- including a code check of pending codes (in case the seller had cleared the codes earlier- some malfunctions like fuel trim issues need multiple consecutive failures to throw the check engine light but will display the failure code on a code checker as "pending" if it's registered a failure but not enough occurrences to illuminate the light.)

Also check the AC system- put a thermometer in the vent and drive around with the AC on full cold and see what it says. Mine reads about 42 degrees.
If it's warm, be careful- these cars are known to have evaporator failures and fixing them is EXPENSIVE!

Overall, the w140 is the nicest car I have ever owned. It WILL need a lot of TLC but it will also reward you with an incredible ride. Again, Just make sure it has a through inspection by a Mercedes guru so you know what your getting your self into.

Good luck!!

Thanks for the reply, but this yellowish cast is on all metal parts.

Normal. MB shoots a layer of wax on new engines to protect them during shipping. If it wasn't cleaned off perfectly when new it will yellow a bit. It really isn't a concern unless you plan on showing the car. A judge may take some points off for it.

Some dealers don't clean it off at all. It is merely a cosmetic flaw.