1995 Toyota 22RE engine, 202,000 miles. The truck has slowly used antifreeze for the last 20 some years, about a cup of coolant every 3,000 miles. There is a small leak where the plastic radiator seals with the aluminum fins so I have always assumed that is where the coolant was going. A while back I noticed that there seemed to be a bit more metal particles in the oil compared to my other cars. I notice this in all my cars but this one seemed to have a bit more than the others. Most people would not have noticed, but I always hold my drain pan in the sunlight and look at the oil.
I sent my oil in for analysis. Sodium has been elevated at about 270ppm in the last 3 samples using non-sodium oil. Lead was also elevated with reading of 25 on the first sample, then 15, and then 10 on the last. Other wear metals were fine. The oil samples were taken at about 1,000 mile intervals during oil changes.
I did a leakdown test. All readings were good. I pressurized each cylinder with the radiator cap off and could not get any air to come out of the radiator. I left each cylinder pressurized to 100 psi for several minutes during this check. I did it with both a warm and cold engine.
I did a coolant system pressure test with the oil pan off. I pressurized the system to 13 psi and put a drip pan under the engine. I was expecting to see coolant dripping from the engine. I had the system pressurized for 4 days and not a drop of coolant came out of the engine. Pressure surprisingly held steady even with the known radiator leak. I put an endoscope into each cylinder and did not find any coolant in the cylinders.
These engines commonly have the timing chain rub into the timing cover and cause coolant to enter the oil that way. This is not my issue as I have always replaced the timing chain guides at 100,000 mile intervals, and the chain has never touched my timing cover. Even if it was the issue, it would have shown up during the coolant system pressure test.
I took a couple rod bearings off. Bearings look fine for 202,000 miles. Plasigauge read at .0015"-.002" which is within factory specs.
My theory now is that there must be a crack in the head or block that only expands when the engine is hot. I can't think of any other way I am getting coolant into the oil. Had I not done an oil analysis, I would have never known. The truck runs fine with no symptoms. Oil always visually looks fine (other than a bit more metal particles than my other vehicles) Coolant is clean with no oil sheen in it.
Any suggestions? I can think of any else other than pull the head off at this point. I also sent in a virgin oil sample to make sure my oil did not have sodium in it as an additive.
I sent my oil in for analysis. Sodium has been elevated at about 270ppm in the last 3 samples using non-sodium oil. Lead was also elevated with reading of 25 on the first sample, then 15, and then 10 on the last. Other wear metals were fine. The oil samples were taken at about 1,000 mile intervals during oil changes.
I did a leakdown test. All readings were good. I pressurized each cylinder with the radiator cap off and could not get any air to come out of the radiator. I left each cylinder pressurized to 100 psi for several minutes during this check. I did it with both a warm and cold engine.
I did a coolant system pressure test with the oil pan off. I pressurized the system to 13 psi and put a drip pan under the engine. I was expecting to see coolant dripping from the engine. I had the system pressurized for 4 days and not a drop of coolant came out of the engine. Pressure surprisingly held steady even with the known radiator leak. I put an endoscope into each cylinder and did not find any coolant in the cylinders.
These engines commonly have the timing chain rub into the timing cover and cause coolant to enter the oil that way. This is not my issue as I have always replaced the timing chain guides at 100,000 mile intervals, and the chain has never touched my timing cover. Even if it was the issue, it would have shown up during the coolant system pressure test.
I took a couple rod bearings off. Bearings look fine for 202,000 miles. Plasigauge read at .0015"-.002" which is within factory specs.
My theory now is that there must be a crack in the head or block that only expands when the engine is hot. I can't think of any other way I am getting coolant into the oil. Had I not done an oil analysis, I would have never known. The truck runs fine with no symptoms. Oil always visually looks fine (other than a bit more metal particles than my other vehicles) Coolant is clean with no oil sheen in it.
Any suggestions? I can think of any else other than pull the head off at this point. I also sent in a virgin oil sample to make sure my oil did not have sodium in it as an additive.
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