Why is my eagle overheating?

[eaglescout526]

I know it’s not MJ tech but I want eyes on this. Since this is my first 6cyl I’m now encountering issues with staying cool. At first I thought it was the thermostat. I took the old one out, tested it, it opened way later than it should have. 
New one in. No change. 

Flushed the block, manifold and core. No change. Yes it’s been burped. 
 

Replaced the radiator cap cause the rubber was basically a rock. Some change but not enough. 

Fan clutch locks up when it should and feels normal when engine is off. 
 

I swear I cleaned the fins out but maybe I didn’t. 
 

Water pump is new. Replaced it when I did the head gasket. And it does rotate the right direction. 
 

headgasket has been replaced. 
 

Any ideas? Did my headgasket blow again? It slowly creeps up and takes about 10 miles of driving before I’m damn near out of the green on the gauge. 

[Eagle_SX4]

I would get an infrared thermometer and start checking temps all around and see if there is a clog in the system. If your radiator is original that is might be the issue, or your water pump is rusted away and not moving any coolant.

 

Even when hot my Eagle never even gets 1/2 up the green.

[hgeranium]

I assume you're not losing any coolant? If it's the head gasket again I would imagine it won't be long until your radiator runs low and you start having chocolate milk. 

 

What kind of 4.0 do you have? Renix? 

[eaglescout526]

4 minutes ago, Eagle_SX4 said:

I would get an infrared thermometer and start checking temps all around and see if there is a clog in the system. If your radiator is original that is might be the issue, or your water pump is rusted away and not moving any coolant.

 

Even when hot my Eagle never even gets 1/2 up the green.

I’ll check around. I can tell you every hose is damn hot to the touch. Like hold it too long and you’ll get first degree burns. 
 

Water pump is new. Should still be new. I had the cap off last night and saw it moving coolant. 
 

Yeah mine is doing it again similar to the head gasket. 
 

And the radiator is the original one. I’m thinking about taking it out and running vinegar through it. 
 

4 minutes ago, hgeranium said:

I assume you're not losing any coolant? If it's the head gasket again I would imagine it won't be long until your radiator runs low and you start having chocolate milk. 

 

What kind of 4.0 do you have? Renix? 

My luck has never shown me coolant loss, just violent boiling and overheating. Never coolant loss. 
 

No, 4.2L 258. 

[hgeranium]

Maybe try the baking soda trick when flushing to see if you can loosen up any clogs in the passages/rad? That did wonders on my 94 C1500 that had buckets of rust and crud in the radiator and passages. I wonder if just putting in a new rad after flushing it would be worth it, at least for peace of mind.

[89 MJ]

Because 6 cyls suck. 

Because it’s an Eagle, so it needs to fight you every step of the way. 
 

Maybe a bad thermostat out of the box?

[Eagle_SX4]

6 minutes ago, 89 MJ said:

Because 6 cyls suck. 

Because it’s an Eagle, so it needs to fight you every step of the way. 

 I have not had any overheating issues with my Eagle. When working the cooling system is way better than the Comanche's could ever be. It takes my Eagle at least 1.5 miles longer to fully warm up than my Comanche.

 

24 minutes ago, eaglescout526 said:

 

And the radiator is the original one. I’m thinking about taking it out and running vinegar through it.

Defiantly make sure it is clear and not clogged up. My radiator is original as well but mine is working great. If you do need a new radiator, as far as I know they are not made for the Eagle. However one for a CJ7 is nearly the same size, the ports are just in slightly different locations.

[eaglescout526]

17 minutes ago, hgeranium said:

Maybe try the baking soda trick when flushing to see if you can loosen up any clogs in the passages/rad? That did wonders on my 94 C1500 that had buckets of rust and crud in the radiator and passages. I wonder if just putting in a new rad after flushing it would be worth it, at least for peace of mind.

Baking soda doesn’t sound like a bad idea at all. Been using that to clean stuff. Maybe I can get it hot enough to where it’ll clear stuff out. My other thought was evaporust again. 

 

2 minutes ago, Eagle_SX4 said:

Defiantly make sure it is clear and not clogged up. My radiator is original as well but mine is working great. If you do need a new radiator, as far as I know they are not made for the Eagle. However one for a CJ7 is nearly the same size, the ports are just in slightly different locations.

I’ll have to do that. 89 MJ said to take my digital thermostat and see if there’s no temp across the radiator somewhere. 

[89 MJ]

6 minutes ago, Eagle_SX4 said:

 I have not had any overheating issues with my Eagle. When working the cooling system is way better than the Comanche's could ever be. It takes my Eagle at least 1.5 miles longer to fully warm up than my Comanche

Oh yeah, I have fought my Eagle’s cooling system much less than my MJ. My comment comes from the fact that in less than the 50k combined miles I’ve put on both of my vehicles, they have had a total of 5 engines and still have had problems with their current engines. 
 

And I’ve grown up around GMs so I’m not used to everything being a fight either like they are with the MJ and Eagle. Absolutely worth it, but a fight every time. 

[hgeranium]

10 minutes ago, 89 MJ said:

Oh yeah, I have fought my Eagle’s cooling system much less than my MJ. My comment comes from the fact that in less than the 50k combined miles I’ve put on both of my vehicles, they have had a total of 5 engines and still have had problems with their current engines. 
 

And I’ve grown up around GMs so I’m not used to everything being a fight either like they are with the MJ and Eagle. Absolutely worth it, but a fight every time. 

Lol my GMC out of my six cars (two of them being VWs!) has by far given me the most issues. And it was nothing but electrical wiring issues. I love that truck but it was an absolute nightmare. I must’ve just been incredibly unlucky picking the truck that I did. My Comanche is by far the most reliable vehicle I’ve owned in comparison

[Gojira94]

I think I read carefully enough not to miss any mention of the heater core. I know relatively little about the 258 setup in an Eagle, but does it have a heater control valve? And if not, it could be restricted enough to cause issues. If you bypassed it and it ran noticeably cooler, that might be telling. And I agree that the old rad may be a restriction as well.

[Eagle_SX4]

20 minutes ago, Gojira94 said:

I think I read carefully enough not to miss any mention of the heater core. I know relatively little about the 258 setup in an Eagle, but does it have a heater control valve? And if not, it could be restricted enough to cause issues. If you bypassed it and it ran noticeably cooler, that might be telling. And I agree that the old rad may be a restriction as well.

Yes the eagles have a heater control valve. 

[eaglescout526]

I have a new control valve on the way. But I’m not sure it it will actually affect anything. It is pretty damn old and crusty thought but not broken apart. 

[watchamakalit]

Burp it from the temp sender at the back of the head. Good chance if everything is functioning properly that there is air in the system.   

[eaglescout526]

4 hours ago, watchamakalit said:

Burp it from the temp sender at the back of the head. Good chance if everything is functioning properly that there is air in the system.   

That was one of the first things I checked after swapping the temp sensor. Coolant came right out. 
 

I’ve got vinegar in the radiator right now. 

[Eagle_SX4]

1 hour ago, eaglescout526 said:

That was one of the first things I checked after swapping the temp sensor. Coolant came right out. 
 

I’ve got vinegar in the radiator right now. 

I find that removing the small hose on the thermostat housing is a better way to completely fill the engine with coolant. It bypasses the thermostat and is the highest point when on flat ground. You can also fill the heater core from the hose you pulled off.

 

*Just be careful when removing the hose so you don't have to replace it.*

[eaglescout526]

1 hour ago, Eagle_SX4 said:

I find that removing the small hose on the thermostat housing is a better way to completely fill the engine with coolant. It bypasses the thermostat and is the highest point when on flat ground. You can also fill the heater core from the hose you pulled off

Those a both great spots. One thing that bothers me is removing one of those heater core hoses results in hardly any water coming out of the core which makes me wonder if any water is getting in their but I’ve felt the hoses get pretty damn hot. 
 

 

[AZJeff]

Some thoughts:

 

If the heater core is plugged up, there is a good chance the radiator is in similar condition

Use an infrared thermometer to check thermostat elbow temps against guage reported temps.

Run a pressure test on the cooling system to make sure it will hold the required pressure (16lbs?). If it won’t hold pressure, boiling is likely to happen.

Antifreeze raises boiling point as well as depressing freezing point.  Be sure to run a proper mix, because a typical modern engine with plain water and a non-functioning pressure cap will almost certainly boil over.

[eaglescout526]

22 minutes ago, AZJeff said:

If the heater core is plugged up, there is a good chance the radiator is in similar condition

My thoughts right now. I remember the core was plugged and the valve is in poor shape and no coolant was ever flowing through it. I did flush that and it probably stirred stuff up and got it into the radiator and plugged some of it. Did flush the core again and took some serious hose pressure to dislodge whatever was in there so chances are this is my issue since it gradually overheats and not almost instant. 
 

25 minutes ago, AZJeff said:

Use an infrared thermometer to check thermostat elbow temps against guage reported temps.

I probably either need a better one or replace the batteries as mine seems to not read “accurately” but nonetheless a goal. 
 

13lbs is the proper pressure. Right now it’s water and whatever else is floating around. I’ll do the proper mix when this is solved. I know I’ve been able to run water in my MJ for a few years with no issue. I’ve moved to having actual coolant since then. 

[watchamakalit]

I would start by flushing the radiator, paying close attention to what comes out. Anything chunky woukd make me consider a new radiator. Same with the heater core. Might be worth trying some flush in a bottle snake oil to see if she won't "come around".