1999 TJ Coolant

JLANEF

TJ Enthusiast
Joined
Jan 9, 2019
Messages
138
Location
Chandler Arizona
I have a 99, 4.0 TJ with 120,000 on it. Past owner is gone and I have almost no past info. Coolant overflow bottle was clogged with red/orange gunk and totally discolored that color. Radiator was gunked up some, but not terrible. I drainer the radiator and the coolant was red/orange after I let it set in a 5 gallon bucket and then took a quart off the top and examined it. The 5 gallon bucket had a 1/8 inch deep level of sediment in the bottom.. Also dark red, probably rust. I have flushed cleaned it twice this week with a flushing/cleaning agent and distilled water, driving it for at least an hour and letting it sit for 12 hours each time. It’s just now staring to come out clean distilled water.

Now the question. What do I put back in? The color has me thinking it had mopar HOAT Coolant in it. Although Jeep didn’t start using HOAT in TJs until 2001, I think someone switched to HOAT intentionally or unintentionally. But I know you shouldn’t mix HOAT and non-HOAT even after a flush. So any ideas?

Anybody have any experience with the new Prestone Coolant they swear is compatible with Hoat and all coolants??

My gut tells me to put back in Zerex G05 HOAT and watch what the coolant looks like in the overflow bottle, which is now a nice new clear one. Any thoughts appreciated!
 
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My gut tells me to put back in Zerex G05 HOAT and watch what the coolant looks like in the overflow bottle, which is now a nice new clear one. Any thoughts appreciated!
Your gut is telling you right. Go with a 50:50 blend of Zerex G-05 and distilled (!!!) water. Don't even think of using tap water to mix with the G-05. :)