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Discussion Starter #1
Never had this happen before.

92 4runner that runs oh so sweetly now has oil in the rad but no rad fluid in the oil and the truck runs GREAT! no smoke or anything.

I've blown a few head gaskets in my time, but never has my vehicle ran great with a blown HG.

Could this be something else?
 

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What engine?

I can't think of any other way oil could get in the coolant, but then, I can't think of a lot of things.

I would pull the plugs and take a good look at them, and run a compression test. That will at least give you some information to go on. You can also run a cooling system pressure test, though if the leak is internal it's not easy to locate it. You can and probably should drain the oil to look for coolant there.

I recommend not running the motor until you find and fix the cause.
 

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Discussion Starter #3 (Edited)
There is no rad fluid in the oil at all..not a drip. Compression is damn near perfect...truck drives like hes brand new. Nothin in the cylinders either....no smoke out the tail pipe at all.

Just talked to another guy that is insisting its my oil cooler (didnt even know I had one)

I just need to research how to diagnose a blown O-ring in the cooler or such...never delt with one before so this should be interesting.

Anyone got advice on how to rule out the oil cooler?

Its a 3.0 V6 Have heard about the HG recalls, but am positive this has been fixed.
 

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Yeah, oil cooler is a good call. My veezy doesn't have one, and although I'm familiar with them, didn't think of them. You may be able to pull the coolant hose that comes from the water pump off of the oil cooler, and pull the hose that goes from cooler to the block off of the block, and directly connect the hose from the pump to the block. If they are different sizes, just pull both hoses off the cooler and plug both of them. You should see oil seeping out of the coolant fittings of the cooler if it is leaking oil.
 

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Discussion Starter #5
Tough ta diagnose when you don't even know how it works.

I've searched the internet and my repair manual and found almost nothing on how this thing is set up or works.

Found a few pictures, but nothin detailed enough for me to understand.

How the hell does the oil get from an oil cooling system to the rad fluid?

Does it run through its own section of the rad?

Just trying to get an idea of how this thing works before I crawl under my truck while its snowing out. :)
 

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The cooler itself is a short cylinder attached to the left side of the block. Coolant comes from the pump through a small hose to the cooler, and another line goes from the cooler into the side of the block. The cooler also must have a couple oil connections where it connects to the block, and there must be coolant and oil passages wound around next to each other in the cooler. Somewhere there's a leak between the oil & coolant passages, probably within the cooler itself.

Diagnose it as suggested - if you see oil coming from the coolant fittings of the cooler, you either have to fix it or replace it. I see from the manual that there are a couple gaskets and an o-ring - I'll bet if you replaced all three it might fix it. I'm sure you could get them from a dealer. There's also a relief valve that might be bad. Worst case, you'll need to replace the cooler - I would look for a junkyard part, or check ebay & craigslist. car-part.com is a useful portal to a couple hundred junkyards around the country.

Check the factory manual, in the ENGINE - LUBRICATION SYSTEM - OIL COOLER section. If you don't have a manual, google 1993 toyota pickup service manual.
 
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