I have read everything i could find in the other posts but still cant figure this out..

Noticed that my 4runner was getting hot so I have changed out the thermostat,radiator cap, draind and refilled the radiator, then changed the fan clutch Twice.

I tested it by driveing at least 10 miles on the highway and it never even thought about over heating, but when I got it home and let it idle, it slowly started to heat up...

Last night I started it up and let it run for atleast 40 min and the only thing the temp gague did was go up to normal. Then I decided to rev it between 1500-2000 rpms then it decided to slowly heat up . I let it heat up for a short bit then let off but the temp still wanted to slowly climb. I ran the heater on high and it started to cool off back to normal.

It seems that for some reason once the truck hits atleast 1500 rpms with out alot of air flow, it will over heat...

could this still be a radiator problem or bad thermostat? The top hose gets tight and from what I can feel, the radiator gets hot all the way around.,(I replaced it two years ago along with the water pump).

No chocolate milk under oil cap, white smoke out of the tail pipe, or water leaking from the bottom of the truck. (thought I would add this since it seems that once people see 3.0 they go straight for the HG).

and by the way, could some one give me a definative answer on if a fan clutch should be hard to turn when the engine is up to normal operating temps? Both of the clutches Ive tried will still spin by hand a little once the engine is warmed up , and even a little hot.

Thanks for any input.

95 4runner 3.0 5-speed, about 170K miles, only mods so far are optima red top,bfg tires, and new fuel filter,recent oil change,plugs and wires,etc..

 

your clutch fan seems ok im thinking the radiator maybe its time for a flush

 

From 96runner
Try the following (by hand):

Engine cold: Spins with difficulty, fan roars at start up
Engine warm: Fan spins freely by hand
Engine hot: Fan will not spin and fan roars as idle is increased

Do you have the fan shroud on?

 

how hot is yours when the fan will not spin?

so far with both of the new clutches they ran like this..


Engine cold: Spins with difficulty, fan roars at start up
Engine warm: Fan spins freely by hand
Engine hot: Fan will spin with about as much difficulty as start up but i dont hear it roar when the engine gets hot, even when it gets close to the red mark. Today is going to be about 80 deg. So I will try it again to see if that makes any difference, and Ill be getting the radiator flushed tomarrow.........

and yes, the fan shroud is on...
Thanks....

 

In regard to the way your fan's working... those are my symptoms exactly... just on a 3rd gen. My overheating only happens at low speed under load.. i.e. pulling a trailer or hitting some trails with hill climbs. I changed the thermostat a couple days ago, but don't have the abillity to "test" it... and it always ran fine on the highway and around town anyway.

 

Sorry, I have an electric fan.

 

From what you describe, it doesn't seem like anything's mechanically wrong with the engine/cooling system. It seems like a killer air pocket. Or have you already purged and purged 'till the cows come home?

 

I had this happen once and it turned out to be the electric 'helper' fan that kicks on when the A/C turns on. That little fan wasn't blowing as hard as it was supposed to and had to be replaced.

 

well, about the purging,,, I did it once when I changed out the thermostat, and once again when I changed out the antifreeze. I plan to get the radiator looked at tomarrow. I couldnt see much movement once the engine warmed up and Im thinking that maybe its restricted just enough that it can handle keeping the motor cool when idleing but just cant keep up after driveing for a bit..."man I hope this is the problem, the radiator is just a few years old but Ive never taken it to get flushed".

About the fan clutch.... I put cardboard infront of the radiator to stop any cool air getting to the fan and let the engine heat up to normal op temp, the clutch kicked in
and walla, I now KNOW the clutch is good. (I kept a close eye on the temp and it never raised above normal op temp. Then I tried to spin the fan by hand just to see what a working clutch will do, it spins about as much as a cold fan....

Kinda missing my 84 4x4 toy pickup. The 22r was alot easier to work with....

 

Good thinking, I may give this a shot...

 

Okay... I tried a similar trick. W3S had a good idea...

I took some folders, taped them vertically, and stacked them 3 wide across the front to prevent any airflow (they went between the a/c condensor and the radiator). I then shut the hood and started driving. First 2 minutes nothing. So i dropped it to 2nd gear (30mph). Still nothing, so i dropped it to 1st gear going about 20-25 mph on the streets around my nieghborhood. I then started to see the temp gauge rise. I would really hammer it up to about 5k rpm and I could literally see the temp gauge go up. So i held it about 3/4 high the whole way home by going into higher gears and letting it cool and staying in low gear for heating up. So i get home and i pull the folder out and i notice the fan is working just fine - as i rev the engine, the fan revs up too: GOOD!

So i get it back to normal operating temp, the fan has gone off. So I try again, this time, not moving. I stick the folders back in there, and turn on the truck. I rev it up a few times and I start to see the needle climb. (You have to have the hood down I found, or else all the hot air escapes). It got about 3/4 the way up and the fan was working great (just no air could pass through). So I removed the folders and reved her up to about 2-2.5k and she started cooling immediately. The fan I found is actually very accurate. My needle when running "normal" sits just below the 1/2 way mark on the temp gauge. The fan did not shut off until it was exactly at it's normal spot just below the 1/2 way mark on the temp gauge. So those wanting to test their fans might try this method. So now that I've replaced the thermostat, and affirmed that the fan is indeed working, hopefully it won't overheat again. If it does, the next step will be having the radiator cleaned professionally.

 

I was having the same problem about a month ago. I took it to get a flush, got it back and everything worked fine, and hasn't even come close to overheating since. Turns out there was something cloging the system...