[lacoppari]

I have a 2002 SLK32 AMG that I've owned since new with 55K miles on it. Yesterday wife and I took a trip in it. Frequently, after driving for 20 miles or so on an interstate, the engine would lose its boost. The engine would continue running smoothly but without the considerable power it has when operating properly. Shortly after loss of boost (power), I could feel the supercharger engaging and the engine would run properly for a little while. This off and on would continue for the rest of the trip.

Last year the same thing happened near the end of another trip. However, the vehicle had not been driven for a lengthily period of time except for yesterday so I forgot about it. The in-town trips are only about 10 miles so the problem never occurs.

Are there any suggestions about what the problem might be before I take it to the local Mercedes dealer? I'm suspecting it's a sensor or the coolant pump on the intercooler cutting off or a clogged coolant line not cooling the charge sufficiently and computer shuts off the supercharger to save the engine.

 

[SLK32Rick]

Your first guess is in the right neighborhood.

Check the pump fuse (charge cooler) in fuse box next to brake booster, drivers side. This should be 7.5 amp specified, some have used 10 amp. If you are lucky, its just the fuse. Note, some early 2002 cars had a 5 Amp fuse, Mercedes put out a TSB to change to 7.5 Amp, and all later cars have the 7.5 Amp.

If not the fuse, the intercooler coolant circulation pump may have failed.
Ideally, a scan by SDS (star diagnostic) will show the culprit or clues, however, even a cheap OBD tool will show the "intake overtemp" fault, which oddly doesn't trip a check engine light.

This pump is located under the passenger (right) side headlight. The only tricky part to replace is refilling coolant and getting the air bubbles out of the loop. Also check for coolant leaks.

Happy top down spirited motoring, with reliable and abundant boost.
R