I need help figuring out some of the problems my TJ has developed

Jared Morin

Jared Morin

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Alright here are the problems I’m running in to. About two months ago the 4.0 engine I have overheated and and dumped all of the coolant out of the radiator, but it did not go out the overflow or blow the rad cap. I replaced the thermostat and it fixed the problem for a while. For the past week or so it had been running at about 215-217 which is hotter than I like it to be. Just yesterday it was getting pretty hot but not in the red so I pulled over and turned it off and when I looked at the engine it was water falling coolant again, the over flow level did not change level and the rad did not blow, it was just pouring coolant somewhere out of the bottom of the radiator. I waited for it to cool off enough to where I could open the rad cap and then I added coolant and distilled water and driver home, on the way home the temp kept dropping to below 150. I drove this morning and the temp never got above 140 and their was a little bit of coolant on the bottom of my radiator. I don’t have a clue what’s going on. I think it might be a bad thermostat and a hairline crack in the radiator. What do you guys think?
 
Jared Morin said:
Alright here are the problems I’m running in to. About two months ago the 4.0 engine I have overheated and and dumped all of the coolant out of the radiator, but it did not go out the overflow or blow the rad cap. I replaced the thermostat and it fixed the problem for a while. For the past week or so it had been running at about 215-217 which is hotter than I like it to be. Just yesterday it was getting pretty hot but not in the red so I pulled over and turned it off and when I looked at the engine it was water falling coolant again, the over flow level did not change level and the rad did not blow, it was just pouring coolant somewhere out of the bottom of the radiator. I waited for it to cool off enough to where I could open the rad cap and then I added coolant and distilled water and driver home, on the way home the temp kept dropping to below 150. I drove this morning and the temp never got above 140 and their was a little bit of coolant on the bottom of my radiator. I don’t have a clue what’s going on. I think it might be a bad thermostat and a hairline crack in the radiator. What do you guys think?
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I've seen systems where the temp sensor would not register the temp correctly because there was no coolant surrounding it. That means it is running hot, very hot, it just isn't relaying the temp correctly.

I don't know that I could fix a system that blew all the coolant out by replacing the thermostat. I would start over and get an OEM radiator, new thermostat, and coolant in there before you lose the motor.
 
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Add new hoses to that mix too. There's a good chance the lower hose I'd blowing coolant if you can't find the leak from the radiator or possibly collapsing under pressure. And either way they don't like running that hot either
 
Goatman said:
Add new hoses to that mix too. There's a good chance the lower hose I'd blowing coolant if you can't find the leak from the radiator or possibly collapsing under pressure. And either way they don't like running that hot either
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Nitpicking but they collapse under vacuum and swell under pressure.
 
mrblaine said:
I've seen systems where the temp sensor would not register the temp correctly because there was no coolant surrounding it. That means it is running hot, very hot, it just isn't relaying the temp correctly.

I don't know that I could fix a system that blew all the coolant out by replacing the thermostat. I would start over and get an OEM radiator, new thermostat, and coolant in there before you lose the motor.
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From what I could tell that seems like that will solve my engine problems
 
"when I looked at the engine it was water falling coolant again "

Where from? Front of the engine? Top? Bottom?

Pull the radiator & have it flushed & pressure checked. Pull the hoses at that point & replace anything that doesn't pass a visual. Check out the bottom of the water pump at that point. There is a weep hole on the bottom. When the bearing goes bad, it leaks, by design. Not sure that would cause a water fall, but maybe a bad hose or bad connection would.
 
Have you replaced the radiator cap? Often they are replaced because they won’t hold pressure, but I’ve seen times where they fail and don’t allow coolant to overflow. Or that can also happen if the overflow aperture under the cap is plugged. This would cause pressure to build and coolant will pour out the next weakest spot in the system.
 
A multilayer hose can easily close down under pressure. The fluid gets between layers and forces the inner down, blocking flow. Fairly common in hydraulic systems.
 
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