Help with cooling system flush, thermostat & water pump

[Redjeepht]

Hey ya'll, I am preparing to change my thermostat and water pump, I know its recommended to flush, but i'm not finding out specifics on how people are tackling those jobs together.

One popular way to flush the cooling system is without messing with the thermostat, (using a hose or filling, drain, repeat). The other way, in the FSM, says to drain it. To flush the RAD. Remove radiator hoses, shoot water from bottom, then it will come through the top To flush the engine, remove the thermostat, replace housing(without thermostat) Add water from the large upper hose from radiator, and it will come out the bottom hose from the water pump that connects to the bottom radiator (where you put the water to flush radiator).

I do not have my heater core hooked up right now, the hose is bypassed. I'm nervous to do this flush, because theres a lot of different information on the forum and youtube...

Also, the thermostat & pump replacement have me confused. I've seen mixed claim (you need to put liquid gasket on the gaskets, you dont need to, you need to teflon all WP bolts, only 1, or blue threadlocker on some or all).

From what i'm thinking, according to the FSM, I will start my flush "mid way" through the thermostat replacement, install new thermostat, WP, then fill it with coolant. I'm sure this is much easier than i'm thinking about it. but for some reason the flushing part is adding some confusion to everything. I'll attatch some pictures showing where I think the water will enter/exit during the flush.

 

[Gilaguy23]

Its not rocket science, just keep in mind if your overheating radiators to get scaled up beyond a flushing. Your second paragraph is how Id do it, no thermo and flush the block good. Far as sealant it can help with small imperfections in the surfaces if you have any otherwise good gaskets will do the trick. A uber thin coat, no oozing out the sides, of RTV has been what I've used in past work on some old vehicles. Bolts? why the hell would you locktite any of them? Bolts that go thru into coolant passages should have sealant on them otherwise they get anti seize. Frankly after years here and reading some of the crap people ask I wonder if they know the difference between a muffler bearing and a roll of 1/2" pipe thread.

 

[Danarch]

Here is some good information.

https://wranglertjforum.com/threads/how-to-flush-the-cooling-system-on-your-jeep-wrangler-tj.1737/

I did mine recently and I ran a cleaner (Thermcore, Prestone, etc) through it for a few days. Then drained the system from the radiator and poured distilled water through it. Afterwards I removed the engine block drain plug, it’s in the drivers side. I’d guess another 3/4 - 1 gallon of coolant came out. I don’t remember the size of the plug, but it is smaller than 3/8”, it’s metric. I happened to have one I use to change the oil in another car.

I did not use any locktite, etc just the gaskets and buttoned everything back up. It’s been running great for a couple of months now.

 

[User4574]

Here is some good information.

https://wranglertjforum.com/threads/how-to-flush-the-cooling-system-on-your-jeep-wrangler-tj.1737/

I did mine recently and I ran a cleaner (Thermcore, Prestone, etc) through it for a few days. Then drained the system from the radiator and poured distilled water through it. Afterwards I removed the engine block drain plug, it’s in the drivers side. I’d guess another 3/4 - 1 gallon of coolant came out. I don’t remember the size of the plug, but it is smaller than 3/8”, it’s metric. I happened to have one I use to change the oil in another car.

I did not use any locktite, etc just the gaskets and buttoned everything back up. It’s been running great for a couple of months now.

8mm drain plug socket

 

[Redjeepht]

Here is some good information.

https://wranglertjforum.com/threads/how-to-flush-the-cooling-system-on-your-jeep-wrangler-tj.1737/

I did mine recently and I ran a cleaner (Thermcore, Prestone, etc) through it for a few days. Then drained the system from the radiator and poured distilled water through it. Afterwards I removed the engine block drain plug, it’s in the drivers side. I’d guess another 3/4 - 1 gallon of coolant came out. I don’t remember the size of the plug, but it is smaller than 3/8”, it’s metric. I happened to have one I use to change the oil in another car.

I did not use any locktite, etc just the gaskets and buttoned everything back up. It’s been running great for a couple of months now.

The FSM does say to use a cleaner before you do a flush, guess I’ll drive it around for a few days with the cleaner in. I just didn’t want to have bad luck and have something really mess up before I fix the WP leak.

 

[DuckNut]

The FSM does say to use a cleaner before you do a flush, guess I’ll drive it around for a few days with the cleaner in. I just didn’t want to have bad luck and have something really mess up before I fix the WP leak.

Flush it with the garden hose first to get the big chunks out. Drain it and then add cleaner and distilled water. Drive for a few days. Drain it. Do it again. Drain and refill with coolant using distilled water. All the rusty, slimy fuzzies in the system act as insulation and you want them gone. I use CLR because it is cheap and readily available.

Tap water will cause the block to rust and that is what plugs up the radiator and heater core. The channels through the radiator are about 1.5 mm and the heater core is significantly smaller.

 

[cpwolf]

How many of these threads are you creating? This is 2 on the exact same topic?

 

[Redjeepht]

How many of these threads are you creating? This is 2 on the exact same topic?

This is the last one. I just thought it would be easier to start a separate thread with questions about the flushing process. I’ll just keep it in one thread next time.

 

[Redjeepht]

I replaced the

 

[Redjeepht]

I replaced the WP & thermostat. Filled up with another water/Prestone flush mix and will drive for a few days before the final flush & coolant.



One thing I’ve noticed that has me concerned. When I let the Jeep idle with cap off, it will consistently overflow water out of the fill neck. Is that because the temperature isn’t hot enough and it’s not yet sucking the coolant through other parts of the system?

 

[KennethS]

Yes, that is normal. It will do that each time the thermostat opens, then the level will drop. You just have to keep topping it off.

 

[TheBoogieman]

I replaced the WP & thermostat. Filled up with another water/Prestone flush mix and will drive for a few days before the final flush & coolant.



One thing I’ve noticed that has me concerned. When I let the Jeep idle with cap off, it will consistently overflow water out of the fill neck. Is that because the temperature isn’t hot enough and it’s not yet sucking the coolant through other parts of the system?

You just blew up the engine!!! @chili_pepper This is SARCASM.