PNWYotaBoy

My runner has been running warm but only at highway speeds. The temp gauge will also show fully warmed up in around 1 to 2 minutes from a cold start up. The truck is not getting into the red, but is getting up to around 2/3 up the gauge. Gauge seems to come down when at idle and then goes back up shortly after moving forward.

So far I've confirmed and/or done
Dirty but oil free coolant
No coolant in my oil
Not losing coolant
Not blowing white smoke from exhaust
Burped the cooling system while running heater and at an incline.
Can't see any other leaks around the head or hoses.

By dirty coolant it looks a little darker than normal, almost murky looking.

Any thoughts on where I should start before tearing the engine apart?

wyoming9

iTrader: (1)

I would look very hard at the radiator if it is still original .

If the coolant is not changed when needed and the age easy to get some tubes blocked or a whole lot .

A Infra Red Temp gun comes in handy for checking this.

PNWYotaBoy

I'll do a flush on the coolant system, but when running the truck with the rad cap off you can see movement of the coolant.

The only other symptom that really makes me wonder is the heating up very quickly. This is before the thermostat even opens.

wyoming9

iTrader: (1)

You can have movement and still have lots of tubes blocked

PNWYotaBoy

Update

Completely flushed the system. Other than some dirty looking coolant; there was no rust or oil in the coolant.

Did a block test that came up negative for exhaust gas in the cooling system. Compression test didn't show anything odd either.

Finally decided to change the water pump, fan clutch and thermostat (single stage 180). Problem still persists. Shows temp going way up even before thermostat finally opens.

Another thing I am noticing is that the when I shut the truck off and quickly turn it back on to accessory, that the temp gauge only goes up to the normal operating temp, instead of the higher temp it was showing.

Decided to pull the temp gauge to make sure it wasn't just showing incorrectly and didn't see anything odd. However, after reinstalling, it now shows hotter than before.

wyoming9

iTrader: (1)

If your at the point that you have tubes blocked in the radiator a normal flush will not fix the problem or even get much of anything out.

That is why the Infra Red Temp gun is so nice you can see the blocked areas because they are much cooler.

Another thing it might be is just dirt and bugs blocking the air flow.

When you pulled the sending unit was it corroded at all??

Then if you cleaned it your reading warmer because it is working better.

Then another thing if your really running the engine lean your soaking lots of heat into it.

Most cooling problems show up when your stuck in traffic .

I just use Toyota Thermostats most after market ones are pretty poor these days.

Good luck

delmert

Kinda reviving an old thread here. But I've had this issue with 3 4runners over the years. First one I had met its end after a hot summer left a mile long oil streak down the highway. 3runner 2, I flushed and that coolant so many times. Had alot of rust in the motor. Couple radiaters new hoses. Finally got green coolant. Still overheated on the highway... rolled that thing into a creek. Pulled the motor an put it in my 84 wit a Weber card.. never ran better, that sucker founded like sex on the beach with a sun set.... 4runner number 3.... guess what it does? I'm about to put a carb on this thing... is the efi system the problem?

old87yota

Nope!

Toyota sold many thousands of these 4Runners with Electronic Fuel Injection, and Toyota (like everyone else) still use Electronic Fuel Injection to this day.

These Electronic Fuel Injection systems are actually quite good for their time and were more advanced (had multi-port fuel injection rather than throttle body injection) than other vehicles on the market. So, the fact that the engine has Electronic Fuel Injection isn't the problem.

However, that does not mean that the Electronic Fuel Injection system is working as it should. You could have worn out components such as an oxygen sensor, throttle position sensor, Air Flow Meter, fuel injectors, etc. that are not allowing for the best fuel mixture.

What tests have you done to see what might be causing your problem?

Have you verified that the gauge is reading correctly?

What condition is the radiator in?

What does the coolant look like?

delmert

Well on my current one I've got an aftermarket gauge. And it runs high 190s on the highway if I'm nice to it. However If I run ac a fan or actually try to accelerate I hit 200. 87 4runner 4.88 gears and 33s
Fluid looks good. Radiator looks fine. Current midwest temp is low 90s 70% humidity