Radiator, Trans. Cooler, or both....

[Airmapper]

I'm in the early phase of 3rd gen ownership. Done very little to it mechanically except change the oil and some filters.

It has right around 240k miles on it. I have no reason to believe the radiator is not original. Someone seen a photo of it on another forum and said due to the faded color of the top they believed it was original.

Here is my situation. It's winter, it's cold, I don't want to do any big jobs until it warms up. I change a fluid here and there, fix interior stuff, lights, short simple jobs so far. I got this as a secondary vehicle and I don't want to do a bunch of work on it or dump a lot of money all at once, but plan to gradually bring it up to standards as time goes on. Eventually I'll catch up on maintenance and it should be good.

But I'm worried about the fluid intermix, if it's gone this long without it, either it never will or it will happen any moment. I know there are a few ways to address strawberry milkshake potential.

New radiator.
External Trans. cooler.
Both.

I've read a ton of recommendations to replace the radiator ASAP, but the reason I always gather is because of the intermix issue.

Is there any pressing reason to replace the radiator other than the potential for intermixing fluids? Is there any reason to replace it at all if I eliminate that chance? Assuming I flush out and cap off the internal trans cooler, so what if it springs an internal leak at that point.

Adding the external cooler does not look like a big job, and I can probably do it some Saturday next month. But once I do that, should I still be planning on a new radiator come spring, or go by the "if it ain't broke" philosophy. 4runner maintains temp well from what I've seen so far, granted it's winter. Maybe do a coolant drain and fill, and call it done?

 

[fourfive]

Get a new radiator and a scan gauge 2 or something similar to monitor your trans temps. If you start to see temps hit 200f or higher with your daily driving then get an external cooler but I wouldn't recommend bypassing if you see temps above 200f with just the radiator because you will most likely see the same temp range or higher with the radiator bypassed. Atleast that was the case for me & when I rerouted my external cooler to run in series with my radiator my trans temps are in a healthier range.

 

[meRockboost]

Depends on use of vehicle: replace radiator only if it's used just for DD.
Or if towing or wheeling add in the trans cooler.
I bypassed mine but ended up running my trans cooler back into the radiator as climbing long steep hills in 4wd would still cause high trans temps.

$100 for a radiator is cheaper than a new transmission. Plus if you flush your engine your cooling system will be top notch for another 200k.

 

[spoonsports86]

i just picked my tr4 up

i am about to order a trans cooler. but i am debating to run it in line or separate also with a fan or with out

 

[mtbtim]

Replace the radiator as preventative maintenance. The potential for a pink milkshake is one thing but you could also just spring a leak or the plastic top could dramatically crack from age and leave you stranded somewhere. With the mileage you have, it's a good idea.

Even with normal driving, no crazy 4wheeling or towing, your trans temps can get pretty high. All you have to do is drive some extended mountain roads and you'll easily see temps around 230.

In my opinion, adding a trans cooler and running it in-series with the radiator cooler is the way to go.

Also, don't forget to turn overdrive off when you're climbing grades and going around 65mph or less. Turning off overdrive locks up the torque converter and will drop your trans temps by 20+ degrees.

Here's a video I made installing a new radiator, thermostat and an external trans cooler in my rig:

<iframe width="560" height="315" src="https://www.youtube.com/embed/2nVbwe2t2T8" frameborder="0" allowfullscreen></iframe>

 

[Airmapper]

Replace the radiator as preventative maintenance. The potential for a pink milkshake is one thing but you could also just spring a leak or the plastic top could dramatically crack from age and leave you stranded somewhere. With the mileage you have, it's a good idea.

In my opinion, adding a trans cooler and running it in-series with the radiator cooler is the way to go.

Tim, do you recall how you monitored trans temp with Torque? I already have that setup, but I don't recall seeing it as a usable parameter. I see a (Method 1) and (Method 2). Did it require a custom PID? I'll have to play with that later.

Great video, I didn't watch it all but I'll be coming back to it when I get closer to that job. I think I've run across your videos before looking up stuff.


I'm debating just getting the external cooler and doing that in the next few weeks to eliminate the risk. It's cool weather now so I don't think it will have issue keeping the trans cool, I might have more issue keeping it warm enough. If I can get Torque working to monitor that will let me keep an eye on it.

But that will let me stage my work better to replace the radiator later when the weather breaks and I'm more comfortable starting in on a bigger task. Also on my plate is a timing belt and probably water pump, changing a radiator at that time would be good.

 

[mtbtim]

Tim, do you recall how you monitored trans temp with Torque? I already have that setup, but I don't recall seeing it as a usable parameter. I see a (Method 1) and (Method 2). Did it require a custom PID? I'll have to play with that later.

Great video, I didn't watch it all but I'll be coming back to it when I get closer to that job. I think I've run across your videos before looking up stuff.


I'm debating just getting the external cooler and doing that in the next few weeks to eliminate the risk. It's cool weather now so I don't think it will have issue keeping the trans cool, I might have more issue keeping it warm enough. If I can get Torque working to monitor that will let me keep an eye on it.

But that will let me stage my work better to replace the radiator later when the weather breaks and I'm more comfortable starting in on a bigger task. Also on my plate is a timing belt and probably water pump, changing a radiator at that time would be good.

I used Method 2 with Torque Pro. No special PID needed.

 

[rallypoint_1]

Wait Tim....I should turn of O/D when going around town under 65mph???

 

[Co4Fun]

Wait Tim....I should turn of O/D when going around town under 65mph???

I was curious on this as well.

 

[mtbtim]

I was curious on this as well.

Grant and Bill, you guys missed the part when I said "When You're Climbing Grades". When you're cruising around town or on the freeway and not climbing grades, keep overdrive on. But, when you're driving up mountain roads, driving mountain passes on the freeway or 4 wheeling up steep trails, and your speed is around 65mph or less, turning off the overdrive will drop your trans temps considerably. If you're driving faster than 65mph, you're engine rpms will be winding out a bit so that's why I don't recommend taking off overdrive until your going 65mph or less.

If you guys are monitoring your trans temps, try climbing a grade with overdrive on. When your temps start climbing towards 200, turn overdrive off and you'll see your temps almost immediately drop because the torque converter locks up and less heat is generated because of it.

 

[mtbtim]

Tim, do you recall how you monitored trans temp with Torque? I already have that setup, but I don't recall seeing it as a usable parameter. I see a (Method 1) and (Method 2). Did it require a custom PID? I'll have to play with that later.

Great video, I didn't watch it all but I'll be coming back to it when I get closer to that job. I think I've run across your videos before looking up stuff.


I'm debating just getting the external cooler and doing that in the next few weeks to eliminate the risk. It's cool weather now so I don't think it will have issue keeping the trans cool, I might have more issue keeping it warm enough. If I can get Torque working to monitor that will let me keep an eye on it.

But that will let me stage my work better to replace the radiator later when the weather breaks and I'm more comfortable starting in on a bigger task. Also on my plate is a timing belt and probably water pump, changing a radiator at that time would be good.

The B&M 70264 cooler I bought has a thermal bypass. It doesn't operate via a thermostat but just by the thickness of the fluid. When the fluid is colder, it's thicker and will route through two main channels and back to the transmission without entering the smaller cooling fin channels. When the fluid gets warmer and thins out, the fluid will then be able to flow through the thinner cooling channels and will start to cool the fluid more.

I do think I'm overall running a little cooler now but I think that's a good trade-off for dropping my trans temps when I'm taking trips in the summer and driving lots of mountain roads.

 

[Co4Fun]

Grant and Bill, you guys missed the part when I said "When You're Climbing Grades". When you're cruising around town or on the freeway and not climbing grades, keep overdrive on. But, when you're driving up mountain roads, driving mountain passes on the freeway or 4 wheeling up steep trails, and your speed is around 65mph or less, turning off the overdrive will drop your trans temps considerably. If you're driving faster than 65mph, you're engine rpms will be winding out a bit so that's why I don't recommend taking off overdrive until your going 65mph or less.

If you guys are monitoring your trans temps, try climbing a grade with overdrive on. When your temps start climbing towards 200, turn overdrive off and you'll see your temps almost immediately drop because the torque converter locks up and less heat is generated because of it.

Interesting so the tranny works harder (torque converter) when OD is on as it's trying to run it in a "higher" gear and really work...like when climbing. And turning OD off just forces it to stay in third instead of constantly trying to reach for the higher (OD/4th) gear. I could see that...hmmm?

I usually just turn OD off when DESCENDING steep hwy grades here in CO so I don't have to use my brakes so much. But, that happens often when I'm around or over 65 mph. What are your thoughts on that?

 

[rallypoint_1]

Ah ok...That's what I was doing. I thought maybe I was doing it wrong.lol I most likely didn't read the post correctly.

Thanks Tim!

 

[mtbtim]

Interesting so the tranny works harder (torque converter) when OD is on as it's trying to run it in a "higher" gear and really work...like when climbing. And turning OD off just forces it to stay in third instead of constantly trying to reach for the higher (OD/4th) gear. I could see that...hmmm?

I usually just turn OD off when DESCENDING steep hwy grades here in CO so I don't have to use my brakes so much. But, that happens often when I'm around or over 65 mph. What are your thoughts on that?

If you have a way to monitor your trans temps, you'll see what I'm talking about when you're climbing a grade. Wait until the temps get up there, 180-200 and then turn overdrive off. You'll immediately see the temps start to drop.

Yes, definitely keep downshifting to utilize engine braking while descending grades but I usually slow my speed by braking and then turn overdrive off when I reach the neighborhood of 65mph. I'm probably being overly anal but I don't like over-revving my engine if I don't have to. If I'm going down a particularly steep and tight mountain road, I'll even shift into second (2) and sometimes even 1st (L) if I really want to crawl down something and don't want to ride the brakes.

 

[Airmapper]

After researching more on replacing the radiator, it doesn't look that time consuming and I think I will do that and be done with it. I was thinking that while simple work it would take all day, and after looking it over, seems more like something I can get done in an afternoon so long as I have all the supplies I need beforehand ready to go.

I tried out the temp monitor with Torque this morning. It was about 27 degrees (F) air temp, and I was running a trans temp of 118-140, mostly holding around 120 while at ~60 cruise speed on mostly flat road. Coolant temp was holding around 180. I'll watch it some more to get a baseline so I know whats going on with future changes.

There are dozens of projects big and small my 4runner needs so I have to hit here and there where I can. If I notice I have any future issues with trans temp climbing in the summer and doing any 4x4 driving, I'll add the external cooler. May just do it for good measure once I get caught up on vital maintenance. Since it's not my main 4x4 I don't anticipate asking too much of it, and now this is on my radar I'll likely be feeling it out on a trial basis before taking it on any trips where I think it might be an issue.

Thank for all the comments and advice. :thanks:

 

[amalik]

Turning off overdrive locks up the torque converter and will drop your trans temps by 20+ degrees.

Tangent for a second from OP,

Is this the case even at low speeds if I click O/D off?

 

[Airmapper]

Since we have 4 speed transmissions, in my vague understanding of how auto transmissions work, O/D off is about the same concept as having a "3" position on the gear selector. When you hit it, if you are in 4th (overdrive) it drops down and grabs 3rd gear and won't try to shift into 4th again until you turn O/D on (or restart the vehicle thus resetting the button on most vehicles.)

I'm not so sure about the description of locking up the torque converter being a function of the button itself. It's true I believe but in a roundabout way.

What I think is happening is a function determined by other rules such as the engine RPM. Dropping down a gear probably causes torque converter lockup because you dropped down a gear and have higher RPM, not because of the button having any control over the torque converter.

With O/D off the transmission should operate as it always does in gears 1-3, it just won't shift into 4 (overdrive).

When climbing a hill in 4th, the engine is at low RPM trying to impart a lot of torque into the transmission, that is a difficult task under those conditions. The RPM is too slow to physically lock up the converter clutches, thus energy is being transferred through the fluid and not via mechanical means. The fluid can't impart energy directly, and the transmission is resisting it due to the load of climbing a hill, so the energy has nowhere to go and dissipates it as heat in the process of churning the fluid.

Under most circumstances the transmission shifting rules would figure this out, but since you are traveling fast the transmission thinks you are in an acceptable speed to be in 4th gear, it doesn't know you are climbing a hill or puling a trailer though because it's designed to shift based on a typically configured vehicle, not at extremes.

Eventually something will give and your speed will slow to the point it shifts, or you press the gas pedal down further and it senses you need more power, but not before you cook the fluid while floating in that limbo zone between shift points.

 

[mtbtim]

Tangent for a second from OP,

Is this the case even at low speeds if I click O/D off?

Yes, I'm pretty sure it helps even at slower speeds. The reason why I say so is I've tested it climbing mountain roads and I'm nowhere close to the transmission shifting into the overdrive gear and I've seen my trans temps drop as soon as I switched off overdrive. When I know I'm going to be climbing a grade, it's a fairly sustained climb (not a short hill), and I'm not exceeding 65mph, I'll turn my OD off.

I could be talking out of my ass here in regards to the slower speeds because I could be remembering incorrectly and I was driving at the speed where the transmission was in between 3rd gear and overdrive and turning off overdrive kept the transmission from constantly downshifting and up shifting back and forth from 3rd and 4th(overdrive) gears.

Just try it out and see what I'm talking about. Btw, I didn't discover this trick. I read it on the this forum sometime in the past and it was explained that turning overdrive off locks up the torque converter. I'm not a automatic transmission expert so I took their word for it.

I think in the very near future, I'll take a drive up a mountain road in the Santa Cruz mountains and video the temp change as soon as I switch off the overdrive.

 

[Airmapper]

Yes, I'm pretty sure it helps even at slower speeds. The reason why I say so is I've tested it climbing mountain roads and I'm nowhere close to the transmission shifting into the overdrive gear and I've seen my trans temps drop as soon as I switched off overdrive. When I know I'm going to be climbing a grade, it's a fairly sustained climb (not a short hill), and I'm not exceeding 65mph, I'll turn my OD off.

I could be talking out of my ass here in regards to the slower speeds because I could be remembering incorrectly and I was driving at the speed where the transmission was in between 3rd gear and overdrive and turning off overdrive kept the transmission from constantly downshifting and up shifting back and forth from 3rd and 4th(overdrive) gears.

Just try it out and see what I'm talking about. Btw, I didn't discover this trick. I read it on the this forum sometime in the past and it was explained that turning overdrive off locks up the torque converter. I'm not a automatic transmission expert so I took their word for it.

I think in the very near future, I'll take a drive up a mountain road in the Santa Cruz mountains and video the temp change as soon as I switch off the overdrive.

What you describe for 1-3rd gear sounds like the function of the ECT power button which changes the shift points to allow higher RPM in a given gear before shifting.

It would be possible such a feature is activated by pressing the O/D off button in conjunction with not permitting a shift into 4th gear. Seems kind of redundant with an ECT power button though.

My Mom has a 1st Gen Tundra I've driven many times, seems I recall hitting O/D off on it will result in more aggressive shifting even in the lower gears. It does not have anything like an ECT power button though.

 

[mtbtim]

Yes, I'm pretty sure it helps even at slower speeds. The reason why I say so is I've tested it climbing mountain roads and I'm nowhere close to the transmission shifting into the overdrive gear and I've seen my trans temps drop as soon as I switched off overdrive. When I know I'm going to be climbing a grade, it's a fairly sustained climb (not a short hill), and I'm not exceeding 65mph, I'll turn my OD off.

I could be talking out of my ass here in regards to the slower speeds because I could be remembering incorrectly and I was driving at the speed where the transmission was in between 3rd gear and overdrive and turning off overdrive kept the transmission from constantly downshifting and up shifting back and forth from 3rd and 4th(overdrive) gears.

Just try it out and see what I'm talking about. Btw, I didn't discover this trick. I read it on the this forum sometime in the past and it was explained that turning overdrive off locks up the torque converter. I'm not a automatic transmission expert so I took their word for it.

I think in the very near future, I'll take a drive up a mountain road in the Santa Cruz mountains and video the temp change as soon as I switch off the overdrive.

Well, I was talking out of my ass at some level. Turning OD off does nothing to reduce your trans temps if you're going at a slower speed. I tested it out this morning climbing a mountain road and confirmed it.

However, when you're at a speed in-between 3rd gear and 4th gear (overdrive) where the trans keeps on downshifting and upshifting between the two gears, turning off overdrive definitely reduces your trans temps. When you're have OD on and you're climbing a grade that doesn't allow you to be cruising in the OD gear, the transmission will kick down to 3rd gear when you give enough throttle response to maintain your speed. When that downshift occurs, your trans temps will start to climb. If you turn the OD off in this situation, you'll see an immediate drop in temperature.

I documented this via video so I'll do a some quick Timmy the Toolman editing and post it here so Y'all can see what I'm talking about.