Another Cooling System Dilemma

HaydukeLives!

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I've commented in a thread or two about my 1999 4.0 M/T needing a cooling system overhaul. This isn't one of those "if it ain't broke, don't fix it" situations. My sh*t is really broke. I believe I've read just about every post in every thread about cooling systems and haven't run across this issue. But if I may stand corrected, by all means....correct away.

My OEM radiator has a significant leak on the top seam and is gently spraying coolant on the front of the engine, inside hood, and components. I want to flush the engine and heater core (the entire system really) before replacing radiator, pump, fan clutch, etc. but I'm wondering if using Thermocure (or something similar) would be wise since some of it is going to end up spraying as described above. If the answer is "no, not a good idea," then how can I flush the engine without a usable radiator? Could I bypass the radiator, pull the thermostat, and only run for a very short amount of time to circulate the solvent? Maybe do this two or three times a day for a week or so. Or is that also a risky idea? I have flushed the heater core several times and I know that can be isolated from the rest of the system, no issue.

Any ideas or advice?

I appreciate any help. I've owned the "Strangler" since I was 25 in 1999 and now I'm finally beginning to replace parts. I'm at almost 200K miles and it has been a very reliable and fun vehicle. The radiator is original.
 

tr21triton

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I would think you could not put the radiator cap on but not tighten it down all the way (so it wont build up pressure) and run the flush through it without it blowing out of the upper seam ! I don't know about driving it like that but it will be safe to run it in the driveway and cycle the fluid throughout the system....
 
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HaydukeLives!

HaydukeLives!

Original TJ Owner
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I have run a zero pressure cap many times, learned this trick many years ago back when we were going down Baja before the road was paved.
By taking the pressure out of the system it reduced the chance of blowing a hose or popping a freeze plug to zero.

What does "popping a freeze plug to zero" mean exactly?

So both of these suggestions sound pretty harmless. It's also helpful in thinking about the big picture or the cooling system as a whole. Just take the pressure off....makes sense.

When flushing the block, is that just a matter of remove the block drain plug and running Thermocure, etc. through the system as described above?

Thanks again!
 

xXDavidCXx

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The simple answer is to replace the radiator, then run the thermocure.
 

txbemis69

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i flushed my cooling system with the old leaking radiator using thermocure. then drained the complete system and installed the new radiator. didn’t hurt anything. after verifying no leaks i sprayed a couple cans of gunk engine degreaser to get engine compartment clean.
 
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mrblaine

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Quail Valley, CA
I've commented in a thread or two about my 1999 4.0 M/T needing a cooling system overhaul. This isn't one of those "if it ain't broke, don't fix it" situations. My sh*t is really broke. I believe I've read just about every post in every thread about cooling systems and haven't run across this issue. But if I may stand corrected, by all means....correct away.

My OEM radiator has a significant leak on the top seam and is gently spraying coolant on the front of the engine, inside hood, and components. I want to flush the engine and heater core (the entire system really) before replacing radiator, pump, fan clutch, etc. but I'm wondering if using Thermocure (or something similar) would be wise since some of it is going to end up spraying as described above. If the answer is "no, not a good idea," then how can I flush the engine without a usable radiator? Could I bypass the radiator, pull the thermostat, and only run for a very short amount of time to circulate the solvent? Maybe do this two or three times a day for a week or so. Or is that also a risky idea? I have flushed the heater core several times and I know that can be isolated from the rest of the system, no issue.

Any ideas or advice?

I appreciate any help. I've owned the "Strangler" since I was 25 in 1999 and now I'm finally beginning to replace parts. I'm at almost 200K miles and it has been a very reliable and fun vehicle. The radiator is original.

Circulate it with the thermostat pulled. Do that a few times a day over a couple of days and then check it. You could temp patch the tank with some 5 minute JB weld and some fiberglass drywall tape to slow down the mess.
 
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HaydukeLives!

HaydukeLives!

Original TJ Owner
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Joined
May 11, 2020
Messages
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Location
Woodland Park, Colorado
Thanks everyone for the advice and for helping me read simple English (LONGJP2). :) Sometimes we all just need a little help.

The Thermocure arrived in Woodland Park from Denver with same day delivery from O'Reilly's. I was pretty impressed considering how low-tech they seem sometimes. I'll begin flushing with busted radiator but sans thermostat tomorrow and see what happens.

It looks like my fan clutch is the type with 4 bolts. Loosen those and it pops right off? Yeah right. We'll see.

Thanks.