***Resolved*** FZJ80 Coolant Temp Hot While Climbing (1 Viewer)

Joined
Apr 12, 2020
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Seattle WA
Hello fellow Mudders, a couple of weeks back I was ascending Stevens Pass (interstate mountain pass) and as I approached the top of the climb, I noticed the coolant temp starting to move from the middle, where it had always been, closer to the red. The FZJ80 had been up this pass and others earlier that month without any issues whatsoever. As I reached the top and started the descent, I kept my eye on it and watched it return the spot right below 50%, where it normally stays. The next day returning, the same thing happened; I paid close attention to it made sure it didn’t get close to the red and watched it return to normal on the descent. I spoke with my local Land Cruiser experts who flushed the system a few months back and they thought this could be a bad fan clutch or a thermostat issue. I decided to purchase both OEM parts before a upcoming trip this weekend but was only able to install the fan clutch. Going across the pass the coolant temp started to rise again just like last time—so much in fact that I decided to pull over at the top and left her running to cool down. This basically happened on most major climbs for the rest of the trip. Turning the heater on full blast seemed to help, but this wasn’t preferable due to it being 90+ degrees outside, and the trail was extremely dusty, so keeping the windows down was difficult. The temp sits fine when idling, when in traffic, and when on the regular highways; it only gets hot while climbing. Do you think this could be a T-Stat issue?

Vehicle Info 96 FZJ80 206000 miles
Head gasket done 40k miles ago
Coolant flush done a few months ago Toyota Red Coolant
New fan clutch and radiator cap installed before my trip this weekend
35 inch tires

Any help would be greatly appreciated, I’m just trying to stay cool. 😎
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flintknapper

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Not a bad thing to replace the T-Stat if it is very old.

But also be sure to use some 'driver input' on steep grades. Unlock overdrive, shift to a lower gear where necessary in order to keep your engine in its power band if you aren't already doing this.

Many folks just leave the trans in drive (OD on) and let it downshift on its own....but too many times that is lugging the engine.

Perhaps not your issue...but just so folks will know.

Lastly, I recommend getting and installing a ScanGauge so you can monitor your coolant temps (and other things) real time.

The dash gauge on an 80 series is notorious for having a big 'dead spot' in the middle where it won't move until you are nearly overheated.

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desmocruiser

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Not to be one to ask a member to search, however there are many threads that are good read‘s to help understand how the gauge was designed to react, it’s shortcomings, and what is normal operation to compare what you are experiencing. In full disclosure, I am not indicating you don’t have a compromise somewhere, just it has been frequently discussed.

If I remember, even some old school members modified the gauge to react more quickly.

My fully loaded 80 with a TRD SC has gotten hot enough in the Summer to kick off the AC compressor climbing Vail Pass. I have gone as far as removing the fog lights in hopes that it would increase airflow enough to remedy.
 
Joined
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What fan clutch was installed? These trucks are very fan dependant, even at speed. Does your fan roar at start up? If you have a new stock blue hub fan clutch and it isn't roaring at start up I would take it back out and drain the oil out and replace it with a higher CST oil. I ran 20,000 CST in mine and it works great in the Utah climate, many threads on MUD about this if you search. Also how old is your radiator? May be time for a new one.
 

77mustard40

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Echo the fan clutch test. On mine when I first got it, I could spin the fan by hand. Installed a blue hub when I did the oil pump seal, crank seal and belts. I didn’t do the MOD but it’s been fine so far this summer.
 
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If what you posted is the only coolant work that has ever been done on the truck I would strongly recommend everything else in the coolant system with new oem parts. Not trying to be dramatic but all those hoses are 20 years old. It only takes one small hole in any one of them to cook your engine or leave you stranded. Thermostats are cheap, just put one in. The heater valve gets brittle and can crack easily when old. Water pump is not really that expensive, has 200,000 on it and is so important. Lastly the radiator. Yes it is expensive. But they do fail and dont cool as well as they age. Just buy a oem one while you can still get one.

In the big scope of things it is not that much for a really critical system. Stick with oem and save a tone of work and just do it all at once.

I am not trying to be a jerk but I have been saying this for years. Think about how much cheaper this all is than doing a head gasket after it over heats and then still having to fix the coolant system.
 
Joined
Apr 12, 2020
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Seattle WA
Not a bad thing to replace the T-Stat if it is very old.

But also be sure to use some 'driver input' on steep grades. Unlock overdrive, shift to a lower gear where necessary in order to keep your engine in its power band if you aren't already doing this.

Many folks just leave the trans in drive (OD on) and let it downshift on its own....but too many times that is lugging the engine.

Perhaps not your issue...but just so folks will know.

Lastly, I recommend getting and installing a ScanGauge so you can monitor your coolant temps (and other things) real time.

The dash gauge on an 80 series is notorious for having a big 'dead spot' in the middle where it won't move until you are nearly overheated.

View attachment 2384963

I have no idea when the thermostat was last changed so I’ll start there!

I had the OD off and as the rpms increased so did the temp. You could definitely tell it was working hard!

The PO had it set up for a scangauge and that will be my next purchase.

Thanks for all you suggestions! I’ll get started on this tomorrow.
 
Joined
Apr 12, 2020
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Location
Seattle WA
What fan clutch was installed? These trucks are very fan dependant, even at speed. Does your fan roar at start up? If you have a new stock blue hub fan clutch and it isn't roaring at start up I would take it back out and drain the oil out and replace it with a higher CST oil. I ran 20,000 CST in mine and it works great in the Utah climate, many threads on MUD about this if you search. Also how old is your radiator? May be time for a new one.

Just installed a new OEM blue fan clutch. It roars at start up. I’ve been reading a lot about changing the oil and will be doing that soon. The PO kept great records and I don’t recall seeing a new radiator on any of the invoices. I’ll check again tomorrow. If the radiator is bad is this something a shop will be able to test for?
 
Joined
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Salt Lake City, Ut. 84106
Just installed a new OEM blue fan clutch. It roars at start up. I’ve been reading a lot about changing the oil and will be doing that soon. The PO kept great records and I don’t recall seeing a new radiator on any of the invoices. I’ll check again tomorrow. If the radiator is bad is this something a shop will be able to test for?
Any reputable shop should be able to tell the condition of the radiator or refer you to a radiator shop who can. Here in Salt lake there is a shop called J-Mac radiator that specializes in that, you may have something similar in your area.
 

Dirty Koala

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New OEM TRAD radiator is about $400, Ron Davis is about $1200. I wouldn’t bother trying to test, radiators wear out and if you don’t have record of it being changed, best to assume it hasn’t and do it while you can still get them. OEM Aisin Water pumps are not much over $100 from Cruiser Outfitters...hoses and thermostats are cheap. Couple bottles of 20k or 30k CST fluid to modify your fan clutch will cost you $10-$15. Do it all at once and save yourself the headache of trying to work around an installed radiator.
 
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Pretty much all the bases have been covered here:

1) real temp gauge is a must. I got the Koso digital one. Scangauge works fine too.
2) Probably time for a new radiator. If you're having temperature troubles, go with an aluminum/plastic one rather than the solid brass. The aluminum ones cool better. Toyota is good, but not a requirement. I got a TYC 1918 for cheap on amazon and it dropped my temperatures about 5-10* across the board for the same conditions.
3) modify your fan clutch so it pulls more air.
4) High RPM actually helps the fan pull more air and circulate coolant, so turn off OD and leave it in 2nd gear if needed. Seems counter intuitive to rev the engine to shed heat, but it works. Side benefit is lower transmission temps as well.
 

desmocruiser

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Old school members? Is the real time temp gauge mod no longer on the short list for new owners?

Well it has been a few years since I built an 80 and have recently renewed my fascination with them, so most things I recall, I consider old school.

I hope all the significant contributions are still being used, but the 80 forum seems like a whole new place!
 
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Calrsbad, CA
My 60 had the same symptoms as the OP with a newish fan clutch and new t-stat. The rad was clogged. New rad cured it. Considering the OP's records and what has been recently replaced, I would replace the rad per Heckraiser's suggestions. And I second(+) getting a real temp gauge; I watch my scan gauge like a hawk.
 
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Va Beach
While it worked, it drove people crazy with it constantly moving and still not providing any better data on temp compare to digital gauge of sorts.
Huh, never knew anyone had any issues with it. Mine seems to work fine. I did have one that would jump around but it was a cold solder issue and after I resoldered it's been good.
 
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Well it has been a few years since I built an 80 and have recently renewed my fascination with them, so most things I recall, I consider old school.

I hope all the significant contributions are still being used, but the 80 forum seems like a whole new place!
Yea I can see that. I don't spend much time on here anymore because it causes me to add to my to do list 😁

I went with a TYC a year or two ago and it's been great. It was thicker core than stock and seems to stay a little cooler and that is also with a black hub fan clutch with 10k fluid but haven't seen it even close to the red with this setup. But for other cars I have used an all aluminum and that's really the way to go. I just put a Mishimoto in my Yukon tow vehicle and it has been amazing. It's a work of art, coolant stays perfect, trans is about 20-30 lower, built in engine oil cooler. Also have a Dewitt's in my Camaro track car and have the same quality in that. Unfortunately I don't think either make a direct fit but they both have universal radiators that could work for the Cruiser.
 
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MoJ

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Thermostat and radiator. Don’t bother with modifying the water temp gauge. Just grab Bluetooth or WiFi capable obd2 module ($15) and the appropriate app for your phone ($10).
 
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I just wanted to say thanks for everyones's help and suggestions. Just put in a new radiator, water pump and thermostat along with some new belts. Hope this fixes the issue. Ill keep you posted after my next trip.
 
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Thanks for everyone’s input, this issue is resolved! I put in an OEM thermostat, OEM water pump, OEM belts, OEM radiator hoses and cap, Landtank modified fan clutch, and a Koyo A1918 radiator. I just took it up the pass on a hot day and it stayed as cool as a cucumber. I’m assuming the issue was the radiator by the looks of it. While climbing I didn’t get over 190 degrees. Thanks again and please let me know if you have any questions. Thanks again.

First pic is the scangauge at the top of the pass.
Second pic is the old radiator.

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