Leaky Oil Cooler O-Rings ?

Sea Knight

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'82 FJ-40---Just when I thought all (or most) of the oil leaks were cured another one emerges, somewhere low on the PS of the block. It isn't coming from the valve cover gasket, or the side plate, or the oil filter gasket, or the oil galley plug. After driving until the engine reaches operating temp, there's a significant coating of oil all over the oil cooler and all the hoses around it. I've cleaned up the area and attempted to ID the source of the leak without any success. There's no leak when in park and idling, or when parked with the engine off. Before I start tearing things apart, has anyone ever sprung an oil leak from the o- rings on the back side of the oil cooler? Any other ideas?

TIA,
Lee :confused:
 

FJ40Jim

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Yes, they can leak at the o-ring on the back of the cooler.

But IME it is more common to leak at the crush washer on the front of the cooler.

Either way, just go to the dealer and order a few of the crush washers and o-rings. Once you have them, the oil cooler can be removed, flushed out and painted. Reinstall w/ new seals and you'll know that future leaks are NOT the oil cooler.
 

Sea Knight

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Yes, they can leak at the o-ring on the back of the cooler.

But IME it is more common to leak at the crush washer on the front of the cooler.

Either way, just go to the dealer and order a few of the crush washers and o-rings. Once you have them, the oil cooler can be removed, flushed out and painted. Reinstall w/ new seals and you'll know that future leaks are NOT the oil cooler.

Thanks Jim. I forgot to mention that I recently replaced the 2 oil cooler hoses. One of them was difficult to dislodge and I probably buggered up the washers and 0-rings while yanking on the hose. Not too surprising that an 0-ring would disintegrate after 25+ years. And yep, the oil cooler is badly in need of repainting. Washers and 0-rings are ordered and as always, thanks for your advice.

Lee :cheers:
 

Sea Knight

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I received a PM last night asking if the oil cooler leak was ever resolved, which reminded me that I never posted the final story.

:doh: It wasn't the oil cooler that was leaking. It was the new fuel pump, which I never suspected. It was defective--apparently it had a ruptured diaphragm. At low rpm it wouldn't leak, but at highway speeds it blew oil out the weep hole at high velocity, coating the entire PS of the engine bay. One of the first targets of the oil spray was the oil cooler, which totally faked me out. I was losing a quart per 100 miles and was convinced it was coming from the block side of the oil cooler. Anyway, I replaced the fuel pump (again) and the problem was fixed. BTW, the culprit was an OEM Kyosan fuel pump, just happened to be a bad one.
 

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