Radiator Replacement On Cj5

All good. I had the same question the first time I did it.
Keep the hoses attached to the engine and remove the radiator. The top hose is the "out" and will act like a faucet that will pour out in front of the engine. You can either unbolt your fan to keep the crud water from being blown all over your engine or run a large diameter hose (I used the hose from my shop vac) up into the end of the outward hose to help the water drain past the fan and avoid blow-around. just be warned, if you keep the fan attached...moving parts = more ways to catch a finger etc hahah.
Take your garden hose and shove it a few inches into lower hose that goes into your water pump and run the engine for a minute or two until it washes all the crud out. keep the block drain plug open too so more stuff can come out through there.

Water will only come out of the top (thermostat housing) hose if its warm enough to open up the thermostat OR the thermostat has been removed. Others mentioned replacing the thermostat anyway so it would be better to remove it. You can make a gasket pretty easy for this area by cutting it from a gasketing sheet. that way you can waste a gasket for this rinse procedure.

 

I'll be sure to post a follow-up. Thanks!

 

Amazing! Thank you so much. I did order a fresh thermostat. Lots of crud and muddy coolant looking down below the old one, so I'm eager to do the washout as you describe.

Sorry to get micro, but do you need to fill up the water a bit before starting the engine? Or will it run okay and pull the water in? Thanks again!

 

Start it up, then start filling with the hose

 

I fill the system first. The top it off after a few minutes, possibly more than once. Repeat the topping off after running the engine and then again after driving a bit.

BTW - Don't ever pour a lot of cold coolant into a hot engine. You could crack the head or block from thermal shock. Trickle it in gradually while it is running. And don't ever open the cap on a hot, pressurized system. Relieving the pressure can allow the entire contents to instantly flash to steam... very very dangerous.

 

With the thermostat removed, you should be able to do enough of a good rinse without the engine running. This should make life easier and that way, you don't have to worry about cracking the block like described above. The only reason to run the engine during the rinse would be to get it warm enough to have the thermostat open a bit if its still installed. otherwise, you'd just be rinsing the lower half out.

I think PeteL is referring to filling the final coolant at the end when you're done?

The first time I did a "flush", I drained the coolant, filled the system up with water, ran it, drained it again, over and over. It took 7x to get it to stop draining "brown". This was after using a chemical flush compound. Big pain in the rear to do it like this. So now I just pop everything open and run a hose to flush with the engine off. Only takes 1x and about a minute of rinsing.
Then I rinse once with distilled water (probably doesnt matter but I'm paranoid) and finally fill with coolant.

Some people (me included) drill a tiny 1/16 hole in the thermostat to allow a tiiiiny bit of coolant to flow past it while the engine heats up. This theoretically does 2 things, Lets the trapped air pocket get past the thermostat so the system can settle faster, and also helps the thermostat touch the warming water sooner as it flows through the hole.

 

There's controversy on using distilled water (with whatever antifreeze you choose).
I am definitely FOR using distilled water. The dissolved sediments from tap water can harden with elevated temperature causing build up inside the system.
Modern systems have extended flush intervals up to 10 years. I changed my 2012 Ram after 10 years and that coolant looked good as new. I flushed system with distilled water. I then used Mopar coolant with the recommended mix of distilled water for service.

 

This is why i use premixed coolant now. I figure whatever they're using to mix it up is what works haha. Also, even though I do final rinsing with distilled, I'm fully aware that the inside of my water passages are not by any means squeaky clean after 60 years. Even after a chemical flush. So the tiny amount of minerals that would be in a little rinse water probably wouldn't make a dime of difference compared to what's already built up in there haha.

 

The shroud is essential to proper air flow and cooling.

 

Got it! It sounds more manageable for me to do it without running the engine. Interesting idea about the hole in the thermostat.

Do I need to do anything with the hose that comes from the heater to the water pump? Or water wont go that way when I flush?

 

Correct. I wasn't referring to flushing, which I have never done.

 

Water should make its way through everything when you get a little pressure coming from the hose. Just make sure your heater shutoff valve is in the open position. Are you going to also swap out the water hoses for the heater and bypass? If so... Wait until after you've flushed the system out and let it drain for a minute. Then, disconnect the heater hose (with a towel/rags crammed under it just incase) from the back of the block, bend the hose around and blow through it to push the water out through the heater and down out of the water pump housing area. This will save you the frustration of unhooking the hoses at the heater and having a big glug of dirty water/coolant spill down inside your heater box and all over the drivers side of the engine bay. Now you can disconnect everything and it'll be mostly empty .

While you're in there, take a look at the firewall under your heater box. Usually if the heater has a leak, there will be signs running down the firewall near the steering box.

 

I had not planned to swap out the water hoses (project already creeping!). If they are staying in place, can I just leave the heater in the on position, and flush water through the whole sytem?

 

Yep!

 

Realistically, most tap water isn't too bad. Many folks are on city water which has been filtered and at worst, may have some fluoride, PH additives, or small amounts of chlorine in it. While these "cleansing" chemicals may make the water taste like sh**, they won't really damage our old cast blocks.

The real issue is well water. Various minerals come unfiltered through the tap. A good well will have very few minerals. This water usually smells good out of the heater and taste delicious. But many have sulfur, calcium, iron, as well as sediment. None of these "additives" are good for a cooling system.

Now this opinion may not hold with modern engines with alloy blocks, aluminum heads, and other metals and plastics in their composition.

As a guy on a well with high calcium content, I avoid my water for any radiator use but would fill out of a city tap without blinking.

 

That makes sense. We're on a well, and it is on the acidic side even with an acid neutralizer. I think distilled is the way to go.

 

Silly question, but how I can tell if it's working? Got everything hooked up and filled yesterday. Looks good and everything fit. About 2.5 gallons of coolant in there.

Ran the Jeep doing some chores for about 30 minutes and back in the garage there was steam coming from radiator. I saw a few mentions online it could be the aluminum coating burning off. Or just a reaction to the weather--lot's of rain and puddles today.

How can I be sure everything is operating correctly? Engine thermometer does not work, so I'm not sure if it's getting too hot.

Also, have a few coolant drips which I'm afraid are coming from the water pump. Should have replaced it when I was in there. Lesson learned, but at least I know how to do it.

Thanks!

 

Get a cheap IR thermal reader from harbor freight for external temp checks, and get a new aftermarket temp sending unit and gauge. Pretty cheap fix

 

This.

But if it gets "too hot" too hot, it will be boiling and blowing steam out the overflow tube.

 

Thank you! I almost picked one of these up last time I was there. Good excuse to grab one. Is there a max temp I should be looking for?