1995 Tacoma overheat

Hello, I have a 1995 Tacoma 3.4 liter, automatic with 251k. I have just replaced the radiator, thermostat, and water pump. I flushed the heater core and a shop has run leak down and compression tests on the engine. What else could actually be causing the truck to overheat? Has anyone had a weird experience with these trucks getting hot?

 

I assume this problem existed before you replaced all that stuff?
I would warm up the engine and feel hose temps all over the place looking for a super hot one. The hot one usually being upstream of a blockage.
Compression test, and leak down won’t help much with testing the cooling system, unless you are consuming coolant.
Good luck, Keep us posted.

 

Yes, the problem existed before. I bought the truck this fall, it ran great, but discovered it wasn't running a thermostat when I bought it, and it eventually started to overheat slightly even without a thermostat in it and would immediately with one installed. Since doing the repairs, I don't notice any change.

The upper hose gets super hot, the bottom hose will only be mildly warm by the time it's overheating. If there is a blockage, what would you do to fix it?

 

I’m honestly not sure how I would clear it out, but locating it is step 1. It sounds like a blockage or poor flow. It’s been a couple years since I worked on the cooling system of this truck, so I’m sorry I can’t be more specific. If there’s not supposed to be anything between those hoses, then there likely is. If the pump is between those hoses, it’s not working correctly.

 

That's what I'm leaning as well. I think there may be some sort of blockage in the engine itself, but I did flush the block before installing the water pump and the water ran clear pretty quickly.

Is there a chemical flush that could be done? If not I guess I'll be pulling a water pump again to see if I received a defective one.

 

How did the compression and leak down look?

 

I don’t have the official numbers, but the shop said they were fine. I’ll ask for that when I pick the truck up tomorrow.

 

It sounds like the PO may have yanked the stat to mask or compensate for this problem.

That’s good news at least

 

That’s definitely the case. There were a couple things that were covered up but the frame is still solid so I want to start making this truck nice again.

 

Fan working as it should?

 

Check the fan clutch.

 

Under what conditions do you notice it overheating? If it stays normal temp while moving at speed but overheats when idling or moving slowly then I'd strongly suspect the fan clutch especially given everything else you've checked and replaced

 

If the engine is cold then you should feel resistance when trying to spin the fan by hand (engine off of course)...if it spins around freely by hand while cold then you've found a problem

 

There is some resistance. Is there a way to bypass the clutch and allow the fan spin with the engine to see if that was also a problem?

 

I haven't driven it more than the 5 minutes to the shop to see if it has a problem while driving after the repairs, but it definitely overheats quickly while sitting still, and before replacing the radiator and water pump it did not matter if it was still or moving.

 

Get the engine hot, then turn the truck off, and try to spin the fan, if it's stiff and doesn't move the fan clutch is good. If the fan spins pretty easily then its toast.

The fan clutch has some weird alien fluid in it that causes it to lock up when hot and spin freely when cool.

Mine would overheat on the trail or idling in traffic and it was a bad fan clutch that was issue. You can also hear it engage and the fan will make a deeper whooshing sound.

 

I'll check that on the fan if I pick the truck up tomorrow if not it'll wait until the weekend.

 

So, I got the truck back. I forgot to ask about the actual test numbers, unfortunately. I installed a new fan clutch and radiator cap, no change. However it idled in my driveway, got up to temperature sat for a while while at idle, but as soon as I started to drive around the block, it began to overheat.

 

Remember the search feature can be a big help.

See post #11
https://www.tacomaworld.com/threads/95-v6-3-4l-overheats.618831/#post-21063167

 

I read through that post but it doesn’t add any new information. It basically starts to overheat when the system is sealed and you add throttle. It seems to stay cool until I hit the gas pedal. If the radiator cap is off it’ll gurgle a bit when I hit the gas but doesn’t go over half way on the temp gauge.