Quick Rise in Coolant Temp — Normal or Abnormal?

[StreetCreeper]

So I'm planning to replace my radiator this week as preventive maintenance. I also happened to get a ScanGauge hooked up recently and have been monitoring coolant temps.

My running temps are normal around 193~ and in city driving I'm in the 1999~ area, so all seems normal.

However, I got curious today and wondered how high the coolant temp would rise if I just sat there in park with the A/C on full blast for 15 minutes.

So I marked time at 4:00 pm on my dash and noted the coolant temp was at 193*. Outside air temp was 91*.

After 15 min, the coolant temp had risen to 218 degrees.





I proceeded to pull out of the parking lot and drive normally. The coolant temp went back down to 198* after about 5 min.

So I'm curious about a few things:

1) Should the coolant temp have risen so quickly and that high in those conditions?

2) How likely would the temp have continued to rise to the point of failure?

3) If abnormal, where should it have stopped?

After noticing this today, I'm seriously considering a new Aisin fan clutch to go along with my radiator but not sure if I should wait and see if the new radiator I put in will improve anything.

Thoughts?

 

[giovannie23]

I was told that 218 219 is normal coolant temp and thats about the point where the thermostat starts to open up and dump the temp back down.

 

[99Runnr]

Doesn't sound like anything abnormal.

Make sure your fan clutch is up to the task.

 

[JayRolla]

If the dash gauge doesn't move dont worry about it. You might need to clock the thermostat jiggle valve to the 6 o'clock position which will drop your Temps about 10*. http://www.toyota-4runner.org/3rd-gen-t4rs/186171-thermostat-fixed-running-cooler-now.html

 

[Joe Z]

If the dash gauge doesn't move dont worry about it. You might need to clock the thermostat jiggle valve to the 6 o'clock position which will drop your Temps about 10*. http://www.toyota-4runner.org/3rd-gen-t4rs/186171-thermostat-fixed-running-cooler-now.html

What/where is the:shrug: "Thermostat Jiggle Valve"?

 

[JRZEE2000TR4LTD]

What/where is the:shrug: "Thermostat Jiggle Valve"?

It's a little port covered by a metal check valve. You can see it at about 2 oclock in this picture.

 

[nc-grayson]

I wouldn't say it's abnormal, but I'll second the fan clutch comments

 

[Rock_Rat]

Just for reference, it definitely runs hotter than mine. Mine is pretty constant at 186*. It will push around 196* and break the 200* mark going up hill for three miles.

 

[ThorInc]

Jiggle valve up, I ran 198 to 204F, jiggle valve down (at 6pm)I run 186.8 to 190.8F and that's the usual range (defies my logic but I have seen it). As for the sudden and continuous rise in temp, I don't think it's normal and since you will be R &Ring the rad, you may as well do the fan clutch. If you wait until the dash gauge moves please let me know what temp it actually starts moving up at?

 

[JohnMc]

If the dash gauge doesn't move dont worry about it. You might need to clock the thermostat jiggle valve to the 6 o'clock position which will drop your Temps about 10*. http://www.toyota-4runner.org/3rd-gen-t4rs/186171-thermostat-fixed-running-cooler-now.html

THIS MAKES ABSOLUTELY NO SENSE!!!!


But for whatever reason it's true.

Even if the fan clutch is in great shape, there might not be enough revs to keep everything as cool as it can possibly get. The hotter the radiator gets, the better it gets at shedding heat (more temp diff vs. ambient air going through it) so as long as it doesn't get hot enough to boil, it's not a problem.

If you're curious, just let it sit like that for longer, you'll see it plateau and stop climbing.

 

[jeremyc74]

I'd say you have a problem developing, and the fan clutch sounds right to me. 218 is way above normal if everything is working right.

I have had a SGII for a while now, and I've never seen the temperature fluctuate more than 4 degrees above normal.

When I first hooked up the SG I would see temps fluctuate between 182 and 186. Never higher, no matter what I was doing. (And I'm in FL, so plenty of A/C and traffic). After a while I did the timing belt, thermostat and radiator, and now the temperature range goes from 186 to 188. If I'm on an open road for a while and come to a stoplight it will hit 190 for just a minute, and then drop back down to 188.

I would assume the slight increase after the TB change was either due to the original thermostat being worn, or just manufacturing tolerance. The jiggler was in the 6 'o clock position on the one that was installed, and I put it back that way.

 

[alumarine]

As long as it stays cooler in "normal" driving conditions I'd say you're fine.

 

[LittleCaesar]

Also clean the fins of your condenser and radiator. But I would guess that the fan clutch is where you need to start.

If the cooling system has been opened it may need a good burping.

 

[StreetCreeper]

As long as it stays cooler in "normal" driving conditions I'd say you're fine.

Under normal conditions while on the road, it seems to be fine. I've not noticed any overheating problems ever, it's only because I recently installed the ScanGauge that I've been able to actually see the temp change with different conditions. But we all know that conditions change and can quickly become abnormal e.g., stuck with on the highway going uphill due to an accident or whatever while its 105* outside.

It's this type of situation that I don't want to be dealing with a subpar cooling system. Especially with the wife and three little kids in the back.

Also clean the fins of your condenser and radiator. But I would guess that the fan clutch is where you need to start.

If the cooling system has been opened it may need a good burping.

I cleaned out the A/C condenser last summer and I'll do it again when I replace the radiator.

Plan to replace the thermostat and radiator cap at the same time. While I'm also thinking it may be that my fan clutch is on the way out, I'll wait until after I change out the radiator to see if there is any improvement.

If not, then I'll probably swap out the clutch too. I checked it last summer and it seemed good — but things change and I would like to get ahead of any potential overheating issues in the near future.

Lot of good advice from everyone here. We are all thinking along the same lines.

 

[nc-grayson]

Small tangent here Woody, any cause for concern with your voltage at 13.2 when idling?

Recently read around hear that 13.8-14.2 is accepted as the norm on these trucks. I'm around where you are.

 

[StreetCreeper]

Small tangent here Woody, any cause for concern with your voltage at 13.2 when idling?

Recently read around hear that 13.8-14.2 is accepted as the norm on these trucks. I'm around where you are.

Nope no problems for me. Everything is bright and working well. There is no dimming of lights or anything when I place extra load on the alternator.

I think anything over about 13v means your alternator is charging. I replaced my alternator last year with an Autozone one since the previous owner had traded in the OEM one as a core on the Autozone one that died on me. So who knows how long it will last, but so far no issues. It tends to vary between 13.2v — 13.9v

 

[St Runner]

I think you are on the right track. Replace the radiator then check the temps. A new more efficient radiator should take care of any temperature swing at idle. If not you already have one thing crossed off the list.

 

[pluton]

Just for reference, my '97(5spd) runs at 192ºF, +- about 3 degrees, under all conditions. But I did give it a new radiator 25,000 miles ago.

 

[jeremyc74]

Small tangent here Woody, any cause for concern with your voltage at 13.2 when idling?

Recently read around hear that 13.8-14.2 is accepted as the norm on these trucks. I'm around where you are.

The voltage regulator has some compensation circuitry in it that will vary the charge voltage based on temperature, and how much current the battery is taking. There's a pretty wide range of voltages it will output. The biggest thing you want to look at is if it's able to maintain that voltage under load. If you're seeing 13.2V with the headlights on and the A/C on high, you're in good shape.

It tends to vary between 13.2v — 13.9v

That's about the same I see. Mine will bump up over 14V if I'm up north and it's cold, but it gets back down in the low 13s once it's warmed up and the battery is topped up.

 

[nc-grayson]

The voltage regulator has some compensation circuitry in it that will vary the charge voltage based on temperature, and how much current the battery is taking. There's a pretty wide range of voltages it will output. The biggest thing you want to look at is if it's able to maintain that voltage under load. If you're seeing 13.2V with the headlights on and the A/C on high, you're in good shape.



That's about the same I see. Mine will bump up over 14V if I'm up north and it's cold, but it gets back down in the low 13s once it's warmed up and the battery is topped up.

thanks Jeremy!