Hi all -

I picked up a used 4runner a couple months back and have had it in my local shop. Currently they found the oil cooler was leaking and working to fix.

When they went to take a look, one of the hoses (I think hose #1 the smaller one) was completely gunked up with Stop Leak. See picture below.



I guess my questions are:

1. What exactly is the oil cooler doing? Is is just that the oil is cooled as it goes around the coils of it and such?
2. Shop claimed 'with it being gunked with stop leak your engine wasn't getting any coolant". The only thing flowing through an engine oil cooler is oil though right, and not coolant? Where would they have even poured in stop leak for it to get in the oil cooler?
3. What are the consequences of this being completely clogged?

This car has been running for some time without any engine lights, etc., I assume if it wasn't getting oil there would have been more catastrophic issues present.

Guess I am wondering is my engine completely screwed by this, or if end of day just need to clean the hose and throw the new oil cooler in.

Thanks ya'll.

 

The oil cooler is a heat exchanger.
Coolant runs through part of it and oil runs through a separate part.
The coolant helps reduce the oil temperature.

If those coolant lines are blocked it will not help with reducing the oil temperature.
In most cases that will not be an issue. If you were wheeling hard or towing heavy loads it might.

If those hoses are blocked they will not impact coolant flow to the engine or impact oil flow.

While they have those hoses off I would replace them along with the cooler if it is plugged.

The stop leak might have plugged up your heater core or heater lines. Does the heater still work?
Stop leak is put into the rad and it circulates throughout the motor to where ever coolant goes.

 

IMHO, all those "stop leak" substances do more harm than good, by far. There are a lot of unintended consequences. Like clogged heater cores, hot water control valves, hoses, coolant ports in the engine, etc. Can make for a LOT more work than just replacing a leaky radiator, or whatever. Some of the things, like the smaller coolant passages in the engine block and head, can be virtually un-repairable.

If it were me, and you're not, I'd replace just about any hose that had coolant flowing through it, to start. Then the radiator. Flush it REAL good, a couple of times. Make sure the water pump is still functioning. Make sure the heater core still allows flow through it. And so on.

Like I say, bad stuff, that stop leak. Better by far to replace the leaky item in the first place. I realize YOU didn't put it in, but you're going to have deal with all the consequences. After you get all done, hawk the temperature gauge for a while. Make sure the cooling system doesn't have any hidden problems.

I wish you all the best.
Pat☺

 

Thank you for the oil cooler 101 and setting me straight here!

Funny you brought up the heater...only the passenger side has heat coming out. Sounds like it could make sense heater core is blocked as well with this gunk? I've heard it can also be a thermostat control issue as well.

Any thoughts on if the heater core is likely shot, or if that is able to be flushed/cleaned? And if it is shot...is it ok to go non-OEM for that?

Thanks for the advice sir! My OCD self was thinking this might be the path I ended up down. I plan on taking the 4runner to a nice 4x4 specialist shop that is used to dealing with Gen3s I found in the next week or so.

I already planned on replacing the radiator to avoid pink milkshake fiascos (perhaps that was the initial thought behind putting in the stopleak), I'll look at the toyota part site and get a list going of hose part #s. See above response to Marc, it looks like I might be dealing with some heater core clean or replacement as well.

 

If heat is good on one side then the heater core is probably ok.
The problem could be air flow. Does air come out the drivers side footwell?
If you put the control to vent check to see if you get hot air out of all vents. I get 160 degrees F out of my center vents.

 

It's possible that the heater core is half-plugged with stop leak. And the air going through then goes on to different ducts without mixing much? Dunno, but I'd still be flushing the heater core and oil cooler. Take off the hoses on both sides of those cores and run a hose through it in both directions. Hopefully you'll see a lot of crap come out when it flows backwards and more water goes through after that.

 

Sounds like the heater core is OK, if you're getting heat out of the passenger side. Now you need to see why the hot air doesn't come out the driver's side. Sounds like an air door isn't switching the air to the right ducts when commanded. Something like that. The core can't get clogged in such a way as to cause the effect you're seeing. If you have heat on one side, you have heat. Now find why the hot air isn't going where you want it to.

I would advise, for whatever it's worth, leaving this trouble for after all the rest. Get a PDF copy of the FSM, and see what door selects specifically for the driver's side. I'll see if I can find the right pictures in what I have.
Just to note, quite often, a clogged duct is the fault of mice/rats/squirrels. Also, leaves and other debris like that get in there and cause clogs. I would say a good visual of the ducting down there might e in order. The heater core can also get clogged/partly clogged by dust and dirt and leaves, etc. Be VERY careful if you decide to actually remove and clean it.
A relatively safe way is to split the case around the core, and blow low pressure air backward through the core. Wear a good dust mask and safety glasses! There will be massive clouds of dust in the air.
Be careful of the two water ducts going into/out of the core. They are very thin, and bend/collapse easily. If you want to remove the core, or even just it's water hoses, cut then off with a very sharp razor knife type tool, Don't twist them, pull them, etc. Cut then down almost to the metal, then peel them off. Always replace them.

Check the rear heater core and it's water pipes/ducts, too. Those pipes/hoses clog, and corrode. You should inspect them on a regular basis. Trace them all the way to the engine compartment for external corrosion, and rotted hoses. You do NOT want a sudden water leak on the way home late at night, after a hard day's work. You know what I mean.

I'll do my best to find the right FSM pages to show the duct work and air doors for you, I just don't have time today. That darned real life thing getting in the way.
Pat☺