Overheating while moving

I'm going to be a noob and say that I've searched but couldn't find an answer to this question that comes up 3 times a day...

The Jeep: 96 Sport, 4.0, AW4, 231, K&N drop in filter, otherwise stock engine.
The problem:
While driving down the road, the temperature will start to creep up. It'll reach all the way to overheating if I allow it. Keeping the trans in 3 helps somewhat, I'm assuming by spinning the waterpump faster. The only way to bring the temperature down reliably is to turn the heater on full. The problem with that is I live in 29 Palms CA. It's over 100 degrees from May through September. Sometimes, it'll creep up but then suddenly drop on its own, like the thermostat suddenly realized it was supposed to be open.

The good: I just flushed the system and it has fresh coolant (premixed 50/50 blend). Radiator is a 2 or 3 row (can't remember) that was installed about 5 yrs ago because it was running hot then too.

The bad: My electric fan isn't working right now. The temp switch went out so we wired it to a manual switch. Then one day while wheeling, the wiring melted on the switch, so the fan is motionless.

The ideas: I plan on getting a new thermostat since the current one is about 6 yrs old. Maybe a waterpump, but based on my searching, it doesn't sound like a waterpump can really go bad so long as it's not leaking or seized. Mine is definitely still spinning, so I am putting that idea on the back burner I think. I want to rewire te fan again and put it back on a switch, but maybe this time also replace the temp switch and have the on/off as an override.

Thoughts?

Also, is this the correct temp sensor to control the fan or is that the one that runs the temp gauge?

Sounds like possible mech fan clutch not doing its job. Time to upgrade to the ZJ fan clutch!

That's what I thought at first, but driving 70 down the highway it would seem would give me more airflow than the fan ever could. Plus, I already did the ZJ clutch.

ok until joe reads this and notices i have stolen all of his advice and passed it on to you, ill try to help.
Change your mixture to 30% coolant 70% distilled water, it will run cooler. Especially because you are in 29 palms.. im right up the road in hemet and found that that mixture helped better than the general 50/50 for our stupidly hot weather.
replace your tstat, they seem to go out about every 2 years.
rewire that fan to your switch, it brings my temps down tremendously when i turn mine on!
How about air flow? anything blocking the air to the radiator such as lights or winch..
and if putting the trans in 3rd helps try installing a separate trans cooler. you can get a heavy duty one for like $40 on summit or jegs. Cant hurt anything, and if it doesnt solve your problem, youre out 40 bucks but are helping preserve the life of your tranny!

mxracer624 said:

ok until joe reads this and notices i have stolen all of his advice and passed it on to you, ill try to help.
Change your mixture to 30% coolant 70% distilled water, it will run cooler. Especially because you are in 29 palms.. im right up the road in hemet and found that that mixture helped better than the general 50/50 for our stupidly hot weather.
replace your tstat, they seem to go out about every 2 years.
rewire that fan to your switch, it brings my temps down tremendously when i turn mine on!
How about air flow? anything blocking the air to the radiator such as lights or winch..
and if putting the trans in 3rd helps try installing a separate trans cooler. you can get a heavy duty one for like $40 on summit or jegs. Cant hurt anything, and if it doesnt solve your problem, youre out 40 bucks but are helping preserve the life of your tranny!

Click to expand...

Always remember that with FREE advice you get what you pay for!

Disclaimer: I operate under the broken-clock principal--I'm right twice a day!

Definitely run 30/70 in your area until you get to freezing time--it does get cold out there at night--then switch back to 50/50. I just dump the coolant into a 3 or 5 gallon bucket then add coolant to bring the mix up or down depending on the season. http://www.google.com/products/cata...log_result&ct=image&resnum=5&ved=0CDYQ8gIwBA#

Definitely consider a trans cooler.

When was the last time you ran a good radiator cleaner through the system? The stuff you put in and drive for 3-6 hours, like Prestone or Zerex.

Life of a DD WP is about 4 years.

I only use Stant SuperStat Premium thermostats.

Highway cooling can be issues like stretched timing chains, coolant flow restriction--radiator/bottom hose, extra heat from the transmission.

Great FlowKooler FAQ on overheating: http://flowkooler.com/cooling_faq/

The coolant sensor mounted in the thermostat housing (the one you referenced from AZ) does not directly turn the E-fan on. It supplies temp info to the pcm that turns on the fan as needed.

Some will suggest that the Duralast brand from AZ should be avoided and I would generally agree, however the description says the unit is manufactured by Wells which is (or at least used to be) a respectable name in automotive electrical management. I have no idea what their current reputation is or how their AZ branded stuff is. Perhaps someone will speak up. I have had a BWD sensor which has been okay for about four years (as far as I know--certainly no mpg or drivability issues) but I am switching to OEM as I get to it. Just did the gauge sender with a BIG difference in readout--now have to determine which is correct--old BWD or new OEM.

In any event you absolutely need this sensor because it provides data for engine management far beyond the E-fan.. Note that it has two contacts in the connector. The gauge sender has one contact.

Finally, since your fan switch melted, I assume you wired it directly to the fan without a relay. As you've learned, this is a definite no-no.

And just for info, the water pump can definitely go bad without leaking or seizing, when the vanes just corrode away. Not suggesting this is your problem.

Darky said:

The good: I just flushed the system and it has fresh coolant (premixed 50/50 blend). Radiator is a 2 or 3 row (can't remember) that was installed about 5 yrs ago because it was running hot then too.
DO it again, then change/install that new T-STAT.

The bad: My electric fan isn't working right now. The temp switch went out so we wired it to a manual switch. Then one day while wheeling, the wiring melted on the switch, so the fan is motionless.
Time to wire it up to a switch..

The ideas: I plan on getting a new thermostat since the current one is about 6 yrs old. Maybe a waterpump, but based on my searching, it doesn't sound like a waterpump can really go bad so long as it's not leaking or seized. Mine is definitely still spinning, so I am putting that idea on the back burner I think. I want to rewire te fan again and put it back on a switch, but maybe this time also replace the temp switch and have the on/off as an override.
This is a good idea
Thoughts?

Click to expand...

You know where i live, it is hotter here as you know..Now when we went on a night run last month, most of the folks ran around 230..Mine got to 200..I am running a 50/50 mix on a stock rad that i had serviced at a SHOP..
I still run the closed system in my 89..

Ok, so definitely getting a new t-stat and temp sensor. Gonna rewire the fan to run through the sensor again with the switch as a manual override. Will definitely use a relay.

I'll get a radiator cleaner and run that through, then reflush and install new t-stat and sensor. Is there any advantage to having someone like Jiffy Lube do the flush (besides the obvious convenience factors)? Do they run a power flush or anything that could knock a blockage out of the system?

If the flush and cleaner still don't seem to help, I will take the radiator to a shop and have them rod it and make sure it's clear. Although when I flushed it, I got a good steady flow from the lower hose when running the hose in the top.

A trans cooler has been on my list for a while...I want to put one under one of my hood vents with a small motorcycle fan or something pushing air out. Maybe an oil cooler as well.

Airflow restrictions, I do have a winch and lights, although the lights are on top of the hoop and above the grille. I think they designed the tabs to hang the lights from as I had to stack washers to space the lights up higher to keep from hitting the hoop...but I didn't want them hanging down in front of the grille.

Thanks for the help everyone!

My bet is that fixing the e-fan will at least keep things under control somewhat.

Could be your tranny slipping and causing overheating as well, but try all the other stuff first, fixing or replacing the tranny is definitely the last thing you should do. If you want, add a temp gauge to the inlet AND outlet lines so you can see how much heat the tranny is cranking out.

Sorry to tag along on the thread, but regarding thermostats: 2000 XJ 4.0 Sport 4WD - All stock.

What is the correct temperature thermostat? Stant Superstat comes in either 180F or 195F.

Once you do all that, double check the lines and make sure you don't have any air bubbles. Same issue happened to a buddy of mine and it turned out to be air trapped by the water pump. Just a thought...

mshanejolly said:

Sorry to tag along on the thread, but regarding thermostats: 2000 XJ 4.0 Sport 4WD - All stock.

What is the correct temperature thermostat? Stant Superstat comes in either 180F or 195F.

Click to expand...

The 4.0l came from the factory with a 195' thermostat for general use ...

What you put in there depends on your driving requirements and cooling system setup.

Its just a 54mm thermostat .... check with manufacturers and there should be in between temp thermostats that might be useful too .... 185/188/190/192

The factory thermostat according to chrysler specs isnt fully open until 220' so a thermostat that offers full flow sooner is an obvious benefit.

Going by the vague info on the stant website .... the 195' superstant should flow better than the OME factory one ... but I have never used one as I prefer the operating settings on a locally available 195' thermostat down here ... 1/4 open at 195' and fully open at 205' .... which seems to work about the same as other brand, 185'/188' t'stats I have used in the past.

I'd change the water pump anyway. Just cause it's not leaking or seized doesn't mean it is flowing as much as it should. The impeller could be corroded or it wore down enough to not flow as much as it should.

Thanks for the help - I guess I'll go with the 195F Stant Superstat.

mshanejolly said:

Thanks for the help - I guess I'll go with the 195F Stant Superstat.

Click to expand...

He has chosen....wisely!

What was that ZJ clutch with the higher output that fits the XJ?
I think it was only one of several that fit the ZJ.
I need to make a note of the year, engine and any other information needed. I am using one now but lost the details.

Make note:

97-98 ZJ HD fan clutch, available from NAPA, part number 272310, $44.

You DO NOT WANT the ZJ MAX COOL--it won't physically fit the XJ.

If you try and buy it somewhere else they will crossover the part number and sell you the WRONG part. Go to NAPA or order it online from NAPA.

joe_peters said:

Make note:

97-98 ZJ HD fan clutch, available from NAPA, part number 272310, $44.

You DO NOT WANT the ZJ MAX COOL--it won't physically fit the XJ.

If you try and buy it somewhere else they will crossover the part number and sell you the WRONG part. Go to NAPA or order it online from NAPA.

Click to expand...

That's what I needed to know, thanks a bunch.

crimsondragon said:

I'd change the water pump anyway. Just cause it's not leaking or seized doesn't mean it is flowing as much as it should. The impeller could be corroded or it wore down enough to not flow as much as it should.

Click to expand...

Yeah, I agree. $40 is all mine cost me.