sharrack

Hey guys,
I'm fairly mechanical but this one has got me stumped.
Drove up a mountain trail in the cool morning and parked at the
summit....truck is overheating , spitting etc.

I figure ......got to be the thermostat.
I let it cool to medium temp for an hour then drive up to next summit.....
running fine, no over heating.

Leave mountain and drive 35 minutes to next mountain and head up hill in mid day heat.....out of nowhere....over heats again.
Wait 35 minutes to medium heat and drive over summit with heater blowing on full and 200 relatively flat miles back to Phx without incident at 70mph.
A/c on back to phx.

I'm stumped..........
***I added a bottle of copper leak fix 2 months ago to seal a freeze plug and have been driving trouble free since in 110 degree heat.

any thoughts ?
Thanks again ...Kenny S

CLin9383

test your fan clutch.

post #5
https://www.yotatech.com/forums/f2/1...stions-216502/

sharrack

Thanks............much to my dismay...........I just tested it and could not get the fan to stop.......... even when hot.
Sounded logical though..............back in the day, we used to clean out the
gunk filled thermostat wire in the front of the clutch to get it to work better.

So now what ??........slow speed on a steep trail ........overheated twice.
All other driving...........needle below the middle even at 112 degrees!

This problem just came out of nowhere......crazy.
Kenny S>

sharrack

just for kicks, i took a toothbush and 409
and cleaned the thermostat on the front of
my fan clutch. like new with no gunk on it.

sharrack

Hey Guys,
So my truck has been running perfect for over a week with no overheating.
The only time it overheated was on steep mtn roads under a load.

i'm headed out again this weekend to the mtns and was wondering if there's
anything or some tricks I need to keep the truck cool on the incline trails.

I'll be driving slower, in 4wheel high maybe even with the heat on.
any other tips?
thanks , kenny S

coops2k

when was the last time it was flushed?
is your over flow tank full - middle - empty?
could it of been an air pocket in the coolant, from the angle you where driving at?

You can get some "water wetter" or "freeze"? it can help the coolant work better.

Slow steep trail reminds me of old British car driving up a hill, they would over heat because the engine had to work harder and their cooling system / fans where not the best.

gdutch

The fan shouldn't ever stop running if it's over 100* outside, as long as you're below like 30 MPH. I know in Texas I hear mine roar every time I take off from a stop. I doubt the fact that your fan is RUNNING is causing your engine to overheat.

Innervision

my 94 runner would overheat while going up hills. It turned out the internals of the radiator were covered in mineral deposits. This limited heat transfer under higher RPMs. Thus overheating when the collant was flowing faster through the radiator (high rpm since water pump is timing belt driven). Not sure how the water pump on the 99 is driven but I would assume higher RPM = high collant flowrate.

Inspect your radiator and see if it is clogged or coated internally.

My guess is the stop leak you put in for the freeze plug issue has clogged the fins, or coated the inside of the rad reducing heat transfer or collant flowrate.

good luck

sharrack

Innervision seems to be on the same page as I am.
I'm just surprised it takes the mtn to bring it to a boil and it never even runs
a bit hot any other way. The gauge never even hits midway on a 110 degree day.

The 99 runner radiator has very limited viewing inside the neck but I don't see any kind of crust.
Guess I'll have to monitor the situation as I travel up mtn roads.
Seems to take at least 10-15 minutes of a steep hill on dirt to get it hot.
I'll try driving a bit slower to see how it goes.

Thanks guys, kenny S>

j-man

Well the cooling system consists of: radiator, water pump, thermostat, fan clutch. Without knowing your service history, could be the radiator is clogged or the thermostat is sticking, but more likely the fan clutch isnt holding tight when it gets hot. I like to change the cheap things first....

sharrack

anyone know a good way to check or get rid of possible
air pockets in the system?
thanks
ks

CLin9383

jack front end up and start truck with radiator cap off and put heater on full blast. rear heater if you have one too. or you can park on an incline if you dont have jacks. let the bubbles come up for 5-10 min and you may need to fill your reservoir if a lot of air bubbles came out. then put radiator cap back on and you are good to go.

sharrack

Cool.........I think I just found the problem. The fan clutch!!
I tested it hot last week and could not get it to stop at all.

So I got the truck jacked up and I'm looking for air bubbles so i grabbed
a magazine just for kicks to try it again.
Stopped in a flash........with almost no restriction.
Off I go..........!!

Thanks guys!
Kenny S

Potomacduck

have a '99 V6 and had the same overheating issues.

I replaced the fan clutch withan AISIN unit from Partsgeek.

Prolem fixed. I idled it the other day in 100 degree heat with the AC full blast. No problem.

sharrack

yeah, i can hear the difference ....... i hear the roar of the
fan.
I'll report back after i get back from the Chiricahua mtns.
kenny s

sharrack

well....., lets just chalk up the 110.00
fan clutch to a mistake even though i stopped
easily stopped the fan when hot.
Truck still overheated on a mtn road twice.
I was able to stop it from boiling over the
second time by blasting the heat.
Ran perfect the other 400 miles!!!
Still baffled

sharrack

Looks like i'll be getting my radiator
boiled out over the winter.
Ks

sharrack

So I got through a 450 mile weekend with the runner overheating on steep
mtn roads twice.
Never on the hwy or any flat trail..

So I'm coming home from work today and happen to look and see the gauge almost full hot.....on the hwy.....113 degrees in PHx.
Pull over .....sit 5 minutes and restart with heater full blast........gauge
falls to level or slightly above immediately.

What in the heck can be causing this crazy erratic overheating??
Any takers?

Thanks , kenny S

brian2sun

I don't know, but I do know this:
You need to take it somewhere and have it professionally diagnosed NOW instead of driving it around hoping it will go away. You are going to warp and/or crack a head if you keep letting it get hot like that. It doesn't need to go into the red to do major damage, all it has to do is go above normal temp a few times to screw the heads up (which it may already be too late).

sharrack

Well..........I consider this forum more of a professional diagnosis location than any shop.
I've been a mechanic for years and like when things make sense.
This simply does not.........
I would feel much more confident if it overheated every time I drove it.
It does not.
I understand the steep mtn road overheating with a plugged rad but why today
of all days in the last 2 months does it overheat on the hwy?