Suddenly running 10-15 degrees hotter than normal -- cause?

Qyota

Qyota

New member
We've had a few hot days recently (mid-90's), and I've noticed something weird going on with my '99 V6. Sunday was 95 degrees, and on a drive into the city, I noticed the temp reading on my ScangaugeII was saying 202F. Normally, this number never gets above 191. The highest it got, putting through a parking lot, was 207. Then Monday, it was much cooler out (about 70). I took a very similar trip in the 4Runner. I noticed the same behavior.

The dash gauge reads pretty much normal, maybe slightly high, but the scangaugeII gives an actual temperature, and it has never been above 191 since I've owned it (about 18 months). I have an external transmission cooler, so I'm not worried about milkshake, but what else could it be? Failing engine fan clutch? That's all I can think of. The temp does come down when on the highway, but still not down to 190, where it should be.

Coolant (Toyota red) in reservoir is right between the High and Low marks.

Any ideas? It's freakin' me out!
 
Register to hide this ad
I daily monitor the coolant and ATF temperature on my 1999 SR5 with the Scangauge II.
The water temperature is always about 204-206 deg. F no matter how cold or hot outside. The ATF is between 160 and 190 on highway with overdrive engaged. Haven't seen it above 190 deg. F yet.
 
Really?? Wow. I've had my SCII for nearly as long as I've had my 4Runner, and it's never gone above 191. Wait, there was one time, about 2 weeks ago, towing a small pop-up trailer on the highway in 85 degree heat. Then it got as high as 195.

Actually, that's probably about when this all started...hmmmm.
 
Anyone know at what temp the clutched fan is supposed to engage? I assume ours has a little bi-metal spring on the front of the clutch that opens/closes the fluid valve.
 
My SCII reads water temp at 204 degress. It's been 90+ degrees outside. Trans temps always stay in the 150 range.
 
When was the water pump last changed? It could be wearing out and not providing enough cooling to the engine. If the coolant passages are getting gunked up, that could also cause insufficiant cooling as well. When was the last time you flushed the cooling system?
 
Not as long as I've owned it. Could probably stand to be done. Timing belt was done at 130K, which was about 11K ago...and they may have changed the WP at the same time...I do not know.

Water pump - not leaking, and not making any bad bearing noises. But, it's on my list of things to replace around 150K.
 
Qyota said:
Not as long as I've owned it. Could probably stand to be done. Timing belt was done at 130K, which was about 11K ago...and they may have changed the WP at the same time...I do not know.

Water pump - not leaking, and not making any bad bearing noises. But, it's on my list of things to replace around 150K.
Click to expand...

Unfortunately, it could be the WP, but it's not cheap or easy and it's hard to say for sure if that's what's causing the problem - it's just a possibility. The water pump is a rubber impeller with fins and if the fins get cracked, broken off, or even just bent over, it causes the WP to not push as much water as it should be and in turn, the engine will not stay as cool. Before tearing into this, I would do a complete cooling system flush first and see if that yields any success (since this is much cheaper and easier to do).
 
I have replaced the timing belt and the water pump 5K miles ago. As I said above the water temperature reads about 204F all the time. LexusFTW has the same reading. If I was you I would keep monitoring the water temperature and would not overreact at this time. When the WP is gone you will see it without Scangauge. By the way, the water pump I have installed has an aluminum impeller. Not the rubber one.
 
the water pump should have been changed the same time the timing belt was done just to save some hassle. As for my temps, i see anywhere from 191-197 and i have a supercharger in this Texas heat. Usually around town i see 193 as the average and that's with the stock 190 degree thermostat. That might be your problem because i have never seen 200+ even when i romp on mine throughout town.
 
Thanks for the info. I guess I'm fine with it being 204 F, I just can't explain why it changed so suddenly. We certainly had hot days like this last summer when it didn't run hotter than 191.

I will do the flush, change the t-stat, and go from there.
 
Also make sure your radiator cap did not break or come apart. A freind of mine overheated just because he had a broken radiator cap.
 
Old Thread

Old Thread I know

My Runners water temp seems to have jumped maybe 10 degrees and Qyota's symptoms seem the same as what I am seeing.

Newer water pump, rad cap, thermostat, and toyota red drained and filled within the last 2years.

Nothing has been changed, added or removed, on it recently either.

I have not driven the Runner for a few weeks because I bought a 1996 Lexus Ls400 to run back and forth to work.

I have drove the Runner all week this week and the temp is at 202 deg or so on the scanguage. Also the outside temps. have been lower this week and in the rain tonight on the expressway the temp was still 202.

I am certain the temperature is was usually reading 190 - 195 even in the 90 + degree heat.

The gauge in the dash is about midway just as it always has been.

Maybe the Runner is just protesting due to being ignored.......

Qyota if you read this did you ever find anything?

I'm thinking fan clutch but.............

I'll reset the scangauge ( pg,56 of manual ) tommorow and see if that changes the reading
 
Last edited:
You can test your fan clutch with a bunch of rolled up newspapers. You shouldn't be able to stop the fan if the clutch is good.
 
cj80cruiser said:
You can test your fan clutch with a bunch of rolled up newspapers. You shouldn't be able to stop the fan if the clutch is good.
Click to expand...

....once the engine is good and hot. When things are cold, it will disengage and you CAN stop it with the newspaper. That is what it is supposed to do. A good indicator of fan clutch health is the roar on start-up, aka 'airplane noise' that goes away after a few moments.

Here is a good write-up off a BMW board. It applies equally to our trucks:visco fan clutch test

I'm not feeling fan clutch in this case. If you are on the expressway, you should run normal temp with no fan at all. On the other hand, a bad FC will overheat dramatically when stopped or moving slowly on a hot day.
 
Last edited:
Thanks,
I'll check the fan clutch.

It doesn't seem as if it is getting hot , and it's really not too hot, it's just that darn little digital gauge is higher now than it was when it was hot outside.

I had the scangauge in the other car for 3-4 weeks, without changing any of the seetings I had for the 4 Runner. I wonder if anything with it changed.
 
You must log in or register to reply here.

Members online

Total: 609 (members: 3, guests: 606)

Forum statistics

Threads
278,316
Messages
3,554,107
Members
248,016
Latest member
Advally Service

Share this page

Trending content

Back
Top