Intermittent Overheating Issues (solved: dirty radiator)

yup, i'll be replacing next week when I return from travels

 

What you are describing sounds normal to me. Do you understand how a radiator works?

 

What stood out to me was the 2/3. Mine never gets much above 1/2.

 

Idling at 85°F with the A/C on is bound to tax any cooling system. Once the vehicle is moving more air is being drawn into the radiator.

 

Where did you get the replacement fan clutch?

If you have (or access to) an infrared thermometer that you can specifically measure the temperature of the water pump housing. Specifically - early signs of a water pump bearing failure is that the pump runs a fever even though the weep hole is not seeping.

 

Hi there, I believe I do understand at a rudimentary level though I am not a mechanic, nor an engineer so I can't say I fully understand how a radiator works I s'pose This experience wasn't normal for my ownership before June of last year and it isn't normal for my friends with 4runners, so it seems the consensus says: not normal.

 

I appreciate the good question and helpful insight. I got it from RockAuto, went with Aisin, and I actually made a youtube video about replacing it, linked in a previous post of mine. Interesting idea to monitor the water pump temp with a IR thermometer, might just do that! Thanks for the helpful tip.

 

My concern was that some aftermarket parts do not function as well as OEM. I'm hoping Aisin from Rock Auto is as good as OEM.

Regarding the water pump - you may want to check the temperature of one of your friend's T4R so that you have a benchmark to compare. (On a known good T4R that is operating normally.)
Most thermostats on gasoline engines are set to modulate at a temperature of 195 degrees F. So you could see a variance in temps, but not a huge amount if everything is working right. My suspicion would be that you may be at the beginning of a water pump failure, and that is why I suggested to measure the water pump housing temp as your truck idles and see if it can see the temp climb on a hot day.

 

Aisin is actually the OEM manufacturer for most all the cooling components I believe! Only difference is a Toyota stamp (& higher price) haha. Yes, I’m suspicious of water pump too. And that’s a great diagnosis idea, thank you! I’ll be going ahead with thermostat and then pending solution water pump next.

 

Well I'm not intimately familiar with the cooling system on the 4Runner, I haven't seen a vehicle manufactured in the last 20 years or so that even has an engine driven fan necessitating a clutch. My past experience with other vehicles is that the cooling fans are electric and are controlled by temperature switches in the radiator. Perhaps your cooling fans aren't coming on at the proper temperature leading to temperatures higher than normal. The fact that it cools down once you drive seems to eliminate all other components such as the water pump or thermostat. Have you observed at what temperature is the cooling fans turn on?

The cardinal rule of troubleshooting is to always suspect and perform the easiest repairs first!

 

Bro, open your hood. Is this your first longitudinal engine in a while?

You want to see something really fucked, check out the new Tundra: both engine driven cooling fan and radiator mounted electric fans.

 

As a matet of fact my 2006 Charger with a Gen III 5.7 was "longitudinal". At least when I changed the camshaft and heads it was.

I just assumed that Toyota was using 21st century technology.

 

No, I'll give you that one, because you said past 20 years. That's what I meant, it sounds like the 4R is your first old-school design in a while.

I'll admit, it took me a while to figure out why my wife's cars were always so quiet on startup: it was the lack of a giant fan whoosh, lol.

 

So you have not monitored any actual temperatures, this is all based on gauge level? Get a bluetooth OBD dongle and monitor actual temps.

 

This thread is messier than I intended haha. I have monitored temps via OBD, and yes those temps are confirming the dash gauge which says I'm at hotter than normal operating temps. I will update this thread with my future findings at a later date.

 

So what is the actual temperature?

 

This kind of sounds like low coolant level, or a big air bubble in the cooling system. See if you can park it on an incline, and check the coolant level once the engine is cold. Make sure to always check levels at the actual radiator cap when stone cold (for safety).

I remember last time I did a coolant change on old car, I filled the radiator, started the car with the radiator cap off, then rocked the car back and forth. Sometimes you’d get big bubbles burbling out, which lowered the level slightly. You top off, keep rocking for a while, refill as needed as it burps, then close it up when it seemed bled/burped. Then check level again when cold in a few days to make sure it hadn’t gone down.

Air bubbles probably work themselves out naturally without doing the above, but that will result in a low radiator level. Make sure to check level at the radiator, because the overflow bottle might flow into the radiator with a big bubble.

If it’s not a bubble, but your level at the radiatior goes low, check for coolant vapor in the exhaust. Could be bad head gasket.

If it’s not this, and your levels stay good then I’d suspect waterpump,

 

/\ This.

 

This is a really good thought. While I have not had reason to disturb the cooling system of my T4R yet, I have worked on vehicles where it is very important to bleed trapped air in the engine cooling system. Trapped air in the cylinder head will lead to a hot spot and could cause a head gasket failure. Some engines have a bleed screw or a bleed port to release trapped air. I don't know if this exists on the 1GRFE engine in the 5th Gen.

 

The 4Runner usually traps some air regardless of coolant exchange method. You will see this when you drain, fill and burp the system, set the correct level in the overflow tank and then after a week or so, the level drops. You add a little more. It drops again-you now think you have a leak. This may continue for up to 500-1000 miles. It's maddening. It will eventually burp out all the air and the overflow level will stabilize. Use a piece of blue painters tape to mark cold/hot levels and monitor.

 

Happy New Year! I'm updating a few of my threads today to start 2025. I'm almost 100% certain that I have solved my "mysterious 'overheating' issue." Feel free to ignore my ramblings below, as they're mostly for myself. Long story short: @Agent_Outside was correct and won the prize because my radiator was disgustingly dirty, and I was too ignorant to understand that! If you watch the video, it's okay to laugh at me. Here's the YouTube video I made about the fix because I could not find any other videos about the topic: https://youtu.be/asRkfHKk6TU

Ramblings... recap to date (1/1/25): in June of 2023, this issue first began while I was 2k miles from home on a road trip. Everything was perfectly smooth on the 4Runner except for this one issue: on warmer days of +80º the engine temps would slowly climb if we were idling with the AC running, but it would quickly come down to normal operating temps once driving +15mph. I monitored temps via OBD Link MX+ on various occasions. I would watch the temps slowly climb up to about ~220ºF on the hot side and anywhere from ~175-200ºF for normal operating temps. Despite what anyone on this forum or elsewhere was saying, it is not normal for a modern vehicle to struggle with operating temps on hot days unless something is wrong. Additionally, this was our 7th major road trip in less than 2 years of ownership, and we had spent time in plenty of hot climates and idling for long periods. Something was out of whack on the truck, and it felt completely out of the blue. However, hindsight is 20/20, and when this began, I remembered that in May 2023, there were a few hot days when the AC was struggling to stay cool, and this should have been a clear sign to me.

Anyway, this "overheating" was easy enough to work around by avoiding idling in hot temps, but this got annoying fast. After replacing the fan clutch in May 2024, I was hoping I had solved the issue. Why did I wait that long? Well, it wasn't running hot all the time and even sometimes ran fine on hot days. Plus, I was trying to avoid throwing parts at the problem, and even though I did this a little bit in the end, I'm glad I didn't do more. So, the fan clutch diagnosis was made by my mechanic, but I had also come to this conclusion myself. The reason was that some sort of airflow issue was the only thing that made sense with my set of circumstances. Replacing the fan clutch did not solve the issue, and fortunately, my wife and I were out of the country for much of the summer of 2024. So there was no urgency for the solution, but I continued to think about it as the "running hot" happened a few times in the early fall during hotter days. All this led up till the first week of December when I read some random forum post talking about replacing the foam that's glued to the top of the radiator. This inspired my curiosity to go have a look. Behold, I found my incredibly disgusting radiator.

However, I had missed the most obvious answer, which came from @Agent_Outside, because I did not know there was a piece of foam blocking my visual of the radiator. I readily admit my ignorance because I was opening the engine bay and looking at the visible cooling fins, but I'm now aware that I was looking at the AC condenser and the radiator is actually about 1 inch behind that and hidden to the naked eye! In the end, I'm extremely hopeful that I've just solved the overheating issue by deep cleaning the radiator, and you can watch that process in the YouTube video that I made in hopes of helping others.

pic attached for toyota's silly choice for radiator bolt locations. yes, you have to remove the bumper for the job.