Driving in Extreme Heat with Heavily Modified Rig (Heavy)

[clearock]

I only skimmed the info peeps r throwing out so if i rehash anything thats why.

what weight r u running, what outside temps r u driving in normally, u have an auto, 2wd or 4wd, how r u using ur 4runner ie (camping, rock crawling, etc), r u cing these temps on the hwy, city slow driving, mtn passes, etc

Just want a bit more info to guide my response....

The 4runner I currentlly use 4 camping/hunting/"over-landing"/rock crawling etc is probably one of the heaviest units of this forum when completely load up when I go out for a long period of time, weights over...

electric fans will only lower ur temps 5ish degrees (which is a lot when ur getting hot), I run pusher e/fans in conjunction with the OEM fan

 

[TravThePro]

Have you tried cleaning your condenser? They can get clogged up and restrict airflow to the radiator.

One thing to consider when switching to electric fans is the additional electric load required. There is still a load on the engine in the form of increased load on the alternator. You may need to upgrade your alternator in order to keep up with the demand. There's no such thing as a free ride.

The Koyo or Champion radiators are a thicker radiator core (advertised 33% thicker) which will greatly increase heat transfer. Combine that with a 170 degree thermostat, fresh coolant with water wetter, and a properly functioning fan clutch and I don't see a reason for electric fans. I don't think Koyo or Champion have provisions for an internal transmission cooler, and they may require a different radiator cap.

I need to buy another radiator/AC condenser comb to clean up and fix some dings I put in them during the engine rebuild.

I love that water wetter! It makes a huge difference for dirtbikes on those extreme heat desert days/slow technical riding. With that being said, I would not run it in the factory plastic/aluminum radiator (I would run it in full metal radiators though). While it is not corrosive to metals in the cooling system, a bunch of people have had issues with it eating the plastic away in their cooling systems.

The Champion does have an internal transmission cooler, but I am not sure what the radiator cap compatibility is.

 

[PrinceValorum]

A simple thing to try would be to drop the mix ratio of coolant to water. 50/50 is recommended for optimum freeze protection with minimal heat transfer losses. A lot of race/track cars will run 25% antifreeze, or even 10% antifreeze, to maximize the cooling efficiency. Fortunately you don't have to worry about freezing, but even 10% antifreeze is enough to protect down to 26F.

If it were me, I would try running 25% coolant and see how that went.

 

[JZiggy]

Lots of good ideas in here, Tim. Here are some of my own ideas and my take on some of the suggestions offered here.

Regearing -- agreed this is likely to make the most difference as it will reduce strain on the drivetrain = less heat generation. Less torque converter slipping, engine running at higher RPMs and more reasonable loads rather than being bogged down all the time.

Electric fans -- A pusher fan in the front of your radiator can help a good deal. My little 1000cfm one certainly does. I would NOT change your mechanical fan to a primary electric fan. I have also personally had bad experiences with this approach.

Mechanical fan -- I know your fan clutch is new, but have you actually confirmed its operating correctly? It is also possible to change the viscosity of the fan's silicone oil to make it hook up more. Reading these two links it sounds like the factory units are sometimes underfilled with silicone oil as well!

Coolant -- Good idea to try a higher water % in your coolant mix as water is a much better heat transfer fluid than ethylene glycol. Redline's water wetter or similar is a strong surfactant and helps the coolant reject heat into the radiator more quickly but I'd leave this as a last resort.

Radiator -- Sounds like a lot of people are suggesting an upgraded radiator. Makes sense to me.

 

[Bad Luck]

I need to buy another radiator/AC condenser comb to clean up and fix some dings I put in them during the engine rebuild.

I love that water wetter! It makes a huge difference for dirtbikes on those extreme heat desert days/slow technical riding. With that being said, I would not run it in the factory plastic/aluminum radiator (I would run it in full metal radiators though). While it is not corrosive to metals in the cooling system, a bunch of people have had issues with it eating the plastic away in their cooling systems.

The Champion does have an internal transmission cooler, but I am not sure what the radiator cap compatibility is.

Thanks for the info. I knew the Koyo radiator didn't have an internal transmission cooler but wasn't sure on the Champion. I've never heard that about water wetter and never considered it to be honest. I wonder if that's a problem specific to water wetter or if it applies to the other coolant additives that function similar to water wetter.

A simple thing to try would be to drop the mix ratio of coolant to water. 50/50 is recommended for optimum freeze protection with minimal heat transfer losses. A lot of race/track cars will run 25% antifreeze, or even 10% antifreeze, to maximize the cooling efficiency. Fortunately you don't have to worry about freezing, but even 10% antifreeze is enough to protect down to 26F.

If it were me, I would try running 25% coolant and see how that went.

That's a really good point about the antifreeze ratio. Like you said you just have to make sure you exceed the minimum freezing point for whatever mixture you decide on for where you are and remember that if you make any winter trips. That would make for a bad time if it did freeze and blew the freeze plugs out or cracked a radiator.

 

[phattyduck]

My cooling system is sound. Fan clutch, radiator, and thermostat have all been replaced. I do plan on re-gearing to 4:88 which I know will help. I’m wondering what else I might be able to do. I’ve heard the Champion radiator might allow me to run cooler. If you have any suggestions, I’d appreciate reading them.

Thanks!

I'd still suspect the cooling system just a bit - the radiator cap. If not new and OEM, change it out.

I had slight overheating issues when I had a weak radiator cap - it got up in the 210*F range in ~105*F heat with a medium load (32's, armor, 3 dudes w/ backpacking gear) on long hills. It was always fine around town, in traffic or on regular freeways (rock solid at 191*F). After replacing the cap, no issues with the same or higher load in harsher conditions. I already had a new radiator, new water pump, new thermostat and coolant (all OEM).

The OEM cooling system is incredibly good, I think it might be as simple as the radiator cap.

-Charlie

Edit: PS. I always run about 40% coolant / 60% water - it has been ok down to as low as -10*F temps on my Subaru, and I'd assume the 4Runner would be fine that way too.

 

[Pyral]

Your rig has a cold intake right? That probably helped you out.

It appears that the water to antifreeze ratio can also have an affect on heat transfer. That's because water is a better conductor of heat, but be warned that there is some disagreement if running pure water can lead to it boiling and becoming steam. The antifreeze raises the boiling point of the water, but the system is pressurized so it should make it more difficult for water to turn into steam.

But the long term fix is upgrading radiator and fan. This is probably a good idea anyway because it appears that these heat waves will happen more often.

 

[mtbtim]

How is the front end airflow over the radiator with the bumper compared to stock? I’m not familiar with the design but is it restricting air flow in combination with the weight?

In my experience the electric fans are nice in that they can run all the time if you wish and you can adjust when then trigger. But in general they are more fragile and prone to failure than the comparatively simple stock setup. Maybe try to find one with pretty robust blades and what not. Haven’t some people dropped in the fans from a Taurus or something?

The CBI bumper with winch does block a decent amount of air flow over the stock set-up but I really think, like others have mentioned, it's more about the weight of the rig and 33 inch tires causing the engine to run really hot in extreme conditions.

 

[mtbtim]

Hey Tim,

Have you considered using an additive in your coolant like Royal Purple "Ice"? I've never used it but I have read that a few guys used it and it seemed to help lower coolant temps, some by as much as 10 degrees in scenarios like you were just in.

I don't think its "the" fix but it may be worth a try until you can re-gear or get a E fan setup.

Amazon.com: Royal Purple 01600 Purple Ice Super-Coolant Radiator Additive - 12 oz.: Automotive

I have not considered this but it's something to think about especially if you know you're going to drive in summer heat through desert areas like I did. 117 degrees is crazy hot. I don't know how people in places like Nevada and Arizona handle it. Low 100's sure. 115-120, F that!

 

[mtbtim]

Tim,
I don't live in AZ, so I can't speak directly from that experience. But I do live in NC where we see extremely humid 95-100 degree summers.

The probable and unfortunate answer is an expensive one- re-gearing. I went from 3.91 (15" wheel base SR5) to 4.88's.

My coolant temps with the old gears hung around 193-198 (which is normal!).
With the 4.88's, I'm rarely if ever over 188 degrees, even in the dead of summer while wheeling with low airflow.

I'm thinking that with your weight + 33" tires, your truck is simply working way too hard to stay at speed.

I agree with you. My rig is super heavy and I'm asking a lot of it especially on grades. Under normal driving conditions in the California Bay Area and with decently hot temps, like the 90's, my rig runs relatively cool. But, loaded down with gear and people and then put it on a steep grade in extreme heat and the engine is saying, "Help me, Help me!" The re-gear is going to happen. I'm going to switch from 4:30 to 4:88 and I think it will help a ton.

 

[mtbtim]

Have you tried cleaning your condenser? They can get clogged up and restrict airflow to the radiator.

One thing to consider when switching to electric fans is the additional electric load required. There is still a load on the engine in the form of increased load on the alternator. You may need to upgrade your alternator in order to keep up with the demand. There's no such thing as a free ride.

The Koyo or Champion radiators are a thicker radiator core (advertised 33% thicker) which will greatly increase heat transfer. Combine that with a 170 degree thermostat, fresh coolant with water wetter, and a properly functioning fan clutch and I don't see a reason for electric fans. I don't think Koyo or Champion have provisions for an internal transmission cooler, and they may require a different radiator cap.

My AC Condenser is relatively free on debris but it wouldn't hurt to give it a cleaning. I think I will probably go with an aluminum radiator, probably the Koyo because I don't want to deal with the fitment issues of the Champion.

After some thought, I don't think I want to do the electric fan mod. Seems like a lot of work with maybe not much benefit over the regular fan clutch.

I'll run a bigger stand-alone trans cooler when I go with the Koyo aluminum radiator. My trans temps can spike too under the right conditions.

 

[PrinceValorum]

It appears that the water to antifreeze ratio can also have an affect on heat transfer. [...] but be warned that there is some disagreement if running pure water can lead to it boiling and becoming steam. The antifreeze raises the boiling point of the water, but the system is pressurized so it should make it more difficult for water to turn into steam.

You're right, a stronger mix of coolant does raise the boiling point. The difference in boiling point between a 50/50 mix, approx 225F by this chart, vs a 25% coolant mix boiling at approx 218F is not particularly large. This would not be one of my primary concerns, especially since the increased cooling capacity of the mix with less coolant would also keep temps lower.

Note these boiling temps are also at standard atmospheric pressure.

 

[HiluxSurf SSR-G]

Do you have an automatic transmission? if yes, you might like to add an inline aux atf cooler with fan to help lower the water temp in the lower tank of the rad.

 

[mtbtim]

A simple thing to try would be to drop the mix ratio of coolant to water. 50/50 is recommended for optimum freeze protection with minimal heat transfer losses. A lot of race/track cars will run 25% antifreeze, or even 10% antifreeze, to maximize the cooling efficiency. Fortunately you don't have to worry about freezing, but even 10% antifreeze is enough to protect down to 26F.

If it were me, I would try running 25% coolant and see how that went.

I have thought of this option. I'm currently running the usual 50/50 mix.

 

[Bad Luck]

You're right, a stronger mix of coolant does raise the boiling point. The difference in boiling point between a 50/50 mix, approx 225F by this chart, vs a 25% coolant mix boiling at approx 218F is not particularly large. This would not be one of my primary concerns, especially since the increased cooling capacity of the mix with less coolant would also keep temps lower.

Note these boiling temps are also at standard atmospheric pressure.

Boiling point increases with pressure. OEM radiator cap is 13 psi. Boiling point of straight water at 12 psi is 242*F. Boiling point of 1/3 coolant/water at 12 psi is 253*F. Boiling point of 50/50 coolant/water at 12 psi is 257*F. I don't see any problem with running a 25/75 coolant/water mix.

 

[mtbtim]

Lots of good ideas in here, Tim. Here are some of my own ideas and my take on some of the suggestions offered here.

Regearing -- agreed this is likely to make the most difference as it will reduce strain on the drivetrain = less heat generation. Less torque converter slipping, engine running at higher RPMs and more reasonable loads rather than being bogged down all the time.

Electric fans -- A pusher fan in the front of your radiator can help a good deal. My little 1000cfm one certainly does. I would NOT change your mechanical fan to a primary electric fan. I have also personally had bad experiences with this approach.

Mechanical fan -- I know your fan clutch is new, but have you actually confirmed its operating correctly? It is also possible to change the viscosity of the fan's silicone oil to make it hook up more. Reading these two links it sounds like the factory units are sometimes underfilled with silicone oil as well!

Coolant -- Good idea to try a higher water % in your coolant mix as water is a much better heat transfer fluid than ethylene glycol. Redline's water wetter or similar is a strong surfactant and helps the coolant reject heat into the radiator more quickly but I'd leave this as a last resort.

Radiator -- Sounds like a lot of people are suggesting an upgraded radiator. Makes sense to me.

Yeah, the pusher fan might happen.

I'm going to start with the re-gear because the extra power is seriously needed and I know it will help drop the coolant temp.

Next will be an aluminum radiator with a big stand-alone trans cooler. I think I will lessen the coolant/water ratio, maybe a 40/60 or 30/70.

 

[mtbtim]

I'd still suspect the cooling system just a bit - the radiator cap. If not new and OEM, change it out.

I had slight overheating issues when I had a weak radiator cap - it got up in the 210*F range in ~105*F heat with a medium load (32's, armor, 3 dudes w/ backpacking gear) on long hills. It was always fine around town, in traffic or on regular freeways (rock solid at 191*F). After replacing the cap, no issues with the same or higher load in harsher conditions. I already had a new radiator, new water pump, new thermostat and coolant (all OEM).

The OEM cooling system is incredibly good, I think it might be as simple as the radiator cap.

-Charlie

Edit: PS. I always run about 40% coolant / 60% water - it has been ok down to as low as -10*F temps on my Subaru, and I'd assume the 4Runner would be fine that way too.

The radiator and cap were replaced 20k ago so I wouldn't suspect an issue with the cap. I think I'll follow your suggestion and go to a 40/60 coolant/distilled water mix.

 

[mtbtim]

Your rig has a cold intake right? That probably helped you out.

It appears that the water to antifreeze ratio can also have an affect on heat transfer. That's because water is a better conductor of heat, but be warned that there is some disagreement if running pure water can lead to it boiling and becoming steam. The antifreeze raises the boiling point of the water, but the system is pressurized so it should make it more difficult for water to turn into steam.

But the long term fix is upgrading radiator and fan. This is probably a good idea anyway because it appears that these heat waves will happen more often.

No cold air intake. I have the stock set-up.

 

[PrinceValorum]

Boiling point increases with pressure. OEM radiator cap is 13 psi. Boiling point of straight water at 12 psi is 242*F. Boiling point of 1/3 coolant/water at 12 psi is 253*F. Boiling point of 50/50 coolant/water at 12 psi is 257*F. I don't see any problem with running a 25/75 coolant/water mix.

I agree.

Just to clarify for anyone else who may have slept through thermodynamics, the boiling point of water is 212F at 14.7psia (pounds per square inch absolute, absolute being in reference to complete vacuum). The radiator cap rated at 13psi is 13psig (pounds per square inch gauge, like what you measure with your tire gauge). Gauge pressure is what the additional pressure is on top of atmospheric pressure, so a 13psig cap would be able to hold 14.7psi + 13psi = 27.7psia.

 

[mtbtim]

Do you have an automatic transmission? if yes, you might like to add an inline aux atf cooler with fan to help lower the water temp in the lower tank of the rad.

Yes, auto trans and I do have an auxiliary trans cooler that is running in-line with the radiator trans cooler. I don't have a pusher fan though.