Overheating problem (1 Viewer)

[mendozart]

Ok, my radiator was starting to weep, so I ordered a new Toyota radiator, and was topping off coolant. My wife was just using for dropping kids off at school, but she went a bit further and LC overheated. I had her shut it off when she called.
Replaced radiator, thermostat, hoses, and water pump, all Toyota parts. Even flushed out green coolant, and went with Toyota red. Changed oil and filter, looked good. After driving around the city for a bit, I took it on the freeway. It was looking good, but then started creeping up a bit. When I pulled over, engine running still, temp dropped to normal. As I would get going again, would creep up, but would drop when I pulled over, engine running. Does this sound like a bad fan clutch? While at operating temp, I was able to stop the fan ala the rolled up newspaper method. Any advice is greatly appreciated.

 

[Mark W]

Water pump is about the last place to look for a cooling problem in the 1FZ. Fan clutch is one of the first. Your symptoms deems to support this as a high probablity. Not enough info to make any definitive statement about that though (air temp and just exactly how hard or easy it was to stop the fan would help.

A better indicator than stopping the fan with something is to simply turn the engine off when it is hot enough so that the clutch should be engaged. if the fan freewheels to a stop, instead of stopping almost immediately as the engine does... it is not locking up.

Also... make sure it is really overheating, not just lying to you due to a faulty gauge. Not common, but it can happen.

Failing head gasket can also cause overheating of course, but I would not jump to that as a first choice.

Mark...

 

[robnicko]

did you replace the radiator cap as well with a new OEM one?
is the overflow getting higher than normal when overheating symptoms are happening?
in my experience when a fan clutch doesnt lock up correctly the overheating happens at slow speeds / idle, in traffic and should cool down once going along due to the wind passing thru the radiator, yours is doing the opposite which is odd
Have you bled the system adequately enough, possible theres an air pocket in there however ive always found that these tend to self bleed after a short while

 

[flintknapper]

Replace your fan clutch with a Blue Hub model or do the fan clutch 'mod' if you live in a hot climate.

IF the fan clutch is original to the engine.....odds are excellent it has seen better days. Replacing should eliminate that as being a potential source for your issue. Also make certain your radiator cap is OEM.

 

[mendozart]

To robnicko and flintknapper, the OEM Toyota radiator comes with a new cap.

 

[jonheld]

To robnicko and flintknapper, the OEM Toyota radiator comes with a new cap.

Typical fan clutch issue. It is the most overlooked item in the cooling system as well as being a crucial component. At highway speeds more air will flow around the front of the truck rather than through the radiator. This is because the front of the 80 is shaped like a brick. The engine fan has to create negative pressure behind the radiator in order to have air flow through it at highway speeds.
If your fan clutch is original, it's now 29 years old and doesn't owe you anything more. I highly recommend a new Aisin blue hub modified fan clutch that is available from a few sellers here. Or simply purchase a new clutch and do the modification yourself. I would not bother messing around with a 29 year old clutch.
You can find them online without paying a surcharge for the red box from Toyota.
Toyota part number: 16210-66020
Aisin part number: FCT-004.

 

[mendozart]

Typical fan clutch issue. It is the most overlooked item in the cooling system as well as being a crucial component. At highway speeds more air will flow around the front of the truck rather than through the radiator. This is because the front of the 80 is shaped like a brick. The engine fan has to create negative pressure behind the radiator in order to have air flow through it at highway speeds.
If your fan clutch is original, it's now 29 years old and doesn't owe you anything more. I highly recommend a new Aisin blue hub modified fan clutch that is available from a few sellers here. Or simply purchase a new clutch and do the modification yourself. I would not bother messing around with a 29 year old clutch.
You can find them online without paying a surcharge for the red box from Toyota.
Toyota part number: 16210-66020
Aisin part number: FCT-004.

I guess now, I just have to decide on which fan clutch to buy?

 

[robnicko]

I guess now, I just have to decide on which fan clutch to buy?

Aisin FCT004 SSDP

 

[Mark W]

I guess now, I just have to decide on which fan clutch to buy?

Confirm that the fan clutch is in fact faulty before just throwing any more parts at the problem.

Mark...

 

[flintknapper]

Confirm that the fan clutch is in fact faulty before just throwing any more parts at the problem.

Mark...

IF the fan clutch is original.....it won't be throwing parts at it. Even if still working at all....it will be marginal. This is a very common problem and one that I would have looked at first, not this late in the game.

My advice would be to install a straight up/stock blue hub fan clutch, then 'mod' it later if needed.

I'm certainly with you with respect to 'throwing parts' at a vehicle in lieu of testing, but in this case.....I can almost guarantee you the OP will benefit from installing a new F/C.

 

[Mark W]

IF the fan clutch is original.....it won't be throwing parts at it. Even if still working at all....it will be marginal. This is a very common problem and one that I would have looked at first, not this late in the game.

My advice would be to install a straight up/stock blue hub fan clutch, then 'mod' it later if needed.

I'm certainly with you with respect to 'throwing parts' at a vehicle in lieu of testing, but in this case.....I can almost guarantee you the OP will benefit from installing a new F/C.

I agree that he will almost certainly benefit from a new fan clutch, particularly if he "upgrades" it. I agree that it is a common problem. I agree that it is very likely the original flaw. I agree that I would have looked there first myself.

But just because the approach to the problem has been to throw parts at it with no real diagnosis, is no reason not to break that cycle at this point. It is so phucking easy to confirm that the fan is bad, there is simply no reason not to do it before buying a new one. It is always nice to know that you are fixing a problem, rather than just whistling past the graveyard when you pull the rig back out of the garage... again.

Hell, it may be that he can simply dump the old tired oil out and replace it with whatever viscosity he chooses without buying a new one. But personally, I would still confirm that it is the problem first.

Mark...

 

[BILT4ME]

I bought my Aisin blue hub clutch from Amazon. It did not solve my overheat issue until I modded it with 56 ml of 15K oil and adjusted the opening points to 118*F in the middle of the travel. Now it roars every time I start, and it has not affected my gas mileage at all.

I suggest to plan on modding it within a year. I was closer to 2 years by the time I actually got to it.

 

[mendozart]

So far I have replaced everything that “needed” to be replaced. The radiator was leaking. The hoses were old, as was the thermostat. After I replaced those parts and drove it around, I found the water pump leaking at the weep hole, so I then replaced it. The fan clutch is definitely the original one, so I don’t mind replacing it. I’m going to buy the Aisin, and will look into the process of modding it.

 

[jpoole]

You are on the right track and when it comes to keeping the 1FZ cool it's an area where letting the parts cannon fire (not saying you did that) is more appropriate as an overheat could lead to lots of costs/work.

To add another data point with off-the-shelf Aisin blue hubs, I installed a new one that would allow my 1FZ to hit 220 F on short test drives that included Summer heat, AC and big hills. I changed the oil and lowered the opening temp and it's done well since including a lot of Summer towing, etc. Most folks have had luck with new off-the-shelf blue hub clutches from what I gather but I've heard of a few instances of the new ones having too little oil, etc. Practical takeaway is that you should watch your temps for a little while after changing a fan clutch to make sure they are staying well below the 220 F mark in most, if not all conditions.

In case you aren't aware, the stock coolant temp gauge is buffered electronically so that it is a poor representation of actual engine temps and of small temp changes. Looks like you have an ODB1 truck so you can't run the easy ODB2 based temp setup. I would add one of the small/inexpensive coolant temp setups so that you can monitor your actual temps. Without this ability you are driving blind in terms of knowing how your fan clutch tune and coolant system are performing.

I've had luck with both of the following setups in the bluehub I'm running now though after a few years with the OG setup coolant temps had started to creep up close to 220 F in mid-Summer, highway towing scenarios. I decided to add a bit more oomph on engagement timing (hole open temp) and oil weight and haven't noticed adverse impacts from that yet. Temps are much improved with the new tune and MPG is in line with what it was before, from what I can tell.

7/23/23 - 50% open at 100, 20kcst to top of oval holes

OG: 45 ml 15k CST oil small hole 50% open at 110 degrees

 

[mendozart]

You are on the right track and when it comes to keeping the 1FZ cool it's an area where letting the parts cannon fire (not saying you did that) is more appropriate as an overheat could lead to lots of costs/work.

To add another data point with off-the-shelf Aisin blue hubs, I installed a new one that would allow my 1FZ to hit 220 F on short test drives that included Summer heat, AC and big hills. I changed the oil and lowered the opening temp and it's done well since including a lot of Summer towing, etc. Most folks have had luck with new off-the-shelf blue hub clutches from what I gather but I've heard of a few instances of the new ones having too little oil, etc. Practical takeaway is that you should watch your temps for a little while after changing a fan clutch to make sure they are staying well below the 220 F mark in most, if not all conditions.

In case you aren't aware, the stock coolant temp gauge is buffered electronically so that it is a poor representation of actual engine temps and of small temp changes. Looks like you have an ODB1 truck so you can't run the easy ODB2 based temp setup. I would add one of the small/inexpensive coolant temp setups so that you can monitor your actual temps. Without this ability you are driving blind in terms of knowing how your fan clutch tune and coolant system are performing.

I've had luck with both of the following setups in the bluehub I'm running now though after a few years with the OG setup coolant temps had started to creep up close to 220 F in mid-Summer, highway towing scenarios. I decided to add a bit more oomph on engagement timing (hole open temp) and oil weight and haven't noticed adverse impacts from that yet. Temps are much improved with the new tune and MPG is in line with what it was before, from what I can tell.

7/23/23 - 50% open at 100, 20kcst to top of oval holes

OG: 45 ml 15k CST oil small hole 50% open at 110 degrees

Do you happen to have any info on a temp monitoring setup for OBD1?

 

[jpoole]

I don't have direct experience with a particular setup but a friend with a '94 FZJ80 has had luck with a low-cost setup that he got online. If you go this route you are spoiled for choice on Amazon and other online retailers. The main pieces you will need to buy are:

• a gauge of some sort (digital, analog, whatever) to show the temps
• a sending unit that is stuck into the cooling system somewhere and that is compatible with the gauge you have
• wiring and mounting pieces for the gauge and sending unit

Here's an example that may be compatible with the 80:

Amazon product ASIN B0BJV5W63R​

​

That may include everything you need if you want to use the "cut a radiator hose" method, the wiring is long enough and 38MM is the correct hose size. Here's a discussion on the rad hose diameters:

Upper radiator hose - 38mm or 40mm?

I am looking at a water temperature sensor that goes in the upper radiator hose (cut the hose and it splices in) and from what I measure on the radiator nipple I have a 39mm but the available sizes are 38mm or 40mm. Any help in determining the actual size? I am also open to suggestions on other...

forum.ih8mud.com

You could also get a gauge/sender setup that doesn't use the "cut a radiator hose" install approach and then drill and tap to install the sending unit. There's a spot on the elbow for the upper radiator hose that works (just aft of the distributor) but you'd need to remove the part and then drill/tap for the sending unit. Here's a post on that ( see post #157 on the following page ):

80 Series Aftermarket Gauge Choices & Mounting Options

Shout out to @Hlteq, he met up with me today to show me his RAM mounts on his rig. 👍🏻 I am going with a shorter & smaller version of his set up. RAM makes several different sized balls. I went with size A, 9/16” ball, rated for a 1/2 pound. I’ll attach a ball to the Wits End Useless...

forum.ih8mud.com

​

Sending unit placement can cause the temperature monitored to vary as there are hotter and cooler sections of the system but for typical 80 operation you want to be aware of relative temps and changes so it shouldn't really matter.

I'd personally drill/tap the spot described above and put the sending unit in that location so that I didn't have to cut the rad hoses and add more leak spots and complication for future hose changes. I'd also look for a digital (easier to read while glancing down/driving) gauge that included a warning indication temp setting. I'd then put the gauge somewhere out of the way, but still visible so that in the long run I wasn't distracted by it but could glance at it when interested. In front of the shifter seems like a good location to me. The warning would be for when something breaks and your engine starts to overheat but you don't notice immediately. Seems like 210 or so F could be a good temperature that you shouldn't hit often but you'd want to know when you do, even if there's not really a problem. I don't know when you start to risk damage on these, temp wise, but Toyota decided to disable the AC system at 220 F so I use that as the temp ceiling that I want to avoid.

 

[lumbee1]

My modded OEM fan clutch went bad and my symptoms were the exact opposite of yours.

Driving it would remain cool however when I stopped, sometimes the temperature would creep up and several times when I parked and shut off the engine, the overflow would boil over.

I got a blue hub in preparation for a supercharger install and swapped the two. After pulling my fan clutch it felt fine and had resistance. I couldn't figure out why it was bad. While walking back to the house I spun the clutch one more time in my hands and it spun like a ball bearing with no resistance. This explains why sometimes it worked and sometimes it didn't.

I also noticed that when I modded it with thicker fluid, the amount that came out didn't match what others posted. I measured what came out and added exactly that fluid back in.

 

[BILT4ME]

My modded OEM fan clutch went bad and my symptoms were the exact opposite of yours.

Driving it would remain cool however when I stopped, sometimes the temperature would creep up and several times when I parked and shut off the engine, the overflow would boil over.

I got a blue hub in preparation for a supercharger install and swapped the two. After pulling my fan clutch it felt fine and had resistance. I couldn't figure out why it was bad. While walking back to the house I spun the clutch one more time in my hands and it spun like a ball bearing with no resistance. This explains why sometimes it worked and sometimes it didn't.

I also noticed that when I modded it with thicker fluid, the amount that came out didn't match what others posted. I measured what came out and added exactly that fluid back in.

When I opened my new blue hub, I only got out about half of what I put back in. Plus, it was MUCH thinner.

After the 56 ml of 15K, I have roaring and so far it has not exceeded 192°F. But I have not had any hot, hard working days on it yet. Just long road miles.

 

[mendozart]

I’m wondering just how accurate my dash gauge really is. The engine itself is not showing any sign of overheating, like bubbling in the overflow tank or anything. I wish the coolant sensor on the block, was easier to get to.

 

[effjay80]

Do you happen to have any info on a temp monitoring setup for OBD1?

Perhaps best mod made to my 94 was inserting a Koso temp gauge. Easy job and very useful source of real time critical info.

Terrible pic sorry but sensor lead runs thru the firewall.