1994 4Runner
Professionally rebuilt engine (S&J; Spokane), V6. Appox 5000 miles. I use the car as a daily driver, and also to take the family skiing (Oregon).

Under all situations this car runs with the temperature gauge just below the half mark except for the following...

When driving from Rhododendron (1,500'; Point A) to Government Camp (4,000'; Point B) everything is absolutely normal. The temperature gauge does not move (A->B = 10 miles). As I continue to Timberline lodge (6,000'; Point C) I experience issues (B->C = 6 miles). About 2/3 of the way up that road (B->C) the temperature gauge start to climb. By the time I reach the final destination the gauge is near, but not into the red. When I park, the coolant is boiling over and out of the reservoir. I'll lose about half the radiator's coolant onto the ground.

Please help in identifying the possible cause of this issue.

Other items to consider:
As previously mentioned under all other conditions everything is flawless
I've had this happen a couple of times and have replaced the radiator cap: did not fix the issue.
I drive up the hill with the overdrive off.
This happened with the prior (original) engine.

Thanks for any suggestions.

 

when u did the motor rebuild did u replace water pump, thermostat, have the radiator looked at for cooling threw it, does it have a couple passages that are blocked,

 

Thanks for the reply. The water pump and thermostat were replaced with the swap. Nothing done on the radiator. What should I be looking for in terms of the radiator? Could it be due to transmission fluid temperature? Once or twice I got a A/T temp warning light.

 

it could be heating up the coolant from the trans running threw, but if u have a hand held temp gun with it running see what the temp is in different areas, top bottom sides, middle, could have a clogged spot causing an issue, how about the cooling fan is it free spinning or firm when u spin it,

 

Radiator and fan clutch are the likely suspects. My guess the climb up T-line road is at a slower pace than Hwy. 26 and the radiator and fan cannot keep up once the vehicle induced airflow over the engine decreases.

Lots of threads around here on the symptoms of a failing fan clutch.

 

Would it only overheat when it's hot out, then have a quick recovery time and be just fine?
Did you find a solution?

 

I have only experienced the problem as described during the ski season (so cold out). I replaced the fan clutch (Autozone, $60ish). Unfortunately, I have not been "up the hill" since the replacement, so I cannot comment on whether this change fixed the problem. I did read a number of the fan clutch-related posts and believe that this should fix the problem. After I replaced the clutch, I did run the engine at about 4,000 RPM sitting in the driveway for about 15 minutes (therefore, no air flow beyond what the fan would produce) and the temperature never got above half. I could also hear the fan "cycle on and off."

 

It sure sounds like radiator related....how many miles on the rad?

 

Just an outside thought here... In the driveway there will not be an engine load persay... Borrow or load a trailer to at least half towing capacity to similate the load conditions of the uphill climb. Shouldn't take more than 5 miles to do this. Only other variable is the drop in atmospheric pressure.

 

x2. Over time buildup in the radiator can cause a significant loss in thermal efficiency. It's likely not fan related if it happens at highway speeds.

 

I used to have the same thing happen in my 92 22re, on t-line rd. I seemed to be the extra strain from going up the mountain. It was worse when the heat was turned all the way over to red (didn't matter if heat was on, only that the lever allowed coolant into the heater core) I flushed the radiator and heater core, disconnected the two hoses connecting the heater core and flushed it extra.

After refilling the coolant it ran fine. Make sure you run the engine with the radiator cap off and the heater core open long enough to open your thermostat and fill the heater core back up and continue topping off until heater core and radiator are completely full.

 

Auto Trans is adding alot of heat And your cooling is not working as adiquate as it used to.
Are you running tire size larger then normal and not regeared for them, This causes the auto trans to build alot heat.

Also be ready to do a headjob, On the 3vze Any kind of heat up and #6 cylinder blows the head gasket

 

^^what he said.... +Trailer test and a thermascan.... Check for hot/cold spots. The coolant temp gauge only lets you know intake manifold temps, not the entire system. Have you checked the fins on the auxillary trans cooler below the cab? That one is often forgotten when trying to diagnose heating problems, its basicly your transmissions "second" radiator.