2.5TD oil cooler repeated failure

[rg]

Thanks, John!

Formerly, I'd be worried about corrosion, but I now feel a bit cheated after having run the cooling system diligently on 50/50 and deionised water for years in the hope that the oil cooler wouldn't fail.

r

[xmexclusive]

Hi Rg

I had an interesting chat recently with the tech man from a industrial rad firm.
They manufactured, supplied and now maintained for a number of their clients.
The maintenance responsibility had made them move away from flimsey finned rads.
This was mainly because of fin clogging in service.
2.5's suffer this crap accumalation between the rads so it is worth a regular clean.
Space limitations made it unrealistic to try their free flow rads.
He did though come up with an idea about corrosion control in the cooling system.
Put in a handfull of sacrifical annode pellets.
Loose pellets in the system may not be a good idea.
I do intend though to try a fixed annode in the header tank though.
Might just extend rad and heater matrix life at low risk and cost.

John

[techmanagain]

........What would worry me on this matter is if the cooler is putting oil into the cooling system, bypassing the cooler then leaves the cooler pipes open.. Would you not get oil seeping from the water pipes on the cooler!!?? Making a mess?....................

In practice - NO - but I don't see why it does not (unless of course the oil pressure is much lower than the water pressure).

[techmanagain]

Correction ...much lower ..........Higher
But then why do you not get a water leak (or do you?)
You tell me!

[xmexclusive]

Hi techman

Leak is always oil to water because of the pressure difference.
The oil leak is often a very small one.
It works its way on to the coolant surface in the header tank.
Concentration in one spot makes it look much larger than it really is.
So it can take many months for the water side of a failed cooler to fill enough to start dripping oil out the lower of the two water pipes.
Will be very difficult to section and pinpoint failure location.
Hence my interest in finding a bad leaker.

John

This post has been edited by xmexclusive on December 05, 2012 07:09 pm

[rg]

Noz.,

Re soft hoses, oil and failure, how long was the oil in your coolant?

I've noticed that the bottom large house has gone a bit thin and soft at the elbow down by the subframe.

I'm not sure if this is age, design, oil, or a combination of all. Should the oil flow up to the tank, or is there any circumstances in which it would settle in this hose?

There's a tiny bit of grey mayonnaise in the top of my tank from time to time, but no more tadpoles, and the oil was only leaking for a couple of weeks.

As ever, your recollections of the experience are highly valued!

Rob

This post has been edited by rg on January 03, 2013 12:48 pm

[noz]

Hi Rob,

The first time I had this problem was with my Blue '96 2.5TD which I bought on ebay and was located in Bristol. I bought it with full knowledge about the problem since it was listed in the description. I got it cheap for that reason. I drove it back home with the leakage problem still there. Once I got home I tried several different avenues until I dicovered that the leak was internal to the oil cooler. Some kind soul on club-xm sold me another oil cooler (sorry, to my shame I cannot now recall who that was) and I fitted it. However, by that time the damage was done to the top hose and the rubber seal on the header tank cap. I simply bought a new one of each and the problem was solved. The thing is, I have no idea how long the PO ran the engine with the oil leak so I don't know how long it takes.


As for the question about why it leaks one way and not the other, I perceive that the internals of the exchanger will consist of thin layers of stainless steel with each alternate pairs welded around the perimeter on alternate sides. I think the leak must start at the edge where two adjacent sheets meet and should be sealed. The continuous flexing due to the increase and decrease in water and oil pressure fatigues the joint and a split forms. However, when the oil pressure is greater than the water pressure then the split opens and allows oil to pass into the water. However, when the pressures reverse the thin SS sheets are pushed together effectively sealing the split. That's why you dont get (much) water going the other way. The shape of the SS sheets act like a non-return valve. Alternatively, if the water side is disconnected all together then the pressure on that side will be zero. The oil pressure may then keep the two sheets of SS squeezed together thus preventing any more oil loss.

The above is pure conjecture since I've never seen inside an oil cooler. I had planned to put an old one in the milling machine and mill of the weld which keeps the bottom on thereby allowing me to gain access to the inside. By doing a pressure test with the core exposed then the source of the leak should be easy to identify and maybe even repair. However, I can't find the old oil cooler now. Unbelievably for me, I must have thrown it out at the time. If anyone has a known leaker and is willing to give it up for analysis then please send me it and I'll take it to bits.

cheers

noz

[rg]

Thanks, Noz!

So it may not have a rapid effect on the rubber, which is encouraging. however, at 186K, my 2.5 is beginning to show it's age a bit, so any adverse conditions may speed natural wear, I guess.

Rob