I have a 2000 Tacoma with 189,000 miles on it, and have had slight cooling issues with it for the past 2000 miles. I have tried a chemical radiator flush from napa, radiator cap, thermostat, cleaned the radiator fins, also had to replace the fan clutch, because it was free spinning when hot and it still over heats at high RPMs (2700 to 3000). It only seems to start getting hot when I am running interstate speeds for long periods, or when I am pushing the motor to climb steep hills. I can drive low speeds/RPMs all day long and it does fine. Best I can tell, there are no leaks, nor am I burning any water, so I hope that knocks out the head gasket idea. I have done all the maitainance myself since I bought it with 87,000 miles in 2005. I am kinda hard on it so it has been alot of work. As far as I know, it has never had a water pump put in it. Do water pumps ever get weak, without leaking? Does anyone know of any issues with the oil cooler? Would the rotation of the needle valve on the thermostat cause all this? (Didn't realize until afterwards that it was supposed to be in a specific position... Stock one was pointing about the 4 o'clock position if I remember right) Any thoughts or advice is welcome, I just don't want to drop the 350 buck on timing belt and water pump kit if it could be something else. Sorry for being so lenghtly....

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The radiator may still have corrosion in it that the cleaner is not removing. Radiator is full and you have gotten all the air pockets out of the cooling system i.e. burped it?

Right before I did my last timing belt change (80k after prior one), I was running at 203 deg around town. When I pulled it apart the pulley on the water pump was caked in burnt rubber......hmmm. My guess is that the hydraulic tensioner was failing allowing the timing belt to get some play and begin slipping as it went over the water pump. The water pump looked ok.

After replacing the water pump and everything else in this kit, my temp dropped to 191 deg around town.

http://www.ebay.com/itm/Toyota-TIMIN...item2a144a37e8

The jiggle valve should have no impact once the thermostat is open.

I have gotten all the air out as far as I know.

I did the timing belt and bearings from napa at 135,000, but have always gone with the "if it aint broke don't fix it mind set".

I don't have access where I am at to a reader, but before I did any of the list of cooling things to it, it was 180 after a long overheating drive and sitting for 5 or 10 minutes before reading it....

That is the kit I am looking at buying, but am a little short on funds to just start throwing money at things that may or may not fix my problem. I was hoping the fan clutch and thermostat was the issue. Probably should have bought the OEM thermostat, but got what I could at the time.

Thanks for the info.

What's your indication it's overheating? The needle a bit too high?

For $20 or so you can get a T-stat from the dealer....it's a 82C or 180 deg F. Normal operating range is 176-203F per the FSM so 180 a few minutes after stopping is not unreasonable...sounds pretty normal really.

Yes, the needle is a bit to high, and seems to be functioning properly. I had a long drive that caused it to climb higher. Like I said, that was at high speeds/rpms, and the needle had already dropped to normal after driving through town and shutting it down before I got the reader on it.

Realized the fan clutch was bad at that point, and didn't have access to the reader after I replaced that and the T stat.

It is kind of hit and miss when it really gets hot. After I replaced those things, I drove it for some distance and tried to make it get hot, but wouldn't.

I am litterally pulling hairs out because it makes no sense to me, or any of the mechanics I know.

Again, thank you for your input.

Any chance that it might be starving for fuel from a clogged fuel filter?.... Maybe causing a lean mixture during times of high demand resulting in pre-ignition and overheating? Any pinging?

Haven't noticed any pinging, but I am quite handicapped in that are. The cooling issue did start after my trip to Mexico for Thanksgiving... Could have got some dirty fuel down there. I will try to get that changed tomorrow and see if that makes a difference.

Thanks for the input, I will report back as soon as the fuel filter is changed.

Well, fuel filter changed and that didn't change the problem one bit.

I am at the point that I just need it fixed, and that might mean a whole cooling system rebuild and hope that fixes the issue.

Anyone have any other ideas?

I would think its the water pump. Or maybe the timing belt tensioner is shot and the belt is slipping on water pump?

Update.

Replaced the tensioner, but didn't have the resources to get the timing belt and water pump changed.

Still overheating, gonna have to nurse it home where I have the right tools to replace the timing belt and water pump.

Gonna go ahead and have the radiator rotted out since I have an uncle with a radiator shop, just to make sure it isn't a blockage in there causing low flow.

Thanks for all the suggestions.

Checked radiator hoses? Could collapse under higher pressure at high rpms.

Clogger radiator fins. Try power washing the front and back side to get out anything stopping the air flow though it. For $120, it might be a good time to replace the whole radiator.

My guess is that once you get to speed the air flow is insufficient to cool the engine.

Then there is always a head gasket issue. Is the coolant blowing out of the overflow tank?

That is a good point. The return hose (lower hose) can be under a bit of suction. One cheap aftermarket lower hose I bought at Pepboys once came with a big metal coil inside. They said it was to prevent the hose from collapsing from suction.

Thanks for all the help guys.

Ended up replacing timing belt, tensioner, pullies, water pump, hoses, radiator and even changed the oil.

PROBLEMS FIXED!!!!!!!!! :-)

On the last road trip, I noticed some wierd wear on my tires.

Pretty sure I have a front driver side wheel bearing going out. :-(

Anyone know what that usually costs to have done?

If not, I am sure a little searching should turn up the answer.

Thanks again,

LTC

Nice! Glad you got it fixed. Now you'll be good for another 90,000 miles.

How did the water pump look? Were any of the pulleys coated in rubber like I experienced (post 2)?

Water pump was still in great condition (spare parts for an emergency?), and none of the pullyes had rubber build up on them. The old tensioner was good, according to the Haynes manual test that is.

I am pretty sure it ended up being a clogged radiator. Instead of having a free rot out on it and giving it a go, I oppted for a new one at 150 bucks through autozone because they had one in stock with a lifetime warranty, and I needed one within a days notice.

LTC

Bearing and seals will run about $70 if you by the OEM ones from Toyota which I HIGHLY recommend. Replacing them isn't hard if you have access to a large press.

Also inspect the ball joints when you pull the spindle off.


FOG

Thanks FogRunner, I replaced the lower ball joints not too long ago, along with the CV axles, rack and pinion bushings, and inner tie rod joint (the one located on the inside of the boot on the rack and pinion assembley).

The bearings seemed fine then, but I am not exactly easy on my truck, and that was quite a few miles back (I guess I forgot to write that down, oops). Doesn't really matter to me because this truck will die with me and I will replace what I have to inorder to keep it running while I can afford it....

LTC