5vz overheat or bad sensors?

this is for my 3rd gen 4runner with the 5vz. But I think the cooling system is the same as the tacos.

What are the chances of both coolant temp sensors being bad. The one at the back of the block that controls the gauge, and the one at the front that goes to the ecu? These are sensors that came in a jdm motor I bought off of eBay. I've been chasing an overheating issue and am thinking the sensors may be bad. My coolant temp has read 240 degrees with no smoke and no boiling. Of course I know this is not a good temp so I'm trying whatever I can to figure it out. I replaced the thermostat, flushed the coolant, new radiator cap, headgaskets are good this has been verified. The reason I'm wondering if it could be the sensors is even though it's been quite hot, I've had no symptoms of an actual overheat.


I did just find the one of the coolant hoses coming from the heater core was collapsed. Could this be the issue? Thanks in advance to anyone who chimes in.

Edit: I forgot to mention it only overheats when driving close to freeway speeds. I can let it idle in my driveway with the ac on all day with no problem.

 

Interesting. Mine was overheating under load but would never over heat moving slow or idling. It turned out that the radiator was super dirty. All the fins were clogged with dirt.

Can you verify the temperature with an IR thermometer?

 

Hoses collapsed is a tell tale sight of a failed radiator cap.

I would replace the cap and bleed any possible air out of the system while the cap is off.

Once bled ensure the thermostat is opening and that coolant is flowing.

 

Ir thermometer reads 190-200 at the upper radiator hose. About 170 at the lower hose

 

Let me rephrase. The return line for the heater core was "kinked" not collapsed sorry for my terminology.

 

Does anyone think this could be bad temp sensors. These sensors came with a jdm engine from unknown origins and I plugged them into my stock U.S. 4runner harness. Today on my drive home it read upto 240 degrees. But I had no symptoms at all, no boiling not even a slight sound. No loss of power. No cutting out of throttle. Nothing, a/c was blowing ice cold, etc.

 

Have you maintained coolant properly? Certainly sounds like passages in radiator are clogged with salts from piss-poor water. As you rev motor the flow thru radiator won't keep up, triggering sensor to get hot. The cap is so small you really can't see inside. For $ 120 I would go with a new radiator... get proper measurement of radiator as Toyota used 5 different ones on these trucks.
Good Luck!

 

I have a 03 3.4L . my problem is temp gauge on dash reads full hot after 2 min. Idle. I replaced hoses (14 years old) thermostat, coolant. Engine runs fine and not hot. I just deal with it until I replace sensor. I heard that to replace the sensor use OEM as the others are crap.

Edit: thanks to the guys on here I figured out my problem.

 

So yes a kinked hose could have something to do with it.
I believe the sensor on the front just tells the ecm that it is warm to kick it off hi idle.
So if it is a sensor just the back gauge one could be you problem.
Could be thermostat.
Does it have a cheap parts store radiator I'm it?
Aka plastic caps and silver fins? If so those are only single core. The steel tanked oem style 3 core are the only way to go imo.
Have you made it thru a summer with this setup b4?
Don't have any parts off stock motor you could try?
How do you know it not a head gasket? They are known for cracking the head in cly 3.

 

I just bought the runner in January, a new oem radiator is in its way! Thanks!

 

Compression test was good when I performed it this week because of this problem. I'm not sure what radiator is in it but it looks old because the top plastic is all browning now. I have not had it during the summer before just bought it In January, blew the stock engine in a puddle, repaired in February with jdm engine, now is the first time the gauges have read this high. I fixed the kinked hose, to no avail. And an oem radiator is on its way to me. Also thermostat is new. And I did the water pump Just before I swapped the engine since it was so easy to get to.

 

How soft are your hoses?
Could they be collapsing under load? It would be hard to tell but if they feel soft I'd replace.

 

Also look up what a radiator funnel is.
They really help with making sure you don't have air bubbles.

 

Something like this?

EPAuto Spill Proof Radiator Coolant Filling Funnel Kit

$22 EPAuto Spill Proof Radiator Coolant Filling Funnel Kit

https://www.amazon.com/dp/B01I40ZQWE/ref=cm_sw_r_cp_api_TJ3zzbJ9YP8NH

 

Yes, totally worth the money.
Select the rite cap and fill it up and since the funnel is higher then the hole system it burps out the air bubbles.

 

A new radiator appears to have solved the issue! Now I'm hovering between 190-195 on a 100 degree day with the a/c on full blast. Thanks everybody for the help.

 

Good deal.