Improving the cooling on our TJs

MountaineerTom

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I read your write up. I am in a same situation as you, working, family and stuff, so will need to do the heater core replacement project in multiple weekends.

That was the biggest frustration. I was afraid I’d forget or lose something. Labeling connectors and stuff and hardware in labeled ziplock bags were a huge help.

Just for the heck of it, I asked the shop that evacuates my a/c system what they would charge for a heater core replacement. If I remember correctly, it was $800 In 2018. I know shops may vary on that price though.
 

TNHEADDUCK

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I think that I have found the root cause for my overheat problems.
I bought this kit for 90$, OIMERRY 28PCS Universal Radiator Pressure Tester for Vehicles, Vacuum Type Coolant System Pressure Leak Tester Kit https://a.co/d/5d7w88n

And ran positive pressure test. At around 13 PSI, I see that the coolant started to leak from the heater core.
I am currently running distilled water with thermocure, so my cabin stinks of thermocure, with this thing mainly pouring under the Jeep from the tube that is supposed to be for condensed water from AC.
With leaking heater core, it is not able to build proper pressure of coolant, and this brings air into the system.
I wish I had run this test before I replaced the fan clutch, before replacing a thermostat and before ordering a new Mopar radiator.

My lessons learned - always run exhaust in coolant (which I didn’t run yet) and positive pressure test. If any of these fails, no point in replacing half of the cooling system.

Were you having to add coolant when you initially started trying to get your engine to run cooler or could you have possibly busted your heater core with your new toy? I have seen people over pressure cooling systems and cause problems they didn't have before.
 

cpwolf

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I feel so stupid, all these years … I always pop these suckers out on other engines, I’ve seen all sorts of mysterious junk come out. But I like to replace the plug with brass. Some people use a radiator petcock, but that’s risky and brass will never seize.

For the TJ’s. To fully flush the system I run the engine with the upper radiator hose off, thermostat removed, garden hose in the top of the radiator going full blast. Then I run the engine. I’ll let it go till that water runs totally clear. Then I’ll remove the heater core hose at the thermostat housing and run the hose through there.

This time around I’ll remove that drain plug and do it the right way.

I can’t do it, the water in Austin TX area has tons of calcium and stuff, I just use gallons of Distilled. It’s a pain compared but gotta
 
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TexasTJ2004

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Were you having to add coolant when you initially started trying to get your engine to run cooler or could you have possibly busted your heater core with your new toy? I have seen people over pressure cooling systems and cause problems they didn't have before.

The original problem was potential overheat. In idle it would start overheating with AC, and also when running on highway, under load if would star going beyond 210.
Took out the thermostat, and started flushing. When flushing, I saw the bubbles never disappear. Coolant small in the cabin was present, but was not really strong.
Then I drained everything, including the block, and filled with distilled water and thermocure. Bubbles never stopped.
Started to feel the stink of the thermocure in the cabin, and suspected the leak.
When the I opened the radiator it was missing maybe half quart of coolant.
Investigated in the cabin, and found the coolant on the carpet in the passenger side.
Positive pressure test reached 13PSI and started to see the leak from heater core.

I think that coolant system is expected to hold pressure up to like 15PSI. This happens when radiator cap blocks the radiator and the coolant still tries to expand. The goal of keeping the pressure is to prevent the coolant from boiling, as increased pressure makes it less likely to boil.
 
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TexasTJ2004

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I can’t do it, the water in Austin TX area has tons of calcium and stuff, I just use gallons of Distilled. It’s a pain compared but gotta

When I removed the drain and opened the radiator petcock, I did run some gallons of ozark just to wash it all from inside. With opened drains, ozark does not stay inside the engine.
But I don’t run the engine with anything but antifreeze or distilled water inside.
 
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TexasTJ2004

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As for the positive pressure test:
This is how it is done (not my video):
He was losing 3 PSI, I was losing it in couple of minutes.
 

TNHEADDUCK

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The original problem was potential overheat. In idle it would start overheating with AC, and also when running on highway, under load if would star going beyond 210.
Took out the thermostat, and started flushing. When flushing, I saw the bubbles never disappear. Coolant small in the cabin was present, but was not really strong.
Then I drained everything, including the block, and filled with distilled water and thermocure. Bubbles never stopped.
Started to feel the stink of the thermocure in the cabin, and suspected the leak.
When the I opened the radiator it was missing maybe half quart of coolant.
Investigated in the cabin, and found the coolant on the carpet in the passenger side.
Positive pressure test reached 13PSI and started to see the leak from heater core.

I think that coolant system is expected to hold pressure up to like 15PSI. This happens when radiator cap blocks the radiator and the coolant still tries to expand. The goal of keeping the pressure is to prevent the coolant from boiling, as increased pressure makes it less likely to boil.

I am fully aware of how a cooling system works, just never heard you mention having a coolant loss in any of your previous post before you started putting pressure on your system. As I stated in an earlier post I think you have been chasing a issue that you really don't have. JMO
 
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TexasTJ2004

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I am fully aware of how a cooling system works, just never heard you mention having a coolant loss in any of your previous post before you started putting pressure on your system. As I stated in an earlier post I think you have been chasing a issue that you really don't have.

I drove TJs abroad in much hotter places than Houston, slightly different model (4 door, LWB) but the same cooling system (other than it was manual, so no transmission cooling). Never seen them reaching anything as high as my TJ reached.
My TJ here is not being driven a lot, made ~2K miles in 2.5 years, so cannot say how much coolant it would lose if it would drive more.
If I cannot run the AC in Chic-Fil-e drive through (engine kept going up in temperature), i have a problem. It is possible that a lot of folks the same problem, but it still does not change the fact that it is a problem.
 
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freedom_in_4low

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Fwiw, I've never pulled the block drain. Yes, it won't drain everything out, but you can still get it out by doing some extra flushes. Say it holds a third of the total coolant charge in there...you drain from the radiator, fill it back up, now that junk is diluted to 1/3 strength. Drain and flush again and it's 1/9. One more time and it's 1/27, and a fourth flush and it's down a couple of percent. On my TJ I used one of those prestone flush kits that installs into the heater hose, and just ran it until it came out crystal clear. Then I fill and flush 4x with distilled to clear the tap water out. Even better if you do the flushes without a thermostat installed so you don't have to wait for it to open.
 

Ericshere03

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I can’t do it, the water in Austin TX area has tons of calcium and stuff, I just use gallons of Distilled. It’s a pain compared but gotta

Right, I should of completed my process … after using the hose. I remove all the tap water, fill with distilled, run the engine to temperature, flush fill one more time, drain completely and then I’ll put in a gallon of concentrate Zerex G-05, distilled water and some RMI-25 (Jeeps system clean and lubes the water pump). Our capacity is about 2.5 gallons, so it’s a touch lite of 50/50, but I live in the desert.
 

Jerry Bransford

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Right, I should of completed my process … after using the hose. I remove all the tap water, fill with distilled, run the engine to temperature, flush fill one more time, drain completely and then I’ll put in a gallon of concentrate Zerex G-05, distilled water and some RMI-25 (Jeeps system clean and lubes the water pump). Our capacity is about 2.5 gallons, so it’s a touch lite of 50/50, but I live in the desert.
I'd stick with just the G-05 and distilled water, the G-05 keeps the water pump lubed.
 

Ericshere03

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I'd stick with just the G-05 and distilled water, the G-05 keeps the water pump lubed.

I been impressed with the RMI product. Even after flushing much older motors, it’s still makes a froth of contaminants in the overflow. I’ve only been using it for 5 years, not enough time for longevity. Plus I always replace everything when doing cooling systems. But I mainly like the idea of keeping corrosion out of the system even after a fresh flush and new coolant.

But check it out, folks seem to rave about it.
 
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TexasTJ2004

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Right, I should of completed my process … after using the hose. I remove all the tap water, fill with distilled, run the engine to temperature, flush fill one more time, drain completely and then I’ll put in a gallon of concentrate Zerex G-05, distilled water and some RMI-25 (Jeeps system clean and lubes the water pump). Our capacity is about 2.5 gallons, so it’s a touch lite of 50/50, but I live in the desert.

The Freeze word in the AntiFreeze does not really apply to us, folks living in hot areas. Here in Houston area we get freezing temperatures maybe twice a year, and all these times my TJ was inside the garage:).
 
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Ericshere03

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The Freeze word in the AntiFreeze does not really apply to us, folks living in hot areas. Here in Houston area we get freezing temperatures maybe twice a year, and all these times my TJ was inside the garage:).

Should call it anti-boil for us … but mathematically 50/50 is optimal, 40/60 ain’t bad. 60/40 provides freeze protection down to -10.
 
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TexasTJ2004

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Finally got my heater core delete kit. Will install it and will rerun t he positive pressure test with 13 PSI to verify that nothing else is leaking
 
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TexasTJ2004

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Installer the heater core bypass and rerun the pressure test. Now I see that I have a tiny leak from the thermostat housing (I am running flush w/o thermostat so didn’t bother to install it properly.
You can hear the whistle from thermostat housing

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