Coolant in oil but no oil in coolant ?
 

Hey everyone - replaced my oil cooler seals today. When I took the 24mm bolt off the cooler, about 1/4 pint of milky oil came out. However, when I drained the coolant before I started, the coolant was totally clear. Is it possible to have coolant in the oil but no oil in the coolant?

Interestingly, the PO must have used some kind of radiator stop leak because the coolant passage in the oil cooler was completely blocked with what seemed like a powdery substance. I suppose I haven’t had any oil cooling for a while now

Are you talking about the transmission fluid cooler in the radiator?

No. I’m talking about the oil cooler mounted to the engine block on the driver side rearward of the oil filter

I had my engine on the 01 tore down to the block not long ago and didn't see any oil coolers. All coolers were in front of the fan. What year is your rig? Do you think this might be an aftermarket add-on?

I can't be sure but it sure sounds like this cooler can be removed and bypassed. The radiator is what normally cools the engine oil and engine.

Auto trans models have the trans cooler in the radiator but that is not what the OP is talking about. My understanding is that some vehicles came with the oil cooler(attached to the block near the screw on oil filter.
https://www.toyota-4runner.org/attac...eoilcooler-jpg

It's possible 2wd's don't have the oil cooler mounted by the oil filter.

Maybe it was condensation?
When you've changed the oil has it looked milky?
Monitor your overflow bottle level when cold to see if it's using antifreeze.

Ahhh... There was a spot that looked like it was for another oil filter but just had a cover on it. Now I know it was for an optional oil cooler. Live and learn. :) Seems a bit redundant but I guess there are some places where more cooling than the radiator can provide might be warranted.

All the 5vz's I have seen have an oil cooler. That is also a second location for an oil filter (the JDM vans that use the 5vz have the oil filter there with the oil cooler on the front location), but not used that way in the US.

To the OP: All of the engine oil passes through the cooler, so you should check what's in the pan. There is something fishy going on...

-Charlie

That's exactly what I thought it was; a secondary location for an oil filter on vehicles in other countries. Probably in vehicles not sold in the USA.

Perhaps they are standard equipment on 4wd because they don't get the air flow when under stress (four wheelin') like the 2wd do.

So much to learn about these rigs...

It is very possible to have a one-way head gasket failure. They do normally mix both ways but sometimes coolant will get into the oil passage since it's under pressure, while the oil does not.

Change your oil and watch it for a while. Water is denser than oil so it'll want to settle to the bottom of the pan. On your next oil change if you've got water in there again, suspect a head gasket.

My 2WD had the cooler from the factory... It also works in 'reverse' as an oil warmer to heat up the oil to engine temp faster than it would otherwise. Good for engine longevity.

-Charlie

Okay. So they are on some and not others whether they are 2wd or 4wd. I guess I was right; they were an option.

I see the coolant flows on the inside of the coolant thermostat so it would make sense for it to flow through the oil cooler with warmer water until the coolant gets up to temp to open the thermostat. Not sure it would make a lot of difference in mild climates but likely help a good bit in cold climates. Especially where subzero is the norm.

Since it operates off the radiator coolant it's still dependent on the radiator for cooling. Might even do more good as an oil warmer than a cooler.

Toyota is quite proud of the oil coolers. At $1500 on ebay for just the body and internals of the cooler; I'd say they are really proud of them.

TOYOTA OEM 96-04 Tacoma 3.4L-V6-Engine Oil Cooler 1571062040 | eBay

I just went out and got my hands dirty looking at my 98 2wd and it has the cooler so this isn't a 2wd/4wd thing. The ebay link shows that it isn't compatible with 01 or 02 T4R's but the aftermarket coolers show that it is so I don't know what to think about all that. Maybe someone will come along and clarify Toyota's thinking or set the record straight.

I'm glad the 98 has it simply because it's pretty much my beater rig. I use it to take my dogs out to the country to let them run and occasionally to do some off pavement exploring with a friend. The 01 is my DD and set up for long distance driving. Because of the short trips the 98 takes; I find it reassuring the oil cooler is helping to warm up the oil quicker. Of course that's one more thing that can go bad but I accept that risk for that rig. I wonder if there's a bypass for them. There must be a way to put a cover, like on my 01, on and close off the line from the thermostat housing.

I'm still blown away at the price Toyota wants for their OEM cooler. Aftermarket appears to be in the $400-$850 range. Used; around $150. The long block for my 01 was $2100 so $1500 just for an oil cooler seems ludicrous to me. If the one on my 98 goes bad; I'll simply bypass it. In fact, now that I think about it, I should replace the two hoses to it sooner rather than later. It is 22 years old and I have no idea if they have ever been changed. Probably not. $51.22 for the set of OEM.

Getting quite an education from this thread!

A picture of the oil cooler.

since some markets and applications use this as the oil filter location, I wonder if with the right nipple you can just thread in another filter to act as a block off.

think I read that somebody actually did that and runs two filters