For anyone with exponential knowledge of the 89 4runner

[j.sinopoli92]

Recently my 89 4r started overheating slightly while i was driving. i didn't really notice any problem until one night coming home from work the temp gauge was WAY above the normal range. Ever since then i have been working on it trying to figure out why it would be overheating. I have replaced the thermostat, flushed the entire cooling system, and replaced the radiator, and it still overheats after about 10 minutes with the engine running. I also noticed that when the temp gauge reads very high, the oil pressure gauge drops all the way down, so i'm thinking that the two are interconnected. I'm not very mechanically savvy, but i have been trying to fix the problem on my own. Any help would be greatly appreciated

 

[TCinVA]

It could be the head gasket, check for gray sludgy oil on the dipstick. Also, it may need a radiator, you could do a pressure check.

 

[fourwd1]

It could be the head gasket, check for gray sludgy oil on the dipstick. Also, it may need a radiator, you could do a pressure check.

I think we can rule the radiator out, he said he replaced it.

But the HG is a real possibility, esp if it's the V6 engine. (helps to say in a post)

Some simple tests like an engine leakdown and a coolant system pressure test would help.

Of course if the coolant is low, the exhaust is white, and the oil looks like a milkshake, that's a real good clue.

 

[SUBTEGRAL]

Yeah, your tail pipe would be blowing massive amounts of white smoke, believe me, if it's the head gaskets.

 

[markfagus]

Not necessarily on the tailpipe smoke subtegral talks about. It depends how back the HG damage is. I just went thru this on my 88 3.0 a few months ago. I had zero some from the tailpipe, no overheating (granted it was cold outside)
I had a slight miss I couldn't get rid of and then did a leak down test on the radiator and sure enough, i had exhaust gas present. I replaced the HG and truck has run perfect ever since.

Since you already replaced the radiator, I am with fourwd1 and my $$$ is on blown head gasket.

Mark

 

[Hyde802]

Some simple tests like an engine leakdown and a coolant system pressure test would help.

I agree with this, this will tell you what you need to know.

Did you bleed the cooling system after the flush?

 

[willyt4r]

fan clutch?

another possibility is the fan clutch. I did the electric fan conversion with the Taurus fan and a Hayden controller.:guitar3:

 

[j.sinopoli92]

Well all those are great suggestions....after i replaced the radiator it started running fine again for about a month, and now about 2 days ago it started to overheat depending on how fast or slow i was going, when i slow down and theres less airflow, temp goes up and when i speed up the temp goes back down. i was talking to a friend of mine and he said my truck might have an electric fan that kicks on if it idles really hot but i didnt know my truck had this feature. Any input?

 

[j.sinopoli92]

I agree with this, this will tell you what you need to know.

Did you bleed the cooling system after the flush?

yeah i bled the whole system, which cleared out some gunk...and that helped but now im having this new problem, and yes fourwd1 mine is a V6

 

[Hyde802]

i was talking to a friend of mine and he said my truck might have an electric fan that kicks on if it idles really hot but i didnt know my truck had this feature. Any input?

I dont think so. But its your truck, go open the hood and look. Did you ever check your fan clutch?

 

[j.sinopoli92]

I dont think so. But its your truck, go open the hood and look. Did you ever check your fan clutch?

Yeah, i've looked and never saw one but i just wasnt sure. And about the fan clutch I never thought of that as a possible culprit because my fan has been working fine. Are there any underlying indicators i should look for if thats the problem?

 

[hoe_nah]

Try and spin the fan with your hand...if it rotates easily its your fan clutch..it should be stiff and turn not even half a spin...

 

[the_dingman]

Water pump could be bad.

Start by ruling out the head gaskets. Check for oil and coolant mix in both places, dark coolant or milky oil will tell you if the head gasket is bad.

If those look good, I would look at water pump or fan clutch.

 

[austintaco]

Fan clutch.