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

[GetSandyFJ60]

I love this truck and I'm so frustrated now after literally several years of trying to resolve this issue. FJ60 1981 2F.
The engine was rebuilt 2+ years ago by Marlin of Marlin Crawlers. Very meticulous. It was replaced in the car by a guy who is less meticulous... but supposedly with new water pump, thermostat, fan clutch and a clutch.

Since then I've:
-replaced the radiator (Mishimoto aluminum),
-thermostat (oem from toyota 190degree, $90, also tried a 180degree, swapped it again when it didn't help),
-fan clutch (aisin 017).
-burped the coolant multiple times with the right wheel on a ramp and an elevated funnel kit so it's way up high..
-swapped the heater valve back to oem.
-removed the exhaust and intake manifold, replaced all the gaskets for exhaust. (The reason this is pertinent is the exhaust leak was blowing hot exhaust on to the temp sender causing faulty readings. Runs really quiet!)
-I took it to a shop that tested for hydrocarbons in the coolant, none, suggesting no head gasket issues.
-They tested the temp sender and the gauge. All good.
-I deleted the rear heater (because it was leaking).

THE BIGGEST MYSTERY of all: If I adjust the temp in the cabin to Warm and not cold, it heats up the engine really fast.
But it does blow hot air. There's no sweet smell of coolant in the cabin, suggesting it's not the heater core. The fan works.
I can run the AC and it will maintain engine temp better than if I push the temp knob to Warm...

Ugh... in the mean time I've dialed everything else in on this truck and I just want to take it camping with confidence that I'm not overheating in the wilderness.

Any insight and experience would be greatly appreciated.

 

[NMfjCruiser]

Does it actually overheat or just indicate hot? I had a similar issue after changing my water pump. Since it would inch toward red but not actually overheat I just drove it frustration. One day it just started working normally. Definitely an air bubble in there somewhere despite my efforts to burp it.

 

[OSS]

THE BIGGEST MYSTERY of all: If I adjust the temp in the cabin to Warm and not cold, it heats up the engine really fast.

When the slider in the dash is moved towards the red zone, the cable you’re pushing/pulling is opening up the water valve in the engine bay.
When that valve opens or opens just a little, the hot coolant from the rear of the cylinder head can then flow through the inside heater core and return back to
the water pump intake.

Usually when the heater slider in the dash is moved to the red zone, the water valve opens which allows hot coolant to flow much faster through the rear of the cylinder head - which has the effect of dropping the temperature at that spot because coolant is flowing by it faster.
Guys think that turning on the cabin heater cools the engine when the engine is running hot - but it’s an illusion. It’s only the area around the temperature sender that gets a little cooler because the coolant flow has increased.

In your case, sliding the cabin heater lever to the red zone can’t possibly actually heat up the engine. It’s not possible. What you’re likely seeing is some sort of coolant flow anomaly in the rear of the cylinder head that’s affecting the temperature sender.

 

[vipergrhd]

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.

 

[GetSandyFJ60]

Does it actually overheat or just indicate hot? I had a similar issue after changing my water pump. Since it would inch toward red but not actually overheat I just drove it frustration. One day it just started working normally. Definitely an air bubble in there somewhere despite my efforts to burp it.

It has not overheated. But it gets hot. 3/4 or more on the gauge. I've felt like it's an air bubble for a long time. I don't know how to get rid of it if that's the case.
When I burp it I elevate the radiator and use the funnel kit, I squeeze the top hose, run the heater on high... I had it running for a while where I had burped it a lot. It stayed at 1/2 temp as long as I didn't run the heat. That was great but then I replaced the heater valve, refilled coolant and I'm back to getting hot really easily.
I noticed the fan spinning freely when the engine was warmed up and I turned it off... Also noticed that the fan wasn't blowing hard on acceleration when the engine was warm. So even though it looks brand new, I replaced the fan clutch... Didn't change anything.

 

[60Works]

Are all the heating coolant lines connected correctly? Water pump small lines to heater and return?

1/4" of heat gasket sticking out the back, none in the front? Marlin is good but it is possible to flip the head gasket upside down and the coolant holes are different front to back.

 

[GetSandyFJ60]

When the slider in the dash is moved towards the red zone, the cable you’re pushing/pulling is opening up the water valve in the engine bay.
When that valve opens or opens just a little, the hot coolant from the rear of the cylinder head can then flow through the inside heater core and return back to
the water pump intake.

Usually when the heater slider in the dash is moved to the red zone, the water valve opens which allows hot coolant to flow much faster through the rear of the cylinder head - which has the effect of dropping the temperature at that spot because coolant is flowing by it faster.
Guys think that turning on the cabin heater cools the engine when the engine is running hot - but it’s an illusion. It’s only the area around the temperature sender that gets a little cooler because the coolant flow has increased.

In your case, sliding the cabin heater lever to the red zone can’t possibly actually heat up the engine. It’s not possible. What you’re likely seeing is some sort of coolant flow anomaly in the rear of the cylinder head that’s affecting the temperature sender.

I recently replaced that heater/coolant valve. The coolant flow anomaly is what I was hoping someone might have experience with. Because if it's not a wicked air bubble it's got to be a flow issue. I've looked at all the threads. I'm 99 percent certain I have everything connected correctly!! ha.

 

[OSS]

Trapped bubbles in the cooling system will always eventually clear on their own after a coolant change after about 2 weeks of daily driving- with no user intervention or fancy burping techniques required.
Burping procedures only speed up the process.

 

[GetSandyFJ60]

Are all the heating coolant lines connected correctly? Water pump small lines to heater and return?

1/4" of heat gasket sticking out the back, none in the front? Marlin is good but it is possible to flip the head gasket upside down and the coolant holes are different front to back.

I will check the head gasket. thank you. And I'll double check and try to take video of the water pump lines to heater etc.

 

[RevISK]

When I burp my 40, I park so the front is basically at a 45* angle up.
Rock the truck, squeeze every hose I can reach multiple times. It always amazes me how much more air is in there, burp funnel or not.

 

[GetSandyFJ60]

I will check the head gasket. thank you. And I'll double check and try to take video of the water pump lines to heater etc.

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?

 

[Mark W]

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...

 

[GetSandyFJ60]

So I just grabbed the image of the gasket off the @Cruiser Corps website. I'm a photographer/photoshop guy so I copied the image, flipped it over, changed the color and sandwiched them together. The biggest tell is that the rectangular tab protrudes from only one side. The tab protrudes from the back of my engine as you can see in the picture above. The green that is visible underneath the purple is where there is blockage or mixed flow when the gasket is flipped. @Mark W I agree with you this is unlikely and for a couple years I've been working under the assumption that Marlin's work was the one constant that I could count on... But unfortunately we all make mistakes. And considering that tab is sticking out the back of the engine, I have to assume this is what I've been struggling to resolve. @60Works I can't thank you enough for pointing this out. I would still appreciate your feedback if you've had this happen before.

 

[Mark W]

So I just grabbed the image of the gasket off the @Cruiser Corps website. I'm a photographer/photoshop guy so I copied the image, flipped it over, changed the color and sandwiched them together. The biggest tell is that the rectangular tab protrudes from only one side. The tab protrudes from the back of my engine as you can see in the picture above. The green that is visible underneath the purple is where there is blockage or mixed flow when the gasket is flipped. @Mark W I agree with you this is unlikely and for a couple years I've been working under the assumption that Marlin's work was the one constant that I could count on... But unfortunately we all make mistakes. And considering that tab is sticking out the back of the engine, I have to assume this is what I've been struggling to resolve. @60Works I can't thank you enough for pointing this out. I would still appreciate your feedback if you've had this happen before.

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The tab is SUPPOSED to be sticking out the back. Your picture clearly shows (in the mirror) that it is.

Mark...

 

[Mark W]

The tab will interfere with the waterpump if you install the gasket backwards and it will not fit. Unless you do something stupid... like cutting it off.

Mark...

 

[yotadude520]

At this point you should install a mechanical temp gauge and using that to determine it’s true temp.

These electronic gauges are not as accurate. I’d recommend an Autometer. On my 87 pickup it was so accurate that I could see when the thermostat opened at 190° as the temp would drop back down to 180-185.

 

[GetSandyFJ60]

The tab will interfere with the waterpump if you install the gasket backwards and it will not fit. Unless you do something stupid... like cutting it off.

Mark...

oh....... I guess I misunderstood. So having the tab in the back is correct.. Well crap. I was literally ready to take the whole thing apart, just happy that the mysterious back flow aberration was resolved. But it sounds like it's not. Why does my truck get hotter when I push the knob to Warm?!! And why can't I normalize the engine temp?

 

[Mark W]

oh....... I guess I misunderstood. So having the tab in the back is correct.. Well crap. I was literally ready to take the whole thing apart, just happy that the mysterious back flow aberration was resolved. But it sounds like it's not. Why does my truck get hotter when I push the knob to Warm?!! And why can't I normalize the engine temp?

The rest of my first post...

Other than the gauge, how do you know it is hot? Have you taken any actual temp readings? Based strictly on the info you have provided so far, my money is on the gauge being the actual problem.

Mark...

 

[GetSandyFJ60]

Yeah I have an infrared gun. It shows temps all over the spectrum. Won't read off the aluminum radiator very well but the top hoses are usually hotter than the bottom. the block varies depending on location checked. That's a good point though. I haven't checked temps with the gun recently. I have a new temp sender that I'll install. The shop said they tested the Ohms or some s*** on the gauge that suggested it was functioning. But yeah, I guess that's the next thing to throw at it.

 

[GetSandyFJ60]

At this point you should install a mechanical temp gauge and using that to determine it’s true temp.

These electronic gauges are not as accurate. I’d recommend an Autometer. On my 87 pickup it was so accurate that I could see when the thermostat opened at 190° as the temp would drop back down to 180-185.

@yotadude520 where do you suggest getting the temp from? Because the temps seem to vary depending where I check them. Top radiator hose?
Thanks.