Radiator Flush

The jeep has been suffering from jumpy-temp-needle for a few weeks which is my clue to fill the radiator up (it has a small leak, somewhere, that I'm maintaining vs. fixing). The last time I popped the radiator cap, it was pretty nasty looking in there, so I decided to go ahead and back flush it with one of those kits that allows you to hook a garden hose to the heater hose. I picked up a jug of the flush chemical on the way home, put it in so it could do it's thing, continued home, and then dug in.

HOLY E36 M3. The stuff that came out of the radiator is the nastiest stuff I have ever seen come out of a car. It looked like the vomit of someone who had gorged on oreos and chocholate milk. It was pretty shocking. There was nothing clear, or green about it. After a few minutes of flushing it started to clear up, so I cranked it with the hose still attached and got another round of chocolate milk, and then finally clean water. Shut the hose off, drained the radiator, added coolant, and then topped it off. As I was about to top off the overflow I peered in and saw that the bottom 2" was rust/mud/toxic sludge, so I pulled it off and cleaned it as well.

Hopefully the Jeep is happier / runs cooler. I suppose this is an endorsement for those back flush kits on poorly maintained high mileage motors. Especially iron block ones.

When I was trying to save the original engine in my $1500 Wrangler, I flushed it until it was clear. To make a long story short, the engine was junk. Upon tearing it down, we were still able to spoon out piles of rusty sludge, even after the flush.

It should run cooler, but where'd the schmutz come from?

Oil in the coolant?

Do those chemical flushes work well? I have never tried one personally.

bluesideup wrote: Do those chemical flushes work well? I have never tried one personally.

I've wondered this too but with the plethora of plastic parts in the cooling system on modern cars on PITA to replace items (radiator, waterpump) I've always shyed away...

914Driver wrote: It should run cooler, but where'd the schmutz come from? Oil in the coolant?

Didn't see anything oily. I assume the schmutz is 20 years of rust from the iron block returning to nature.

bluesideup wrote: Do those chemical flushes work well? I have never tried one personally.

I'm sure that most, and maybe all, of the crap that flushed out would have with water alone. OTOH, if the chemical did have any effect, then I'm OK with the $3 I spent on it.

just flushing the rust and little bit of chemical seepage from the oily and hot bits of the engine probably did wonders...

Is there any advantage to waiting a month or two and doing it again?

mad_machine wrote: just flushing the rust and little bit of chemical seepage from the oily and hot bits of the engine probably did wonders... Is there any advantage to waiting a month or two and doing it again?

I had the same thought. Give this fresh change enough time to get the remaining schmang all nice and stirred up, and repeat.

I'll probably make that call based on the appearance of the coolant.

While changing the head gasket on my Neon, I put the gasket on upside down. They said it couldn't be done.. What happens when you do that is the oil pump fills the cooling system with oil in about 20 seconds, resulting in the chocolate milk syndrome. It ook 6 full cycles of Prestone coolant flush to clear it up (after flipping the gasket, of course). But it worked. No way repeating the cycle from time to time wouldn't help.

I've run junkyard motors on water (rules say no coolant) for a short time and almost all of them looked like you describe after one season. The good ones we use water wetter in, but that stuff costs money.

In reply to NYG95GA:

I did something similar when I attempted to go all 'oem' on my older supra with Toyota Red coolant. Note to all noobs or others without the experience/information, Toyota red + traditional green = brown crud/smegma. That took about 6 times to completely flush out. Only after 5 years and two cross country trips am I convinced that the crud is out. However, what a great lesson in a precipitate formed in chemical reaction. I think it only forms when heated, not mixed in a jar, ask me how I may know...

Eric G

Do notice that those instructions on the flush tell you not to mix it with the antifreeze. Oh, they don't say it directly, but you're told to drain the coolant, than run the flush with bare water. Then drain and flush that. Then put in antifreeze.

That's because antifreeze and flush don't always get along so well together. Form a gel or crystaline goo sometimes, as I recall. Never actually seen it myself, but I've seen pictures of it in various cooling shops on the various posters hanging on the walls.

foxtrapper wrote: Do notice that those instructions on the flush tell you not to mix it with the antifreeze. Oh, they don't say it directly, but you're told to drain the coolant, than run the flush with bare water. Then drain and flush that. Then put in antifreeze. That's because antifreeze and flush don't always get along so well together. Form a gel or crystaline goo sometimes, as I recall. Never actually seen it myself, but I've seen pictures of it in various cooling shops on the various posters hanging on the walls.

The one I had said to drain the radiator, put in the flush chemical, top off with water, drive, and then flush. It didn't mention flushing with clean water prior to putting in the chemical though. I assumed the instructions to drain the radiator were simply to give room in the system for the chemical, and since mine was low, it held it. :shrug: