Overheating (1 Viewer)

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Jun 3, 2015
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FZJ 80 family - needing help with some overheating issues.

On my 1995 FZJ80, I have been having some overheating issues mainly in the summer (above 80 degrees) taking on hills or pulling a heavy trailer on hills even in winter. I had the top end fully done +/- 30,000 miles ago, new radiator, thermostat, Blue fan clutch all Toyota/OEM parts replaced. I am still struggling to solve this issue.

One shop recommends I do the clutch fan mod, and another is saying that will not fix it based on the car is heating will it is moving and getting air. The other is saying I should do a thermostat mod with drilling a 0.25" hole in the thermostat.

Any advice?
 
I've never heard of drilling a hole thru the thermostat. You can buy different temp rated ones for not much $, so seems like a wasted effort, that is a band-aid fix, not addressing the problem.
Has this been recurring for years, or more recent development?
Seems like you've done plenty of work on it. Are all hoses new/er? How heavy is the trailer? Running AC during hill climbs? Heater on while towing in winter?
What kind of fluids are you running?

Here's some general suggestions: check your heater core, make sure its operating correctly. Get a lower temp rate T-stat. Make sure coolant is flushed, not just topped off. Make sure all (not just radiator) is flushed, and in good shape. Replace as needed, and consider bypassing rear heater if questionable.
 
So, I've towed a ~4000 lb load across the country with many mountain passes on a stock cooling system and it is horrible. I made it, but the stock cooling system is barely up to the task of keeping our engines cool when towing at USA freeway speeds. After the trip, I have since replaced every component of the cooling system, including all heater hoses, radiator hoses, water pump, (my blue hub fan clutch is already modded), and radiator. I did a lot of research and determined that the stock LC radiator is just not good. While it is built like a tank and uses extremely high quality components, it is actually pretty bad at cooling the engine for modern demands. After reading enough threads, I went for that cheapo TYC radiator. This almost killed me because I normally go OEM wherever I can, but the Arizona guys swear by this radiator for its superior cooling ability. I fully expect that I will only get a fraction of the life out of this cheap radiator, but my cooling woes are gone. It is unbelievably better at cooling these engines than the overbuilt brass dinosaur that is the OEM version.
 
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I've never heard of drilling a hole thru the thermostat. You can buy different temp rated ones for not much $, so seems like a wasted effort, that is a band-aid fix, not addressing the problem.
Has this been recurring for years, or more recent development?
Seems like you've done plenty of work on it. Are all hoses new/er? How heavy is the trailer? Running AC during hill climbs? Heater on while towing in winter?
What kind of fluids are you running?

Here's some general suggestions: check your heater core, make sure its operating correctly. Get a lower temp rate T-stat. Make sure coolant is flushed, not just topped off. Make sure all (not just radiator) is flushed, and in good shape. Replace as needed, and consider bypassing rear heater if questionable.

@YMT It's been doing this for the last +/- 3 years but mainly on hot days or towing on hills. Only does it on steep hills. I can drive it from Portland to Seattle with no problem. All new hoses from Toyota. Do not know the trailer wait. Yes, on running the AC during hill climbs? We put the heater on while towing in spring from San Diego to Portland and still had issues.
On the fluid, I'm running Prestone Antifreeze + Coolant 50/50.

Thank you for the current feedback.
 
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:bounce: :bounce2::bounce::bounce2::bounce::):):):bounce::bounce2::bounce::bounce2:
 
@Jason031 The fan clutch mod certainly won’t make your situation worse and might help. Which radiator are you currently running?
 
@baldilocks I'm running a new OEM Toyota radiator installed 4 years ago.
It has an Aluminum core or copper core? If it’s copper, switching to the Aluminum unit will probably help. I ran a brass/copper CSF radiator for a couple years and it would always fall behind during warm months.
 
Are you gearing down for the hills? Specifically holding 2nd gear at 3000-4000RPM for the entire grade. Even if the rest of your cooling system is dialed in this will help on the hills.

Just yesterday I made the climb up three passes on US20 (starting in Newport, OR, ending in Sisters, OR) without issue. We were fully loaded for camping, it was in the mid 90F range and I had the AC on the whole time. 2nd gear played a key role.
 
Are you gearing down for the hills? Specifically holding 2nd gear at 3000-4000RPM for the entire grade. Even if the rest of your cooling system is dialed in this will help on the hills.

Just yesterday I made the climb up three passes on US20 (starting in Newport, OR, ending in Sisters, OR) without issue. We were fully loaded for camping, it was in the mid 90F range and I had the AC on the whole time. 2nd gear played a key role.

Second gear has NO torque convertor lock where third gear has TC lock so if you can have it 3rd on 3000 rpm its better and fix your cooling system

If you have the option to disengage the CDL on Low you can drive it on 4rd TC locked up
 
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This may be a dumb comment and not at all applicable, but I did not consider it on my first trip on my 97. Did you switch the overdrive off? I ran hot from So Cal to the Sierras, when my cousin asked me that. Switched it of for any climbs after that and seemed to help.
 
Second gear has NO torque convertor lock where third gear has TC lock so if you can have it 3rd on 3000 rpm its better and fix your cooling system

If you have the option to disengage the CDL on Low you can drive it on 4rd TC locked up

It just depends on how steep and long the climb is. For moderate climbs OD off is plenty but for the steeper ones I go with 2nd to keep it above 3000rpm. A few years ago going up Teton pass I had to use 1st since it was so steep and I was behind a slow motorhome.
 
If you've done the blue fan clutch mod consider using heavier oil. That made a 10 degree difference for me at highway speeds and on hill climbs. My truck ran around 206 most days. Now it rarely goes over 196. I'm running 35s with full armour and an auxiliary fuel tank so the truck is heavy all the time. I switched to 30K weight oil.
 
It just depends on how steep and long the climb is. For moderate climbs OD off is plenty but for the steeper ones I go with 2nd to keep it above 3000rpm. A few years ago going up Teton pass I had to use 1st since it was so steep and I was behind a slow motorhome.
The peak torque for the 1FZ-FE is about 3400 RPM IIRC. If you keep your engine RPM in that range while pulling mountain hills, youo are staying in the engine's "power band" and you get more work per revolution. It the engine will run "cooler" because it is doing it without overworking it. If you are below that RPM, you are lugging the engine. If you are above it, you are burning excess fuel for what you need unless your next gear pushes you too far below.

I would strive to keep the RPM between 3000 and 4000 during those pulls. That will be it's happy range. The 3FE is about 200 RPM lower than that IIRC.
 
So Cal has been toasty the last two weeks, upgraded water pump and Wits End blue fan clutch dramatically lowered temps 190- 203 max. That’s air full blast and typical stop and go traffic in 104+.
 

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