Cooling / Overheating issue. Super mysterious. Tried everything. (1 Viewer)

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yotadude520 said:
Here's the gauge that I can vouch for


On where to install read this post.

forum.ih8mud.com

Builds - Woodrow, the 60 - Tilda Bogue Service Station

Next up. June 1986 FJ60. We shall call it Woodrow.
forum.ih8mud.com forum.ih8mud.com

Search block plug 2F on here too and you'll find some pictures/threads about it!
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I’ll do it. Thank you.
 
GetSandyFJ60 said:
First, I'm sad to report that Marlin @Marlin Crawler passed away roughly a year ago... RIP. He was clearly dearly loved, especially in the 4x4 and crawling world...
Second, Holy crap... Is that the head gasket sticking out the back of the head? @60Works ? Have you experienced this issue? I need to be certain, of course, before pulling everything apart. In case the picture is confusing it's an oval shaped mirror on an extension arm looking at the back of the block. Is that metal gasket sticking out an indicator that it's installed incorrectly?

View attachment 3608848
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The gasket is supposed to stick out the back. You're good.

To install it incorrectly a tech would need to cut off the extra in front so the water pump would mount. I've seen it done by a young newbie who didn't want to pull the head after torquing it down.
 
Mark W said:
If someone wanted to install the head gasket backwards, they would have to cut the tab off of the back end in order to do so. The tab is there for exactly this reason. To ensure the gasket can not be put in backwards. Not an easy mistake to make. It would also deprive the rocker arms assembly of oil... not an easy thing to miss. Doubtful in the extreme that Marlins's guys did this.


It sounds like the only indication of overheating/wonky cooling that you have is what the gauge is telling you. Sounds/smells/changes in power?

Have you actually checked the temp with anything besides the factory gauge? Handheld infrared sensor for example?

You say that someone has checked the gauge and sender. How did they check?

It is a widely know glitch in the FJ60s is for the resistor that drops the voltage for the temp gauges and gas gauge to fail intermittently. When it does, the temp read high (overheating usually) and the gas reads empty.

I have also seen the temp gauge read hot, to varying degrees all on its own. I have been kinda a part-time surrogate dad for the daughter of one of the guys here on mud when she is in Alaska. When she took her Alaska acquired '60 south, she got as far as Tok and called me, because it was overheating badly (she thought). When I got there the next day, I soon realized that it was not really overheating. The gauge was lying for it's own personal and unrevealed reasons. She headed off on the rest of her trip with an infrared sensor in the glove box, simply checking it every once in a while over the next days to ensure that the gauge was still just doing it's own thing and that she could ignore it.


Mark...
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I've been able to resolve the temp high/fuel low spikes by cleaning the electrical connection at the fuel sender on top of the fuel tank. Advice from an old Mudd thread. It worked temporarily. When I changed the sender/float with new OEM; the problem went away and never returned.
 
vipergrhd said:
Did you know that the thermostat could be installed backwards? I found out mine was due to the temp. gauge was always on the hot side after i installed it correctly the temp. went down. Just my 2 pennies.
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Yep and easy to check this is the first thing i'd do. Had this happen recently on another vehicle.

Also if the thermostat does not have a bleed hole in it you can add one to help get the air out.
 
bhsdriller said:
Yep and easy to check this is the first thing i'd do. Had this happen recently on another vehicle.

Also if the thermostat does not have a bleed hole in it you can add one to help get the air out.
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I put a 180° thermostat in (ring gasket up and spring side down) a year and a half ago. With the problem persisting I swapped that out for the Toyota OEM 190° thermostat that cost 3X everything else at, $90 and it has a bleed hole for air. One suggestion was to drill a couple more bleed holes in case there is air trapped that’s preventing the thermostat from activating. My plan is to do that and replace the temp sender and add another temp gauge on the side of the block. But if I’m honest this feels like a bandaid on a broken arm. My temp gauge really feels like it performs normally. I don’t feel like I’m solving for the actual issue. The temp gauge shows hotter temps when I push the control knob to warm!! That’s just really weird. And the engine doesn’t stay at normal operating temp. The new gauge will help clarify if all of this is reality.
 
bhsdriller said:
Yep and easy to check this is the first thing i'd do. Had this happen recently on another vehicle.

Also if the thermostat does not have a bleed hole in it you can add one to help get the air out.
Click to expand...
I put a 180° thermostat in (ring gasket up and spring side down) a year and a half ago. With the problem persisting I swapped that out for the Toyota OEM 190° thermostat that cost 3X everything else at, $90 and it has a bleed hole for air. One suggestion was to drill a couple more bleed holes in case there is air trapped that’s preventing the thermostat from activating. My plan is to do that and replace the temp sender and add another temp gauge on the side of the block. But if I’m honest this feels like a bandaid on a broken arm. My temp gauge really feels like it performs normally. I don’t feel like I’m solving for the actual issue. The temp gauge shows hotter temps when I push the control knob to warm!! That’s just really weird. And the engine doesn’t stay at normal operating temp. The new gauge will help clarify if all of thisthis is reality.
 
GetSandyFJ60 said:
I put a 180° thermostat in (ring gasket up and spring side down) a year and a half ago. With the problem persisting I swapped that out for the Toyota OEM 190° thermostat that cost 3X everything else at, $90 and it has a bleed hole for air. One suggestion was to drill a couple more bleed holes in case there is air trapped that’s preventing the thermostat from activating. My plan is to do that and replace the temp sender and add another temp gauge on the side of the block. But if I’m honest this feels like a bandaid on a broken arm. My temp gauge really feels like it performs normally. I don’t feel like I’m solving for the actual issue. The temp gauge shows hotter temps when I push the control knob to warm!! That’s just really weird. And the engine doesn’t stay at normal operating temp. The new gauge will help clarify if all of thisthis is reality.
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Poking around with the infrared gun I discovered the air rod injection tube (not sure what it’s called) is really hot. On further inspection found that the hoses coming off the smog pump were reversed. Probably been that way as long as I’ve had the truck (20 yrs). Swapping them has likely decreased the smog output but didn’t bring the temp down on the air rod. Any experience with this? Is it normal for the rod to reach 300+degrees?

IMG_0080.jpeg


IMG_0092.jpeg
 
The air injection manifold is bolted directly to the exhaust ports. 700°F exhaust is exiting those ports. I’ve never measured my air injection manifold, but I can assure you — you never need to.
 
GetSandyFJ60 said:
Poking around with the infrared gun I discovered the air rod injection tube (not sure what it’s called) is really hot. On further inspection found that the hoses coming off the smog pump were reversed. Probably been that way as long as I’ve had the truck (20 yrs). Swapping them has likely decreased the smog output but didn’t bring the temp down on the air rod. Any experience with this? Is it normal for the rod to reach 300+degrees?

View attachment 3610518

View attachment 3610650
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The pictures are of the fan clutch that I removed (10k mi. Looks brand new) Aisin FCT-017. I replaced it with the same exact thing because that’s what is recommended in the searches that I did. Amazon $58.
The weird thing: The fan blade SPINS FREELY right after I turn the engine off. And it doesn’t blow air the same way it does when the engine is cold. Both of these things seem counter intuitive and are the reason that I replaced it. Am I wrong? Is the replacement also faulty? Is the Amazon Aisin FCT-017 not the real deal?
It wasn’t hard to replace and I’ll do it again if there is a fan clutch that works better.

IMG_0105.jpeg


IMG_0106.jpeg


IMG_0107.jpeg


IMG_0100.jpeg
 
There’s nothing wrong with your new fan clutch.

The fan is supposed to spin freely under certain circumstances.
  1. After fan has spun fast at higher RPMs (driving speed) but radiator isn’t too hot
Inside the clutch is a silicone oil that can flow into another chamber to decouple the fan - allowing it to spin freely.
When the radiator is hot with hot air blowing over the clutch, the bimetal temperature sensor thingy in the clutch rotates an internal valve, preventing the oil from migrating to the outer chamber. This keeps the fan spinning.
But when the radiator cools down a bit, the valve opens up and the oil can then travel to the outside chamber- allowing the fan to spin freely.
When the engine is first started and everything is cold, the oil is more vicious and pooled, so the fan engages even though it’s not needed — until centrifugal force spins it out.

If the fan clutch never de-coupled the fan, the fan would ROAR at highway speeds and all the time at higher RPMs.

My explanation above isn’t exactly how it works but it’s sufficient to get a general idea how the thing operates
 
Last edited:
OSS said:
There’s nothing wrong with your new fan clutch.

The fan is supposed to spin freely under certain circumstances.
  1. After fan has spun fast at higher RPMs (driving speed) but radiator isn’t too hot
Inside the clutch is a silicone oil that can flow into another chamber to decouple the fan - allowing it to spin freely.
When the radiator is hot with hot air blowing over the clutch, the bimetal temperature sensor thingy in the clutch rotates an internal valve, preventing the oil from migrating to the outer chamber. This keeps the fan spinning.
But when the radiator cools down a bit, the valve opens up and the oil can then travel to the outside chamber- allowing the fan to spin freely.
When the engine is first started and everything is cold, the oil is more vicious and pooled, so the fan engages even though it’s not needed — until centrifugal force spins it out.

If the fan clutch never de-coupled the fan, the fan would ROAR at highway speeds and all the time at higher RPMs.

My explanation above isn’t exactly how it works but it’s sufficient to get a general idea how the thing operates
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Thank you for the detailed description and the education. Freewheeling at highway speeds with low radiator temps makes perfect sense. Add fan clutch to the list of unnecessary replacements I’ve done to resolve this thing. I haven’t had time to replace the original temp sender or add an additional temp gauge. I will report back when that happens. Thanks again.
 
I got $5 that says either air in the system (I've seen this persist far longer than I thought possible) or the temp sender.
 
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