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Old 04-14-2011, 06:05 PM   #1
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Default What is the RIGHT way to flush my radiator/cooling system/heater core on a 1996 XJ?

I looked around here in the forum and could not really find anything specific on how to flush my radiator, heater core, engine block and whatever else gets flushed when maintaining the cooling system.

Please HELP!
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Old 04-14-2011, 06:07 PM   #2
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take the motor out, throw it away. buy a new motor and radiator andheater core. and wa la your done jk lol im kinda curious to know myself. i use a vac pump on all our stuff at the shup but i want to see how ppl on here do it.
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Old 04-14-2011, 07:25 PM   #3
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So I located the plastic drain valve on the side of the radiator but it will not budge. I dont want to tweek on it too hard I am afraid it will break off. How do I get the darn thing loose???

If I disconnect the lower radiator hose, can I flush it the same way as if the drain plug was removed?

It has been so long since I have done this I just want to make sure I do it right.
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Old 04-14-2011, 07:44 PM   #4
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how I'd do is it take hoses off and replace them, better safe then sorry. Take a garden hose in the upper radiator outlet and spray until water runs clean. ( be sure to take thormostat housing off) repeat for radiator and heater core. heater core you can use compressed air to flush and using CLR will help clean it.

If your really methodical after you flush everything with just water recconect everything and fill radiator with water and super flush, that'll ensure everything is clean and good to go.

This is just what i do. there are many many more opinions, just gotta go with what your comfortable with. plan on about 2 or so hrs.
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Old 04-14-2011, 08:23 PM   #5
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http://www.cherokeeforum.com/f2/help...38/#post769003
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Old 04-14-2011, 08:26 PM   #6
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Quote:
Originally Posted by ottis1986 View Post
how I'd do is it take hoses off and replace them, better safe then sorry. Take a garden hose in the upper radiator outlet and spray until water runs clean. ( be sure to take thormostat housing off) repeat for radiator and heater core. heater core you can use compressed air to flush and using CLR will help clean it.

If your really methodical after you flush everything with just water recconect everything and fill radiator with water and super flush, that'll ensure everything is clean and good to go.

This is just what i do. there are many many more opinions, just gotta go with what your comfortable with. plan on about 2 or so hrs.
Well I dove into it head first. I pulled everything apart like you are saying and flushed out everything. There was a lot of nasty mud looking stuff coming out due to rust.

That being said, looking into the opening where I took the thermostat off, is it normal for there to be rust inside like on the block looking part due to the jeeps age?

Also, there is some kind of vacum switch tied in with the heater core lines in and out. Looks like some sort of crossroads the way it is set up. I squirted water in the heater line that I pulled off the t-stat but not sure if it flushed the heater core due to that vacuum switch being tied into it.

Can someone shed some light on this? Also, will a cleaner get the rust out of the engine block? I don't want to wind up with a blown head gasket.

HELP!!!
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Old 04-14-2011, 09:11 PM   #7
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Quote:
Originally Posted by Marks2000XJ View Post
Well I dove into it head first. I pulled everything apart like you are saying and flushed out everything. There was a lot of nasty mud looking stuff coming out due to rust.

That being said, looking into the opening where I took the thermostat off, is it normal for there to be rust inside like on the block looking part due to the jeeps age?

Also, there is some kind of vacum switch tied in with the heater core lines in and out. Looks like some sort of crossroads the way it is set up. I squirted water in the heater line that I pulled off the t-stat but not sure if it flushed the heater core due to that vacuum switch being tied into it.

Can someone shed some light on this? Also, will a cleaner get the rust out of the engine block? I don't want to wind up with a blown head gasket.

HELP!!!
I would not mess with the radiator petcock, opens a big chance of a leak down the road, for a flush you can drain the coolant and please be responsible and use a container to catch it. Refill with water/vinegar 50/50 mix, turn the heat all the way up, let idle with rad cap off, topping off as needed, once the thermostat open youll notice a big drop in the level, top off replace cap let idle for 45mins or so, drain repeat if needed. Once clean, refill with 50/50 mix of water/ anti freeze.
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Old 04-14-2011, 09:18 PM   #8
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I would not mess with the radiator petcock, opens a big chance of a leak down the road, for a flush you can drain the coolant and please be responsible and use a container to catch it. Refill with water/vinegar 50/50 mix, turn the heat all the way up, let idle with rad cap off, topping off as needed, once the thermostat open youll notice a big drop in the level, top off replace cap let idle for 45mins or so, drain repeat if needed. Once clean, refill with 50/50 mix of water/ anti freeze.
Do I use just the white vinegar? I assume that because it is somewhat acidic it will eat the rust off after running it through? Hope I am correct in my thinking.

And yes, I gave up on the petcock. I knew it would break if I cranked on it very hard!
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Old 04-14-2011, 09:24 PM   #9
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Quote:
Originally Posted by Marks2000XJ View Post
Well I dove into it head first. I pulled everything apart like you are saying and flushed out everything. There was a lot of nasty mud looking stuff coming out due to rust.

That being said, looking into the opening where I took the thermostat off, is it normal for there to be rust inside like on the block looking part due to the jeeps age?

Also, there is some kind of vacum switch tied in with the heater core lines in and out. Looks like some sort of crossroads the way it is set up. I squirted water in the heater line that I pulled off the t-stat but not sure if it flushed the heater core due to that vacuum switch being tied into it.

Can someone shed some light on this? Also, will a cleaner get the rust out of the engine block? I don't want to wind up with a blown head gasket.

HELP!!!

as far as the rust there is flushes with rust remover, just look at the parts store and or check online for the kinds and info.

as far as the vaccum switch i dont know, my 99 doesnt have them, as far as flushing it did you take the hose from tstat and water pump off? flush it back and forth a couple of times. with both heater hoses off you will be able to tell if its flushing.

The vaccum lines might be what is used to stop the heat, when you have the a/c on I dont know for sure??
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Old 04-14-2011, 09:36 PM   #10
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Quote:
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as far as the rust there is flushes with rust remover, just look at the parts store and or check online for the kinds and info.

as far as the vaccum switch i dont know, my 99 doesnt have them, as far as flushing it did you take the hose from tstat and water pump off? flush it back and forth a couple of times. with both heater hoses off you will be able to tell if its flushing.

The vaccum lines might be what is used to stop the heat, when you have the a/c on I dont know for sure??
Yes, I took the two hoses off the t-stat, one from the radiator and one from the heater inlet line. I also took the hose off the bottom of the water pump. When I squirted the hose in the heater inlet line it came out the bottom of the water pump where I took the hose off. Does that mean it went through the heater core?

It is too dark out now or I would take pictures of that vacuum switch that is tied in with the heater core lines coming in and out of the firewall.

You posted above that the switch may cut the flow off when using the a/c. That makes sense.
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Old 04-14-2011, 09:38 PM   #11
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If the vinegar and water works just as well as any cleaner I can buy, I would rather save myself some money and use it.
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Old 04-14-2011, 10:01 PM   #12
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That "cross roads" octopuss is the Heater Control Valve. It is vacume controlled to shut off the flow of fluid to your heater core when the AC is activated or when the temperature switch is set to cold. When you set the control to heat the valve opens and directs the coolent to your heater core. Carefull messing with the unit as your vehicle ages so does this plastic valve. Just replaced mine a few months back after noticing my coolent recovery bottle going empty twice in a month. The valve cracks at the hose connections.
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Old 04-14-2011, 10:10 PM   #13
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Quote:
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That "cross roads" octopuss is the Heater Control Valve. It is vacume controlled to shut off the flow of fluid to your heater core when the AC is activated or when the temperature switch is set to cold. When you set the control to heat the valve opens and directs the coolent to your heater core. Carefull messing with the unit as your vehicle ages so does this plastic valve. Just replaced mine a few months back after noticing my coolent recovery bottle going empty twice in a month. The valve cracks at the hose connections.
So should I have turned the ignition on (not actually cranked the car) and slid the hot/cold **** all the way to hot where it would open the heater line going to the core? Or does the heater control valve always stay open until you turn the a/c on, even when the car is off?

I just wanted to know if I flushed the heater core when I put the hose to the heater inlet line and the water flowed back out the bottom of the water pump.

Hope this makes sense.
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Old 04-14-2011, 10:28 PM   #14
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The heater control valve was discontinued on '97 up......at least I thought it was. If water was squirted in the t-stat heater hose and it came out the water pump, u flushed the heater core.

Last edited by djb383; 04-14-2011 at 10:30 PM.
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Old 04-14-2011, 10:52 PM   #15
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(The heater control valve was discontinued on '97 up......at least I thought it was.)


That may be true, since Marks2000XJ mentioned a cross roads of tubes with a vacum switch, I took that to be the Heater Control Valve similar to my 96 XJ. Since they added coil packs in 98, they may have also removed the valve.

Would have been nice if they left only the two hoses going into the firewall like late 70 & 80 models. Then all you needed to do was cut the hose and install a flush tee. Hook up the garden hose, remove the radiator cap and power flush the whole system.
Back before anyone thought about the environment.
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