Hard Transmission Line Leak at clamps - PeachParts Mercedes-Benz Forum

rhodes2010 · #1 01-31-2009, 01:18 PM

So the 300SD is leaking trans fluid and at first I thought the flex hoses at the radiator....
But it is where the clamps are located.

There are three clamps that hold the hard transmission line to the block.

The clamps are rubber insulated (when new). The rubber on mine went hard
and in the front clamp is gone. Then the steel on steel rubbing starts.

Now I have a hole in the line.

Fastlane does not have the clamps or the hard lines (just the flex line).

So... I have decided to weld the hole shut, then I'll reinsulate the clamps
with probably rubber tubing.

As a precaution I'll do the passenger side line too and put it to rest.

Really hard to get out the connector clamp on left side below oil lines.
Probably the only bolt on the car that is difficult.

So this is not really a question as much as an FYI/Precaution.

Anyone else ever had to deal with this one ?

kerry · #2 01-31-2009, 01:28 PM

I would cut the line, slip rubber hose over it and clamp it. I've installed a number of transmission coolers this way with no leaks over tens of thousands of miles.

rhodes2010 · #3 01-31-2009, 01:40 PM

If I were trapped or broken down away from home and shop I probably
would too.

But it seems without flaring the end and under pressure there could be some risk.

Anyone know the pressure these lines are under ?

Are both sides the same pressure ?
(As in the Power Steering system where there is a low and high side).

On these cars I pretty much put the time in to keep them in full
factory functional condition. I depend on them both as daily drivers.

But thanks for the tip.

TheDon · #4 01-31-2009, 01:52 PM

I did a repair like that on my 300D two years ago and its still holding just fine.

you could go to the junkyard and find a 300D and see if it has good lines and swap them out.

DeliveryValve · #5 01-31-2009, 01:55 PM

Brazing the line would be fine.

I've replace rubber the grommet by using pieces fuel line hose. Works really well and has a reinforcing mesh built into it.

pawoSD · #6 01-31-2009, 02:23 PM

I doubt the pressure in those cooling lines is so high that it would blow a rubber repair off....especially if you slip the hose over a few inches of the hard line and double clamp it.

sixto · #7 01-31-2009, 04:59 PM

There shouldn't be much pressure drop across the transmission cooler. Certainly nothing as significant as across the steering box.

Fuel or oil rated hose will do a good job as a clamp insulator if plain rubber lasted 25 years.

Sixto
87 300D

techguy512 · #8 01-31-2009, 07:57 PM

This happened to me, and I replaced the passenger side hard line about 2 years ago. The line was under $60 from the dealer. I isolated the clamp using a couple layers of rubberized cork gasket material wrapped around the line under the clamp.

turbobenz · #9 01-31-2009, 08:45 PM

I soldered mine

kmaysob · #10 01-31-2009, 09:24 PM

braze it

pawoSD · #11 01-31-2009, 10:22 PM

Quote:

Originally Posted by techguy512

This happened to me, and I replaced the passenger side hard line about 2 years ago. The line was under $60 from the dealer. I isolated the clamp using a couple layers of rubberized cork gasket material wrapped around the line under the clamp.

Problem is, they're not making them anymore, and they only have a couple left in the world!

We found this out when my dad's project SD needed some new lines (old ones had been ghetto repaired and he wanted it fixed right)....so he ended up having to bring the remnants of the old line to a local shop and they took the old fittings and put it on new lines. Cost $90 per line (he only needed one though thankfully)

The replacement lines from MB are about $80 for one side and $180 for the other, IF they even have any left.

rhodes2010 · #12 02-08-2009, 04:22 AM

So - the final word on this repair.
I believe braising would have been perfect.

But our stainless steel tube and fitting shop chose not to
drop a weld on the worn through crack and took a piece of 1/2 inch
stainless tube, split it and put it over the leak, then welded it around
the ends and across the split - pressure tested it, and all is good.

The explanatino given to me was that trying to drop a bead of weld
on the crack would leak into the area of flow and restrict fluid flow.

2nd thought was to remove the afflicted area (cut out the cracked piece)
and weld in a new piece.
This came with two problems, we did not have any metric tube sizes,
only inch sizes in 1/8ths. The other problem was the coating that my welder
said was on the tube. He praised the lines as being incredibly high quality
as evidenced by 20 + years and no corrosion (galvanized or something)
but said this made it a challenge to bond.

In the end a 1/2 sleeve covered the crack, did not restrict flow, and the line
retained the original length, connectors, and structural integrity.

I replaced the clamps with new insulating rubber and moved two so that
they were easier to reach from beneath with straight drive tools.

Good luck to anyone that has to do this.

tangofox007 · #13 02-08-2009, 10:37 AM

Quote:

Originally Posted by rhodes2010

Good luck to anyone that has to do this.

Anyone with a vehicle of that vintage would do well to inspect/replace their clamp cushions. They tend to disintegrate after 20 or so years, allowing metal-to-metal contact between the line and the clamp.