I have a 96 XJ. My cooling system has been flushed 2 times. Each time a few month later the coolant turns brown. It is still green now but changing. The old owner never flushed the coolant and mix the colors. As a result I get brown coolant after a while. There are no leaks and it has a brand new t-stat.

Today I turned the petcock and nothing came out of the radiator. My guess is that it clogged up by brown gunk. Now what should I do from here? I'm trying to do a very thorough and final flush to get the gunk out.

Should I flush it and chemical clean it? Or,

Replace the radiator?

 

Most likely the po used stop leak in the cooling system.
I would change the radiator and flush the heater core and engine block separately with a garden hose.

 

I bought that peak flush kit. Will that flush both the block and heater core??

 

Yes but I usually prefer to use a garden hose to shoot all the crap out till it's clear.

Seems more effective..

 

Remove the bottom rad hose from the water pump, the heater hose and top rad hose from the t-stat housing. Stick the garden hose in the heater hose, then in the top rad hose, then in the nipple on the t-stat housing. Much better flush than a heater hose T fitting and it's free.

No such thing as a final flush......keep tabs on the coolant color, check frequently (engine cold).

 

You're supposed to attach a garden hose to that kit.

I only got the petcock to turn one time around. (I used a long flat head to reach it and turn it) that's all I could get it to go with the flat head. Shouldi try and turn it more?
I really dont want to take apart half the front end to get to it.

 

That does seem a whole lot more effective. What about flushing the radiator if I can't get anything to coneout of the petcock?

 

Don't mess with the petcock. The garden hose stuck in the top rad hose that u disconnected from the t-stat housing will flush crud out the botom rad hose u disconnected from the water pump. Re-read my 1st post....3 hoses disconnected.

 

Right. That's what I thought I just wanted to now sure I was right. Would it be worth it to run one of those flush cleaners in it?

 

Lots of people do......I'm not a big fan of those chemicals so I don't use them.

 

Alright well thanks Alot for all the advice it was very helpful.

 

kinda sounds like someone mixed dexcool and regular coolant in your jeep.

 

I'm pretty sure they did that or put stop leak in it. Everything operates perfectly fine except for thegunk build up.

 

The 4.0L is a cast iron block/head....rusty brown is the color neglected coolant turns too, in cast iron motors.

 

it seems the po ran straight water in your engine and left it in there without putting regular coolant back in forming rust,i had the same problem with a 64 chevy i had and had to flush and flush to get it clear.between your flushing,do what the other guys say wit the water hose flush and flush again.its nerve racking but it will come clean.