How necessary are steel-reinforced return lines? - PeachParts Mercedes-Benz Forum

strelnik · #1 05-09-2009, 08:17 PM

I am replacing the injector return lines on the 1971 220D that I have bought. The car needs some cosmetics and some maintenance, but was driven onto my car dolly. The engine is VERY strong. It needs other things.

One replacement tasks involves the injector return lines.

Fastlane sells them without steel reinforcement. I have seen them for more $$ without reinforcement

How necessary is the steel reinforcement?

What REALLY surprises me is that the lines are push-on 1.9 mm ID with a 3.2 mm OD, about 1/8".

When I saw them, I thought someone had taken the spring clamps off.

Now I discover they don't have spring clamps!

However, I still want to put some on, so if anyone knows a source of 1/8" spring clamps, pls let me know. This is 5 min extra with a set of needle-nose pliers, the cost is minimal, I see no down side.

Your thoughts please on:

1. Steel-reinforced vs plain injector return lines

2. The need for spring clamps to keep these lines on (one came off while doing other things and caused a small problem)

As always I submit this for review with boundless admiration for my most worthy colleagues (sorry, just watched a movie in Chinese, they talk like that, lol).

Strelnik

techguy512 · #2 05-09-2009, 08:20 PM

Quote:

Originally Posted by strelnik

How necessary is the steel reinforcement?

Steel reinforcement? Never heard of it. There's zero pressure in the return lines which is why press on is A-OK. Why would they need to be reinforced?

#3 05-09-2009, 08:24 PM

The reinforcement is cloth, not steel. Clamps are not needed at all. The hose should cost $12-15/meter.

strelnik · #4 05-09-2009, 08:25 PM

Quote:

Originally Posted by techguy512

Steel reinforcement? Never heard of it. There's zero pressure in the return lines which is why press on is A-OK. Why would they need to be reinforced?

All I can tell you is:
1. They are sold that way by some people and
2. I am trying to find out how much overkill this is, or is it necessary.
3. Voila.

cmbdiesel · #5 05-09-2009, 08:42 PM

Maybe the steel is for appearances?

I just paid $11 and change for the return lines on my 300SD, from the dealer.

Simpler=Better · #6 05-09-2009, 10:28 PM

Home depot 1/8" tubing supposedly works too.
Spring clamps can be ordered from McMaster-Carr.

Jeremy5848 · #7 05-09-2009, 10:47 PM

Viton is used for biodiesel, otherwise any 1/8 inch ID rubber or plastic tubing will work. Clamps are unnecessary as long as the tubing fits tightly onto the ferrules. Inspect occasionally for (a) softening due to chemical reactions, if any, and (b) hardening with age and heat.

Jeremy

Brad123D · #8 05-09-2009, 11:07 PM

I use the yellow (neoplene ,I think ?) lines used on chain saws/Small engines. Fexible, strong and works great. Don't want it rubbing against any thing, of course. And you get to watch the fuel bubble through them. Get the size right and no spring clamps needed.

#9 05-09-2009, 11:45 PM

Quote:

Originally Posted by Brad123D

And you get to watch the fuel bubble through them.

Bubbles are not a good thing...

Lycoming-8 · #10 05-10-2009, 03:30 AM

I was very surprised to read the content of this thread, as our 1968 220D has all steel return lines. These are all attached to devices somewhat like the spool part that banjo bolts pass thru. When did the return line design go to the cheapie version like used on the 123 cars? The old system only has one section of flexible hose connecting the steel lines from injector to injector with the main steel line back to the tank.

chetwesley · #11 05-10-2009, 03:34 AM

Quote:

Originally Posted by ForcedInduction

Bubbles are not a good thing...

When you have clear lines, you come to realize that there are always small bubbles in the return lines. I used hardware store clear tubing on my old 300SD and on my 240D, and both always have bubbles in the return tubing and no problems with fuel supply or air in the system (no problems with the tubing either after more than 1 year).

pawoSD · #12 05-10-2009, 08:56 AM

Quote:

Originally Posted by Brad123D

I use the yellow (neoplene ,I think ?) lines used on chain saws/Small engines. Fexible, strong and works great. Don't want it rubbing against any thing, of course. And you get to watch the fuel bubble through them. Get the size right and no spring clamps needed.

I used some of that on our W123.....its neat to see the green fuel in them.

winmutt · #13 05-10-2009, 09:13 AM

Those clear lines get hard and brittle pretty fast. I would only use that in case of emergency.

compu_85 · #14 05-10-2009, 10:52 AM

Bubbles inside the return lines aren't a problem. On these cars a leak there will cause fuel to get pushed out (as opposed to VE pump cars with a preheat fuel filter, which causes an air leak on the suction side). On one 300D I saw the lines were so bad you could see them pulsing with the transfer pump!

-J

73MB280SEL · #15 05-10-2009, 11:36 AM

Lycoming,

Ditto on my '69 220D. The return lines are steel, not fabric coated rubber hose. I don't know when they switched to rubber hose for return line, but the steel return lines make more sense to me.