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Unread 10-18-2006, 01:02 AM   #1
Woody
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Interesting things to note, upkeeping the 94 JGC

Okay, the previous owner had installed a 180 degree T-stat (I bought the ZJ over two years ago) and had the ECM reprogrammed so that it wouldn't run rich. Well over time, the ECM lost it's reprogramming and had gone back into thinking it had a 195 T-stat. So please save your money, and don't do this, your Jeep knows you messed with it and will eventually unlearn what you've attempted to teach it.

I put a brand new 195 T-stat in it, and found out something funny recently. Drove it 70 miles (to Fairbanks and back, with a quick stop at a buddy's house right before driving home and noted that it never seemed to reach full operating temp. It seemed to hover around 180-190, but never to the 195 line. To ensure my mine wasn't playing tricks, I installed a new sending unit. Still doesn't get to 195. I even replaced the fan clutch, still no 195. Then I started thinking about it. Even pulling the trailer all the way up here, even wheelin in AZ during the middle of July with the A/C on, I've never seen it get to 195. My ZJ runs slightly on the cold side. I did have it checked and it does go into warm running mode where it leans out so that it doesn't cook the CAT, but it does seem strange.

I have the feeling, I might put an electric fan on and probably hardly ever use it.

Oh well.


I replaced the power steering pump today. A buddy of mine had a brand new one that he bought for his TJ and never installed. He went with a HD setup that runs his hydraulic winch now instead. I had to tap the mount holes as TJ's mounts are not threaded like the ZJ's, but alas it did fit. Put on a new pulley as my old was one cracked. (don't know how that happened) I replaced this for two reasons; A. the pump was the original and I'm fastly approaching 200K. It's definately outlived it's expected lifespan. B. I've been having problems steering at idle for the last year. Some times it's not so bad, but others times, I cannot turn it without goosing the throttle. At least with the stick, I push in the clutch and have at it, but the auto caused me a few problems back when it was in. My idle is aroung 500 when warmed up all the way, 750 when cold. At 750, it was okay, but not great. At 500, I was turning the wheel without the help of hydraulics. So, I replaced the pump. I noticed right away that it was quieter, and that I still had old fluid in the box. So pumped it out again and it was perfect. I got it warmed up and could turn from full lock to full lock with the pinky. Oh how I love the steering feel.

Also today, I have completely disabled the ABS system of this vehicle. When I broke a rear axle shaft recently, I didn't have an ABS shaft available. I had four non ABS ones, and figured with as quirky as the system was in 94, I'd be better off without it anyway. So I pulled the tiny 3 amp fuse in the block by the passenger's door and made the little light go away. Kinda nice. The braking feels the same, but I pump it a little now instead of just punching the pedal when I need it. Probably a good thing to practice as the Burb I'm fixing doesn't have ABS either.

I'm mostly just attempting to pass on the fact you should really maintain your Jeep properly. When you get to 200K, don't be surprised if you have to spend some coinage to whip it into shape. With the prices of new cars today we need to find ways to keep the old ones around awhile longer. A few hundred a year is nothing compared to paying thousands a year in car payments plus the maintenance of a few hundred a year.

Plus if you keep your eyes open as I have, you can pick up things like the PS pump for free. It's amazing what people give away, when they forget others can use it.

Keep wrenching and have fun Jeepin'.

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Unread 10-18-2006, 07:18 AM   #2
PlatinumZJ
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So, Woody, Maybe the gauge doesn't read very accurately and the temp is really 220, like everyone else's jeep?
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Unread 10-18-2006, 07:40 AM   #3
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id go to a hardware store and buy one of those laser thermometers. Id check the temp of the upper radiator hose and compare it to the dash gauge. then return the themometer because its like 100 bucks.
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Unread 10-18-2006, 02:47 PM   #4
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Well, I did a OHM test on the sending unit and it's working. I did also check my guage with the proper voltage and it checks good. So, I run cold.

Oh well.

I just fixed the rear defroster with conductive paint, and it works great. $10 well spent.
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Unread 10-18-2006, 03:27 PM   #5
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Woody,

Oddly enough, my jeep runs "cold" too, and i have recently put a new Tstat in, 195 degrees of course. However, it still runs around the 180-190 degree mark. Rain, shine, winter, summer.

i never really thought about it much untill now. I had read somewhere in the forum that warmer climate vehicles are equipped with a lower temp Tstat. so i thought mine ran that cool because it was a florida vehicle.
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Unread 10-18-2006, 04:04 PM   #6
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180 thermostats are never a good idea in any car unless you have a chip that is designed for it, or better yet, a custom wipe and reprogram, but only a few places can do that. The probem is people do it for performance, but since you end up running rich and tainting the air/fuel ratio it can actually lower performance
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Unread 10-18-2006, 05:56 PM   #7
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The left side of the gage has different increments then the right side (past the 210 mark)

This is where it should be in a perfect world. Mine is just off the 182.5 mark, so I guess I run about 10 degrees colder then one would expect.
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Unread 10-18-2006, 05:58 PM   #8
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I used that picture to determine where I was to begin with. Great diagram Steve.

I'd rather run slightly cold than hot, so I'm good.
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Unread 10-18-2006, 06:09 PM   #9
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Yea mine runs cold and I freaked out while trying to solve a high CO issue (these both happened at the same time) so I yanked out the coolant sensor and placed it in a pot of water on the stove. Then I plotted resistance vs temperature (from a meat thermometer) as I slowly increased the burner. I compared them with the FSM valves. Everything looked fine. I concluded that the engine is either cool or the dashboard gage is frigged. I simply donít think about it anymore Ö but it did bother the sh_t out of me.
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Unread 10-18-2006, 06:24 PM   #10
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You could get a 210 T-stat and it might work for your problem.


We always had problems with the mom's Chrysler minivans never getting to operating temps in the winter. Those wouldn't even put out heat. It took one hour of driving to get the vents to put out hot air. The defroster would work before that, but not all that great.
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Unread 10-18-2006, 06:33 PM   #11
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I actually looked for 210 degree one, as it would have helped in my high CO emission issue (as high CO is usually incomplete combustion) but I could find one. Ended up replacing the Cat
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Unread 10-18-2006, 06:38 PM   #12
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Hmm... Napa had a 210 for mine, the guy said it would be perfect for a winter up here, but decided since I do a lot of low RPM off-roading that I would go with a 195 that was good for everything.
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Unread 10-18-2006, 07:32 PM   #13
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196 huh? I run pretty close to 200. I'm always a smidge below 210, no matter what. Although, sometimes I would get in the Jeep, start it up, and the temp would be past 210 for a minute, then go down to about 200.
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Unread 10-20-2006, 05:45 PM   #14
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Mine always ran between 200 & 210, then changed the thermostat (with two different 195 F ones as I was sure the first ran too cold) and it just seems to run much cooler than expected now.[below 182.5F]
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Unread 10-20-2006, 07:01 PM   #15
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Quote:
Originally Posted by greasefingers
Mine always ran between 200 & 210, then changed the thermostat (with two different 195 F ones as I was sure the first ran too cold) and it just seems to run much cooler than expected now.[below 182.5F]
Remember, if your thermostat is bad or miscalibrated, you will run hotter, or colder, accordingly. It is always good practice to put a new thermostat in a pot of water, and bring it to a boil on the stove. Have a thermometer in the water to monitor when the thermo begins to open. Lacking a thermometer, a 195* thermostat should open just before the water boils (212* at sea level). It should fully close again when heat is removed.
If your engine is running 180-190 (assuming your gauge is accurate), then your thermostat HAS to be off (5* isn't that bad IMO). Granted, some engines run cooler than others, but none will ever stay at 180* with a closed thermostat... the heat has to go somewhere. I think your thermostat is off.

A story:
'98 ZJ 5.2
I recently installed an electric fan from a "98 ZJ 5.9. I used a Dakota Digital (DD) electronic fan controller & Bosch 70A relays:
http://www.dakotadigital.com/index.c...prod/prd43.htm
I mounted the unit in the overhead console, in the little compartment made for the garage opener remote. I soldered a 1/8" X 1/4" brass bushing into the thermostat housing and mounted the temperture sensor there (the DD electronic unit has the ability to use the stock gauge's sending unit, but I wanted to use an independent source). By pressing a button on the unit, I can measure the temperature of the coolant right above the thermostat, on it's way to the radiator. I also put in a new RoberShaw 195* thermostat.
I checked the reading using my RayTek infrared thermometer, (at the thermo housing. The rubber hose will show a false low value), and it's nearly dead on to the DD controller display. The OEM gauge seems to run maybe 2 degrees high (the OEM gauge monitors temperature on the engine side of the thermostat).

I mention all this because I learned some things monitoring both temperature readings. As the engine heats up, the OEM temp will gradually build up until it reaches operating temp. The sensor in the thermostat housing remains quite cool during this time, then as the OEM gauge approaches 195*, the thermostat opens pretty fast, as evidenced by the DD display shooting right up to ~192* After that, both reading are about the same. I never realized what a temperature difference there is across the thermostat, and what a good seal it makes preventing water from going to the radiator. I thought for sure there was a lot more leakage.

I have the low speed fan set to come on at 210* & high speed at 216*.
In 70* weather, I can drive the 10 miles (hwy/streets) to work & never have the electric fan come on. Temperatures cycle between 198-206*. The fan motor draws ~26A on low, and ~45A on high.
Sorry for the dissertation, but maybe this is some new info for someone.
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