My Mercedes 300D 87 is leaking Diesel fuel (front, near engine)we just moved to a knew location my mechanic is in Los Angeles and I am scare to drive 45miles, I got some guy through craigslist.com he said I need a "Fuel thermostat" meanwhile he had change the line and putsilicone while waiting for the thermostat part, the car runs for 3 days without leaking and then started again and even more...I read somewhere the "fuel thermostat can be bypass, since I leave in S. California...Will it be ok to drive the car back to L.A (45miles) without any problem andhow to bypass the "fuel thermostat? Thanks

 

Driving your car will be fine, I drove my 190D with the same problem for months before fixing it. If it were a gas car then definately not. Since diesel requires compression, even if the engine happened to be soaked with fuel it probably wouldn't do anything. But you don't want to bypass problems because that may cause more issues down the road.

You might want to take a look at your injectors. The o-rings break apart over time and are common for leakage too probably because of the sulfur in diesel fuel.

 

Thank you very much, now you are talking about the O-Ring! will it be the "fuel injector seal O-Ring injection pump"?

 

I'm not sure which o-ring goes with the injectors. I boughttheinjector pump seal o-ring,and found out it'slike 2 inches in diameter (which is way too big for injectors) and the delivery valve o-ringpurchased waslike a centimeter diameter (which may be it or too small). Don't know

 

I have the same vehicle. There are several things that can cause fuel leaks. An experienced mechanic should be able to spot the problem. The easiest most obvious leak is the little return hoses going from injector to injector. Anyone can replace these, and they are a usual problem.Very cheap, only useMerz. My next problem was that someone replaced an injector line with a non-Merz part. These lines carry high pressure fuel and they vibrate. MBZ clips all the lines together to prevent vibration to separation. Aftermarket lines often don't fit the clips for restraint, and then they break, and you're running on 5 cylinders. It can be driven spewing fuel, but not fun. Now I am replacing the o rings at the base of the injector lines at the injector pump.(Which is what brings me to join this site today.)I am looking for info on this as I have no book, Yet. I live in Long Beach. I know nothing about the "fuel thermostat", and I think silicone is not indicated in a diesel fuel system AT ALL. I could be wrong. You may call me anytime on my verizon cellphone @ 310 488 6017. But wash the engine and look at EXACTLY where it is leaking, first. I will council with you over the phone, and give you some guidence, but I have my hands full of my own projects, and am reluctant to do other people's work. Diagnosis is the most difficult part of Medicine, and mechanics. I can help with the diagnosis if you can identify the EXACT location of your leak. Even Women can "clean" their engines. Don't be afraid to spray a little high pressure water on this engine. But use your head and be careful with where you aim the nozzle. You (probably)have a 124D, with a 603. engine. The only responses that you should put any faith in, are ones from people who have the same engine/year/model vehicle, or have had the same problem. The return hose leaks are the most common problem throughout the general class of MBZ diesels over the years, and is not specific toonly 124D's .Good luck, Will

PS. You should refer to this vehicle in the vernacular as "1987 300D Turbo" I expect that's what you have, statistically.

 

Don't replace the whole fuel thermostat like everyone says. Replace the O-ring that is leaking and put a new thermostat valve in the valve body. This will save you more than half the money of the entire assembly that everyone advocates replacing. I have a kit available on eBay right now that supplies the new OEM thermostat and viton (biodiesel compatible) O-ring along with instructions to explain how to do the repair.

 

Do you still have this kit listed on ebay? I am attaching a photo of my leaky part which I think is the Diesel Fuel Thermostat you are speaking of...
Chris

 

That is exactly whats leaking on your car in the picture. I don't have any more of the kits in stock, but I can put one together for you if you can wait a week for me to get the parts + however long it takes to ship to you from PA. Let me know, you can email me directly at: Devicefuljake@gmail.com

 

Thanks so much for your reply. I know my mechanic will give me the third degree about the rebuild kit and tell me I need to replace the whole unit. Is this the kit? http://cgi.ebay.com/ebaymotors/ws/eB...category=33603
I am in a bit of a rush as I have a road trip coming up. What is sound reasoning for rebuilding versus replacing the whole unit.
C

 

I have a '95 E300 diesel that has been leaking at various points since the new ultra-low sulfur diesel was introduced three years ago. My MB dealerships in PA and GA (my good indie mechanic retired) both replaced seals up and down the fuel delivery system on an as-needed basis. While it only cost $0.28 in parts, the labor each time was $500 or so to remove the manifold. I have spent about $2500 so far and it still has some small leaks. While Chevron (the oil company) sent out a Tech Alert on the new diesel formulation and the possible increase in rubber seal degradation due to a change in lubricity, MB continues to deny any knowledge of the problem. I spoke to the MB "seals" rep in GA and he denied hearing anything bout it. I emailed him the Tech Alert. Meanwhile, Volkswagen has been replacing their rubber fuel line seals with silicone. Go figure.