I was towing my camper with my 100 series Land Cruiser down to Chatfield this weekend and my temp gauge started climbing up to near the red line. I have a scanguage and the reading got to 242 degrees. It cooled down a little after i turned on my heater. I've gone down the internet rabbit hole and it could be anything from a bad thermostat to a leaking head gasket. Has anyone else had overheating problems with their 100 series? I'm going to take it to a shop this week to get looked at. Thanks
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Land Cruiser getting Hot
- Thread starter chillbill
- Start date
coolant level all good?
i hear the heater tees give issues.... has that been replaced?
i hear the heater tees give issues.... has that been replaced?
Most commonly the top radiator tank will get a minor crack and slowly leak fluid. Is your radiator 'ol brown or nice black?
When it's good and cool, see how much coolant will fit. If it takes more than 1 gallon you probably have a leak somewhere.
If it's nice and full then it could be the t-stat but not to common in my experience.
When it's good and cool, see how much coolant will fit. If it takes more than 1 gallon you probably have a leak somewhere.
If it's nice and full then it could be the t-stat but not to common in my experience.
HDavis
Hard Core 4+
- Joined
- Feb 13, 2019
- Messages
- 1,137
One day my 100 series got up to 225 and it turned out to be a bad thermostat. It had 219k at the time.
SteveH
Hard Core 4+
How about the fan clutch. Normally not engaged on the freeway, but with towing it might have been called upon. If it windmills (spins freely) when parked cold, it may have lost its oil.
DaveInDenver
Rising Sun Ham Guru
Maybe along your thinking @SteveH, I assume it wasn't too hot over on the Front Range so perhaps the opposite, the fan clutch has seized? On the highway if the fan is locked it works against you creating an interruption to air flow and cooling. If it's freewheeling I'd think highway would be alright but in town would overheat.
Please explain the interruption.
DaveInDenver
Rising Sun Ham Guru
The fan being locked to the engine RPM prevents it from spinning at the RPM the air flow would otherwise cause. The physical term is turbulent air flow. Imagine holding up a fan spinning at the equivalent of 20 MPH when the head wind is 30 MPH.
Or a plane or boat prop. When one of those spins fast it creates a wake, which is the medium being forced to accelerate, moving the craft forward. If you disengage a hypothetical clutch as the boat is drifting the prop will just turn slowly. The pressure on each side of the fan is equal. If you hold it still or try to spin faster than air speed there's a pressure differential created, it might slow you down or speed you up but either way it's disturbing the air or water.
Trying not to get too technical but air flow in this case is relative to pressure, flow rate (cubic feet per minute, for example) and speed (RPM). The fan blades have a surface area that creates the flow necessary to move enough air over the radiator to meet cooling demand.
We talk a lot about these same things electrically. Pressure is voltage, flow rate is current, the two are related by resistance. If pressure is the same then for a given flow the resistance is in essence zero, which is what you want on the highway when just driving down the road is pushing plenty of air through the radiator. You don't need a fan and free wheeling saves energy and doesn't "resist" air flow.
It's the original reason for a fan clutch in the first place. Way, way back I know you remember and see on the Mercury. When the fan was hard connected to the engine it was forced to spin with the engine RPM.
But without a shroud that was OK, the air could flow from the edges. it wasn't optimal cooling but the radiator oversized and lots of surface, it wasn't too much of a problem. As things improved the clutch became necessary.
The fluid in the clutch is temperature sensitive. When it gets warm it thickens and the fan spins up with the engine. When it cools it thins and lets the fan just turn at the speed of air going through the radiator. So on the highway the fan is usually just spinning proportional to the air flowing through, which is a different RPM than the engine most of the time.
You usually notice it overheating in traffic first because the nature of them is the fluid leaked and it no longer engages but the opposite is possible when it becomes contaminated and never thins, too.
Oh, yeah, then electric fans came in. Those only turn on in traffic, right? On the highway they're just spinning freely. You can limp home with a dead electric fan by just never stopping for too long.
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Great explanation Dave! I'd always thought the fan clutch came about for lower noise and to improve PTO efficiency but that makes a lot of sense.
At the same time, I've had a free-wheelin' fan clutch on my 100 and while it made lots of noise it never caused overheating. The cooling system is pretty effective on the 100 in my experiences abusing it. 242F is hot enough I'd think it's half dry or something blocking water flow (like the T-stat).
At the same time, I've had a free-wheelin' fan clutch on my 100 and while it made lots of noise it never caused overheating. The cooling system is pretty effective on the 100 in my experiences abusing it. 242F is hot enough I'd think it's half dry or something blocking water flow (like the T-stat).
The fan clutch on Bart (FJ62) engages all the time at hiway speeds, cycling off and on nearly constantly. Been that way forever. OEM fan clutch. With the engine rebuild in 2004 this was noticeable and several clutches were tried with similar results. This is the engine that pings badly on 91 octane w/ ethanol and with much less pinging w/ ethanol free. 93 octane was available back in 2004 and advance could be bumped up to 12* btdc but stock 7* is set now. Coolant temps are rock steady at all speeds including at super slow speeds when rock crawling the Rubicon. What’s going on @DaveInDenver?
DaveInDenver
Rising Sun Ham Guru
Noise and sapping energy are important. But so was lower then front end profile, using only just enough radiator. Clutching the radiator fan solved a lot of things.
it's not a perfect system. The fan clutch senses passively by the temperature of the air that's come through the radiator. The fins on it are a reverse radiator or heat sink in that they collect and soak heat into it.
Bart's engine makes more power than stock, right? So the temperature gradient across the radiator is different. Hot coolant is fed in, cool is pushed out. If you didn't add another parallel core row then more of the core is warm but not enough to overheat.
Also gotta keep in mind we also screw things up with winches and bumper and lights. Toyota says "We did all this fancy simulation, modeling and wind tunnel testing." We say "OK, great, hold my beer." ARB also knows this, so they put chin ducts in the bumper to force more air in. Maybe those are pushing more hot air over the clutch.
There's really no way to draw a perfect conclusion. I bet with rigorous testing you could find some weather conditions, speeds and engine RPMs where it balances, doesn't ever come on, might stay engaged longer, etc.
But mostly I figure all you can say is you heavily modified the truck and it's not overheating, so the periodic cycling is just an interesting curiosity and only mildly irritating. It's a lot of words to arrive at "Shrug, I dunno."
One thing I might mention is Toyota temp gages are not necessarily honest. They build in a pretty wide dead zone where the needle doesn't move much. So the gage may look pretty much the same at the t-stat value +/- 10°F. They go from ambient to operating and from operating to overheat fast. But if the needle moved too much during normal operation the dealer would be swamped with people worried that they're overheating at 205°F when normal is 195°F.
That brings up an interesting (at least to me) point. In Imelda I got the opposite effect. Going downhill on cool days the ARB would push too much air through (especially before it had a winch), the engine temp would drop and the heater would go cold. Kirsten always hated that when her feet would get a blast of winter air.
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cbmontgo
Hard Core 4+
A few years back, my 100 did the same thing one day. Luckily, the timing belt service was due, so I took it in to have it done while the cooling system was drained down. Their thought was that it was a bad thermostat.
New thermostat, water pump, and timing belt and the issue never came back. That was over 80,000 miles ago.
New thermostat, water pump, and timing belt and the issue never came back. That was over 80,000 miles ago.
Rzeppa
Rising Sun Member
I wonder why the old orange metal fans in our early rigs never had highway speed cooling issues?
Inukshuk
Rising Sun Member
The heater T issue is they fail catastrophically.
@chillbill T-stats are easy and inexpensive. Visit Mr T and get one!
View: https://youtu.be/1EII6jJC00U?si=NWPReG5ZAdNpgUUU
AlpineAccess
Hard Core 4+
I would replace the thermostat (get a new gasket at same time). Install with the bleeder at the 12 o'clock position.
Run some water through your radiator fins with a garden nozzle and then using AC condenser foaming cleaner, spray it through, let it sit, and wash out with a garden nozzle on a more forceful setting. You'll be surprised how much junk builds up in them over 20 years.
Throw your thermostat in water on the stove and see if it opens at 180-200 as a further confirmation.
Run some water through your radiator fins with a garden nozzle and then using AC condenser foaming cleaner, spray it through, let it sit, and wash out with a garden nozzle on a more forceful setting. You'll be surprised how much junk builds up in them over 20 years.
Throw your thermostat in water on the stove and see if it opens at 180-200 as a further confirmation.