bclundy

Hey, I just purchased a 1993 4runner with 150k miles and stick shift that has an overheating problem. It starts right up, no immediate problems. Driving it around town at relatively slow speeds, the temp gauge sits right about in the middle. When get you on the freeway and speed up the temperature slowly and steadily increases until it gets into the red. I pulled over before it was in the red and cut the engine off and opened the hood. There was some coolant leaking out of the overflow and you could hear some hissing from the water boiling in the radiator but none came out of the cap. I let it sit for 15 minutes or so and turned it back on and it steadily went back down to the middle of the gauge. So I got back on the freeway and continued driving. The gauge started to go up again so I turned the heater on and it slowed the gauge down quite a bit, but it still crept up. Whenever it would get close to the red I'd pull over and stop. After about ten minutes the temp would go back down to center while the 4runner was running. While it sat running I opened the hood and checked it out. The fan was working fine and I didn't notice anything unusual. No smoke in the exhaust that I noticed. There did seem to be a slight hissing sound, almost like when you turn the volume up high on a radio but no music is playing, it seemed to be coming from the head. Anyways, I continued home stopping every time the gauge went up and allowed the engine to cool back down to normal before proceeding again. I suspect a blown head gasket or perhaps cracked/warped head, or the radiator. The vehicle is overall in great shape and the gentleman I purchased it from seemed to take very good care of it. Before I purchased it, he told me that he had the coolant flushed, replaced the thermostat, temp switch, and temp sending unit. He also told me that the water pump is new and the radiator isn't leaking. I'm going to pull out the thermostat tonight, and check the radiator for bubbles to see if the head/gasket is blown. I'll post the results on here when I'm finished but I'd really like a second opinion or two before I tear the head apart. It does also have a rear heater which may not have been bled but I'll look into that as well. If you got this far, thanks for your time, I hope to hear what you think.

wii_tarded

My first guess would be the radiator is clogged. Is it a V6 or 22re? If V6, does it have the oil cooler on the driver's side of the block? It would make sense to me because the water pump would keep pumping to the top of the radiator, and if the coolant had nowhere to go but the overflow tank, then none is getting back to the engine. I had replaced a radiator before for around $180, (plus coolant cost). That would be my first "stab" at it if I were to just start throwing parts at it.

bclundy

Its got the V6 in it, I haven't had time to poke around the engine yet, not sure which side the oil cooler is on. I'll definitely check into the radiator being the problem though.

nv4runner

The oil cooler is on the driver side of the engine behind the oil filter. It looks like a metal canister. A coolant hose for it runs right under the oil filter.

bclundy

Got it, thanks. Ok I pulled the thermostat out last night but didn't get a chance to drive it. The radiator does look pretty bad, there's some white build up/corrosion inside of it. There was also small bubbles coming up to the surface inside the radiator when the cap was off. Still wondering about a head problem. And when it was idling, you could see the water just sitting there without the thermostat in. When I gave it some gas it started circulating but as soon as I let off, it stopped circulating. Is that normal? The fluid we drained out of it looked very dirty and grey and it had been changed recently.

ZUK

iTrader: (1)

Not sure about the slow flow as viewed thru the radiator cap....but replacing the radiator will fix the highway problem. I had the same thing happen to me on the highway with my 87 22RE Runner with 210k on the radiator. It took me too long to diagnose it as the radiator so I had to also deal with a blown head gasket afterwards.

ZUK

iTrader: (1)

I'm afraid that the engine must have heated up too many times because the bubbles are almost a sure sign of a blown gasket.

bclundy

Thanks for the help, I'm going to replace the radiator on Saturday. I bought some head gasket sealer...can't remember what it's called. Nanotechnology something in a lime green bottle. But I'm gonna try it on the head gasket and hope it works. I'll keep you posted on the results.

aa1911

iTrader: (1)

use this stuff when you refill, it's about 1/3 the cost of Toyota long life and just as good. Had similar radiator woes a few years ago with mine (at about 155k too) on I-5, mine was due to a sloooow leak tho...

http://www.valvoline.com/products/br...antifreeze/105

Zerex (valvoline) Asian vehicle coolant, last time I bought some was 8 months ago, was $11 at NAPA vs. $30 at Toyota

bclundy

Thanks for the help guys, I put a new radiator in today and it runs like a clock now. I'm pretty certain there's a leak in the head gasket though. There was oil in the coolant and some bubbles coming up in the radiator. Should be able to fix it with that stuff I bought though.