My '98 Tacoma (3RZ 2.7L) has been running hot (not overheating, gauge @ ~3/4) since the weather has warmed up here in western NY. I replaced the thermostat 2 weeks ago, checked the belt and had the coolant flushed yesterday, but it hasn't fixed the problem. No white smoke, no antifreeze smell and I'm not losing any coolant so I don't think its a head gasket, but plan on getting a compression check done. When I turn the heat on it does cool down. I was under the impression that water pumps don't die a slow death, so I don't think it's that. At a loss. I searched the forums here and didn't find much on this problem. A friend at work refered me to this site; good stuff here.

 

Try testing your fan clutch.

 

Waterpumps do die a slow death in my exp.
It could likely be a blockage or gunk in the cooling system. Flush the system and refill it with 50/50 distilled water/antifreeze mix.

 

He said he already flushed it. Here's some info on fan clutches:
http://www.popularmechanics.com/how_...e/1772922.html

 

Thanks for the link... The more I read on the fan clutch the more I think that's the problem.

 

I'm getting nowhere. I replaced my fan clutch and it still ran hot; so I took out my thermostat and that didn't change anything. I took it to a toyota dealer who did a pressure check and was told the radiator is ok. He also said it wasn't the head gasket and recommended that I put in a factory thermostat as the codes he pulled all indicated a bad thermostat, (no ˟˟˟˟˟, it's not in there). I'm at a total loss here. The only thing I can think is that I'm using the green antifreeze instead of the red.

 

Color of the coolant shouldn't matter. So it sounds like about the only thing you haven't checked is the water pump? Many times they have a weep hole that will indicate if it's on its way out. I'm not sure if your 2.7 has that or not.

Rob

 

But will a leaky water pump result in hotter temps? I've had a leaky pump before and the temp was fine. But I guess there are no other culprits, so maybe that is it. Or maybe it's the temp gauge itself.

 

a leaky pump is just another failed pump, because the system has to be pressurized.

a bad radiator cap will cause this to happen. replace that and see.

i temp guage doesnt lie because he turned on the heater and temp drops.

 

Toyota tech said the radiator was ok

Rob

 

radiator cap will cause this to happen. this was the problrm I had. You mught also want to check into a cap that rus cooler as well. I was told they have them as well, but don't really no.

 

make sure the water pumps not cavitating (air in the pump or highest coolant point in the engine) check your oil

 

How are your hoses? Long long ago I was stumped by a similar problem, replaced damn near everything in the cooling system except the hoses because they didnt leak and looked fine. Well, one was apparently worn out, and was actually sucking shut under pressure. Replaced that with a new stiff one and all was well.

You did burp the system, right?

edit: this was not on a toyota, I dont know how the hoses are on these trucks, it simply might not happen on them...

 

So, I have a 99 that was doing the same thing...yada,yada,yada....I did all that you did with no fix, so.....I stuck a thermometer with a probe on it between the fan shroud and radiator when the engine was running and warmed up to measure air temp...probed the drivers side...160 deg, probe the pass side, 165 deg, probe the middle....95 deg...the radiator appeared to be fine, but was at least 50% internally plugged with some powdery, pink deposits. The reason the fan clutch did not come on was the cool air feeding to it through the center section of the radiator. I opened up the old radiator - I will try to post a pic. Bottom line - new radiator - problem resolved...

 

I haven't seen any leaks in the water pump and the hoses don't collapse. I think I'm going to start with replacing the radiator cap, then the water pump and radiator if necessary.
Thanks for the great advice on this.

 

Try checking the resistance on the temperature sender for the gauge... just so you know its good.

I also second slus on the cooling system bleed... I haven't torn down one of these engines so I'm not familiar with the coolant passages but typically any air trapped in the head will just create small hot spots... some motors are worse than others, so this may or may not make a big difference but its cheap and easy to do.

I would suggest a snug fit coolant funnel from sears or an auto place; it creates a water tight seal on the radiator cap spout. Make sure the funnel is kept full of distilled water and the air will make its way out over the next 20-30min. also any bleed screws should be used to help bleed air out...

typically if the radiator cap is failing it will allow air into the system and coolant out of the reservoir... eventually this results in boiling coolant in the overflow reservoir once the warm motor is shut off... if you notice/hear it then the radiator cap is more than likely the culprit.


Good luck with it

 

yeah man, get a small piece of flat steel or something to try to push into the fins of the radiator. If its not easy to push down the fins, clogged up radiator. This was my problem even after changing the waterpump, t-stat and cap with a flush.

 

If you aren't losing coolant then your cap is not the problem (particularly at relatively lower temps)....The water pump is typically is not a problem if it isn't leaking....Anyway, a great way to tell is to buy a cheap thermometer with a probe as I mentioned earlier - this way you could tell if your water pump is performing and if your radiator is internally (or externally) plugged or not. If you are not losing coolant (as you have said) then my money is on the radiator being plugged. Matter of fact (how's this for great internet bravado...) I'll bet you $10 that your radiator is the problem.....

 

Yeah a pic of that would be great, you're talking about a plugged core right? Or in other words the coolant wasn't making it through the center of the core.

 

Yea the core was blocked - I split a few tubes and they were completely plugged. I guess about 40%+ of the tubes were blocked with a pinkish, powdery material. I guess the PO hadn't ever flushed....

Here is a pic: