My '98 Cherokee had 144k miles when I bought it, and I swear the prev owner never changed the coolant.

After replacing my radiator core early in the summer, I decided to bypass it by running the inlet and outlet house together. I flushed the radiator very well, cleaned all the sludge out of the overflow bottle and refilled with antifreze. After a week of driving, I started noticing small amounts of contaminant floating around under the reafiator cap. I then drained and added a gallon of distilled white vinegar to the system, drove it for a day and flushed well again.

The antifreeze is very clean looking, but I don't want to hook the coolant lines back up to the brand new heater core without cleaning things out better. I'm sure the same brown sludge that was at the bottom of the overflow tank is sitting in the radiator as well.

Any good chemical flush additives to recommend? I used the Prestone flush liquid, but got better results with the vinegar, to be honest.

Here's the residue I'm talking about...

 

Mercedes has a citrus flush that a lot of owners swear by, supposedly better than the chemicals. It will expose a weak radiator, though. The citrus, combined with Dawn dish soap did a number on my 1982 300D.

 

I have used powdered Cascade dishwasher detergent multiple times with very good results. Used it on a Dexcool clogged radiator once and the radiator look like new brass when done. This is a proven flush used by Caterpillar too.
With these organic coolants (Dexcool, HOAT GO-5, Prestone "any make any model") it is imperative to keep a close eye on them and change at the first sign of discolouration. Once this type coolant breaks down it forms an evil emulsion that will EAT radiators,heater cores, head gaskets and water pumps. These coolants WILL NOT provide corrosion protection if system contains any rust at all. From the factory with green engine blocks these coolants will last 5 years but if neglected...they become a nightmare.
If you go back with a OAT/HOAT coolant FLUSH,FLUSH and flush until system looks like new again.

 

As bigbadon said, you can use Cascade. I've also heard you can use C.L.R, though I don't know how much you're suppose to use.

 

Anything that can neutralize the rust in the system, so it can't spread? I like these ideas so far, and I plan on replacing the radiator anyhow, so I'm more concerned with getting the block clean... bit at the same time, I don't want to start filling my block with all kinds of detergents and solvents, then eat up a head gasket. Also, as mentioned before, my heater core is brand new and hasn't had the cooling system plumbed into it, so I'm good there.

Thanks for the suggestions guys, keep em coming!

 

One thing you could do is replace your freeze plugs and try to flush out the block itself best you can. The freeze plug will get "mud" caked on the back of them, and can rust them from the inside out.

These were a couple of my freeze plugs when I had to replace them due to that lovely little hole there on the bottom left. The top right is one that was OK, with the mud cleaned off of it.



I had to replace my entire cooling system. The only piece remaining is my heater core that has a very small leak as well. How was that job, by the way?

I did backflush the core completely. Didn't use any additives, although I should have probably, but my coolant is pretty nice and green now with very minimal crud.

I wouldn't suggest doing the freeze plugs without doing everything else first, though. Last resort kind of thing, but good security. You don't wanna do what I did and blow one while going up a hill that you can't pull over on. If you do replace them, USE BRASS!

 

A clear water flush is all you need to rinse out the Cascade,so that is not a concern.
The problem with organic coolants is that they take awhile to coat metal surfaces with corrosion inhibitors and during that time the system is vulnerable to get contaminated. The old silicate antifreeze would immediately coat surfaces with silicate (water glass) and form a protective barrier. The HOAT is a hybrid coolant and does contain some silicate so it is somewhat better than the "any make,any model" antifreeze. Air is the enemy. Do not keep removing the radiator cap and keep the reservoir at mid level.

 

Since the overflow bottle is removable, and clear, it seems like a good place to see how well a solution can clean the inside. I might pull it and use some dish soap to see how clean it gets.

Any reason to not use CLR in the block??

 

Never heard of any reputable mechanic using CLR and it would have to be neutralized afterwards. A Cascade flush is 30 minutes at operating temperature,drain and rinse.

 

Well, did quite a bit of looking around elsewhere on the internet, and found a forum on BobIsTheOilGuy.com which made mention of using CLR or Simple Green. The idea of CLR intrigues me because of the product's emulsive nature against calcium and scale build up, but I wonder if it would be too harsh... and with a label that specifically warns against using the product on aluminum, I think it might be too aggressive for the thin aluminum within a radiator.

While checking out CLR's website, I found this....

http://www.jelmar.com/proline/Metal_Cleaner.htm



"Great for aluminum, brass, bronze, copper, chrome, pewter, stainless steel*, gold, Rose gold, nickel, silver plate, sterling silver, titanium, palladium, tungsten and cobalt."

I'm going to call CLR on Monday and inquire about its effectiveness as compared to original CLR, and I might end up using some. I will keep this thread updated, and if the results of my flush are impressive, I'll do a little write up.