I have a 1997 cherokee sport. inline 6 / automatic.
i've had no heat for over a year now. i didn't drive it much last winter because of this reason. I flushed the heater core and the rest of the system with water today using a garden hose. Lots of dark brown crap came out. I did this till the water ran clear. Flushed both ways. I now have heat! I plan on driving it some till end of september then reflush and change to preston for the upcoming winter.

my question is.
I did this 3 years ago when i first bought the jeep and had good heat for awhile. I flushed it again today and have good heat once more.

why is my cooling system always getting plugged up with crappy brown stuff?

 

Yes. But don't wait. You'll forget and crack your block. Ask me how I know. Drive it sround the block, flush it again. Get all that crap out. A better way is to unplug the radiation drain and stick your garden hose in the raidiator cap. Drain and fill constantly while the motor is running. Watch your heat. As the thermostat opens up you'll get a surge of brown trash. Do this flush for 30-45 minutes.

Pressure test then fill with coolant. The water will create more rust and brown stuff. Get coolant in it ASAP so it doesn't rust out again.

 

One thought is that a previous owner had an issue with a coolant leak and put some kind of stop-leak in it. I had a similar problem with my Cherokee. This issue eventually cost me a radiator when it was -40°C. Let me tell you, doing a rad swap in the driveway at that temperature was NOT FUN!!!

My rad was plugged to the point where only the top 1/3 would defrost so the driver side tank split off the core. This was a few years ago now and I am still finding brown sludge forming in the bottom of the overflow tank.

I would continue flushing it until the brown sludge is completely gone. That crap is more harmful than good. As you have already experienced, it has plugged your heater core. How much do you want to bet that its also plugged off a portion of your radiator?

Keep flushing and good luck!

 

You know...
I recently had to flush out the small hose that leads to the overflow bottle as it was completely plugged with rust. What a fun job that was. Using a coat hanger and running water. Grr!
I know the previous owner put a new radiator and water pump before i bought it.
Maybe your right, it might take several flushes till it remains clean.

Luckily, it's pretty easy to flush the heater core.

 

I'm sure you already know this, but just in case....
Make sure you have the heat set to full hot when you're flushing the heater core. It's easy to forget that.







or so I hear.


From a friend.

 

Update:

Fresh coolant now in the jeep. I did another flush. Some more brown junk came out but it was mostly clean. I'm sure it will be good now. Heat still working great!

 

Use some Amway SA8 laundry detergent in there. A quarter cup. Run it that way for a few weeks - it won't hurt anything.

Then flush again, refill with coolant, and enjoy a nice, clean cooling system.

Some folks say Dawn dishwashing liquid does the same thing. Dunno, haven't tried it.

 

I used Prestone's flush product with great success... It dislodged so much crap that the radiator began leaking (I suspect the PO used a stop-leak product)

Anyhow, when I went to replace my rad and water pump after three flushes with the product in the system, the inside of my water jacket was spotless, as was the backside of the pump itself, albeit with lots of evidence of corrosion on the impeller.

 

My guess as someone also said above would be that someone put stop leak in the system at some point. That stuff kills everything in the cooling system over time, especially if you ever let the vehicle set.

 

If you did not use a block cleaner for the system the system is not clean, that's why it all came back so quickly. You need to clean/flush it possibly several more times till the water is very clear "TWICE" then add more coolant. Then yours may be like mine and run you out if the heater is on for very long, I have heater on windows down.

 

Do what others suggested and use ONLY distilled water.

 

When refilling. No need to use distilled water when flushing.