180 theromstat in 4.0?

210 is perfectly normal and the engine is supposed to run at that temperature. It was designed to run that warm which helps it burn the fuel more cleanly and with less smog output. If you attempted to make it run cooler with a 180 degree thermostat, the engine would simply take longer to warm up but it would still run at the 200 to 210 degree temperature. Plus during that longer warmup, the computer would keep the engine running a richer air-fuel mixture for longer than it should or is necessary. Use only the factory specified 190-193 degree thermostat.

Jerry

Thanks, Jerry. I am just concerned that in the summer months and during long mountain pass climbs, the engine temp will go TOO high. Should I be concerned as long as I have good coolant?

Thanks,

Carl

Yep, Normal both my TJ and my wife's YJ run 210.

HarryS

All you can do to help prevent overheating is having a good clean radiator free of hard water deposits and a good fresh 50:50 mix of distilled or deionized water (NOT PLAIN TAP which causes hard water deposits) and coolant. Distilled and/or deionized water can be found in any grocery store, distilled water is most commonly bought for use in irons. :)

Jerry

my cousin has an 89 cherokee that had overheating problems. we changed EVERYTHING on it. u name it, we probably changed it. he finally found a guy in denver that told him that the cap and the coolant bottle are not made by the same company. what ends up happening is that the cap does not match the bottle perfectly. all they do at the shop was take a box of caps and a box of bottles and try to match them up as best they could. they found a good set and installed it. his car doesn't overheat now and he can finally run the A/C! ps. be careful with hot steam-it can carry a lot of energy and flash burn your skin...

Thanks, Jerry and everyone else. I'll have the coolant changed. Is the hissing sound normal? I'm concerned about too much pressure building in the cooling system and/or a headgasket leak. Do these headgaskets usually hold up well?

Thanks,

Carl

Carl Saiyed did pass the time by typing:

When an engine cools down it makes all sorts of hissing and burbley noises, that's just the radiator cooling down and sucking from the overflow bottle. The AC makes similar noises as well as it equalizes.

The radiator cap prevents too much pressure from building up. If it does the cap will open and coolant flows into the overflow bottle. It's normal for coolant to do this, that's why the bottle has a high/low mark.

Hi Carl, If your worried about a head gasket, take to any radiator shop, it's easily tested for. If you change your coolant by every two years, the acid will never be strong enough to eat through the gaskets and freeze plugs, and if you didn't accidentally run it to far on a blown hose or belt, and over heat, and warp the head/block, chances are you'll be OK. God Bless America, ßill O|||||||O mailto: snipped-for-privacy@aol.com

Thanks guys. I just bought the Jeep, the PO said it was maintained well, but I am going to get the coolant changed anyway. I'll run a compression test when I do the tune up, and I'll have them run a coolant pressure test.

Thanks,

Carl

Just to reiterate, a cooler thermostat does not help control overheating. Only a properly working system will cool correctly. KH

Going to a 3 core radiator did the trick for me!

3-core radiators don't always help the engine to run cooler, especially if you tend to do a lot of low speed rock crawling. The increased depth of a 3 core over a 2 core restricts air flow through/past the channels and in low air flow situations, can make the difference in overheating or not overheating. I will stick with 2 core radiators for my rock crawling Jeep. :)

Jerry