How to flush the cooling system on your Jeep Wrangler TJ

[Feralkid]

I flushed used thermocure and flushed my coolant system really well back in January until in ran clear. I went through a lot of hose water, distilled water, and then fresh coolant. I drained drained the radiator last week (in June of same year) and my coolant was looking kind of grayish and there is black bits floating around in it. The black stuff is sludegy, not hard. I sent some coolant to Blackstone for an analysis and they said there was no trace of oil or engine exhaust and that the coolant was fine, as far as coolant goes.

I think the best thing for TJs and their rust prone blocks is just to do a bleed and feed every 6 months to a year. A bleed and feed is basically just draining the radiator and refilling it. If you do that periodically enough, the bad stuff gets diluted enough to stay fresh. You can buy a gallon of concentrated prestone and a gallon of distilled water for well under $20 so it doesn't cost much. It takes about 2.4 gallons to drain the radiator and refill.

The black stuff was probably one of your hoses breaking down. You should give your hoses a squeeze to feel for soft spots before it bursts on you. If it were me, I would change all the hoses if I saw black sludge in the coolant.

Most modern coolants have a 5 year/150k mile change interval. I use Zerex G-05 that was specified for a 2006. The older green coolant has a 2 year/30k mile interval. If you have green antifreeze and you are flushing the cooling system and changing the hoses there is no reason you couldn't upgrade to Zerex G-05 at the same time to extend the service interval.

Jeep 4.0 blocks are no more rust prone than any other engine. There is no need to drain and refill the radiator every year.

You have to remember, when you're on this forum you are dealing with internet autists that have ass burgers about the Jeep TJ.

Does it make a difference whether or not you get every last bit of rust out of the engine block's coolant passages when you flush it?
No, not in the real world...

In most cases, the only thing flushing the coolant system instead of simply changing the coolant accomplishes is satisfying an obsession.

 

[carmangary]

My antifreeze looks like toilet water after 6 months. So, there is a reason for me to drain the radiator that often. Not sure how it goes for other but this is my 2nd 4.0L engine and they both were this way. A drain and fill costs under $20 and takes 30 minutes. Not a big deal.

I was thinking that black stuff might be coming from the hoses, too. They aren't all that old. I think they have about 50K miles on them. I'll probably swap them out for good measure just because it is easy.

 

[Feralkid]

My antifreeze looks like toilet water after 6 months. So, there is a reason for me to drain the radiator that often. Not sure how it goes for other but this is my 2nd 4.0L engine and they both were this way. A drain and fill costs under $20 and takes 30 minutes. Not a big deal.

I was thinking that black stuff might be coming from the hoses, too. They aren't all that old. I think they have about 50K miles on them. I'll probably swap them out for good measure just because it is easy.

Considering how the quality of everything has declined since the covid hoax bail out, I wouldn't be surprised.

A few months ago I was shopping for a lower radiator hose since my power steering pump was leaking oil all over it and I had to reject an ACDelco hose because the layers weren't bonded together. I rejected a Dayco because it's diameter was slightly too large. Finally found a Gates hose that was acceptable.

 

[Captain Phoenix]

covid hoax

 

[MikeE024]

My antifreeze looks like toilet water after 6 months. So, there is a reason for me to drain the radiator that often. Not sure how it goes for other but this is my 2nd 4.0L engine and they both were this way. A drain and fill costs under $20 and takes 30 minutes. Not a big deal.

I was thinking that black stuff might be coming from the hoses, too. They aren't all that old. I think they have about 50K miles on them. I'll probably swap them out for good measure just because it is easy.

We know Thermocure makes the rust turn black.

My guess is the black stuff is from the Thermocure bonding with rust still attached to the block when you put fresh coolant in the system. That would help explain why it wasn’t a solid like you'd see in the coolant from an old rubber hose.

 

[carmangary]

I had considered that. There is also a bit of black sludge in the coolant. I supposed that could be dissolved converted rust that is working its way loose. I hope some more radiator flushes will get it worked out.

 

[MikeE024]

I had considered that. There is also a bit of black sludge in the coolant. I supposed that could be dissolved converted rust that is working its way loose. I hope some more radiator flushes will get it worked out.

At most, I'd run distilled water through the system one time, and then get your coolant mix in there. If you don't drain the block, you can add a gallon of concentrate to offset the water in the block, and then fill the rest up with 50/50. You can always adjust the ratio by putting more water vs coolant in the reservoir.

I wouldn't change hoses that were recently installed unless there is a clear sign that one should be changed.

I don't see a point in doing the Blackstone lab report if you aren't going to trust it. I'd get some new coolant in there and move on. You may find that you're good to go.

 

[SlippyFist]

I'm looking to flush and replace the coolant on my '05 4.0 Wrangler Sport, and have been trying to follow this thread. The coolant in the expansion tank is rancid like pond water. i can't even tell what color it used to be. i actually got a whole new replacement expansion tank bottle just to put a clean one on. i had noticed that while the A/C works, it doesn't blow very cool air out at all and I'm assuming replacing all the coolant with fresh clean G05 will fix that.

what i got:
4x Gallons of *PREMIXED* Valvoline Zerex G05
1x 32oz BlueDevil 3-in-1 Radiator Flush
some Gallons of Distilled Water

So basically i plan on following the directions of the radiator flush - draining the radiator, flushing with distilled water, then filling with and running with the radiator flush, then flushing with more distilled water, then filling with coolant.

when i go to fill up with coolant, how much do i use? all the posts ive seen about it say to fill with 5.25 of the un-mixed coolant, and then topping off with distilled water, which would be 10.5 quarts? and then i need to add more to the fill line the expansion tank, right? what about burping air out? i think i saw a post where someone said after he fills up he runs his jeep with the radiator cap off for a bit to let the air burp out that way.

Also how many total gallons of distilled water should i have on hand? i plan on running down the street to wal mart and picking up at least 6 of the 1 gallon jugs, but i'm not sure if that'll be enough for all the flushing i need to do.

I also got a replacement washer fluid tank because that too is disgusting on the inside.. i know this isn't the topic for it but i was curious if someone knows offhand how to get the pumps/motors out of the back of the washer tank. do they just pull out? i'm gonna do it at the same time as the coolant tank since one of the mounting bolts for the washer tank is in an annoying place that is easier to get to with the coolant tank out of the way

 

[carmangary]

I'm looking to flush and replace the coolant on my '05 4.0 Wrangler Sport, and have been trying to follow this thread. The coolant in the expansion tank is rancid like pond water. i can't even tell what color it used to be. i actually got a whole new replacement expansion tank bottle just to put a clean one on. i had noticed that while the A/C works, it doesn't blow very cool air out at all and I'm assuming replacing all the coolant with fresh clean G05 will fix that.

what i got:
4x Gallons of *PREMIXED* Valvoline Zerex G05
1x 32oz BlueDevil 3-in-1 Radiator Flush
some Gallons of Distilled Water

So basically i plan on following the directions of the radiator flush - draining the radiator, flushing with distilled water, then filling with and running with the radiator flush, then flushing with more distilled water, then filling with coolant.

when i go to fill up with coolant, how much do i use? all the posts ive seen about it say to fill with 5.25 of the un-mixed coolant, and then topping off with distilled water, which would be 10.5 quarts? and then i need to add more to the fill line the expansion tank, right? what about burping air out? i think i saw a post where someone said after he fills up he runs his jeep with the radiator cap off for a bit to let the air burp out that way.

Also how many total gallons of distilled water should i have on hand? i plan on running down the street to wal mart and picking up at least 6 of the 1 gallon jugs, but i'm not sure if that'll be enough for all the flushing i need to do.

I also got a replacement washer fluid tank because that too is disgusting on the inside.. i know this isn't the topic for it but i was curious if someone knows offhand how to get the pumps/motors out of the back of the washer tank. do they just pull out? i'm gonna do it at the same time as the coolant tank since one of the mounting bolts for the washer tank is in an annoying place that is easier to get to with the coolant tank out of the way

Engine coolant has nothing to do with your AC. It won't make it colder.

Distilled water is cheap. I'd get 10 gallons to start with. Mix it with concentrated coolant when it is time to put that back in. For my 98 TJ, after draining the radiator, it takes about 2.75 gallon of fluid to get it full. If you are able to drain the entire block, check the manual to see what the total capacity is.

If it is really dirty, you may want to get one of those flushing kits and flush with a water hose while the engine runs. The flush with distilled water a few times. Then drain and fill to the right concentrate with distilled water and concentrate. Get a coolant meter thing from the parts store for $5 and that will tell you whether to add water or coolant.

 

[SlippyFist]

Engine coolant has nothing to do with your AC. It won't make it colder.

Distilled water is cheap. I'd get 10 gallons to start with. Mix it with concentrated coolant when it is time to put that back in. For my 98 TJ, after draining the radiator, it takes about 2.75 gallon of fluid to get it full. If you are able to drain the entire block, check the manual to see what the total capacity is.

If it is really dirty, you may want to get one of those flushing kits and flush with a water hose while the engine runs. The flush with distilled water a few times. Then drain and fill to the right concentrate with distilled water and concentrate. Get a coolant meter thing from the parts store for $5 and that will tell you whether to add water or coolant.

i dont have the concentrated coolant, i have the premixed, so i never add water to that right?

as for flushing kits, i got the bluedevil 3 in 1 kit (really its just one bottle of stuff that you cycle through your engine).

i'm not trying to over complicate this or spend too much effort on this, this vehicle is mainly just a bad weather backup for my daily driver, but i am trying to handle this sort of maintenance as it comes up.

After I fill the radiator up, do i then also add coolant to the fill line in the expansion tank? also, is it necessary to run the engine for a bit with the radiator cap off to burp air out?