Injector line leak
 

I have a huge diesel leak coming out of the area in between the hard line and the injector. At idle it is just pouring out and foaming all over the place. I recently replaced all of my injector return lines, and this is definitely a hard line or injector leak. Why would this happen so suddenly? It is going to the cylinder closest to the firewall. The car doesn't run particularly roughly when this is happening, but noticeably worse than usual. What should I replace- injector, or hard line?

I saw a nasty crack at the end of one of those hard lines; which appeared for no good reason. Have you taken it off for inspection?

Not yet. I'll have to deal with it tomorrow- too much studying to do right now... :eek:

absolutely- the first step is removal and inspection of the metal lines. Takes five minutes with a a few wrenches.

If the leak is right by the attachment nut, that is usually caused by overtightening of the nut. That causes the ferrule to overstress the hardline and vibration cracks often result. However the hard lines can leak right in the middle, as I had one on the 220D develop a very small pin-hole which saturated the engine compartment. We were on a long trip and had to have it brazed in a small farm town in southern Wyoming.

Update
 

I just took the injector line off and found no visible cracks. I put it back on and ran the car again, and the fuel is definitely coming out of the threads. Should I just grab a new line from the junkyard and try it out, or could the injector be the culprit?

You would have to pull the injector and have it tested. YOu may have a hairline crack that only makes it's presence known under pressure.

What is the condition of the braided return lines?

Also, what is the condition of the threads on the injector and the nut?

Is the compression fitting between the injector and hard line clean and smooth? An errant metal shaving can also cause a no sealing issue.

get some teflon tape and put on the threads at the top of the injector. This may work - and I believe that the very top of the injector wouldn't see temperatures much hotter than the average hot water pipe, so you should be ok.

How do the threads on the injector look? If there is a significant deformity in the threads, it may cause the leak you are seeing.

The threads on the line look fine. There are no gaps or cut lines in them at all. The compression fitting appears to be in order as well, as it slides around with ease. There weren't any chunks missing from that area either.

I replaced all of the braided return lines in the last few months, one by one as they fell apart. The braided lines connect to the injector lower down on the injector than the steel line. The leak is clearly coming from around the threads, dripping down the injector, and pooling on the ground. I guess I'll grab another line tomorrow- the worst case is that it doesn't solve it and I need to have the injector tested. The junkyard can't want much money for one of those lines. Maybe I should just get an injector too- what are the chances the replacements will leak like these?

A new line from MB dealer is around 35$$
http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=123105&M=617%2E912&GA=722%2E118405&GM=716%2E005++++++++++++++717%2E400&CT=M&cat=1 43&SID=07&SGR=105&SGN=03
..should be given a nice flush before install...

I'd do this before I put teflon tape on it.

It is the compression flare itself that does the sealing, not the threads. This is a high pressure connection (2000± PSI) so if the compression fitting is leaking you will not be able to seal it with teflon tape on the threads. Could be a mis-alignment of the fittings but since you didn't disturb it prior to it starting to leak I suspect ither the injector or the hard line is at fault...most likely the line has a hairline crack at the compression flare so I would swap it out with a new one and see what happens. Good luck.

I finally got to a PNP to get a new injector line (after a month...), put the line on, and am still getting leakage around the threads. If I shine a flashlight directly at it I can see a little tiny squirt coming from under the threads. I guess it's new injector time.

hard injection fuel lines
 

it is also important to have all plastic clips holding the lines to the bracket in place in order to avoid metal fatique especially on the W201/W124s and later models.