Improving the cooling on our TJs
- Thread starter TexasTJ2004
- Start date
I think that the reason why it turns black is chemical reaction between rust and Diammonium Phosphate.
This is why it did turn black on a second flush, because there was barely any rust left.
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I have drained the block like 5 times during my flushes. Is there any problem with doing it?
I work on the cooling systems with a serious eye towards solving the problem and getting done with the job in the least amount of time possible. So, we pull the thermostat and do several flushes with hose water until it runs clear. Then we flush with distilled to dilute the tap water to a tolerable level. After that, we mix the coolant 2/3 to 1/3 distilled which when mixed with the water remaining in the block brings the dilution rate to 50/50. After the drive around flush and Thermocure if needed, takes us about an hour start to finish. That runs into most of a day if you dick with draining the block and waiting on the thermostat to open every time you flush it again.
Got it.
For me it is my hobby, so I could afford myself to spent the time that I spent. If I would work on somebody else’s Jeep, I would do the same as you guys.
Pulled my drain plug and nothing happened at first. Odd.
Then I see something is blocking the flow, so I push whatever it is in with my 8mm socket.
After the flow stops, I stick a magnetic extender in the hole and I get gobs of ferrous material.
Any idea where this metal could come from?
Is it the water jackets rusting away?
Then I see something is blocking the flow, so I push whatever it is in with my 8mm socket.
After the flow stops, I stick a magnetic extender in the hole and I get gobs of ferrous material.
Any idea where this metal could come from?
Is it the water jackets rusting away?
Was wondering g if pulling the lower hose would drain it all without pulling the block plug?
Gotcha. I haven’t worked on the coolant system on mine yet, will be replacing hoses etc this fall. We used to do that in the XJ but the rad drain was up high (the rad was a lot shorter)
It will not. Lower hose connects to water pump. Anything lower than water pump will stay in the block and anything on water or higher will drain from the drain valve in the radiator
This looks horrible. No pieces of metal are supposed to come out. I didn’t get any. Do you have a picture of the thermostat housing as well? Do you have a picture of how the inside of drain plug looked like?
Update on my progress:
Ran exhaust gas in coolant, no issues.
At first replaced the fan clutch, didn’t really help a lot. The thermostat was opening properly, but still was not running asit should ( too hot).
Then I found that my heater was leaking. Was detected with positive pressure test. I added a bypass, so no heating.
I think that I would run the pressure test, found the leak in t he heater, add a bypass and run the flushes (3 blue devil and 2 thermocure), skip replacing t he thermostat and fan clutch, I would be in perfect shape as well.
There was a lot of rust inside the block, which thermocure seems to have removed.
So, my conclusion - if you are running hotter that you should, run exhaust in coolant and pressure tests. If there is a leak, you got it, it will fail to cool properly as it cannot build pressure. The tests themself are pretty simple, the tools are cheap.
Then do flushes, I think thermocure removes only rust, so you need run something like Prestone or BlueDevil as well.
You might find out that similar to my case, you had a leaking heater and rust and dirt inside the radiator and the block.
If all this didn’t help, then it might be a good point to start replacing anything.
In order to do all the above, you need to use radiator drain valve, engine block drain plug and radiator cap. This is all you need to run the tests and the flushes.
Ran exhaust gas in coolant, no issues.
At first replaced the fan clutch, didn’t really help a lot. The thermostat was opening properly, but still was not running asit should ( too hot).
Then I found that my heater was leaking. Was detected with positive pressure test. I added a bypass, so no heating.
I think that I would run the pressure test, found the leak in t he heater, add a bypass and run the flushes (3 blue devil and 2 thermocure), skip replacing t he thermostat and fan clutch, I would be in perfect shape as well.
There was a lot of rust inside the block, which thermocure seems to have removed.
So, my conclusion - if you are running hotter that you should, run exhaust in coolant and pressure tests. If there is a leak, you got it, it will fail to cool properly as it cannot build pressure. The tests themself are pretty simple, the tools are cheap.
Then do flushes, I think thermocure removes only rust, so you need run something like Prestone or BlueDevil as well.
You might find out that similar to my case, you had a leaking heater and rust and dirt inside the radiator and the block.
If all this didn’t help, then it might be a good point to start replacing anything.
In order to do all the above, you need to use radiator drain valve, engine block drain plug and radiator cap. This is all you need to run the tests and the flushes.
MountaineerTom
LJ Enthusiast, Retired USAF Weapons Loader
Supporting Member
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Probably just many years of rust built up and it finally broke loose. This was from the engine block drain?
Looks like a good time to do a thorough Thermocure flush.
Yes, from the engine block drain.
The engine is currently filled with thermocure and distilled water.
The test does not say whether it is a bad gasket or not. It tells if you have exhaust gas inside your coolant. The main reason for it is usually the gasket, but can be a crack in the head as well (lower probability, but still possible)
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