the_supernerd

I just purchased a 2005 Tacoma with the 2.7 2TR-FE engine. It runs great and has no signs of a bad head gasket, but I recently discovered what appears to be oil in the coolant. Is there any place on these engines other than the headgasket where oil would be able to get in the coolant? There appears to be no coolant in the oil, so it must be near an oil pressure line.

I have attached some pictures of the coolant. Can that possibly be anything other than engine oil in it?

williamj

To me that looks like contamination of your reservoir and not oil from the engine in your coolant. If it came from the engine it would most likely be mixed up from the water pump, and that is still completely separated.

I would check compression just to verify.

doitright

That does, indeed, look like motor oil.
Has it ever been brought to a quick-e-lube (by whatever brand name) for an oil change? Screw-up could have poured old oil into the cooling system...
(you may not be able to answer that question since you probably don't know the vehicle's history that well)
Have you an aftermarket oil cooler installed? This would be a thing that screws in between the engine and the oil filter with a couple of hoses running to it.

If I were to guess at the source of oil contaminating the cooling system, it would be either the head gasket (bad), or one of the o-rings on the timing chain cover (much less bad). Possibly a crack in the timing chain cover under the water pump, but fairly unlikely.

If it is a head gasket, it would NOT show the typical head gasket failure symptoms, since it isn't a problem between the combustion chamber and the water jacket -- there isn't oil in the combustion chamber.

I would suggest for now just cleaning it up and monitoring it. If that is 100k miles worth of oil and it isn't getting any worse, then you can probably just live with it.

the_supernerd

I have now owned the truck for about a year, and it has not developed any other symptoms of a bad head gasket or similar problems. I cleaned out the overflow tank, and I occasionally squeeze the radiator hose with the cap off to push any residual oil out that has floated to the top of the radiator. After the initial cleaning, there is not much oil that accumulates in the overflow, but it still appears. Since oil floats on water, I am thinking that residual oil in the cooling system is still slowly working it's way to the top and getting pushed into the overflow. I am really thinking that someone either put oil in the radiator, or used a dirty funnel.

I had a mechanic look at it right after I discovered the problem, and he said it passed a cooling system pressure test. He also put UV dye in the oil, and none of the oil in the radiator glowed under the UV light after I drove it for a week. It is also showing no signs of coolant in the oil, either.

I am planning on flushing the cooling system with a garden hose and the thermostat removed to make sure I get all of the oil and contaminated coolant out. I also need to replace the water pump as it is starting to leak a small amount, so I will check for cracks on the timing cover while it is off.