Hey all, just got done replacing the evaporator case and cleaning the heater core and all... Last step is to flush out the cooling system (nice and brown throughout). I've heard of people using CLR and I just happen to have a few bottles here. Any objections?

My plan:

1. Mix 1 bottle of CLR and tap off rest with hose water.
2. Turn heater on high and let it idle at temp to cycle it all through (should I top off the radiator after the "burp" of the thermostat?)
3. Remove lower radiator hose and let all the gunk drain out.
3a. Should I do one more round of CLR or move on to 4?
4. Refill one more time with just hose water (again, should I let it burp?)
5. Drain
6. Replace thermostat
7. Refill with 50/50 with definitely letting it burp and topping off.

Thanks for your help. Just this and change transmission fluid and I've done a total overhaul on the whole damn thing

-Tyler

so did it work? im considering doing this on my jeep grand cherokee

I'm sure the CLR will eat your rubber hoses, I'm almost positive it will as it's acidic.

I have used a targeted dose of CLR for clogged heater cores as a last resort, but I wouldn't use it as a general cooling syste flush.

There are LOTS of good cooling system flush products available in your parts store for that. From mild to wild. You may need to do it multiple times if the cooling system was severely ignored.

Use a high quality thermostat like one from Jeep or the Stant SuperStat. 195 degree. New radiator cap as well. Good luck!

It is mildly acidic and abrasive.

2 or 3 tablespoons of Automatic Dish Washing Detergent. Found out quite by accident when the Mom decided the radiator needed a quart of oil added to it. Ran until it just reached operating temperature.

Car went another 100,000 miles with no "H20" issues.

Ron

Shouldn't hurt the rubber. Can't see anything wrong with it. It's probably milder than the heavy duty stuff I've used in the past.

It's not in there long enough to hurt the rubber unless your hoses are gone as it is.

How do u know it's all out of the rad, since the bottom rad hose is several inches above the bottom of the rad?

Flush it wit a hose

Why didn't I think of that......it'll flush up.

I took off the upper and lower hoses then duct taped the hose to the upper radiator inlet and let run for 10 min. Then stuck the hose in the thermostat housing and taped off and flushed for 10 min.

I have used CLR on several vehicles w/great results!

Its a GREAT product

Well I went as planned and it actually worked quite well. Dumped a lot of gunk out, but I can see it didn't get it all.

However, I did install a new thermostat and seal and it looks like it ate through the seal (I guess one flush afterwards was not enough). You can see the seal bubbling as if acid is eating at it; or maybe I'm just being a Negative Nancy and just want to blame the CLR and it is really just a faulty seal with 200*+ worth of coolant bubbling its way through? It is puking coolant where the thermostat housing meets the block. And I mean puke - projectile vomit even. It pukes probably a pint-ish of coolant. But what I don't get is this...It only lets loose after the Jeep has been turned off. After I buttoned it all up last night, I drove it for 5 minutes and let it sit and idle for probably another 10: no issues. But I get home, park it in the garage, step back at its magnificence, and then it exploded like I popped a water balloon what had to be about a minute after I had turned it off.
And just now I got back from driving for nearly an hour with no problems; I stop at advance to pick up some R134 and come back out in the parking lot to another pint of puke. Crank it back up and it's all sunshine and rainbows.

It's obvious the thermostat seal is the culprit...A Fel-Pro at that. Part of it may be my fault as I didn't apply any RTV on the motor side of the gasket (it was late and had a 7am class in the morning...I was DONE). But why is it happening only after being shut down for a minute or so and why with such pressure? I mean it just POPS when it lets loose.

T-stat housing attaches to the head, water pump to the block. T-stat could have slipped out of its groove in the head thus preventing the gasket from properly sealing. I've always applied sealer to both sides of gasket. It's probably sucking air back into the system, when the motor cools.