Living in southern California it can get quite toasty in the summer but up until now we haven’t had a day over 75, but last week we had a triple digit day with it peaking to around 105. This uncovered a hidden issue with the Jeep, as we where driving though Thousand Oaks we noticed that the coolant temp was pegged at 260. We quickly pulled into a gas station and and checked the coolant level, all looked good but after idling for a few minutes the temperature went down and took about 2 quarts of coolant. We made it to our Los Angeles location but was running hot the entire time.

Because of this we wanted to beef up the cooling system, so after some research we decided a conversion to a 92+ system was best. The two types of cooling systems are Open and Closed, the 90 jeep comes with a closed system, this means that the system is closed and has a inline recovery tank that allows for expansion, this type does not have a radiator cap and fluid is filled though the recover tank. The Open system is different as it has a radiator cap and a overflow tank instead of a inline tank, this recovers the extra coolant when the system gets to hot.

Each system has its advantages and disadvantages

Open system Advantages:

• Ease of filling system
• Overflow tank
• Simple hose routing

Open system Disadvantages:

• Overflow tank only works one way without special cap

Closed system Advantages:

• No overflow tank to worry about, recovery tank takes the overflow and also fills when needed

Closed system Disadvantages:

• No radiator cap
• Coolant must be added to the overflow tank
• Complicated hose routing
• Plastic recovery bottle can crack

So the game plan for this retrofit would consisted of the following:

1. CSF 3 row all steel radiator – radiatorbarn.com
2. Water Pump
3. High Flow Thermostat 195 Mr. Gasket
4. All new hoses
5. Heater Control Valve

We started the conversion by removing the old system, started by draining the coolant by pulling the lower hose and collecting it into a 5 gallon bucket. Remember coolant is extremely toxic to animals and kids so take care with storing it. After the system was empty we unscrewed all the hose clamps and pulled them all out, we then went to the radiator and removed the radiator bracket, transmission lines and sensor, at that point the radiator could be lifted up. Once removed there was more room to easily replace the water pump and thermostat.
We decided to use a high flow 195 degree thermostat, we went with a high flow one to allow more coolant to circulate though the 3 core radiator.

A few challenges we had was the upper heater core and the heater control valve was two different sizes,  for this we could have gotten an adapter but we went the simply way and just used a hose clamp and cranked down on the hose until it fit the smaller size.

I have been running the Jeep now for 8 months with this setup and three electric cooling fans without issue, if the fans are left on full time the temperature sits around 180 with them on auto it will get to 210 then back to 190.

I also decided to install a mechanical temperature gauge because the electric Jeep gauge was showing inaccurate, the switch under the gauge controls the auto / on function.

The CSF radiator is working good at keeping the system cool. I did have one issue that was caused by a clogged AC Condenser, and after removing it the temperatures stabilized (removed AC) I later converted the AC into an OBA On Board Air system.

We started by removing the transmission from the Jeep and carefully examining all the components, we took a close look at the torque converter and quickly noticed that the oil bearing was stuck to the shaft. This would explain why the transmission was slipping, but since we had the Jeep apart we decided it was smarter to go ahead and put in a new torque converter and rebuild our spare transmission. 

The first step in the process is to source the parts, We have used Transmission Parts of Oxnard in the past and decided to stop by the shop to see what they had.  After a few minutes we where on our way with a new torque converter and all new seals and bushings for the transmission, the owner of the shop had a look at our clutch pack and we both agreed that it was unnecessary to replace them at this time because they had minimal wear. We also inspected the oil pump and sun gears for signs of wear but they all looked good with very minimal wear. 

Digging into a transmission may sound like a daunting task but it is really a strait forward repair and with a little patience anyone can do. We also recommend downloading the factory service manual for the transmission you are working on, this will have many detailed images and tips for working on your transmission.

After returning to our garage we carefully installed the new parts and reassembled the transmission, on this transmission we are able to use the torque converter to align the oil pump before bolting down (some transmission models require a special tool to be used).

We then installed the new torque converter and bolted back up the transmission, after filling it with 9 quarts of Dexron III fluid we started it up and then cycled it though all the gears to make sure the fluid has filled all the passages in the valve body. We let it idle to operating temperature  and checked the fluid level once more, after that we took it for a test drive. It drove good but it was not shifting properly, leading us to the Throttle Position Sensor (TPS) being faulty. Tests using a volt meter showed the sensor to be faulty and after replacing it and adjusting it to the proper voltage the Jeep then shifted properly. 

The total cost for rebuilding the transmission and new parts came in at a whopping: $245, if we had taken the Jeep to a transmission shop we would have paid over $1400 for the same repair. 

Some of the appealing factors for this purchase were:

1. Laredo edition, this means the Jeep has power windows and locks.
2. NP242 transfer case, this transfer case provides 5 different modes of operation (2WD, 4WD Part Time, 4WD Full Time, Neutral, 4WD Low Part Time) this makes it ideal for highway and off highway use. 
3. The 87 – 90 use the same transmission, we already had one from an 88 Cherokee that we rebuilt. 
4. Body was in good shape with only a few minor dings, paint on the other-hand was in horrible shape. 
5. Dana 30 High Pinion front axle and Dana 35 rear with LSD, both geared at 3.73 gear ratio.
6. Factory Tow package prewired with class III hitch.

The criteria for the build was to create a reliable and comfortable daily driver (DD) that is also highly capable off highway in many different situations, this is not a rock crawler but more of a all terrain build. Because of that the Jeep must ride smooth on the highway yet still have enough flexibility to go over a wide range of terrain. The interior must have most the luxuries of modern vehicles yet still provide the ruggedness you would expect from an sport utility vehicle.

The photo to the right was taken on the first day we got the Jeep, right after the tow truck dropped it in the driveway.

The following series of articles will detail each step of the process building this Jeep from a Junker to a Off Road Machine, we will include many photos and detailed technical information that may help you on your own build. 

Here is the breakdown of the steps:

1. Purchase the Jeep, Transport home, and Register at DMV
2. Create plan for the Jeep, including what hardware to purchase, etc…
3. Rebuild transmission and get the Jeep drivable
4. Sand, Prime and Paint the body
5. Install Rubicon Express Lift kit
6. Install custom Slip Yoke Eliminator (SYE) and new driveshaft 
7. Rebuild the Roof Rack to make it more aerodynamic
8. Strip the interior, install Peel-n-Seal and replace the interior
9. Install the Electronics, Radio, CB radio, and GPS 
10. Drive It

Stay tuned as we will continually update the site with more Jeep Build articles, we will also update this page with links and other information for the series.