87 300SDL leaking Fuel Preheater Thermostatic Valve continued - PeachParts Mercedes-Benz Forum

julio.garcia.fc · #1 08-23-2013, 12:28 AM

Well, I may have made a mistake. This forum advised rebuilding the old, leaking Fuel Preheater Thermostatic Valve and I got lazy and just replaced it. The brand new one leaked like a sieve. So, I thought maybe i got a bad one (highly unlikely) since all my connections and hoses were bone dry and it was leaking out of the plastic and C clamp joint, like the old one. I even replaced some of the hoses.

I sent in for a replacement. All connections are bone dry again, but it is leaking from the exact same place. What am I doing wrong? This cant be that hard! Is there too much pressure? Is something else wrong? I cannot explain this.

Any insights?

julio.garcia.fc · #2 09-14-2013, 11:56 AM

RESOLUTION:

In case this helps someone, here is what happened. First, here you can find all the parts from MB:

FUEL FILTER,LINES AND THERMOSTAT. Fits: Mercedes 300 SDL | Mercedes-Benz of South Atlanta

The second valve, leaked like sieve, like the first one, but after a long drive, seemed to seal better. But it still leaked.

After ordering 2 brand new, leaky valves, I decided to rebuild it. I noticed that getting the parts directly from MB was no more expensive than ordering online, so I went to the dealer. They told me that they no longer had the rebuild parts in stock and that I could only buy the whole valve. I explained my situation and they suggested the two bad parts probably came from the same warehouse and probably had dry o-rings. So, I ordered the third one from them.

When I installed the third one, I checked all my connections and took it on a hard, two hour drive to the mountains. Based on my experience with the second valve, I thought it may be good to get it up to operating temperature for a while for it to seal correctly. This is 100% anecdotal opinion, but, it could not hurt.

Two weeks later, it is completely dry. This valve is working perfectly. YMMV.

Next, replace the engine shock ruined by the diesel and check the engine mount.