My 3rd Gen is heavily modified and way heavier than stock. Also, the mods on the front end, steel bumper, winch, trans cooler and lighting have effected the amount of air flow to the radiator. Due to the engine working harder because of the extra weight and due to the reduced air flow, my rig has experienced some overheating problems.

Installing this Koyorad Aluminum Radiator is a last ditch effort before I employ more drastic measures to keep my engine temps down.

So far, the preliminary results look promising.

Check out the video.

when i put mine in, the first thing i noticed was a bigger gap between the aluminum tank and the core support. i thought i did something wrong, but the stock radiator tanks are crimped and a little wider.

THat is one heavy duty radiator!

Been running this rad for a few years now. It's super nice. Also foam tape the fan shroud to make the system as efficient as possible.

Hey Tim just curious what made you pick Koyo? I know there’s a few other brands of all aluminum like Champion, CSF, Frostbite from Holley, and I’m sure more.

I only knew of Koyo and Champion and I knew Champion had previous fitment issues. Never heard of the other brands you mentioned. Koyo makes good products, so it seemed like a safe purchase.

Sounds like you've addressed most of the potential things that could be causing your issues.

I'm very interested to see what the results are for you with this larger radiator. Adding Rows to the radiator is a very interesting thing. Sometimes it's totally the correct solution. I can't tell you how many times in my life we've added a larger radiator into Ag and industrial equipment and it was exactly the ticket needed. I've seen other times were adding thicker radiators caused all kinds of weird problems. Airflow is a funny thing, and as you increase the depth of the stack, you can affect other parts of the system.

The only thing I would have to add, is actually to verify cooling fan function. I know you mentioned in the video that you replaced the fan hub prior to some of the mods, but I have had experience in the past where new to fairly new fan hubs, have failed. Probably unlikely, but worth considering.

What kind of temperatures were you seeing on the hot 110° day?

On that very hot day driving through Nevada near Vegas, my engine temps got to 215 F. I turned off the AC, opened all the windows and turned the heat on full blast. If I didn't do that, I know I would have overheated big time and would have been stranded. I made it home but it wasn't fun.

So far, this Koyorad radiator seems to be making a nice difference. I've driven it in hot temps with the AC on full blast and the highest temp I saw was 194. The only thing I haven't done is load my rig down with extra weight to mimic the weight I carry on trips and then drive up grades in hot temps. I did take a light bar off the front of my bumper that was for sure hindering air flow, so the Koyorad radiator is not the only change I made.

I expect that all aluminum radiator to fix your heat issue. As it has more surface area to dissipate the heat off of. The light bar removal would have helped as well. I think, even fully loaded, with your light bar back on you heat will stay down. :-)

I totally understand where your thinking is on this for sure. No one wants an overheat situation.

Depending on the pressure cap, boil protection is around the 250F range. Most of the increase in boil over is from the pressure, not the coolant mixture.

I wonder what the Toyota spec is for max temperature on the 5vz?

You never want to take any Toyota engine to H. This is will warp the aluminum. On the 5vz just the heads. As the cast blocks can mostly take the heat. On the all aluminum engines. It's most likely game over with major warpage. Blown head gaskets. Etc. At 3/4 to Hot it's time shut it down go save engine from damage.

Sent from my SM-A536V using Tapatalk

I absolutely agree with what you said. The problem with the analog coolant gauge is it's a poor indicator of the engine temp you're running at. The needle doesn't react until your engine is really hot. At what temp the needle actually starts to rise, I don't know, but I've gotten to 215 and the needle was still in the same location it would be if you were at the normal operating temp of high 180's to low 190's. In my opinion, a 30+ degree change with no needle movement is problematic. This is why I like using a secondary means to monitor engine temp. At first I used the phone app Torque Pro but I've since moved to using a Scan Gauge in each of my 3rd Gens.

I don't glance at my scan gauge constantly while driving, so if I burst a coolant hose, I still might not catch it in time before major engine damaged occurred. I mostly closely monitor it when I'm driving in adverse conditions. The ambient temp is high, 90's and above and I'm driving loaded down with gear and/or driving up sustained grades. This is the time I'm also closely monitoring my auto trans temp. Knowledge is power in these circumstances and I've more than once on trips pulled over to the side of the road and idled my engine until my engine and trans temp have gone down. When I'm creeping up on a 210 engine temp or a 220-230 trans temp, that's when I start to consider pulling off the road and giving my rig a break. I'd rather it take longer to get to my destination than burning up my engine or trans and then never getting to my destination. That day I was driving in Nevada and the ambient temp was around 110-115, I saw carnage all over the highway. There were passenger cars and trucks pulled off with what clearly looked like to me they overheated their vehicle.

I always highly suggest that people use an alternative means to monitor important things like Engine Temp, Auto Trans Temp and Charging Volts.

It would be interesting to know what Toyota says is the max safe temp for these engines. But, all I know is I don't want to test it out with either of my 3rd Gens. For me, 215 is the point I don't want to go much further past. I've heard from different sources, that 230-240 is the danger zone.

Yeah, it would be interesting for sure. I haven't found anything published online yet. I need to look in the service manual and see if there's something in there potentially.

I have thought about taking the coolant temperature sensor, warming it up to the point that would trip the light on the dash just to see what sort of a water temperature we end up at. Probably could do the same thing with a potentiometer after getting some scaling measurements done.

Temperature is a funny thing in gas and diesel engines. Some engines run so screaming hot that it's ridiculous. 230F is just a normal day. And there's others that are trying to lay down and die on a guy when they hit 205.

I actually got the temperature light to turn on one time on my 99 4runner after I bought it used from a lifetime of neglect, and hadn't repaired a bunch of the issues it had. The radiator was junk and had some Mickey Mouse patchwork done on it on the upper tank. I figured I for sure was going to have a head gasket let go or something warp. Surprisingly nothing happened. That was about 10,000 miles ago of mostly trails and spirited driving knowing the people I bought it from minutes past history, there's probably a really good chance that the overheat light has been on more than once in it.

380k miles and still counting. Pretty incredible really how durable and long-lived these 4runners are, in spite of people doing stupid things...lol.

I keep thinking I want to go down the road of financial ruin and add bumpers, 34-35" tires, crawl box, front locker, gears, and all the other cool stuff to the rig. I've been thinking this way for a couple years now.

Tim, reading your comments about overheating, and the other thread about guys debating tire sizes and some regrets.....Makes me wonder if I need to just leave well enough alone or not.

Please do keep us posted on your findings with this new radiator. That would be pretty "cool" if that unit gives you enough heat rejection to solve your issue.

There's no engine temperature light. There is a transmission temperature light that comes on at 284*F/140*C...

Lots of modern cars run multistage or controllable thermostats to vary engine temperature based on running conditions. My wife's old '08 Mini Cooper S would run at 225*F while cruising and 185*F if you floored it - and it cost $300 for the thermostat and needed to be replaced every ~100k miles. My Volt runs the gas engine between 190*F and 220*F depending on conditions and load. Lower temps is better for reliability and power, higher temps are better for efficiency and emissions.

-Charlie