E300td oil cooler leak - advice please

[johnsco]

Evening Buddies
On Saturday, my beloved E300TD sprang a bad oil leak on the inboard coupling union to the oil cooler rad in front of the N/S front wheel.
God knows why - It just happened out of the blue.

Oil all over the place !!
Shouldn't have too much rust around there for a while !

Easy I thought.
Must be the seal between the steel oil pipe and the aluminium heat exchanger.
I got two open-ended spanners ... One on the nut and one to support the square section boss of the heat exchanger.
It's the right-hand-side one in the photo.

Will it unscrew ?
Will it heck.
The nut appears to be rusted solid to the pipe.
Not to the threaded union on the heat exchanger, where there is a very small amount of rotation.

I am presuming that the nut should rotate on the pipe.
(It must do)
After much application of wire-brushing, WD-40, some heat and very gentle application of a Barnsley enforcer (a tap with the hammer), it still won't budge.

It's not easy to support the pipe and get a lot of rotational force on the nut.
I've left it to soak overnight with another application of WD-40.

Has anyone done this before ?
What type of seal goes between the pipe and the heat exchanger.
Part Number ??
Advice please
Thanks
Johnsco

 

[johnsco]

The overnight soak with WD-40 did the trick.
It eventually unscrewed - But it fought me every inch of the way.
See on the photo how corroded are the aluminium threads beyond the position where the nut was seated.

Not easy to see why it leaked.
There appears to be a male cone on the end of the pipe which mates with a female cone on the rad.
But there's no obvious sign of any seal.
Is it just a metal to metal fit ?
If so, then there's no point in just reassembling it as it is.

I'm considering making a thin conical copper sealing ring to go in the joint and then I can pinch the joint up onto this.

Does anyone have any more info ?
Thanks
Johnsco

 

[ringway]

John, is this any help? Link

 

[GordonTarling]

If it were me, I'd try wrapping that joint with PTFE tape and re-assemble. If it still leaks after that, the chances are that one part or other has cracked, so needs replacing. If you want to check for cracks, be sure to use a good light and a high-powered magnifier, as the crack would be small until the joint is tightened, when it will open up.

 

[johnsco]

Thanks Gordon
You may well be right.
I might try plugging off the ends and dye penetrant testing the components.
I can't think of any reason why the seal should have failed so suddenly.
It certainly had not come loose !!
I'll give it a check out later.
Cheers.
John

 

[Smiley]

May be a new pipe will solve it once and for all - looks like it is more likely to be a corrosion problem with the pipe than the heat exchanger boss?

 

[MPG]

I recently had a similar leak with my XJS. The only problem being that no matter how much I tried to use penetrating fluid or a big hammer the connections simply wouldn't undo. In the end I had to saw through the pipes and remove the oil cooler with the stubs of the feed & return pipes still attached ! If Mercedes are anything like Jaguar, you may be surprised at how cheap replacement pipes are, in which case my advice would be to replace them now. For the XJS they were just 15 quid each from the Jag Heritage Trust.

 

[johnsco]

Thanks Smiley and MPG.
I couldn't believe how difficult it was to get the pipe nuts undone.
I was beginning to think it was old age (on my part) !!

The pipes look rough, but I've wire-brushed the end that was under the nut and it doesn't look to be corroded through.

I suspect the threaded boss on the ali heat exchanger may be cracked, as I can't think how the metal to metal seal can have failed so catastrophically.
But - I'll check it out tonight and let you know.

Regarding replacing the pipes ...
1. The screwed union at the other end of the pipe isn't particularly easy to get at, so I don't want to replace the pipe unless it really is U/S.
2. Having looked at the diagram on the Russian site, it looks horribly as if the heat exchanger and the pipes may come as an assembly (although I find that a bit hard to believe).
The car is an E300TD ... WDB2100252 .........
That might make it a bit tricky to change.

One option, if it is the heat exchanger boss that is cracked, is to cut the pipes and take the oil cooler out of the circuit by bridging it out.
I never use the car for caravan towing, and there are a couple of threads on the forum which indicate that this car is over-cooled anyway.
So - That's an option.

Cheers for now.
John

 

[Number_Cruncher]

No, the pipes are available on their own, see;

Êàòàëîã

 

[johnsco]

Thanks Number Cruncher
I was looking under "Engine Lubrication" ... "Oil Lines"
This looks more promising.
Cheers.
John

 

[Number_Cruncher]

>>I was looking under "Engine Lubrication" ... "Oil Lines"

That's where I looked first until I remebered how the parts screens are laid out - I had similar trouble looking for the transmission cooler pipes on my W124.

EDIT: Knowing what you do as your job, forgive me if I'm telling you something you've already checked, but, are there any cracks near the pipe end?

 

[spock500]

I had the same thing, never did figure it out -

http://www.mbclub.co.uk/forums/engine/64054-not-very-cool-cooler.html

 

[johnsco]

The problem is diagnosed.
There is a pin hole in the aluminium boss of the heat exchanger.
If you look at the photo in post #2, there is a very scabby area just to the right of the threaded length of the boss.
It's just to the right of the thread-length covered by the pipe nut.
I'm not sure whether it is corrosion or whether it's an area of very poor attachment welding or soldering by the manufacturer.
The hole showed up using a red dye penetrant test - Although the indication was somewhat inconclusive due to the rough surface over the whole circumference.
I then confirmed it by cleaning it up and following Gordon's advice in Post #4.
Sure enough, the oil was coming from the pin-hole and from nowhere else.
The pipes are a bit scruffy, but they are OK.
I think a new oil cooler is the answer.
I'm not sure that aluminium soldering is reliable enough on a part this old.

When I get it off, I'll take a better photo of the leaking area, and update this thread on progress.

MANY THANKS TO ALL WHO HAVE HELPED AND ADVISED.
John

 

[Number_Cruncher]

Does the fitting unscrew from the cooler boss?

 

[johnsco]

It looks as if the threaded union may be welded or soldered into the square-section boss.
I'll know better when I get it out and can have a look at it on the bench.

One side of me says - "This ought to be repairable"
The other side of me says - "Don't risk it ... The consequences of a sudden oil loss are just not worth it".

I was lucky when this happened (Well - Sort-of).
I was on the A64 from Leeds to York.
Suddenly, there was the dreaded "beep" and the warning came on telling me that the engine oil was at the lower limit.
Panic !!
"Oh Bother", I said.
Stopped at the next lay-by.
Engine oil off bottom of stick, and serious amounts dripping from under the nearside front corner.
Fortunately, I had about half a litre in the boot.
This barely brought it onto the end of the stick, but was enough to cancel the warning.
I stopped at the next service station (The Total one just a bit further along the road).
Decided I'd better buy a 4-litre can.
How much ?? "40 quid, Sir"
"Oh Bother", I said again.
Anyway -It was sufficient to get me home.

I guess the cost of a new rad will be a kindness, compared with that sort of a sting.

Seriously though - That's why I feel I need to mend it with a new one.
I don't want to risk that sort of carry-on (and unnecessary expense) again.

It could have been worse.

Cheers.
John

 

[johnsco]

That's the animal ... £ 197 + VAT from Euro Car Parts ... Ouch.

Might get it a bit cheaper yet.
Cheers
Johnsco

 

[Dieselman]

I'm pretty sure the angled boss does screw into the cooler body, in which case either have it aluminium welded (not soldered) or visit a hydraulics firm for a new coupling.

When fitting a new one or repairing this one I would install a drain tap/bolt to be able to drain the last 1.5 litre of old oil on an oil change. I undo a union and let it run, but will get round to installing a plug sometime.

 

[johnsco]

Thanks Dieselman.
Just too late ... I ordered a replacement yesterday.
The cost is a bit of a hit, but I don't resent it as much as the £40 I paid at a roadside garage for 4 litres of oil to get me home.
I usually pay about £18 for a 5 litre container of Millers.

Good idea to fit a drain plug to the rad.
I've noticed that you cannot normally drain the rad and the connecting pipes (which are quite long).
I found the coupling nuts an absolute pig to undo (See Post #1).
Years of salt exposure appear to have frozen the pipe nuts both to the threaded boss and to the pipe.
It was not easy to use two open-ended spanners (one of the boss and one on the pipe nut) and to hold the pipe at the same time to stop it twisting round.

OH !! THE FUN WE HAVE !!

Cheers
Johnsco

 

[GordonTarling]

Glad you found the problem. Now all you've got to do is fit the new one!

 

[johnsco]

Cheers Gordon - I'm working on that one