HITDOGG

Hey guys, I have a 96 I'm having a little bit of a sporadic problem with. Memorial Day, I took it up and ran an old dirt road in the mountains. Had to pull over at one point, and let it cool off, temp was up in the red, and boiled a little over. Ran fine the rest of the day after that, although I did have to run the heat some along the trip to keep it in range. So, got it home, did a flush of the coolant system, replaced the thermostat, and radiator cap. Drove it for about 2 weeks straight with no problems. Then after a longer trip than normal, about 100 mile round trip, the water pump took a dump. After vacation, replaced the water pump, and fresh coolant. So I drove the thing for about a week or so, back and forth to work, around town, etc, etc, with no problems. Never touched the 210 mark. So last Friday, took about a 50 mile round trip, in some stop and go traffic, temp outside, hotter than a 4 balled tom cat, temp starts creeping up. I had to run the heat to get it to settle down. Most everything is new, with the exception of the fan clutch. Does this sound like my problem? I haven't tried spinning the fan with the vehicle hot, but with it cold, the fan wont make but about a 1/4 turn. Any advice where to look? Thanks in advance!

BlueRidgeMark

1. Your symptoms are a good match for a fan clutch.
2. There is no reliable test to determine if it's working properly.
3. A new fan clutch is cheap.
4. Replacement is a pretty easy job.

I think all that adds up to, replace it and see how it goes!

HITDOGG

Thanks! Sounds like a great place to start.

HITDOGG

Hey guys it's been a while. So here is where I am at, and it's kinda weird to me. So after a couple of times of running in the "red" on my 96, I have noticed something. After replacing the usual coolant problem parts, electric fan, mechanical fan clutch, thermostat, radiator cap, water pump, and doing a flush this is what I have going on. Daily driving to and from work, hot days, air conditioning running, or even if I let it sit and idle, the temperature does fine, gets just shy of the 210 mark. But if I drive down the highway, speeds in excess of 60-65 mph, the temp starts to get a little past the 210 mark. Even if it's just a short trip on the highway. I don't get on the highway much with it, but it kinda takes out any road trips in the thing if it's hot outside. Anybody have a clue? Thanks in advance!

fb97xj1

I dont see an issue. The factory thermostat is 195. Normal operating temps are 210. Just shy of 200 or just a little over 200 is nothing to worry about. For what its worth, the last time i checked my 97 using the code reader, it read just shy of 200 when the gauge reads just shy of 210. This was just after a long drive.

HITDOGG

Sorry, you must have read that and replied prior to my edit. I thought the temp reading straight up was 200 degrees. But it's 210. And it gets a little past that, and will boil over if I don't help it out. It just puzzles me that it only happens when I get on the highway. I can let it sit and idle, with the air conditioning on, and it won't over heat.

PatHenry

It shouldn't be boiling over at slightly over 210 - before I changed out my bad t-stat and fan clutch I'd drift into the 230-ish range with no boil-over at all. I'd wager that you have too much water in your coolant mixture. If it were me, I'd just replace the coolant with a name brand 50/50 premix and go from there.
Have you done an oil analysis in the recent past?? If I had red-lined the temp as you've described then I'd be keeping a close eye out for block/head damage and an oil analysis is a great way to do that.

HITDOGG

I would agree with you on all of that. But this thing only gets over the 210 mark if I'm driving down the highway, at speeds over say 60 mph. I can let it sit and idle, on the hottest days, and the temp hand not get over 210.


And to clarify, it's only boiled over on me one time. If I have noticed it getting up in that range without and signs of leveling off, I'll usually turn the heat on. But again, I only have to worry about it driving on the highway. Back and forth to work, it does fine.

PatHenry

Ok, I must have misread the prior post (common problem for me... ). Given that it's only drifting up on the highway, I bet if you put a Mopar t-stat in it your problem would go away. The t-stat helps control the speed in which the coolant flows, and yours is probably flowing too quickly (or in other words, not spending enough time in the radiator to transfer the heat out of it) when you've got the engine rev'ed up for extended periods of time.
T-stats can be picky, even out of the box, so it's not uncommon for one to not function in spec even when new.
Just a thought - of course.

PatHenry

Also a very trusted member posted recently in another thread that a -little- over 210 is perfectly normal. If it's like 220+, I'd worry, if it's below that, you could try the Mopar t-stat if it bothers you.

EZEARL

Don't see where he's replaced the radiator. Could be it's gotten to the point it can't hold enough coolant for the system to cool it down at the speeds he's talking.

PatHenry

Excellent point. It doesn't take much to clog up those little passages.

EZEARL

For sure!

kbeam418

Mine does the same thing, yesterday I drove 83 miles at 75 mph in 100f heat, mine is usually between 210 and the next line over once the ambient temps hit 90f+ and stays there granted I've got a seeping thermostat gasket so I'm sure the temps could be lower. One thing to keep in mind our Jeeps are not aerodynamic driving above 60 mph is giving the 4.0 a workout, combine high ambient temps, high wind speeds and a confined hood the cooling system is having a heck of a time keeping temps in check. If it levels off you're fine the cooling system is doing it's a job, if it keeps going above the line after 210 (218f) something is wrong.

BlueRidgeMark

I think EZ may be onto something here.....