99 tacoma v6 overheating

Hello all, first post here, sorry if it's in the wrong spot/asked before, couldn't find much to directly help though.

Having some coolant overheating issues. I've got a 99 v6, I believe 3.4L, 5vz-fe, 5 speed manual, TRD SR5.

Cruising along on flat ground, at highway speeds (~60 mph), in 5th gear, the temp can usually reach 208-210 or so, give or take. If I shift to 4th and maintain my speed, it will usually cool it down, maybe 201-204 F° range, even if I start going up small hills.

If I'm on the freeway, going 70-75 in 5th gear, the temp is better, in the low 200s, so higher RPMs seem to keep it cooler. I live on the coast, but made one trip inland in July, higher elevation of around 3600-4000ft, and I seemed to have less power, but it seemed to run cooler at highway speed in 5th gear, again, low 200s instead of 210 or 212.

I've replaced the coolant thermostat, the radiator, the temp sensor, and yesterday, the fan clutch, didn't seem to make a difference on the test drive, it got to 206 or 208.

Wondering if it could be the water pump, but from what I've heard, you know when those go out cause the go out all at once, so it doesn't seem as likely.

I first noticed the problem last december, only because I got a scan guage, and could see the actual temperatures. the temp needle on the dash, seems to be in the same spot that it has always been, as far back as I can remember.

So, any ideas on why it could be running so hot, or is this within the realm of normal operating temps for this truck? Since it can hit 212, maybe higher, on the highway, it just seems a bit much.

Sorry for the long post, but I'd appreciate any help/suggestions! Feel free to ask for any clarification or extra details.

 

Did you put the jiggle valve on the thermostat in the downward position, or the 6oclock position?
Using Toyota red coolant?

 

~210 is the highest it gets?

That seems fairly normal.

I think you are suffering from the "actual temp" vs. the "filtered" temp you get form the dash needle. It's totally normal for temps to vary by 10-20 degrees or so. If you're working harder, it gets hotter. The dash gauge filters out those normal temp variations and just gives you a warning if it gets to a point the engineers determined was problematic.

Do you ever get a temp warning light? If not, you're fine.

 

Welcome aboard new member
Temps sound ok to me

 

If crap coolant has been used, the fins on the water pump can get built up with crud and make the pump ineffective to varying degrees.

I would disagree that 210 is ‘fine’.

While 210 isn't necessarily Going to do damage in itself, it’s not the ideal operating temp because you are closer to the the upper end of the temperature range before damage would begin. The thermostat should open at approximately 180 degrees. Unless you have a specific aftermarket one that is specifically designed to open at 170 or 173 and I think there are a couple other temps that you can find. But the OE is 180, maybe 181 I’d have to look to be certain.

For example after I got all my coolant system in proper working order with proper coolant and all flushed and purged of air, except for my missing the lower fan shroud, I run between 183 and 190 at the highest.

edit, air in the system can also make for higher operating temps. So higher temps Doesn’t necessarily mean you water pump isn’t good.

 

@96BlueTacos I don't remember jiggle valve position, I've seen different people saying different things on the position, I think I went with whatever my Haynes manual said. I use the yellow/green Prestone coolant. Haven't checked for air in the system yet, guess that should have been first. But I've drained it a couple times, when replacing the thermostat, and again for the radiator, plus some for the fan clutch, wouldn't have figured it'd get air each time, I'll check though. I just noticed yesterday doing the fan clutch, that I'm missing the lower fan shroud as well, was wondering if that could cause it.

@jbrandt that's about as high as it'll get on the highway, 210 or 212, maybe 214, but I usually shift to 4th before it gets that high. I have hit 220 before, climbing up steep logging roads in 1st. I know there's going to be variation, and the dash needle only gets about halfway to redline, it's still just higher than it seems it should be.

 

I'm not a Toyota specialist, but I've read and heard from many here on TW, that you should only use Red Toyota Coolant in these trucks.

 

You can use green coolant just as long as it’s not mixed with orange / red. Checking the thermostat would be the first thing to do.

 

Ya I wouldn’t recommend anything other than the factory coolant. They designed it for the engines. I.e. for the metals it contacts, the viscosity, weight, and all of that chemical engineering is done for a reason. Corrosion can wreak havoc on the coolant passageways and I’d prefer just avoid it by using what they intended to use.

the jiggle valve goes down

See thermostat installation (b)

 

Eh there’s 4Runner forum guys with high miles an no issues that have been running green. Radiators, hoses, cast iron, and aluminum are all used in many other vehicles spec’d for green just like ours are which happen to be spec’d for red. By this point in time the only original parts on a vehicle that aren’t supposed to be replaced won’t know or care what coolant you’re using.

 

Ya I know... I still disagree as I will post a picture of the coolant passageways from the 22re I just rebuilt, where the previous owner, and first owner, I’m now the second, always used that green shit because he’d heard it was fine too.
The internals of the 22re say something different. And why not just use the right stuff?

 

Anecdotes are anecdotes. Let just assume Toyota did their due diligence in designing their fluid to properly extract heat from their engine block. It’s really not a big deal to just go to a dealship and buy a couple full strength bottles and some distilled water. Why take the risk?
New radiator, flush the block well, fill it with Toyota red coolant and then look up how to purge the air with a funnel. Make sure the thermostat is in the proper position, and then if your still running hot, then I’d think about water pump.

 

probably new a water pump/timing belt job

 

Many of those same people would probably buy OEM gas if they could.

Now if only there was a reliable place to source OEM air for the intake...

I've had the green 50/50 shit from O'Reily's in my radiator for many years. The engine is color blind, it doesn't know the difference.

 

Your argument is interesting, but use whatever you want. I wouldn't be surprised if there had been a mixture of red and green from the first owner if you had a build up in there. Ultimately it's just good that we're changing the coolant in the first place.

 

If you are suggesting by saying “the engine is color blind” that metals don’t react to chemicals, and potentially have an adverse reaction? Are you a chemical engineer? Do you know what alloys react to what chemical under certain circumstances? Do you know the exact alloys used in creating the engine?

Because I don’t, but someone who’s specialty is chemical engineering designed them to work best with the fluids they made for it.

Because again anecdotes are anecdotes, I’ve seen that shit green coolant first hand Corrode the interior coolant passageways in the block.

 

my use of that anecdote is to point out that I can find an anecdote that says the opposite. I use Toyota red because that what they recommend for best longevity.

Are you that dense?

 

Are you a chemical engineer?

What I see you're saying is that my anecdotes = bad, your anecdotes = good.

I'm saying that the materials our engines are made of are the exact same materials that most, if not all other engines are made of. Same metals, same chemistry.

I don't doubt there are minor differences. Do those differences matter? Probably not, especially if you take care of your vehicle and change the fluids occasionally.

 

Let's be objective here. You're saying the engineers speccing green for engines with aluminum heads and iron blocks had caused these engines to have build up and didn't know what they had in their own department? Do Toyota engines use some unique source of aluminum for the heads and cast iron that no one uses in engines specced for green? Radiators, coolant lines, and heater cores all get purchased without any idea of the available kinds of mixtures and types of chemicals they'll be housing.

There was no indication to that effect in what you stated.

 

Oh goody
Its Red vs Green
AGAIN