Overheating with AC on

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MACKSDAD

MACKSDAD

Joined
Aug 8, 2020
Threads
34
Messages
190
Location
Nor Cal
My 100 series is overheating when I have the AC on only. It’s not super hot but the trans temp and coolant gets to around 205-210 going up the mountain to my house. I noticed today if I turn off the AC when I do go up the highest it would reach was 193 and the trans didn’t go over 170 which seemed more normal to me.

I just replaced the fan clutch , new fluid, new thermostat, and my radiator is only a couple years old denso unit.

Is there anything anyone can suggest I check next based off my symptoms only being a problem with AC on? & no I don’t want to drive home without it on 107-112 degree days.

Thanks!
 
Heater core? Mine was leaking from old/cracked hoses running into/out of the front heater core. Core, itself, was fine…but bad hoses/core could be your issue.

Easy to bypass the heater cores. Someone makes a kit. You could bypass it and see if it solves the issue.
 
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b004a855-397f-4e54-860c-e33ad263de17-jumbo1x1_L.V.HEATCARSAFETYPkg.transfer.transfer_frame_1685.webp
 
Hello MACKSDAD,
Here's a couple of other things to consider.

Radiator Cap.
If it's old, replace it with an OEM Toyota / Lexus one.

Are you using Toyota Red or Pink Coolant?
If not, I believe there's only 1 aftermarket equivalent that's also Red.

When's the last time you had your Timing Belt / Water Pump replaced?

What year is your LC / LX?
Early (1998 to 2002 I believe...) has an Auxiliary Fan.
Late (2003 to 2007) does not.
One of the threads below discusses this.

Here's 2 threads to check out.

LandCruiserPhil

Thread 'How to get peak AC performance from your 2003+ 100 series'

As of 2003 Mr T deleted the electric condenser fan from our 100 series Land Cruiser. Along with the fan delete they changed the way the air ducts into the radiator. The fan delete and re- ducting works great at speed but AC performance suffers when stopped or setting in heavy traffic. Recently I had my AC go hot on a 113° day Click HERE for the story.

Some interest was shown on creating a bolt in set up for adding back in the electric condenser fan. I put together a kit with the needed parts to bolt in a factory or factory replacement electric fan in a 2003 - 2007 LC or LX470...
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Rpreme

Thread '2UZ-FE Normal Operating Temperature'

Hi Mudders!

I've searched the 100 series forums and couldn't find a definitive answer.

What is the normal operating temperature for the 2UZ-FE during normal driving conditions? In cooler and warmer climates?

I currently have a 98 with 169,000 miles still equipped with the original radiator that was recently flushed at Toyota. I installed my scangauge II and been reading 195-197 at its peak. Would like to know what is safe operating temperature for safe measure as I am running the original radiator.

Any feedback or personal experience would be greatly appreciated!

Good luck.
Tom
 
G-Cat said:
Heater core? Mine was leaking from old/cracked hoses running into/out of the front heater core. Core, itself, was fine…but bad hoses/core could be your issue.

Easy to bypass the heater cores. Someone makes a kit. You could bypass it and see if it solves the issue.
Click to expand...
Could be this but not experiencing any symptoms typically involved with that but mine looks original so that’s a helpful start!
Snow Wagon said:
Hello MACKSDAD,
Here's a couple of other things to consider.

Radiator Cap.
If it's old, replace it with an OEM Toyota / Lexus one.

Are you using Toyota Red or Pink Coolant?
If not, I believe there's only 1 aftermarket equivalent that's also Red.

When's the last time you had your Timing Belt / Water Pump replaced?

What year is your LC / LX?
Early (1998 to 2002 I believe...) has an Auxiliary Fan.
Late (2003 to 2007) does not.
One of the threads below discusses this.

Here's 2 threads to check out.

LandCruiserPhil

Thread 'How to get peak AC performance from your 2003+ 100 series'

As of 2003 Mr T deleted the electric condenser fan from our 100 series Land Cruiser. Along with the fan delete they changed the way the air ducts into the radiator. The fan delete and re- ducting works great at speed but AC performance suffers when stopped or setting in heavy traffic. Recently I had my AC go hot on a 113° day Click HERE for the story.

Some interest was shown on creating a bolt in set up for adding back in the electric condenser fan. I put together a kit with the needed parts to bolt in a factory or factory replacement electric fan in a 2003 - 2007 LC or LX470...
  • Like
  • Love

Rpreme

Thread '2UZ-FE Normal Operating Temperature'

Hi Mudders!

I've searched the 100 series forums and couldn't find a definitive answer.

What is the normal operating temperature for the 2UZ-FE during normal driving conditions? In cooler and warmer climates?

I currently have a 98 with 169,000 miles still equipped with the original radiator that was recently flushed at Toyota. I installed my scangauge II and been reading 195-197 at its peak. Would like to know what is safe operating temperature for safe measure as I am running the original radiator.

Any feedback or personal experience would be greatly appreciated!

Good luck.
Tom
Click to expand...
I have a 2001 . I think I reused my original OEM cap when I changed the radiator. Not sure if they go bad? This is on my list to do forsure.

Timing belt was done 60k ago along with water pump. I was going to change it when I did my fan clutch bracket but I decided not to because it looked in perfect condition still.

I’m using zerex red coolant mixed with some napa red coolant. (Was what I had laying in garage) does the Toyota red really work that much better?
 
Radiator caps can go bad.
I'd absolutely replace it.

Yours should have an auxiliary fan.
I believe it should come on when the A/C is turned on, and also when your engine reaches a certain temperature.
I'd make sure it's coming on.
If it's not coming on, could be either the switch or the fan motor.

Good luck.
Tom
 
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Bump. Replaced radiator cap. No difference. Aux fan seems to be working . Trans temps were around 220 today going uphill in 90 degreee heat. AC on.

Trans fluid looks clean and at correct level. Brake fluid is a little high it looks like which I saw somewhere someone say that could cause overheat. Maybe it was on @2001LC other thread.

The trans and water temps are almost going up at the same time. But the meter on the dash stays right in the middle the whole time. What temp would dictate the needle going up higher than usual?

Thanks
 
2001LC

Thread 'Radiator fins need cleaning! Alert Alert Alert'

I've a 06LC w/192K I just bought. In reading history I found PO complained of engine temp raising when both front and rear AC on. Toyota Dealership diagnosed with clogged radiator fins. Recommended new OEM radiator, $600 for the US spec Radaitor plus coolant and labor. They should have added radiator cap and thermostat to job, as best practice.

Got me to thinking about the radiators I've been replacing. All have debris built up on lower third.
This one hand some extra grasses along with general clogging on lower third.
Radiator Clog (3).JPG

Over the years/miles debit builds up in condenser and...
  • Like
 
MACKSDAD said:
Bump. Replaced radiator cap. No difference. Aux fan seems to be working . Trans temps were around 220 today going uphill in 90 degreee heat. AC on.

Trans fluid looks clean and at correct level. Brake fluid is a little high it looks like which I saw somewhere someone say that could cause overheat. Maybe it was on @2001LC other thread.

The trans and water temps are almost going up at the same time. But the meter on the dash stays right in the middle the whole time. What temp would dictate the needle going up higher than usual?

Thanks
Click to expand...
Coolant is not circulating effectively around causing the engine coolant temperature to go up. Could be the thermostat which is the gatekeeper to allow the coolant to flow around. Could be the water pump to push the coolant all the way around the system. The water pump is mechanically driven or spun by the viscous fan clutch connected by the drive belt spun by crankshaft through the crank pulley. Having a clear coolant is good but wouldn’t be able to tell if the radiator has a reduced flow rate (clogged partially). These are the things I would check to eventually solve the overheating.
 
220°F of transmission temperature is high (safe threshold is around 200°F max, if maintained through prolonged periods of time that would cause AT problems. After around 30 minutes of driving around, I would check the overflow plug in your AT pan, remove to see if there’s a little of overflowing fluid, if there’s none at all, that needs a top up.
 
All best to post year of 100 series. In your signature line. Also any mods.

All 3 Radiators, fins, must be keep clean.
Thermostat jiggle valve must be at top.
Air must be removed from system. We check it is. By removing radiator cap, when engine cold (in AM before sun up.
Cap must be working properly.
Reservoir must be working properly. It's hose must be straight and go to the bottom, and can not have any obstructions.
Best to have correct coolant, OM states for your year.

AT must have correct ATF, and be at correct level.

Fuel trims. If running lean, cylinder head temp goes up.
 
2001LC said:
All best to post year of 100 series. In your signature line. Also any mods.

All 3 Radiators, fins, must be keep clean.
Thermostat jiggle valve must be at top.
Air must be removed from system. We check it is. By removing radiator cap, when engine cold (in AM before sun up.
Cap must be working properly.
Reservoir must be working properly. It's hose must be straight and go to the bottom, and can not have any obstructions.
Best to have correct coolant, OM states for your year.

AT must have correct ATF, and be at correct level.

Fuel trims. If running lean, cylinder
Click to expand...
I just put on a new rad cap. Doesn’t seem to have air in system. Even driving slow in 55 degree weather gets the water temp up to 190 pretty quickly. Transmission only goes over 200 when I’m going uphill to go home (about 40 mph up a grade for about 15 mins) I have a new thermostat I installed with jiggle valve at 12 o clock. I do notice the smaller fan on passenger side infront of radiator only comes on if I have ac on. Is that normal ? Or shouldn’t it turn on when engine is warm? Going to check trans fluid now. Dipstick says it’s full but going to check fill plug now.
 
I guess there’s no fill plug on the 01 trans? I only see the drain .
 
MACKSDAD said:
I guess there’s no fill plug on the 01 trans? I only see the drain .
Click to expand...
you should have a dipstick under the hood near heater T's
 
Curious, what is the max that the water temp should be? I have a scan gauge and I've had the rig (2000, has bumpers and winch) less than a year.

Got the Scangauge for Christmas and was running at 188°F no matter what, everywhere, in all types of weather for a couple of months, then I did some mild offroading and since then it's been wanting to run hot.

It can be 60° and cloudy or 106° and sunny and either way, it will rise to about 204° water temp under load.

I've hosed out the radiator pretty thoroughly and coolant is full.
 
Cruiserlab said:
Curious, what is the max that the water temp should be? I have a scan gauge and I've had the rig (2000, has bumpers and winch) less than a year.

Got the Scangauge for Christmas and was running at 188°F no matter what, everywhere, in all types of weather for a couple of months, then I did some mild offroading and since then it's been wanting to run hot.

It can be 60° and cloudy or 106° and sunny and either way, it will rise to about 204° water temp under load.

I've hosed out the radiator pretty thoroughly and coolant is full.
Click to expand...
I’d check thermostat and fan clutch health first. 180-190 seems to be pretty average for most people.
 
MACKSDAD said:
I just put on a new rad cap.
Click to expand...
OEM?
MACKSDAD said:
Doesn’t seem to have air in system.
Click to expand...
"seem" Very easy to determine.

Park overnight, after reaching operating temp and ~3K RPM for ~3 minutes or more. Park on level ground or better yet, with front end higher than rear. This places radiator cap at high point. Air travels to high point!
In the morning, after engine has cool down for ~8 hours. Remove rad cap, before sun-up. Coolant should be to the very top of radiator. No air whatsoever.
MACKSDAD said:
Even driving slow in 55 degree weather gets the water temp up to 190 pretty quickly. Transmission only goes over 200 when I’m going uphill to go home (about 40 mph up a grade for about 15 mins)
Click to expand...
That is to hot ECT and ATF.

I just drove my 03LX w/323K miles from Den on I-70 west over the continental divide 252 mile, to GJ in the AM. Did not shut off engine the whole way. Running long distances at speeds of ~82 MPH where I could (75MPH speed limit). Other times crawling along for the many road construction projects. Actually pushed it very hard for a few minutes hitting 110 MPH. Climbing multi pass from 1 mile high (Denver) to 2 mile altitude (Eisenhower & Vail passes). OAT range was 64f to 74f.
ECT never over 187f, ATF temp never over 165f.
I'll note I shift a lot. You never see me brake, except emergency running the Rocky Mountains. Point, I don't baby the engine or AT, I push them to their limits.
IMG_1500.webp

MACKSDAD said:
I have a new thermostat I installed with jiggle valve at 12 o clock
Click to expand...
OEM?
MACKSDAD said:
. I do notice the smaller fan on passenger side infront of radiator only comes on if I have ac on. Is that normal ? Or shouldn’t it turn on when engine is warm?
Click to expand...
Normal
MACKSDAD said:
Going to check trans fluid now. Dipstick says it’s full but going to check fill plug now.
Click to expand...
ATF should be at ~160F, engine idling, pull AT dipstick. It should read in HOT range. Best if at or tad above high hot notch.

Again. All 3 radiators fins must be clean.
I drove an 06LC back from GJ to Den. OAT range 91f to 69F. It ran around 194 to 200F 06 - 07 do run hotter, with their different fan blade & fan clutch. It would go to 210F with AC on, which it should not go over ~199F. I send the morning washing bugs and Moab dust from its radiators.
2001LC

Thread 'Radiator fins need cleaning! Alert Alert Alert'

I've a 06LC w/192K I just bought. In reading history I found PO complained of engine temp raising when both front and rear AC on. Toyota Dealership diagnosed with clogged radiator fins. Recommended new OEM radiator, $600 for the US spec Radaitor plus coolant and labor. They should have added radiator cap and thermostat to job, as best practice.

Got me to thinking about the radiators I've been replacing. All have debris built up on lower third.
This one hand some extra grasses along with general clogging on lower third.
Radiator Clog (3).JPG

Over the years/miles debit builds up in condenser and...
  • Like
 
I am going to agree on checking the radiator, condenser, and trans fluid cooler fins. Seems to me the most likely thing that would impact the engine and transmission temperatures.

Second guess would be thermostat / water pump or maybe coolant level, but I believe that would only show up as a hot engine temp.
 
I wanted to offer my input. I recently replaced the radiator on my 2000 LX470 with a new Denso unit. I took my rig wheeling 3 weeks ago and I noticed on my scanguage I had crossed 200 degrees for the first time ever. Then I hit 215. Trans temp hit 200.

I was legit shocked. I came home, double checked and attempted to burp my cooling system to no air bubbles coming out.

I have been piecing together my timing belt kit and this prompted me to test my Fan Clutch. Every test passed except when the LX is at operating temp, I turn it off, I should not be able to turn my fan by hand. My fan clutch should be fully engaged. It isn’t. I can freely spin the fan, at full operating temp. My fan clutch is not working correctly at cooling. I will be doing a full timing belt replacement, fan clutch, fan bracket, and all pulleys. As soon as this is done, I will report back.

But I suspect, the fan clutch might be the culprit in your case as it was in mine.
 
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