99xj 4.0. I'm going to flush the system tomorrow and have a couple of questions. First, what is the benefit, if any, of removing the thermostat for the flush? Second, when I run the jeep to circulate the coolant to the heater core and engine block, I put the lower radiator hose and cap back on, right?
Thanks,
Mill

 

Flush the heater core, motor and rad separate of each other to prevent crud from moving from one place to another.

Disconnect the top rad and heater hoses from the t-stat cover. Disconnect the bottom rad hose from the water pump. Stick a garden hose in the heater hose and flush. Stick the garden hose in the heater hose nipple on the stat cover and flush. Stick the garden hose in the top rad hose and flush.

 

djb, this is awesome. am I running the engine at any point?
Mill

 

Negative.......after all 3 areas r flushed, let everything drain good before buttoning it all back up. Fill the rad slowly with 50/50 coolant/water until coolant remains at the top of the rad. Leave the rad cap off, start the motor and let the motor idle. Keep the rad full while the motor is idling and warming up. When the stat opens, some coolant/air will "burp" out the rad. Install a new rad cap, turn motor off and check for leaks. For several days, check coolant level in both the rad and bottle, motor COLD. Bottle should be about 1/3 full, motor COLD and the rad should be full to the top, motor COLD.

 

That sounds like a good way to do it. I may flush mine that way....

Bill

 

Absolute best way to flush the motor is with both the t-stat cover and water pump removed. stick a garden hose in the t-stat hole in the head and flush out thru the pump hole in the block.

 

With at least 1 gallon of water left in the block the best idea would be to add 1 gallon of undiluted antifreeze to the radiator then 50/50 after that. Of course check with a tester when done (its a lot cheaper than replacing the engine block).

 

I did as aforementioned and split the cooling system up. completely disconnected the heater core and radiator from the engine. I also removed the Tstat, but reinstalled the housing. I sprayed water into the inlet of the water pump and started the engine using the water pump to flush the head/block. I didn't get much gunk out of the engine or radiator. the heater core on the other hand was full of it and didn't dislodge until I flushed it backwards with the hose. I did the same thing with the radiator. I flushed both areas in both directions multiple times.

 

how easy is it to get to the pump hole in the block? I'm replacing my t-stat today, so I could do this.
Mill

 

U have to remove the water pump.....doing so exposes a 3"-4" hole in the block where the water pump impeller rides.

Flushing as I explained above (removing only hoses) works great. The key to keeping a iron block motor clean internally is frequent/routine flushes. The color of the coolant will always tell u when its time for a flush.......but only if one checks the color of the coolant (routine maintenance).

We do a simple drain/refill each year. Takes about 30 minutes, including adding 2 1/2+ gallons of fresh 50/50 and idling the motor (rad cap off) 'til hot. Doing a flush as well takes just a bit longer.