Driving in Extreme Heat with Heavily Modified Rig (Heavy)

[mtbtim]

The auto transmission temps r the the major contributor to the engine temp increase with the heavily (weight added) modded runners, getting heat-soak from said that is transferring to the engine. I believe may peeps r not understanding the difference between overdrive and T/C lock up. The amount of heat being introduced to the system when the auto trans is not locked is massive and when U add hills and weight to the vehicle they can quickly overcome the cooling ability of the OEM and modded cooling system if not monitored. There R any # of things one can do to help cooling (ie increased air flow, larger amounts to fluids, fans, decreasing weight, etc, etc.) After modding my 4runner (adding large amounts of weight) one of the best mods I did was to add an idiot light to show lockup, this taut me how to drive said and lower my temp massively. Removing the trans lines from the radiator and running a standalone cooler removed the trans temps being added directly to the engine coolant, the trans "cooler" on the bottom of auto rads were places there to help warm the trans fluids and bring them quickly to operating temps the trans fluid required (depending on what fluid is used these operating temps can be significantly lowered). By watching lockup my trans temp run 120-130degs on the hwy normally.

The trans lock timing and be altered by running diff gearing, with dual tcase (4.7 in one) I could get the system to lock up at 9mph on the trail.

You are right that some don't know that locking up the torque converter can lower their automatic trans temps, but I'm not one of them. During the drive through the desert, I was driving with overdrive off and I was regularly in that sweet spot between around 45 mph and 60 mph that allowed the torque converter to stay locked and keep my trans temp down. When my engine was screaming at around 208, my trans temp was at a very optimal temp, around 180. Can the trans cooler in the bottom of the radiator add heat to the coolant? Sure it can. Is it having the affect you think it is, I don't agree. On my 2000 that is very stock, I can have my trans temp at 230 on a sustained grade that's not allowing a high enough speed for the torque converter to lock up with overdrive off but my engine temp is at a very comfortable 190-194.

The strain on the engine due to the weight I'm carrying is what's causing the engine to run hotter and it's not because the trans cooler is adding excessive heat to the coolant.

I can also run a trans temp of 120 to 130 on the highway as long as I'm not climbing a grade or driving in extreme temps like 115-120 degrees. But, maybe you know this but maybe you don't. 120 - 130 is not an optimal ATF temp. Optimum temp for ATF is around 170. There is such a thing as running too cool. This is why engines have thermostats so they will run at the optimum temp for the engine oil to lubricate the engine properly.

 

[mtbtim]

It sounds like you may be pushing the 4Runner platform to its limit with all the bolt on armor, gear, tires, etc. I'm all about the 4Runner but if I was going to drag all that gear and people into the back country it may be safer, more comfortable and more reliable in a heavier duty platform to start with. Just my .02.

I tend to agree with you. I was just wondering what some guys are doing that have similarly built rigs and regularly drive in extreme temps. I think the re-gear will help out quite a bit. I don't plan on driving my rig in environments like I just did very much if at all again. I do like Death Valley and even in the spring, you can be faced with some pretty hot temps. I did a trip this last spring and there was one crazy steep grade that I gave my rig a rest a few times on because my engine temps were spiking.

 

[mtbtim]

Working in transport refrigeration, when I see high engine temps I immediately start with with a radiator/condenser wash-out to see if that corrects the issue. These are engines that run for hundreds of hours at a time in temps from -30F to 120F+, sometimes higher. If dirt, dust, and bugs are clogging the airflow, you're not getting efficient heat loss.

I have no idea where you'd go for a car or truck, we use a wide-spray pressure washer and Hydra-Brite acid solution on most models.

It's only been in the high 90's here, 2002 auto on 33's, front and rear ARB, Sherpa roofrack. Seeing 184 at 65 mph, 188 at idle. Both with AC on.

No doubt a cleaning of the cooling fins could help. How much it would help, I don't know. My AC condenser wasn't that dirty the last time I checked but I will give a cleaning soon because it couldn't hurt.

My rig can handle high 90's no problem, but take that temp and put me on a sustained grade causing my engine to work hard, my engine temps will no doubt climb. The 215-220 temps I was driving in is a whole other ballgame. With the grades I was climbing and the extra weight I was carrying, the engine wasn't liking it even on fairy flat sections of the highway.

 

[mtbtim]

What were your transmission temps doing Tim?

I received my OBDLINK MX+ yesterday.
I made an 1 1/2 hour trip in 96* degree weather (~105* intake temp. ). Lots of uphill/downhill on the interstate with the cruise set @ 81mph and AC on. I found that the trans temp would spike when the calculated load hit 65-70%. I actually hit 249* at one point when I exited the interstate and my airflow over the radiator dropped down. My water temp never went past 210*.

I came home early this morning when it was 20-25* cooler. Running no AC and doing 77 MPH. Trans temp didn’t have any major spikes.
I was shifting OD OFF both ways when the calc load hit 65% on the uphills.

I learned what I long suspected - I need a trans cooler.

My 2001 rig is basically stock with 32 inch MTs and 99 tall springs.

My trans temp was good because I was turning overdrive off where appropriate to lock the torque converter. When my engine temps were very high, my trans temp was at a very optimal 170-180. They were sometimes higher than that when my rig was crawling up a steeper grade, but for the most part, I was able to keep my trans temps down when I was driving in the extreme heat through the Nevada desert.

 

[mtbtim]

You could have turned on the heater full blast and then opened the windows so you don't get steam cooked. Turning on the heater helps in dissipating heat from the coolant

I used that technique when I was driving up the steeper grades. On one crazy steep and sustained grade in Nevada, I had the heat on full blast, windows down, AC off and the lowest I could get my engine temp was 208. It wasn't fun doing this but it was better than the other option of pulling off on the side of the highway to give the engine a break and cool off a bit.

This was my worst driving experience ever in one of my rigs. But, knowledge is power. If I wasn't monitoring my engine temps, I could have been one of the many people we saw stranded on the side of the highway that had no clue they were overheating their engine. Our analog temp gauges are pretty much worthless. By the time the needle starts to rise, you've already overheated your engine big time. On the trip, there was no difference in needle position from an optimal 188-192 engine temp and the high of 212 I got my engine to.

 

[Endlessblockades]

I used that technique when I was driving up the steeper grades. On one crazy steep and sustained grade in Nevada, I had the heat on full blast, windows down, AC off and the lowest I could get my engine temp was 208. It wasn't fun doing this but it was better than the other option of pulling off on the side of the highway to give the engine a break and cool off a bit.

This was my worst driving experience ever in one of my rigs. But, knowledge is power. If I wasn't monitoring my engine temps, I could have been one of the many people we saw stranded on the side of the highway that had no clue they were overheating their engine. Our analog temp gauges are pretty much worthless. By the time the needle starts to rise, you've already overheated your engine big time. On the trip, there was no difference in needle position from an optimal 188-192 engine temp and the high of 212 I got my engine to.

What amazes me is the blissful ignorance a majority of 3rd gen 4runner drivers have been operating under (factory needles only) all these years. That is a testament to Toyota's engineering. These have gained a reputation for reliability even though I suspect many drivers were unknowingly operating at above optimal temps - yet these have soldiered on. I cringe when I remember the times I flew up to Tahoe (sea level to 8k) without a care (nor complaint from the rig) not knowing I was running a hot trans and coolant system! Seeing 249 degrees transmission oil reading on my UG on a desert dirt climb was a wake up call. Those issues have been addressed thanks to content from people like you. These can take a lot of abuse, but I think that a modern "must-do for a new-owner" maintenance Top 3 List should include a metrics tool!

LBJ/Radiator/OBDII app or gauge.

Good luck on your quest, Tim - we all benefit when you encounter an issue!

 

[clearock]

You are right that some don't know that locking up the torque converter can lower their automatic trans temps, but I'm not one of them. During the drive through the desert, I was driving with overdrive off and I was regularly in that sweet spot between around 45 mph and 60 mph that allowed the torque converter to stay locked and keep my trans temp down. When my engine was screaming at around 208, my trans temp was at a very optimal temp, around 180. Can the trans cooler in the bottom of the radiator add heat to the coolant? Sure it can. Is it having the affect you think it is, I don't agree. On my 2000 that is very stock, I can have my trans temp at 230 on a sustained grade that's not allowing a high enough speed for the torque converter to lock up with overdrive off but my engine temp is at a very comfortable 190-194.

The strain on the engine due to the weight I'm carrying is what's causing the engine to run hotter and it's not because the trans cooler is adding excessive heat to the coolant.

I can also run a trans temp of 120 to 130 on the highway as long as I'm not climbing a grade or driving in extreme temps like 115-120 degrees. But, maybe you know this but maybe you don't. 120 - 130 is not an optimal ATF temp. Optimum temp for ATF is around 170. There is such a thing as running too cool. This is why engines have thermostats so they will run at the optimum temp for the engine oil to lubricate the engine properly.

I wasn't really replying to u, and already know u know about T/C lock up from ur other posts, by u not replying to my earlier ?s in this thread made it clear u didn't want any feed back from me specifically...

"The strain on the engine due to the weight I'm carrying is what's causing the engine to run hotter and it's not because the trans cooler is adding excessive heat to the coolant."

Of course weight is the issue, work=heat, plus ur higher outside temps then where I am, and as u know it's not only ur engine working harder but ur trans and the trans is capable of adding more heat to a balanced system quicker then the engine. I was very clear that the "cooler" was adding some I never said all, there is also heat that is transferred conductivity when the heat in the trans itself getting hotter then the engine, and when the heat in the trans gets hotter then the coolant that heat is transferred to said.... As u and pretty much everyone here knows, so that isn't something I need to rehash in a thread about heat.

"But, maybe you know this but maybe you don't. 120 - 130 is not an optimal ATF temp. Optimum temp for ATF is around 170." This is based on fluids developed from the 90's that required more heat to thin out for where the system and as I stated u can run lower temps with many of the more modern fluids, and yes 120 is getting on the to cold side even 4 said

"This is why engines have thermostats so they will run at the optimum temp for the engine oil to lubricate the engine properly." oil isn't the oil reason as u know combustion temps, etc. Only making the point as there is always more when u look at the system holistically, and one can't go into ever aspect in a reply to a thread.

I wish U (Tim) the best in life (not that u need my best wishes) and u don't have to agree with me,(this was not an attack on u and me reply is towards anyone that would read this thread looking 4 help with heat) I am sharing what I a learned from overlanding/wheeling/camping/etc out of a 3rd gen 4runner with far to much weight fully loaded and I do so without overheating and breaking down (I do a lot of preventative maintains).

Maybe it's just me but this forum seems to have an underlining hostility, especially when u don't drink the Toyota fan boy kool-aid

 

[JZiggy]

[MENTION=222826]clearock[/MENTION] I don't see any underlying hostility in any of this thread. Just folks sharing their experiences and opinions in a straightforward way. It's OK to disagree or offer contradictory information -- example, I did not realize that modern ATF was designed to run at cooler temps. That's good info and I wonder if there's some background reading available on BITOG or something.

 

[2021nightshade4x4]

You are right that some don't know that locking up the torque converter can lower their automatic trans temps, but I'm not one of them.

…

Can the trans cooler in the bottom of the radiator add heat to the coolant? Sure it can. Is it having the affect you think it is, I don't agree. On my 2000 that is very stock, I can have my trans temp at 230 on a sustained grade that's not allowing a high enough speed for the torque converter to lock up with overdrive off but my engine temp is at a very comfortable 190-194.

The strain on the engine due to the weight I'm carrying is what's causing the engine to run hotter and it's not because the trans cooler is adding excessive heat to the coolant.

I can also run a trans temp of 120 to 130 on the highway as long as I'm not climbing a grade or driving in extreme temps like 115-120 degrees. But, maybe you know this but maybe you don't. 120 - 130 is not an optimal ATF temp. Optimum temp for ATF is around 170. There is such a thing as running too cool. This is why engines have thermostats so they will run at the optimum temp for the engine oil to lubricate the engine properly.

Depends when and in which gear your transmission is programmed to permit lockup. Do you happen to know what 4Runners allow? It could literally be anything: A Mopar 545RFE will lock up only in 5th, a ZF 6HP26 will lock up in any gear. There is definitely a balance - torque converter life is significantly shortened by excessive lockup cycles. There are tons of angry owners of Range Rovers and BMWs who followed maintenance religiously, never towed, and still had trans fail at 60k due to seals failing preventing the E clutch from having enough line pressure to do it’s job. Result: drivers lost gears 4/5/6 and those that didn’t (yet) had RPM bouncing 100-200 RPM as the lockup clutch built and subsequently lost pressure, struggling to stay put.

The “strain” and higher temps in your engine is a combination of extra heat being produced when timing advances, and when your engine runs at a higher RPM.

I don’t think the laws of physics would allow 180 degree transmission fluid to “add” any more heat to coolant that’s already 208 degrees. If anything, the transmission fluid would stand to be even cooler if NOT for the 208 degree coolant.

I think the same logic is applied to the belief that running the A/C “adds heat” to the coolant and causes your engine to overheat. There is most certainly heat at the condenser, but not nearly as much as the engine is producing. It would, if anything, be trying to shed some of that 208 degrees through both air and conducting through metals/fluids of lower temps.


Sent from my iPhone using Tapatalk

 

[PrinceValorum]

Result: drivers lost gears 4/5/6 and those that didn’t (yet) had RPM bouncing 100-200 RPM as the lockup clutch built and subsequently lost pressure, struggling to stay put.

That's exactly what my dad's Ridgeline does. Around 45mph and light throttle, the rpms pulse like that, and I read on the Honda forums that it was the TC locking and unlocking. Honda didn't have a fix for it. Some people convinced the dealers to replace their TCs, and it fixed it for a while but ultimately returned. Doing a drain and fill on the ATF fixed it for a few thousand miles, but far less than the recommended service interval.

The thing that blew me away is that people still rack up 300k+ on them somehow. I'd really like to know more about the how and why behind all of it.

I don’t think the laws of physics would allow 180 degree transmission fluid to “add” any more heat to coolant that’s already 208 degrees. If anything, the transmission fluid would stand to be even cooler if NOT for the 208 degree coolant.

I think the same logic is applied to the belief that running the A/C “adds heat” to the coolant and causes your engine to overheat. There is most certainly heat at the condenser, but not nearly as much as the engine is producing. It would, if anything, be trying to shed some of that 208 degrees through both air and conducting through metals/fluids of lower temps.

You're right. Heat can only flow from a hot body to a cooler one. Same as how objects don't roll uphill. It's why you have to put work in to remove heat (HVAC, refrigeration, etc).

Running the A/C reduces the temperature delta and the potential for heat transfer, since all of the heat being dumped from the condenser is now being blown across the rad. Instead of cooling the rad with cool ambient air, you're using "partially thermally saturated" air, like trying to mop up a spill with a wet towel.

 

[phattyduck]

That's exactly what my dad's Ridgeline does. Around 45mph and light throttle, the rpms pulse like that, and I read on the Honda forums that it was the TC locking and unlocking. Honda didn't have a fix for it. Some people convinced the dealers to replace their TCs, and it fixed it for a while but ultimately returned. Doing a drain and fill on the ATF fixed it for a few thousand miles, but far less than the recommended service interval.

The thing that blew me away is that people still rack up 300k+ on them somehow. I'd really like to know more about the how and why behind all of it.

Totally off topic, but you can keep the Honda 6-speed auto happy with trans drain+fill every 10-15k miles (factory interval is 30k miles). They last 200k+ miles when over maintained, and die a fairly early death if not.

-Charlie

 

[2021nightshade4x4]

Totally off topic, but you can keep the Honda 6-speed auto happy with trans drain+fill every 10-15k miles (factory interval is 30k miles). They last 200k+ miles when over maintained, and die a fairly early death if not.

-Charlie

This has now become the theme among manufacturers spanning several continents.

Owner’s manual maintenance schedule used to protect the owner, and the car. Now the manual is but a mere showcase of every compromise the company had to make to qualify for those last few CAFE credits.

If there’s any bit of advice I’m going to give (having learned the hard way myself) it would be to cut your fluid change intervals in HALF.

For EVERYTHING. Oil. Coolant. Trans. Power steering. Brake fluid. Diffs. Transfer case. Go ahead and break out your manual tonight, flip to the schedule and rewrite your own on a piece of paper.


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[mtbtim]

I wasn't really replying to u, and already know u know about T/C lock up from ur other posts, by u not replying to my earlier ?s in this thread made it clear u didn't want any feed back from me specifically...

"The strain on the engine due to the weight I'm carrying is what's causing the engine to run hotter and it's not because the trans cooler is adding excessive heat to the coolant."

Of course weight is the issue, work=heat, plus ur higher outside temps then where I am, and as u know it's not only ur engine working harder but ur trans and the trans is capable of adding more heat to a balanced system quicker then the engine. I was very clear that the "cooler" was adding some I never said all, there is also heat that is transferred conductivity when the heat in the trans itself getting hotter then the engine, and when the heat in the trans gets hotter then the coolant that heat is transferred to said.... As u and pretty much everyone here knows, so that isn't something I need to rehash in a thread about heat.

"But, maybe you know this but maybe you don't. 120 - 130 is not an optimal ATF temp. Optimum temp for ATF is around 170." This is based on fluids developed from the 90's that required more heat to thin out for where the system and as I stated u can run lower temps with many of the more modern fluids, and yes 120 is getting on the to cold side even 4 said

"This is why engines have thermostats so they will run at the optimum temp for the engine oil to lubricate the engine properly." oil isn't the oil reason as u know combustion temps, etc. Only making the point as there is always more when u look at the system holistically, and one can't go into ever aspect in a reply to a thread.

I wish U (Tim) the best in life (not that u need my best wishes) and u don't have to agree with me,(this was not an attack on u and me reply is towards anyone that would read this thread looking 4 help with heat) I am sharing what I a learned from overlanding/wheeling/camping/etc out of a 3rd gen 4runner with far to much weight fully loaded and I do so without overheating and breaking down (I do a lot of preventative maintains).

Maybe it's just me but this forum seems to have an underlining hostility, especially when u don't drink the Toyota fan boy kool-aid

No worries and I didn't take offense to anything you said. Your delivery of information made it sound like gospel and I wasn't agreeing with your sermon. Of course the trans cooler is adding heat to the coolant. Is it the majority of the reason for my high engine temps? I still say, no, it isn't based on what I've seen with my stock rig like I mentioned in my previous comment. I can run a very high trans temp with a normal engine temp on my stock 2000 rig. The culprit is the load on the engine, not the load on the transmission. Your original comment on this thread made it sound like the transmission heat via the cooler in the radiator was the main culprit for the high engine temps I'm experiencing. We disagree obviously.

I've never heard that the optimum temp for ATF could now be something lower than 170 degrees. I've read quite a bit on the subject and haven't read anything to that affect. If you could share some links on it, that would be great. What I have read is when you run 150 or lower for long lengths of time, condensation can build up in the trans and we all know how much auto trans love water.

And yes, there's more than one reason for the optimum engine temp but oil temperature is one of them.

Anyway, I think I've said enough.

 

[D'arce]

This has now become the theme among manufacturers spanning several continents.

Owner’s manual maintenance schedule used to protect the owner, and the car. Now the manual is but a mere showcase of every compromise the company had to make to qualify for those last few CAFE credits.

If there’s any bit of advice I’m going to give (having learned the hard way myself) it would be to cut your fluid change intervals in HALF.

For EVERYTHING. Oil. Coolant. Trans. Power steering. Brake fluid. Diffs. Transfer case. Go ahead and break out your manual tonight, flip to the schedule and rewrite your own on a piece of paper.

I fully agree with you on this one. I don't know if half is the right number but it's beyond crazy to think that politics influences factory oil change intervals.

Back to the thread at hand...I remember reading that you (Tim) have 33" tires. When the time comes for new tires, one thing that you could consider is going narrower if it suits your driving needs. Keep the height but less rolling mass may help.

 

[4x3Lander]

Wow. Thanks for the insight. Still playing with my new OBDLINK MX+. Found the pid and added it to my ever evolving dash.
“Status of Lock Up Sol Off/On”

Here I am unlocked before getting on the interstate. Temps up a little.

On the interstate. Achieved lock. Temps fall.

Not to derail this thread, but how did you get the AT Temp sensor? I have the same app for my 2002 and have never been able to find a working transmission temp sensor.

Slowing down for merging traffic. TC unlocks. Temp rises.

Achieve lock. Temps fall.

I make my exit. TC doesn’t lock in the 45mph zone.
Temps rise. Quite a bit in a mile @45mph.

It locks back up after the speed limit goes up and cools back down and I arrive at my destination.

I now have my eye on it. Thanks for your idea.

Not to derail this thread, but how did you get the AT Fluid Temp sensor? I have the same app for my 2002 and have never been able to find a working transmission temp sensor.

 

[ch1966]

Not to derail this thread, but how did you get the AT Fluid Temp sensor? I have the same app for my 2002 and have never been able to find a working transmission temp sensor.

 

[4x3Lander]

Thanks so much! I’ll give this a try to see if I can get it to work.

 

[diverscale]

Had my 1998 V6, automatic in death valley, and it had a new radiator, and approx 1 years old aisin clutch fan at the time. We were fully loaded, coming from Quebec, which could compare to at least some of the weight of your armor.

Scangauge is in the truck. I did monitor, and from memory

It was very, very hot (during summer) in death valley, and the truck coolant temp would be higher than usual (usually 87-89 celcius, 188-190F), but would keep around or below 95 celcius (200F) most of the time, and I could always hear the clutch fan being on it's ''max'' setting, very loudly.

Only once it went over 212 (went to 101-103 celcius), and it was on a long, slow uphill drive, and I was not going easy on the truck at all.

Pretty normal that in higher ambient temps, you see higher coolant temps. We just don't happen to have scangauges in every of our cars, and also, the clutch fan system calls for more temp variations than a fixed speed electric fan. Happened to me, and was not really surprised. As long as I heard that clutch fan scream, I was happy and A/C was going full-blow.

 

[Unner]

My two cents... There is probably nothing wrong with your 4Runner, you are meticulous with maintenance. The only thing working against you is the age of the vehicle and things like corrosion that could impact your cooling ability. I think if you weren't monitoring your temps you would have been fine to leave the AC on and keep going, but I would have done the same thing as you because that is how I am. I know mine runs 186-193 normally. 195 or 198 on really hot days and I'm working the engine in stop and go traffic or up long highway grades, but that is when temps are in the mid 90s, 100 at most. The humidity down here is killer, but that doesn't really impact the engine much.

These things are rated to tow 5,000 lbs from the factory with nothing special added. I have to imagine Toyota did some extreme weather testing towing at or near that limit. Otherwise you'd have people pulling trailers through the desert overheating. I would also assume that even with your rig loaded down and the larger tires killing the gearing, it isn't as hard on the engine as towing 5,000 lbs with a stock 3rd gen.

I do think the regear and possibly a better radiator would help keep the temps down though, which would be a good thing.

 

[ch1966]

[MENTION=120071]mtbtim[/MENTION]
Any luck with your truck Tim?

I’ve been thinking about yours while working on mine.

Your thermostat may be sticking or not opening fully.


I threw a 170* in mine.

And added a trans cooler + 6qt drain and fill.

I baselined the following results on a road that gains 1000’ in altitude in less than 3 miles at 7%-12% grades.

Baseline run ~25 mph +-
2nd gear mostly
All temps measured at the summit.

Here’s the same run with a new thermostat

And with the trans cooler added in line and drain and fill

The temperature relationship between the coolant and transmission fluid is interesting.

Good luck. I’m watching to see what you figure out.