Oil leak at oil cooler - PeachParts Mercedes-Benz Forum

seo · #1 09-12-2014, 10:21 AM

Hi. I have a '85 123 300D with turbo. The other day, after a highway speed drive, I noticed a little oil on the hood, right blowing back from hood/grille gap on the driver's side. Not even a teaspoon. I wiped it off and didn't think any more of it until the next time after I was driving on the highway, same thing again.
It appears to be coming from the oil cooler, which must have a tiny leak, and then the oil gets blown out through the gap when driving fast enough to create some air pressure in the engine comparment.
The leak is not apparent, even though I pressure-washed the oil cooler and then watched for a drip of oil to work itself out. Didn't happen.
I can take the radiator up to the radiator shop, and maybe they can repair it. Or I can take a radiator off a wreck I have.
Has anyone seen this kind of leak, have any ideas or good advice?
Thanks in advance.

leathermang · #2 09-12-2014, 10:36 AM

Treat it like a slow tire leak...
take it off..
clean really well...
put under water and apply a little air pressure to it... does not take much..
and a couple of drops of dishwashing cleaner in the tub of water...
and your leak shows up easily..

You may be able to to just silver solder the actual hole..
after making it very clean...

mach4 · #3 09-12-2014, 10:47 AM

Most leaks from the cooler area are hose or fitting related. You'll need to monitor things for a bit so you can determine the actual source, then proceed as needed. Oil cooler radiators don't rust (at least internally) like coolant radiators and they're not under much pressure so the failure rates are pretty low.

When were the hoses replaced?

I'm wondering how oil migrates forward to exit between the hood and grille when all the airflow is towards the rear.

Weird.

Diesel911 · #4 09-12-2014, 10:52 AM

I have 2 Oil Cooler Hose endes that I modified so I could use pressureized Air to test the Oil Cooler. But, I doubt if that is an option for most People.

Removing the one from the other Car seems to be the best option except that removing the Oil Cooler Hoses often resuts in a stripped Nipple and that could happen to either one of the Oil Coolers if you remove them.

Details on how to try to avoid stripping the Nipples when the Hose is removed can be found below.
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Diesel911 · #5 09-12-2014, 11:09 AM

Fixing the Leak.

On most items constructed like the Oill Cooler the common leak areas are the Cores where they attach to the end Tank and the Bracket areas.

The cores are suject to vibration and corrosion. The Brackets vibration and heat expansion and contraction Stress.

There is low temp agout 760 degree Aluminum Repair Rods that you can use with a Propane Torch that I think would be OK for the Tank area or a Bracket crack but If the Core is corroded through or cracked I think you would be better off replacing the Oil Cooler.
Harbor Freight sells the Aluinum Repair Rods and one of the names for them is something like Alumaloy.

There is also low Temp Silver Solder that can adhere to Aluminum but I would confine that to a pin Hole on a non-stressed area of the Tank.

There is a Mercedes authorized repair if the Nipples get striped but it requires cutting the old Nipple/s off drilling and tapping and new NIpples that are actually the same Nipples that screw into your Oil Cooler Housing.

Alumaloy
Alumaloy Part 3 - YouTube

Junkman · #6 09-12-2014, 12:37 PM

The lower nipple on my cooler was cracked and the reason new cooler lines didn't completely stop a leak. The correct drill and tap are expensive enough that they will pay labor if you don't have a drill press. An quicker fix is to replace the cooler if you have or can find a replacement.

seo · #7 09-12-2014, 12:37 PM

I went down and started the car up with the hood opened, and once the oil got warm oil started seeping out of a little hump in the middle of the top tank, it looks like a solder repair that I'd never noticed because it was painted like the rest of the tank. From the comments above, I gather that the tank is aluminum. The fins also? I think the first repair I'll try is to ream the pinhole out a little, just down to bare clean metal, and then try some two-part epoxy putty. I've had amazingly good luck patching leaks with it. I'll let you know if it works. Thanks for all the comments. In preparation for maybe having to take the cooler off for repairs, I think I'll start it in on a regime of penetrating oil.

Diesel911 · #8 09-12-2014, 04:33 PM

Quote:

Originally Posted by seoseo

I went down and started the car up with the hood opened, and once the oil got warm oil started seeping out of a little hump in the middle of the top tank, it looks like a solder repair that I'd never noticed because it was painted like the rest of the tank. From the comments above, I gather that the tank is aluminum. The fins also? I think the first repair I'll try is to ream the pinhole out a little, just down to bare clean metal, and then try some two-part epoxy putty. I've had amazingly good luck patching leaks with it. I'll let you know if it works. Thanks for all the comments. In preparation for maybe having to take the cooler off for repairs, I think I'll start it in on a regime of penetrating oil.

There is another repair that you can make if there is enough room and the Screw end will not go down into the Core of the Cooler.

Get a really short Sheet Metal Screw with a wide heaf on it. Drill the hole so that the screw will thread into it tight.

Degrease the Screw whith Brake Cleaner and the Hole and scrap away the paint of where the Screw head would make contact with the Metal. Take that JB Weld and coat the Screw Threads and the bottom of the Screw Head and screw the screw in and let the JB Weld cure as per the Instructions.

After that is done if you want you can scrap the Paint off a large area of the Cooler around the Screw and either apply the JB Weld over the Screw Head and the adjacent area round the Screw or do the same an lay piece of Figerglass Cloth over it and then saturate the Figerglass Cloth with JB Weld.

When that has cured come back later and apply more JB Weld over the Fiber Glass Cloth.

I have seen the Screw type repair listed in realy old Repair Manuals with the excption that it said to use a Fiber Washer under the Screw Head instead of the JB Weld. But that repair was on Radiator Tanks

Regular Tin and Lead Solder does not stick to Alumiun well. Also the Oil Cooler can get very close to the heat of the Soft Solder Melting Point. If it can be used to repair Aluminum it should say so on the lable of the product.

leathermang · #9 09-12-2014, 05:43 PM

I am asking this because I do not know the answer...
What is the oil cooling tank made from ?

Lots of these suggestions will probably work well...
As to the JBWeld.... when using it... do not use it like a glue... but do use a patch ( the screw head counts as that too ).... be sure the area is really clean... AND SCRATCHED UP some...as the JBWeld is a physical bond...not chemical... after cleaning make scratch marks in the surface with an awl or knife...
and be sure to leave it ' thick '.... so if you use the screw... do not screw it all the way down... leave a sixteenth of an inch of JBWeld under it... and if not on a level surface use duct tape to keep it from running out from under the screw head. It may look stiff... but will bleed down hill....
and put some kind of heat lamp on it if you possibly can..... AND NO pressure for at least 24 hours.. just like the tube instructions say...
It is great stuff if you know and follow the rules..

If the oil cooler is brass... like a radiator..... remember that the usual solder you have in your tool box is typically Rosin flux... but for radiators you need ACID flux solder... use normal precautions with that stuff...

Solder BY ITSELF..... not very strong.. but like the JBWeld.... a inch or so of contact area holding on a patch ... very strong...

charmalu · #10 09-13-2014, 11:16 AM

The Oil Coolers are made of Aluminum.

Charlie

leathermang · #11 09-13-2014, 11:30 AM

Alumaloy promotion youtube videos.... I think the stuff is amazing...

https://www.youtube.com/watch?v=TZ5sD9hQTyw

https://www.youtube.com/watch?v=yJ3uMVkZ2Lc

https://www.youtube.com/watch?v=q1ofGPbOZWU

http://www.harborfreight.com/8-piece-low-temperature-aluminum-welding-rods-44810.html

Of course.... if you work on cars.... it is often nice to get to know your local Welding Supply Shop.... and they are more likely to know the latest stuff and the rules for using it....

cooljjay · #12 09-13-2014, 04:05 PM

In my eyes, any leak in that area means stop driving the car and it also means no bandaid fixes....if somethings goes in that area, it will dump the oil out in moments....

tangofox007 · #13 09-13-2014, 04:18 PM

Quote:

Originally Posted by charmalu

The Oil Coolers are made of Aluminum.

Charlie

That might be true some of the time. But it's not true all of the time.

I have never personally encountered a radiator oil cooler that was not made of brass.

Diesel911 · #14 09-14-2014, 02:17 AM

Quote:

Originally Posted by cooljjay

In my eyes, any leak in that area means stop driving the car and it also means no bandaid fixes....if somethings goes in that area, it will dump the oil out in moments....

All fixes depend on understanding of what you are working on and what you are going to use to make the fix and also how to clean it properly.

There is people out there who in the same situation would just smear JB Weld over the area without removing the Paint, roughing it or cleaning it; nearly assuring that it is not going to work.

In this particular case I don't favor any Epoxy coating that is just on the surface because of heat expansion and contraction. It could be at some point the exterior Epoxy Patch would pop off

charmalu · #15 09-15-2014, 02:16 AM

Quote:

Originally Posted by tangofox007

That might be true some of the time. But it's not true all of the time.

I have never personally encountered a radiator oil cooler that was not made of brass.

You may be right, but the Cooler in our 80 240D looks like the picture in this thread.

1983 240D oil cooler lines, both are on the bottom of my car

I do know the ends of the 123 and 126 are aluminum, or seem to be. The steel nut of the cooler line a lot of times strips the aluminum threads of the cooler because of the dissimilar type metals causing corrosion.

Now the center part could be brass.

Charlie