Fj60 running hot (1 Viewer)

[Louiehenry]

so my 60 series was over heating, replaced the water pump, thermostat, and fan clutch
Still running hot. I did forget to replace the gasket on top of the thermostat, and was wondering it that could cause it to overheat! Any other thoughts as to what it might be?

 

[Output Shaft]

Get a cheap infrared temperature gun (Harbor Freight) and first verify that the engine actually is running hot and not the temperature gauge acting up.

A missing top gasket on top of the thermostat won't cause the engine to run too hot. It will cause it to run too cool.

If the engine really is running hot, (by verifying with the IR gun) the radiator could be the problem. Plugged up inside.

 

[Trapper50cal]

How did you refill your anti-freeze? The reason I ask is that this can be tough to do
correctly...and running not enough coolant (not completely full) can make it run hot too...
At least that's what I experienced when my water pump was leaking through the weep
hole and I was low on coolant.

 

[Output Shaft]

Ohhhh and I forgot to mention....
If you're seeing high temps immediately after draining & refilling some coolant, the gauge will always read hot until all the air is purged out. Gauge is showing fake hot. Engine not hot.

Burping the Temperature Sender on a 2F after a Coolant Change

 

[Louiehenry]

Well, I can hear it boiling, which leads me to believe I didn't bleed it correctly. So I guess I'll do that and see if it fixes it

 

[Output Shaft]

50/50 coolant boils at 265°F in a pressurized system and at 225°F if not pressurized. How's the radiator fill cap doing?

 

[mrlocksmith]

If it runs hot on the freeway or under load and you have ruled out everything else, there is a spring that keeps the lower rad hose from collapsing under high suction @ freeway type driving. Mine was missing and once I replaced it things worked fine.

 

[BlackCat]

My gauge has a mind of its own- sometimes it's at a quarter, sometimes it's at half way, sometimes it's just slightly above half. IR gun shows it never over 195ish. It'll read 185 and show 1/4 on the gauge, it'll also read 185 and show over half on the gauge. Point being, make sure it's actually running hot.

 

[Landpimp]

No, there is no spring on a stock 60, that's an aftermarket hose if it has a spring

If it runs hot on the freeway or under load and you have ruled out everything else, there is a spring that keeps the lower rad hose from collapsing under high suction @ freeway type driving. Mine was missing and once I replaced it things worked fine.

 

[mattressking]

Prior to this, what was the gauge doing?

I've found that a majority of the issues are due to incorrect sensors or bubbles.

Like Landpimp said, none of the coolant hoses have a spring to prevent collapsing. How is the heat front and rear? Get the seal for the thermostat, refill the truck and bleed. Once that is done and you have heat from both heaters, take it for a drive. Once back, shoot the radiator for temp if its still high then determine if its just the gauge measuring high due to a bubble.

If radiator temp looks good, make sure your overflow bottle is filled to the full mark when the truck is hot. Wait for the truck to be ice cold, check overflow, if its empty or really low, fill it again to halfway or a bit more. The truck will suck up the coolant to slowly eliminate bubbles and fill itself properly.

Last but not least, once all that is done, drive the truck, let it cool down, pop the coolant cap off then go to the Coolant Sender, slowly unscrew the sensor and you will see fluid start to leak out. This will bleed out any air that might remain under the sender. If you don't take the cap off, you will introduce more air to the system.

I just did this last Saturday on my rig when doing new lines and waterpump. Worked like a champ, took about an hour extra to bleed it completely and temps are rock solid.

 

[NeverGiveUpYota]

Can you clarify that last part 'If you don't take the cap off, you will introduce more air in the system.' Do you mean the cap as in the radiator? And if your pulling the sensor to bleed out air from the highest point, wouldn't opening the radiator cap make it so the air won't fully release?

 

[Output Shaft]

When the hot engine cools down, the once hot pressurized coolant contracts & sucks up coolant from the overflow tank in the process. But the return poppet valve in the radiator cap requires some significant negative pressure to open it. Near the end of the cool down, the radiator cap closes due to insufficient vacuum and it stays closed. But the engine can continue to slowly cool down even further over night, creating a vacuum (negative pressure) in the cooling system that's not quite strong enough to open up the radiator overflow flow back valve.

You might see this in the morning with a semi collapsed coolant hose somewhere. When the engine is in this state (stone cold in the morning) there can be enough negative pressure (vacuum) in the cooling system that if the temperature sender is removed, a bit of air can be sucked into the sender fitting when it's being unscrewed.

Unscrewing the radiator cap first (on a stone cold engine) will equalize the pressure in the cooling system, and any bit of air that gets sucked back in won't matter because it will be in the radiator & will get purged out.

 

[mwebfj60]

^^^^That's some next level stuff OS^^^^

 

[mattressking]

When the hot engine cools down, the once hot pressurized coolant contracts & sucks up coolant from the overflow tank in the process. But the return poppet valve in the radiator cap requires some significant negative pressure to open it. Near the end of the cool down, the radiator cap closes due to insufficient vacuum and it stays closed. But the engine can continue to slowly cool down even further over night, creating a vacuum (negative pressure) in the cooling system that's not quite strong enough to open up the radiator overflow flow back valve.

You might see this in the morning with a semi collapsed coolant hose somewhere. When the engine is in this state (stone cold in the morning) there can be enough negative pressure (vacuum) in the cooling system that if the temperature sender is removed, a bit of air can be sucked into the sender fitting when it's being unscrewed.

Unscrewing the radiator cap first (on a stone cold engine) will equalize the pressure in the cooling system, and any bit of air that gets sucked back in won't matter because it will be in the radiator & will get purged out.

OS nailed it and explained it better than I ever could.

 

[ttate]

OS, that's a really descriptive reply, but went a little over my head. Yesterday, I had a similar issue as the op, but not sure if his was quite the same, note my truck is a 62. Drove the truck a little over 60 miles, which is fairly common. Temp gauge got a bit higher than normal, but not alarmingly high. When I shut the truck off, I heard the boiling coolant, took a peak, and saw the coolant about level with the full line in the reservoir bubbling to the point some was being misted out of the relief hose (enough to wet the drive).

That said, I think I understand what you're saying about expanding/contracting nature or the coolant and negative/positive pressure of the cooling system, but am having a hard time relating that to what parts could be the root cause of the overheating. My first thought was t-stat, but I wouldn't think it'd cause that much influx in temp, and all hoses were replaced around a year ago.

 

[Landpimp]

boiling as in boiling out the overflow bottle or just making a boiling sound, they will gurgle sometimes when sitting if there is air trapped, sometimes they just gurgle when shut off.

but for me, I have never has an issue with refilling(burping) a cooling system on any 40 or 60. After I fill the rad and let it run for a bit, I park it on a hill(20% grade) with the nose up, leave cap off and let her run with BOTH heaters at full blast, I go back and check and add more 50/50 as needed, when it wont take anymore I cap it off. Then check the overflow to see if it needs any coolant......add if needed

if you grab the upper radiator hose and hold it for 5 seconds or so without burning your hand....its not overheating. (I prefer a temp gun)

put the gasket on top of t-stat before you do anything else or you will have to open the system again to do so.

Well, I can hear it boiling, which leads me to believe I didn't bleed it correctly. So I guess I'll do that and see if it fixes it

 

[Output Shaft]

a hard time relating that to what parts could be the root cause of the overheating.

My overly detailed description above was an answer to Never's question previously. Not the answer to the op's question.

If the coolant boils in the engine after shutdown when the engine wasn't overheating while driving, that likely is because the coolant isn't pressurized to 14-15 psi when it's hot (as it should be).

Replace the radiator cap.

If the radiator cap doesn't hold pressure, the 50/50 coolant is gunna boil at 223°F (instead of 265°F). It'll boil every time the engine is shut down.

Once the coolant boils, air pockets are created in the top of the head, which will create hot spots the next time around (until they purge out) which will make the engine run a little hotter etc, etc. A downward spiraling circle.

1. Replace the radiator cap
2. Fully burp the cooling system.

The upper radiator hose should feel hard when you try to squeeze it when the engine is hot.

Also, if there's a lot of air in the cooling system (low radiator) the cooling system won't be able to pressurize fully when heating up, since air is much more compressible than water. The lower the pressure of the cooling system, the lower the boiling point.

 

[ttate]

boiling as in boiling out the overflow bottle or just making a boiling sound, they will gurgle sometimes when sitting if there is air trapped, sometimes they just gurgle when shut off.

but for me, I have never has an issue with refilling(burping) a cooling system on any 40 or 60. After I fill the rad and let it run for a bit, I park it on a hill(20% grade) with the nose up, leave cap off and let her run with BOTH heaters at full blast, I go back and check and add more 50/50 as needed, when it wont take anymore I cap it off. Then check the overflow to see if it needs any coolant......add if needed

if you grab the upper radiator hose and hold it for 5 seconds or so without burning your hand....its not overheating. (I prefer a temp gun)

put the gasket on top of t-stat before you do anything else or you will have to open the system again to do so.

I'd consider it a little more than a typical gurgle, but not a "holy boiling nightmare." I've never experienced anything quite like it. Like I said earlier, it ran a little warm, but not so that I felt it couldn't wait the 10 minutes until I was home. Just a little stumped.

 

[ttate]

My overly detailed description above was an answer to Never's question previously. Not the answer to the op's question.

If the coolant boils in the engine after shutdown when the engine wasn't overheating while driving, that likely is because the coolant isn't pressurized to 14-15 psi when it's hot (as it should be).

Replace the radiator cap.

If the radiator cap doesn't hold pressure, the 50/50 coolant is gunna boil at 223°F (instead of 265°F). It'll boil every time the engine is shut down.

Once the coolant boils, air pockets are created in the top of the head, which will create hot spots the next time around (until they purge out) which will make the engine run a little hotter etc, etc. A downward spiraling circle.

1. Replace the radiator cap
2. Fully burp the cooling system.

The upper radiator hose should feel hard when you try to squeeze it when the engine is hot.

I will try that and thanks for the input! It's just hard to imagine that much air being introduced to the system this long after replacing the coolant. Thanks for the help, guys.

 

[1987cruiser]

so my 60 series was over heating, replaced the water pump, thermostat, and fan clutch
Still running hot. I did forget to replace the gasket on top of the thermostat, and was wondering it that could cause it to overheat! Any other thoughts as to what it might be?

Has your cooling system always ran with antifreeze. If not could rusted inside passage.