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Old 11-17-2006, 04:32 AM
Jassper Jassper is offline
Join Date: Aug 2002
Posts: 134
602 engine fuel preheater

Hello everyone,

while doing some work on washing fluid heating I noticed a faint smell of diesel as if there was a leak somewhere. After a closer inspection I located the culprit - the fuel preheater was leaking. The front part with plastic cap leaked and also the cap, that was supposed to sit there firmly, could be wiggled by hand.

The good news is that at the dealership you can order not only the entire preheater (which comes at a rather high cost) but also all of the inner parts separately to renew it yourself. There are 6 parts inside of which I ordered 5 (left the bimetallic cap out. It was expensive and didn't seem breakable) - including all seals, springs etc etc.

The cost for those parts was $4. (The bimetallic cap would have costed $15 new). I took the preheater out (2 bolts) and disassembled it. An easy procedure - takes about 2 minutes and is fool proof (better not try to prove that statement wrong though). Replacing all of the parts and putting the preheater back together makes another 4 minutes.

The biggest trouble is attaching all 4 rubber hoses back and tightening them. The manouvering room is very scarce there. But it can be done.

The result - a new (rebuilt) preheater, no leak, no diesel smell.
1991 W124 300D 2.5 Turbo
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