Oil in the Coolant Expansion Tank
 

:icon_cankick:


Hello,

This is the first in a thread (not very long I hope) that I'll put together while I look into a couple of odd observations.

The first thing I noticed was an Oil patch under the very front of my problem child, an XK8 2002 with a botched-up job of a 1999 engine/gearbox fitted to it cause the original engine and gearbox were "stolen"... :icon_really: but that's for a different thread.

The patch was way ahead of the engine, under the radiator and, when traced, appeared to be coming from the radiator hose (on the right looking onto the engine bay from the driver seat, I think the upper?).

Opened the expansion tank and dipped my finger in: very nice looking translucent brawn oil with a bit of emulsified gunk oil for good measure. :icon_really:


After a bit of research and a quick call to the dealer, the source of the oil could be the engine or transmission (though experience says 95% transmission). At about the same time I started to get odd noises each time the gears change up, particularly when cold.

I had a look into transmission cooling and apparently the oil runs into something the JTIS calls the "Transmission Oil Cooling Plate" (integrated onto the side of the radiator). This aluminum cooling plate is the prime suspect for now, but the worrying thing is that this mystical part does not have a part number and is apparently completely integrated into the radiator.

Needless to say, the car is currently on sabbatical for a couple of days until I take it to a mechanic friend of my nephew to see what could be done.

btw, I am in a small country called Jordan and the closest radiator I could find is two or three weeks away; second hand in Yorkshire for about 100 GBP + shipping + 55% import duties and taxes and

Updates and pics will be posted us they come... wish me luck

This isn't entirely daft (having seen a guy blow up a Triumph Vitesse engine by filling up what he thought was the radiator and was actually the rocker box) - is it possible that some worthy has topped up the engine oil via the expansion tank ?
I'd guess if you had that much oil in the coolant for any other reason you'd be picking bits of con rod out of the bonnet.
Could also account for an oil leak from the rad hose......

Interesting take on things, but the oil in radiator fluid is a rather new happening... I changed the expansion tank from the original cracked one about a month ago, and I'm pretty sure that it was coolant that I poured back in...

Also, forgot to mention that the engine oil didn't drop and it look nice and clean...

Well, JTIS does say the transmission oil cooler is located inside the radiator outlet tank so a leak is conceivable.
I've got no idea what the pressure of the transmission oil is inside the cooler so it may be you're getting a friendly interchange of fluids with coolant getting into the transmission oil and vice versa.
I'd imagine if you remove both transmission oil lines to the cooler, cap one off and blow compressed air into the other with the coolant reservoir cap off you'd hear bubbling if there was a major leak. I've never heard of this happening but that doesn't mean it can't.

Well such failures were actually quite common with radiators having metal side tanks. Usually right after a radiator shop has repaired a radiator with integrated transmission cooler and didn't solder the joint right. The transmission side is usually at higher pressure than the coolant side.

A cheap repair is to plug the transmission line outlets on the radiator and run the transmission lines to a separate cooler. Should be lots of them around in junkyards in a place as hot as Jordan.

The purpose of integrating the two is to help the transmission fluid warm up faster. Not a problem in a hot climate.

Plums - is there a test (other than my compressed air one) OP can do to see if this is the problem ?
Are you confident the transmission oil pressure at the exchanger is higher than coolant pressure ?
If he's got coolant in the oil it will be awkward to get it out of the torque converter.