603 new fuel return line faulty? - PeachParts Mercedes-Benz Forum

dlssmith · #1 01-04-2020, 01:08 PM

After having the injectors out, I replaced the return lines on the 603 with new from Cohline bought from an Amazon seller. Came in a 1 meter length. I cut it up with a sharp knife and stuck it on and it leaks on three fitings. Not all of them. Seems to fit snugly. Wasn't old, quite pliable. I can acquire OEM and will but would there be any reason they leak other than poor manufacturing or misfit?

Diesel911 · #2 01-04-2020, 02:05 PM

You did not say how you removed the old ones. Some people nick or scratch the little nipples and that causes them to leak.

Also possible is that if the Injectors were removed and installed with an socket not deep enough it tweeks/bends the little nipples.

It is rare but sometimes the little nipples leak around the swedged in area. However, it would be extremely unusual to have 3 of them like that.

Take a good look at the little nipples and see if you can see any deformity.

dlssmith · #3 01-04-2020, 02:17 PM

I forgot to mention that I used the old return lines for a week or so while waiting for the new ones to arrive. Even the old ones sealed. And removing the old ones was not complicated, I just grabbed them with a needle nose plier and pulled. I don't think it likely that the nipple is damaged since it is hard steel and wasn't contacted directly with the pliers. The more I think about it, the more I wonder if the return line material is just crap. I removed the new return lines this morning to look at them and the nipples and they slide off quite easily. They may just be a bit big.

Diseasel300 · #4 01-04-2020, 05:59 PM

The hose shouldn't just slide off the nipple. If the size is correct, it should be a very snug fit. Once installed, you shouldn't be able to pull it back off unless you're really pulling and rocking it at the same time. OE size was 3mm, I replaced mine with 1/8" viton hose 2 years ago and haven't looked back.