Hey Guys and Gals.
I was driving my wife's 2000 XJ today and noticed the torque converter wouldn't lock in until I was doing over 50 MPH. and it would unlock when I coast and slowdown with out hitting the brake.
I can tell its locked in when I'm driving along and bump the throttle. If it's locked in the tac won't move if it is not locked the the tac (and engine) rev when the accelerator peddle it tapped.
Searching these threads I discovered that there is a brake peddle switch that is in the TC lock up circuit. I wonder if this is not adjusted properly.
50+mph seems kinds high (inefficient) for it to be just lock in.

I'm not all that pleased with the gas milage (16.5 mpg) and wonder if it is because she's driving around with the TC unlocked all the time?

Another problem, We are loosing coolant at a pretty consistent rate. I did a cooling system pressure test and it shows there is a very very slight leak. I did a cylinder compression test and all cyls were between 177 to 187 psi (kinda rules out bad head gasket). This is a 2000 Cherokee with 72kmi on the clock. I can not see coolant leaking anywhere. The bottle empties every few weeks. I'm about ready to replace radiator???

Thanks in advance for your insight,
Brian

 

the brake switch would not keep the tc from unlocking
it could be the tps if it is going bad it can make it shift ode or the tc to act up

16.5 mpg is about right

the coolant leak is going to be hard to find if its small clean the engine compartment and start looking

 

With a flash light and mirror, check the water pump shaft weep hole for signs of coolant.

Pretty typical place to check for slow leaks.

 

Hi Brian:
I had the same problem. I replaced the water pump and since the thing always ran a little hot I went ahead and swapped out the radiator for a nice fat two row. It didn't help.
The problem was a cracked head and the only place fluid was leaking was out of my tail pipe. It's a factory defect.
A new, not remanufactured head was the answer. The new head was a heavier casting that the original that I purchased from Quadratrac along with a new set of lifters and it was expensive, but it worked. Mine is a 2001 cherokee, 4.0 and had 27K miles when the problem started. You can easily swap out the head on a weekend.
Jeff

 

Thanks Guys, I'll take a fresh look at it tomorrow in the daylight.

Cracked head would be a bummer.
I have the engine out of Cherokee #3. It's torn down and at my machinist. He'll hot tank and magniflux the block and head - hopefully if there is a crack in that head he'll find it.
Thanks