plastic oil line - which material? - PeachParts Mercedes-Benz Forum

franklynb · #1 01-04-2011, 06:39 PM

After my roadside adventure in the arizona desert I'm seeking a source
for the plastic oil line used to connect the dash gauge and oil cannister
on most 616/617 models.
I know the replacement part still exists -- from Fastlane --

but, I want to experiment with making my own line from the barbed
parts.

Any idea which material? which source?

I measure 5.9mm OD, which probably means its a 6mm nominal; and
1.4mm wall thickness. The minor diameter of the barbed part is 3.5mm, making it
a "press fit" within the 3.2mm ID; and the major diameter of the barb is 4.2mm.

Does Viton work for this application? It appears to have an appropriate temperature
service range, but pressure rating is "iffy". PTFE?

layback40 · #2 01-04-2011, 08:31 PM

It is not worth the risk of experimenting.
If your experiment was to fail, it would probably do so near the filter where its much hotter. You would have no warning until no oil pressure & maybe a seized motor.
Best let MB keep their little secret & spend a couple of Pennies on the right part. Its worth getting a new line, junk yard ones will be old like the one you have that sounds like it has started to leak.

Jeremy5848 · #3 01-04-2011, 10:56 PM

I used 1/8 inch plastic line to install a mechanical oil pressure gauge under the hood on my OM603. To protect the line from heat and abrasion, I ran it inside 1/8 inch I.D. rubber vacuum tubing with heat-shrinkable tubing to seal the ends to the connectors.

My OM617 is gone and I don't remember -- did Mercedes use metal line for the gauge?

scottmcphee · #4 01-04-2011, 11:36 PM

Polyethylene tubing? Nylon tubing?

A lot of new "mechanical type" oil gauges come with a length in the package.

Any good auto shop can tell you what it is, and probably have something like it kicking around and sell you a length.

Brad123D · #5 01-05-2011, 12:45 AM

I used braided stainless line from summit racing. They are -3 I think. They sell the AN lines with ends already on them in different lengths. The problem is adapting to the oddball/metric Mercedes connections. I used the old fitting at the oil filter and mig welded an adapter to it. I fabbed an adapter for the oil pressure gauge from a metric brake bleeder, welding an adapter to it also. Then pressure tested everything. It worked great for me, but if you can't weld, that may be a problem. Getting this wrong could easily be an engine fatality. Getting it right can prevent said fatality.

franklynb · #6 01-05-2011, 12:13 PM

Quote:

Originally Posted by layback40

It is not worth the risk of experimenting.
If your experiment was to fail, it would probably do so near the filter where its much hotter. You would have no warning until no oil pressure & maybe a seized motor.
Best let MB keep their little secret & spend a couple of Pennies on the right part. Its worth getting a new line, junk yard ones will be old like the one you have that sounds like it has started to leak.

On the other hand, I've experienced failure of the M-B part; admittedly old; under the
least desirable circumstances-- midnight in the desert, 40 miles from nearest exit.
Not fun. Had I had a length of correctly chosen plastic tube on hand, I might have
saved $2500 in towing bills, alone. Perhaps not.

Of course you can make the same argument for carrying a $47 spare.
I had a vacuum pump, water pump, alternator, regulator and starter in the spare kit.
No oil line, unfortunately.

And no way to "fake one" from readily available part.This is the means I seek.

I don't think M-B has a secret. As others note, lots of oil lines are plastic these days.
I expect some improvement by using a present day polymer, rather than a 30 year old
"design choice", which appears to be thick polyethylene. Both Viton and PTFE have
higher service temps -- at some tradeoff in malleability.

Brazing/welding a custom fitting or custom forming a hard line are within my scope of
activity, and I considered using braided hose. Good suggestion. I'm also looking for
simpler,less costly, high performing replacements. Hence,the question.

Randy · #7 01-05-2011, 12:27 PM

Just find a seller of new oil-pressure gauges; either buy an entire gauge and use the plastic line, or buy the install kit with the line in it.
Alternative for engineers: McMaster-Carr catalog.
Good luck. your bearings deserve the best.

Diesel911 · #8 01-05-2011, 03:38 PM

I have the Connector that goes to the Oil Filter Bottom and it still has a piece of pastic line on it.
The ID is 3mm and the OD is a hair under 5mm.

Ther is a lot of Platic Gauge lines available and they will hold the pressure. However, that does not mean that the ID will be correct or that if the ID is correct when you shove it over the Barb on the Stock Connectors it is going to hold.

There is also one of those skinny plastic lines that feeds the Fuel Injection Pump Oil just waiting to crack and spew Oil.

funola · #9 01-05-2011, 04:50 PM

$2500 tow for an oil gauge line leak? Ouch!! If you had a match or a cig lighter, you could have drove home if the leak was near the gauge. Heat the line up till soft and bend it 180 degree and tie some wires around it to keep it from springing open and drive on! If no match or cig lighter, use your battery and heat up a piece of wire to ignite tinder soaked in diesel then build a fire and make some charcoal to soften the oil line.

The Mercedes oil line is definitely not polyethylene. It's nylon. As I recall it has 2 layers for chaff protection- a well made quality part. Probably yours was damaged by some heavy handed mechanic pulling the cluster without undoing the oil gauge connection first.

Quote:

Originally Posted by franklynb

On the other hand, I've experienced failure of the M-B part; admittedly old; under the
least desirable circumstances-- midnight in the desert, 40 miles from nearest exit.
Not fun. Had I had a length of correctly chosen plastic tube on hand, I might have
saved $2500 in towing bills, alone. Perhaps not.

Of course you can make the same argument for carrying a $47 spare.
I had a vacuum pump, water pump, alternator, regulator and starter in the spare kit.
No oil line, unfortunately.

And no way to "fake one" from readily available part.This is the means I seek.

I don't think M-B has a secret. As others note, lots of oil lines are plastic these days.
I expect some improvement by using a present day polymer, rather than a 30 year old
"design choice", which appears to be thick polyethylene. Both Viton and PTFE have
higher service temps -- at some tradeoff in malleability.

Brazing/welding a custom fitting or custom forming a hard line are within my scope of
activity, and I considered using braided hose. Good suggestion. I'm also looking for
simpler,less costly, high performing replacements. Hence,the question.

franklynb · #10 01-05-2011, 04:52 PM

Huh?

I took my line sample from the same place, but slightly ABOVE the break in the line, which was at the junction of the oil filter fitting. It measures quite a bit larger in OD <+1mm> and ID <+.5mm>.

Are you sure you have a OEM line? I would expect the section around the fitting to be too distorted to provide a good measurement -- which is why I took a fresh sample 20mm up the tube.

Mine is from the 1980 W126 300SD that blew a piston. I'll double check my measurements.

Quote:

Originally Posted by Diesel911

I have the Connector that goes to the Oil Filter Bottom and it still has a piece of pastic line on it.
The ID is 3mm and the OD is a hair under 5mm.

Ther is a lot of Platic Gauge lines available and they will hold the pressure. However, that does not mean that the ID will be correct or that if the ID is correct when you shove it over the Barb on the Stock Connectors it is going to hold.

There is also one of those skinny plastic lines that feeds the Fuel Injection Pump Oil just waiting to crack and spew Oil.

Diesel911 · #11 01-05-2011, 10:54 PM

Quote:

Originally Posted by franklynb

Huh?

I took my line sample from the same place, but slightly ABOVE the break in the line, which was at the junction of the oil filter fitting. It measures quite a bit larger in OD <+1mm> and ID <+.5mm>.

Are you sure you have a OEM line? I would expect the section around the fitting to be too distorted to provide a good measurement -- which is why I took a fresh sample 20mm up the tube.

Mine is from the 1980 W126 300SD that blew a piston. I'll double check my measurements.

Mine came from a 617 Engine in a123 Chassis Car from in the Junk Yard; I do not know what year or even if it was an engine with a Turbo.

It look like an OM tubing but I have no way to know for sure.

The Oil Pressure Gauge line on my Mercedes is still intact so I cannot measure the ID on that.

I cut the tubeing a took the Oil Pressure Gauge Fitting in order to figure out an adapter for hooking up a Bypass Oil filter.

I took the measurments about 1-1/4 inch above where the Tubing is shoved over the Barb.