Is HOAT coolant required for a 2002 WJ?

Upside · Dec 3, 2011

I have a 2002 WJ 4.0 and the manual says it uses the same coolant as the 4.7. I know the 4.7 needs the HOAT coolant for lubrication of the water pump and corrosion prevention.

The reason this came up is I had the coolant flushed about 1500 miles ago and the water pump started dumping coolant out of the weep hole today. It could be just because it has 112,000 on the original pump or it could be because they didn't refill with HOAT coolant.

Is there any difference between a 2002 and a 2000 4.0 water pump?

bhicks · Dec 3, 2011

What is HOAT coolant? I recently flushed my coolant and the pink stuff came out so I flushed it completely and added the univeral green stuff? Was that okay? I ran the universal green stuff from autozone in my 4.0 for years with zero issues.

dukeryder · Dec 3, 2011

I wouldn't worry about it.

I have the 4.7 and before I bought it, it had a recent waterpump change and they put the green crap in there. I had to replace the radiator right after I bought it, and was ignorant about the HOAT coolant and before I went out and bought some Prestone I did a little searching on what the proper coolant I should use. I didn't go to the dealer and shell out the bucks for the HOAT, instead I bought ZEREX G-01 which you can get at O'reilly's NAPA or Pep Boys. The Zerex is good chit, I used to run it in a Mercedes that I owned a few years back. It's less than the Dealer charges and is as good or better, meeting or exceeding the HOAT specifications.

The Green crap will just need to get changed sooner than the HOAT. That 4.0 motor has been the same basic design and engineering as AMC straight sixes going back like 50+ years! I can almost guarantee that even running Prestone you will never see any adverse affects.

Ravie · Dec 3, 2011

It's really just extra protection. The long life coolants can all be mixed with the regular/short life coolants...but it will basically change how long you can go before they need to be changed again. Dex-Cool had a lot of problems with eating gaskets and water pumps, but it was a little different design. HOAT is basically a formulation with a standard Ethylene Glycol base, but with other differences that allow for better corrosion protection for aluminum componets, as well as silicone to aid in lubrication.

You could probably use any one of them except for Dex-Cool.

Personally, for a few extra bucks I will probably buy Zerex G-05.

My $0.02

Upside · Dec 3, 2011

Ok thank you for the advice guys. I will top it off and plan on changing it again next year.

WJWKXJZJ · Dec 4, 2011

One of the best things you can do is use distilled water rather than tap. Tap water contains carbonates, phosphates, and other mineral compounds which don't need to be introduced into the cooling system anyway.

Using distilled for the dilution water puts you a step ahead. The additives in the coolant don't have to be sacrificed to neutralize what's in the tap water to begin with.

Ravie · Dec 4, 2011

^ damn good advice.

teckman02 · Dec 4, 2011

http://www.jeepkj.com/forum/showthread.php?t=50273

Trying to find actual ethylene glycol is almost impossible these days and due to the 3.7(or any engine in the KJ) uses a aluminum head on a iron block so you'd have to change the coolant once a year or the coolant turns to acid.Ethylene glycol is high silicate based.

Your cooling system is designed for a silicate based coolant and HOAT coolant is silicate based but can last longer with the different metals your engine is made out off before you need to change it due to acidity levels.

OAT coolant(any "universal","all makes/models",and dexacool) is silicate free and likes to eat some forms of plastic(google dexacool and 3.1/3.4 GM V6's),so happens the water pump impeller on the KJ's water pump is the same plastic that does not agree with OAT coolants.You also can not mix OAT coolants and HOAT coolants,cancels out there protective additives when done so.

fresh350 · Dec 4, 2011

honestly with jeeps i find that using dealer fluids and parts tend to work out in the long run... the extra money that i spend on dealer parts i think is worth it (i have about 160k on mine and still have original front end parts, water pump, ect...).

Upside · Dec 4, 2011

Well the guys who did the flush put in regular green coolant and I'll be changing it back next month. Either with MOPAR fluid or the Valvoline G-05 stuff.

The new water pump and thermostat are in and working great. The temp is just a bit lower, needle sits between the 2 and the 1 on the gauge lettering. It seems that the I-6 runs a bit hotter than the V8 that I had in my ZJ, at least the "gauge" indicates it that way.

Is HOAT coolant required for a 2002 WJ?

Upside

bhicks

dukeryder

Ravie

Upside

WJWKXJZJ

Ravie

teckman02

fresh350

Upside

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