I have not replaced any vacuum hoses yet and I really need to but I keep forgetting to get an assortment of hoses every time im there. It has been so miserably hot I have not had the patience to track down the vacuum hoses in the bay for leaks. I will replace them all because at 250k+ I feel it is a necessity. I want to put in as many new parts as I can to get a nice baseline for other maintenance.

I have not checked fuel pressure, but when I changed the fuel filter, I did not de-energize the system and it seemed to have a lot of pressure to me, even after opening up the gas cap. It sprayed like a wild beast but then again could be built up pressure. I still dont think fuel pressure is an issue. If anything fuel related, A bottleneck would most likely be in the injectors.

I looked up more info and tech writeups about the plenum gasket and I am going to take a look at that once my engine cools down. I checked the oil dipstick and it has evidence of some gas in it with a sheen and the smell of gasoline. Could this be additional evidence pointing to the plenum gasket?

I find your answers and other posts to be quite knowledgeable BustedBack. Is this an adequate test for plenum gasket leak?

I have an OBD reading of P0748: ECM detected an open circuit or shorted condition on the solenoid circuit.

I've ordered a new Governor Solenoid that will arrive 2pm today. It seems to make sense since ive adjusted TV and kickdown (though have not adjusted bands yet) and even if it is still good it is an old part and should be replaced for that reason alone. When it comes in I have to drain the trans again anyway so I am going to adjust the bands this time. All i could find was an open end wrench in 5/16" so I hope that will work.

Working on this Jeep is fun! I just wish it was not so darned miserably hot.

That test sounds like it might work, it makes sense.

I havent done the test yet as I had to visit parents today. The heat wave here reached 105 and driving 100 miles in it aggravated a sticking thermostat. On the way home, it kept getting kinda hot so I turned off the A/C and it would cool down to about 200, but would surge close to 220 or 230 causing me to feel a bit anxious.

I got home, and popped the hood, the hose was spewing boiling coolant from a crack in the hose at the clamp due to immense pressure buildup from the closed thermostat. Then it started thundering and storming like a ***** and I had to get indoors. Fortunately, I was able to obtain a new thermostat, coolant, and new upper radiator hose and I am going to flush and fill the system tomorrow morning at o'dark thirty. I still have some RTV sealant so that is just going to have to do for a gasket because I forgot to ask for one.

The transmission feels like it is shifting somewhat after changing the governor solenoid but it totally lacks engine power, it feels weak except when I first start it up cold and it surges forward but then seems to catch and bog down. Ill worry about the cooling problem for now however. One thing at a time. =)

Extremely fun fighting the heat and a July 20th deadline for moving interstate!

Hah, gasket sealant! Well, I have now installed the thermostat with a gasket AND RTV blue. I have performed the warm up and cooldown 2 times now and it still heats up to 220 mark and the hose is really pressurized. I replaced the thermostat, gasket, and the upper radiator hose, and I flushed the radiator out through the draincock.

I know there still may be some air in the system that is heating up and building pressure at the highest point of the radiator hose, when that cools down is it going to eventually fill the hose, or could there be another problem I need to look for? The pump works great, I ensured I did not drop contaminants into the open holes, and when I flushed the radiator it was discoed from the engine and flushed to the draincock into a bucket. A good amount of metal dust particles was evident but nothing crazy looking.

Im beat.

Is it the original radiator as far as you can tell? The could be some scaley junk clogging the tubes in the radiator, could be a build of junk between the condensor and radiator and blocking air flow. Maybe try running a higher water to anti-freeze ratio, like a 70/30 mix.

The radiator has wear due to small rocks on the front side but it is rather negligible for a vehicle this age. There is a small amount of paint that has cracked due to heat on the upper radiator-hose connection, but it looks like this is not the original radiator. It seems too new. Looking at the front of the truck, the high pressure hoses that go into the left side look much older than the radiator itself.

I put in 1.5 gallons of water and 1/2 gallon of Antifreeze/Coolant (75/25) since i am tired of spraying a bunch of poison on the ground I have to clean up. I would rather it be even more diluted when I have to deal with it, and my wallet thanks me too.

I had to install the thermostat twice. I am absolutely certain that it is seated perfectly in the machined groove, i used a small amount of RTV blue on the gasket plane, to include around bolts. I mounted the sticky side of the gasket to the thermostat housing, and applied a 1/8" bead of RTV blue to the fibre side of the gasket. I allowed to get a little tacky for 5 minutes before sticking the two surfaces together, but did not tighten. I allowed some of the RTV blue to moosh through, and allowed it to set for 50 minutes. After the set-wait, I tightened the thermostat housing mounting bolts evenly to cant-turn-the-wrench-easily-ft-lbs. Thermostat area has remained dry.

Testing after each change, the upper radiator hose gets super hot to the touch. It highly pressurizes to where it is difficult to squeeze. Coolant return line is hot as well. Did not check the lower line. (blah!)

This morning taking the wife to work the oil pressure gauge was walking up to the halfway mark when it never does this. I contributed it to being cold. The engine started heating up quickly and reached 210 after 3 miles. In the parking lot, I carefully relieved pressure on the radiator cap (wasnt blasting hot yet) which spurted coolant out until zero pressure.

I inspected the cap which had a little junk in it, but not enough to cause any issues. No milky substances under the cap, in the radiator, oil, or reserve bottle. I pressed the cap plunger and spring in several times in case it was stuck and replaced the cap. When I got home, I ran the truck for about 20 minutes with heater on, 20 minutes with air conditioner on, and then some time after that with no A/C or heat. I shut down three times to check connections and such.

Since I replaced the radiator cap, the upper line has had some pressure buildup but easily squeezable, and has remained very hot to the touch. When squeezing, it bubbles and gurgles. The lower radiator hose is warm to the touch but not hot. Coolant return line is still hot. With A/C all the way, temperature has almost reached the 210 mark by about 1/8". I am going to take it on a 15 minute trip to NAPA to get a new radiator cap just for good measure and to troubleshoot. Then if within limits, I will take it to highway speeds.

Now, on taking a second look at the radiator, it may have been a salvage radiator. It looks newer than the vehicle and all, but there are spots that show pitting that is evident of many years of service life.

When I turn off the engine after it has been running for more than 5 minutes, there is a hiss coming from what seems to be the left side of the radiator. It isnt the cap, and I cant find the leak by spraying soapy water on the lines.

If you have the A/C on and then shut the engine off you will hear a hiss, it's just the A/C low side and high side equalizing, completely normal. 210 degrees is not too hot, that is pretty much a normal operating temp. Be careful with the RTV on the t-stat housing. If you get to wild and use too much, the extra will moosh toward the t-stat and could get hung up in the t-stat.

I was told by a knowledgeable fellow about the pressure equalization right before I got on the forum to see your answer! With the RTV I ensured it was only enough to make a small bead, and moosh out the outside edges. =)

NOW it is starting to get a little tiring trying to chase this down. The first pic below is my engine bay. Just wanted to add a picture. The second is the temperature gauge after driving about 4 miles in-city and then sitting idle in front of the house with A/C on for about 7 minutes or so. At this point, the engine started revving slower and had a bog-down type of sound so I quickly turned it off. I also replaced the radiator cap with a new one with a safety valve. I have a very bad NAPA store here, so i dont have a NAPA cap.

If I get the radiator flushed and backflushed properly, it will cost me 130. If I get a new radiator put in professionally here, it will cost me 159 out the door. I could do it myself, but the radiator costs 129 so it makes sense to take a damn break and let someone do it for me for $30. Think a new radiator will spell the end? Or is the needle on the gauge still in acceptable range? Seems so hot to me.

I changed pieces of vacuum hoses that looked like they needed replacing, broke two very brittle ones and cannibalized some vacuum lines from my Jetta to fix those. I took out the battery and removed the battery seat, checking the switch and vacuum box beneath that.

Everytime I think I have solved it... I need MOPARts =P

I removed the throttle body again and then took off all the new parts I put on it and cleaned the throttle body completely with simple green... and inspected the upper manifold while i had it open. A little wet residue but other than that relatively clean. New Throttle Position Sensor, Manifold Absolute Pressure Sensor, Intake Air Controller, and Gasket.

I might be able to blame part of the "overheating" on the weather. Here in KY it is hot and miserably humid, reducing the effectiveness of the cooling system. Since I am moving to Colorado, I am taking all these things seriously. I drove about 20 miles today with the A/C off and it stayed at 200 I would say. Then I drove about 10 miles with the A/C on, and it only crept up a little over the 210 mark. These were also highway speeds above 55.

The electric fan from my Jetta would be great to use except it would be eaten by the mechanical fan. What are the consequences of removing the mechanical fan and replacing it with one or two electrical fans pulling air directly through radiator/condenser? I feel I might have to keep the fan clutch on the shaft but the blades are relatively weightless after centrifugal forces are taken into account. Not only that, but replacing mechanical fan with electrical fan should reduce engine load by an ever-so-small amount.

None of my parts came in today so it is valve cover gasket replacing time, and modding time too!

I can get better pickup and drive-ability if I manually shift into (2) and then after vehicle speed reaches 25-30ish MPH shift into [D].

Will this have any adverse effects? I imagine it will save the clutch if I can actually use my 2nd gear. If I shift into (1) even though (1) is only supposed to have 1st gear, it feels like I am still in 2nd gear. Almost like I only have 2nd and 3rd gear... but only if I manually shift.

After replacing the Governor Pressure Solenoid there was much less shudder and felt like acceleration was a little stronger and a lot more smoother. I scanned the vehicle and still received P0748 Gov. Pressure circuit detected open condition. The Governor Pressure Sensor and pigtail will arrive tomorrow.

If that doesn't fix the condition, im at the end of my abilities with the transmission I think.

If it's an automatic, there is no clutch to save....and you can run it to the redline before you manually shift if you want, but that is not a recommended practice....

Well thats a good thing then. =) It does not go to 2600RPM before I shift at any time. Ive never had the engine past 3200RPM period.

I am a little frustrated that I cannot find the part I need. NAPA near me doesnt ever answer their phone, and carquest has people working behind trhe counter that shouldnt be.

This is the code im trying to work:
P0748 (M) Governor Pressure Sol Control/Trans Relay Circuits An open or shorted condition detected in the governor pressure solenoid or relay circuits

I have replaced the Governor Pressure Solenoid.

I cannot find the Governor Pressure Sensor/Transmission Temperature Thermistor (with E-clip) at any of the auto parts stores.

When I go to AutoZone, they cannot find this part listed in their system. It frustrates me because I know someone has to have it as it is a commonly replaced part. I know what it looks like but none of the pictures in the system matches the actual part. When I replaced the solenoid I wiggled and disconnected the pigtail to the temperature sensor in order to clean the governor body thoroughly.

Where can I find this part?

You may have to bite the bullet and visit the dealer for the part you seek.

Despite my contempt for Stealerships, I did indeed bite the bullet and called up the local Jeep dealership and they quoted me $109 for the part. When I got there, they had gotten out the wrong part. I pointed out the discrepancy and the service guy got the right part which cost $120 but because of that minor mistake he gave me the part for the price of $99. *shrug* I took it and ran. =D

Yay!

Letting it cool down, having coffee, and eating a pork tenderloin biscuit. I gotta say today just might be a great day. I think it is just good luck since you said to go to the dealer, BustedBack. Haha