92 FJ80 Overheating Going Uphill (1 Viewer)

[Woofythewolf]

I mean it SHOULD, but that assumes "normal driving" in "normal conditions".
Now for the Landcruiser, Toyota probably increased these bounds a lot vs other vehicles (like old jeeps), but I suspect they didn't mean pedal to the floor for 5 miles while under significantly reduced vehicle speed.

Most people would assume that hills requiring full torque in 3rd gear to get up aren't 5 miles long, and they'd be right to assume that.
Those are very extreme/unusual circumstances, and it wouldn't make sense to design to the requirements of .1% of users vs slightly increasing mpg for 99.9% of users. So they go with the 99.9% option and assume that the .1% of users will just have to drop into 2nd and go slower (2nd gear with its 1.5:1 ratio requires only 2/3rd the engine torque to achieve the same wheel torque). BUT, if it can be made to work even in those extreme circumstances, then why not do it for those who need it?

Toyota already showed us that thicker silicone oil is a valid method to improve cooling system performance with the supra.

 

[Michael Hanson]

I would think going up the hill slow is normal. Over heating is not. Mike

 

[Marco Lau]

I would think going up the hill slow is normal. Over heating is not. Mike

definitely not. OEM radiator never overheated, but it will run hot uphill with AC, as the needle creeps past just shy of 3/4.
WIth my brass/metal CSF unit as a replacement, it would overheat just on highway going around 75-80 with AC and my aftermarket temp gauge registers @ 215-220F,,,,replaced that with a all alum. Ron Davis, 192-195 on highway with AC, >200F on 4Lo or hill climb with AC...

 

[AndrewInf]

1FZ in my case but I replaced the radiator with a new Koyo unit, new Aisin blue hub fan clutch refilled with 15k cst fluid, I sealed the fan shroud on with foam, flushed the system multiple times, swapped to Toyota red coolant, all without alleviating my high temps.

The thing that fixed it was a new thermostat. The unit that was in there looked perfect, obviously worked somewhat, but I never did a stovetop test or anything so who knows, maybe it wasn't opening all the way. I replaced it as a "why the hell not" with a new Toyota unit (looked just like the one that was in there) and it was like night and day. Normal around-town temps on the Ultragauge went from 198-201 to 188-190, very soon after took a trip up to Los Padres and it handled that long uphill section of I-5 (one of those ones with tons of warning signs about "turn your A/C off!"), no problem. Ran a little hotter on those uphill hauls, but on par with my old pre-themostat replacement around town temps.

tl;dr: try a new thermostat, yours could be sticking even if it's not that old, could be some crud from your heater core got in there and is binding things up. As a $0 check you could leave the thing out and see if the temps still climb out of control on uphill grades. If the temps still suck then you have at least eliminated that possibility.

 

[jonheld]

I mean it SHOULD, but that assumes "normal driving" in "normal conditions".
Now for the Landcruiser, Toyota probably increased these bounds a lot vs other vehicles (like old jeeps), but I suspect they didn't mean pedal to the floor for 5 miles while under significantly reduced vehicle speed.

Most people would assume that hills requiring full torque in 3rd gear to get up aren't 5 miles long, and they'd be right to assume that.
Those are very extreme/unusual circumstances, and it wouldn't make sense to design to the requirements of .1% of users vs slightly increasing mpg for 99.9% of users. So they go with the 99.9% option and assume that the .1% of users will just have to drop into 2nd and go slower (2nd gear with its 1.5:1 ratio requires only 2/3rd the engine torque to achieve the same wheel torque). BUT, if it can be made to work even in those extreme circumstances, then why not do it for those who need it?

Toyota already showed us that thicker silicone oil is a valid method to improve cooling system performance with the supra.

Well, maybe it's me then.
I've driven my old 91 since 1991. Pulled a trailer across the country 4 times. Up and over I70 through the Eisenhower Tunnel heavy on the throttle in 2nd gear keeping it around 3500 RPM. Never had an issue.
The ONLY time in 25+ years I saw the temperature gauge move, was when the original fan clutch needed to be replaced and she couldn't hold temp at highway speeds.
But then again, I'm very proactive when it comes to maintenance and only use OEM parts.

 

[Woofythewolf]

In my case I have never seen it move either, except when the fan clutch failed while stuck in traffic one day. I was fine as long as I was above 30 mph, but traffic wasn't allowing that.
But I also have an FZJ80, and ours don't move until its way too late. I ended up getting new head because it warped 30 thousandths after that. It never even boiled over, it just got too hot on an engine that never had the headgasket PM done. (it wasn't worth it to my parents for an old vehicle "on its last legs")

Now that I have a digital temp meter (installed after doing the cylinder head), I've seen it climb to 203F on long grades like the grapevine in California. That was maybe an 85F day, climbing a 5 mile long 6% grade, in 2nd gear at 3800 rpm, going 55 mph at close to full throttle. So pretty much the same as your case. The dash gauge didn't move at all (as it is designed to, to reduce customer complaints) while the digital climbed 20F.

203F isn't overheating yet, but it's definitely warm. If I was in Arizona doing that on a 105-110F day, it definitely would've overheated. If I was towing a trailer at the max weight rating (so doubling the amount of weight I'm trying to pull up the hill), I have no doubt it would've overheated: that would be full throttle, at 3800 rpm, for 11 minutes instead of 5 1/2 minutes. (I would've been in first gear going 27 mph instead of 2nd going 55).

That's about as extreme of a situation as I ever expect to run into. If you have many drag-adders at once (big high rolling resistance tires, roof rack, RTT, a lift, lots of weight), are towing, or just have unusual environments (like the grapevine and Eisenhower Tunnel grades, or high temps like Arizona), then it stresses the vehicle to the limits of what a vehicle is normally designed to do.

And when you have multiple of those factors working against you at once, then maybe you should consider modifying the vehicle to be better suited for the job. Such as if I wanted to regularly tow a track car over the grapevine, I would probably take out my clutch and put in 20k fluid.


Edit: I guess what I'm trying to say is don't expect an even brand-new OEM cooling system to be entirely faultless when pushing it through extreme scenarios.

If its having problems on little hills and stuff, you've got an issue like bleeding or bad OEM parts (my brand new stealership thermostat almost overheated my fresh cylinder head job. That was a scare). If its having problems because you're at GVWR with giant tires and racing up a 5+mile mountain in hot weather, then its time to mod stuff because the stock system probably wasn't meant for that.

 

[reverendfj80]

Hey quick update.. After the new radiator was installed by a local shop (life got in the way so I handed it off) I was still overheating.. Per @Rush and @jonheld I went back to check the fan shroud.. Lo and behold there was about a 1.5" gap toward the bottom of the shroud and radiator (shroud wasn't inserted in the tab at the bottom of the radiator.. Reinstalled the shroud to make sure it had a good seal to the radiator and problem solved.. Just got back from the sierra nevadas and it drove like a champ.. With all the changes, I think the larger, all metal (no plastic) radiator did the trick.. I also believe my thermostat had issues.. Now it appears the temp gauge ticks up a hair then comes back down when taxing the engine.. Previously, gauge stayed in one place and then started to move up and kept going.. Thanks for all the suggestions.. Still don't have any heat out of the dash... Rear heater works fine.. More to do..

 

[okidokidodj]

Hey quick update.. After the new radiator was installed by a local shop (life got in the way so I handed it off) I was still overheating.. Per @Rush and @jonheld I went back to check the fan shroud.. Lo and behold there was about a 1.5" gap toward the bottom of the shroud and radiator (shroud wasn't inserted in the tab at the bottom of the radiator.. Reinstalled the shroud to make sure it had a good seal to the radiator and problem solved.. Just got back from the sierra nevadas and it drove like a champ.. With all the changes, I think the larger, all metal (no plastic) radiator did the trick.. I also believe my thermostat had issues.. Now it appears the temp gauge ticks up a hair then comes back down when taxing the engine.. Previously, gauge stayed in one place and then started to move up and kept going.. Thanks for all the suggestions.. Still don't have any heat out of the dash... Rear heater works fine.. More to do..

My 1997 LX450 is overheating on uphills also. I replaced all the cooling system parts with OEN except Radiator which I used all metal CSF but still over heating. I will double check the Fan Shroud Gap. What Kind/Brand of Radiator (parts no.) is your Radiator? Thanks in Advance.

 

[Michael Hanson]

Hi, No heat from dash back flush the front heater. Mike