Hello, I just bought a 93 4runner 4x4 with the 3.0 V6... It is over heating and I could use some ideas on the possible causes... I am fairly mechanically enclined and have researched as much as possible... To no avail! It over heats when driving with the rpm's any lower than 3-4k. Once it starts overheating, I can rev up the rpm's to 4k and it will cool down. If I go any faster than 65 in 4th gear it will also overheat. I've checked and or replaced all that I can possibly think of aside from water pump. I've Changed thermostat, checked cap and fan clutch. It does fine in colder weather, but with spring hear and it getting warmer out, it's back to overheating. It also runs kind of rough and idles around 500 rpm's when it gets warm. I am currently running it without the thermostat, and seems to be doing fine. But I would like to figure out the real solution... Any ideas or input would be greatly appreciated!! Thanks!

Also, the friend I bought it from just did the head gaskets... Really hoping it isn't the problem!

 

Went through this with 87 runner few weeks ago I finally weigh my radiator it was 20 pounds supost to be 14 new radiator no problems

 

I would check/replace the radiator if its worn, fins are all bent or if its leaking. There is also a little canister that cools the engine oil which is called (Engine Oil Cooler), pic link is below:

https://images.search.yahoo.com/imag...hspart=mozilla

where both oil and coolant circulate. If that canister is bad, it might be causing your overheating issue. Since is discontinued by Toyota, you may need to pull one from another 4 runner. I had to replace mine a few months back.

I do not think you have a head gasket issue unless you have the following:

Water in oil
Water in the cylinder(s)
signs of clean spark plugs
White smoke out the tail pipe
Having to add coolant often

Aside from that, let us know what happens.

 

Thanks for the response! I have no visible signs of a bad HG.. So I wasn't thinking that was the issue. Is there a way to test the oil canister to see if it's bad? If it is bad, would that cause low oil pressure when idling? Oil pressure runs low unless rpm's are up high as well.... And once it heats up, or driving freeway oil pressure is low as well.... Thanks again for the input!

 

My first guess is radiator clogged. I'd take it to get flushed out (or even replace) and see if that changes things. Sounds like you already replaced/removed the t-stat. Is your fan working properly?

 

I do not know of any tests to the canister. Your oil pump could be bad if pressure is low.

 

I'm with the others on the radiator being clogged. At that age it's almost a certainty. Easy enough to look though, just lower the water level in the radiator below the fins and look at them. Are they clogged?

Have seen impellers on the water pump degrade with age as well. Virtually impossible to check w/o disassembly, but your 'reving will cool it down' description seems to point to an impeller.

If the head gaskets were reversed, this is a big problem and is quite possible. There's little tabs sticking out of the head you can see from underneath which will show R&L on them.

fyi: low oil pressure is normal on these motors. Anything over 5psi at idle and 35psi at speed is normal.

You can turn the idle screw in a little on the intake and that'll raise your idle. Unless you have a vacuum leak, which you ought to test for.

 

I bet your friend did the head gaskets because of the same overheating prob.....agree with the other in that it's a waterflow issue....clogged radiator.

 

If you don't replace the radiator, you can have it professionally flushed. The Preston kit that you can buy does not put enough pressure to knock all of the gunk out of it. My local shop uses something similar to a carwash wand and when they flush a radiator, it looks like mud coming out. Some nasty stuff.

While I have a radiator out, I use my water hose and flush forward and reverse on my heater core but I don't use high pressure on it. Changing a heater core out is a big job so take it easy on it.