Anybody got any idea where I might start looking for the source of oil in my antifreeze? I checked the antifreeze in my D25U (late production) a few days ago and found some oil in the sample of antifreeze I took from the side spicot to use for the testor. It's not clabbered up and I haven't noticed any antifreeze in the oil but am a bit concerned. The Cat runs well and it is holding the oil level so it's not pumping oil but it's there just the same.

Any ideas??

Thanks,
Tom

Not many opportunities for oil to get into cooling system. First thing comes to mind is the loss of sealing at the oil transfer fitting between the block and the head that supplies rocker arm lubrication. Cracks and casting perosity are also candidates. Do a cooling system pressure check and see what happens. Don't forget the pony motor also shares the cooling system.

The most common is the precup seals or hole in precups but as OM says lots place head gasket may be putting fuel in it also

Thanks OM and Willie. Am I correct in assuming an "oil transfer fitting" is more than just a oil passage from the block to the head? I don't recall a lot of detail in my parts or repair manual to identify exactly where the port might be. Shouldn't be much of a problem to locate once the head is pulled. I'm also assuming there is only one port, with the oil return via gravity back into the block. At this point, the "oil" looks like lube and not diesel but don't know that for a fact.

I'm assuming communication between oil and cooling right now and the cooling system probably doesn't get pressured up enough to reverse the process and put water in the oil.

If I pressure up the cooling system and my leak is internal, it might be awhile before I notice antifreeze in the oil. I'll make up some sort of inner tube boot to go over the radiator fill and put enough pressure to measure over a period of time. Any idea how much pressure I can safely put before I start blowing critical parts out the tailpipe?

Thanks,
Tom

Most times the common cause of oil in the radiator is a bad cooler. Since oil pressure is higher than coolant pressure, it can force oil into the coolant.

Looking at the parts books, the D311 shows 3 ferrules with seals between the head and block (along with the gasket). The D318 uses a slew of them on water passages, but there are some on pressure oil passages which I assume are where the U series D2 uses them. J series doesn't show them at all, just gasket.

That is also my initial bet unless you can find compression leak from blown head gasket or leaking PC chamber. There are test kits for compression gases in the coolant which you can use to find a slight leak.

PC chambers are the most common site of a leak of compression.

""""Most times the common cause of oil in the radiator is a bad cooler. Since oil pressure is higher than coolant pressure, it can force oil into the coolant.""""

What walt says bears repeating! easiest repair there is and very $$$ to miss it and tear down an engine looking for the leak.

but the D2 doesn't have an oil cooler at all in the late production does it? and never had a water to oil cooler?

Oil feed line ferrule connection is about 1/3 back on the head, one line comes from #2 main bearing.
Oil cooler, if it has one is air cooled, no connection to cooling system.
Pre-com leak would be compression only and you would see bubbles in radiator tank and having problems keeping water in it. If it is a slobberer you could get an oil/fuel black goo with a pre-com chamber leak.
I don't exceed 15 psi on cooling system pressure check. Trick is to get things air tight so that you can observe a leak down check. Soap bubble check all your connections. A good test would be to hold pressure for 24 hrs.

The fitting is a compression tube fitting #3B8995 shown in the oil lines & filter diagram in the parts book.
I can't remember if this fitting connection area is open to the sump or if it passes through the head gasket.
Don, ya got a head off a D2 down there that you could check for us?

Another area to check would be the pony head gaskets. I have seem some pretty oily head gaskets where it appeared that compression and/or near liquid lock was capable of forcing that pony oil that we forget to drain with the petcocks past the head gasket that was not sealing very well. I'm going with the assumption that you are dealing with small quantities of oil here.

Oil coolers on the 5U's were apparently done away with sometime in 1956----between 5U 17000 and 18000. 5U 18019 does not have cooler and 5U 17000+ does have oil cooler set up (with side core built in radiator).

Sure would be good idea to check oil cooler if its got one.

Delta Dirt