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Jeep Cherokee AC rebuild

Jeep Cherokee AC rebuild

My old AC compressor failed in spectacular fashion while driving on the interstate. There was a huge bang form under the hood and the engine sputtered until it cleared itself of all the Freon that it sucked in through my K&N filter mounted right behind the AC compressor.

Later, I found a big hole in the side of the compressor. I also found one of the compressor pushrods under the AC mount. I guess that is what made the hole.

I picked up a used compressor off Ebay and a new dryer from Autozone. Found Freon at Big Lots and got a bottle of PGA oil and a flush kit from the parts store.

To remove the broken compressor, I first loosened the belt. In my 1991 Cherokee, than means loosening the power steering pump. I don’t have an air box anymore so access to the adjuster is easy. All the bolts are turned by 13mm wrenches.

With the belt loose, I removed the four bolts that hold the compressor to the engine adapter. These tend to gall so I used an impact wrench to remove them. I have had them break by just using a ratchet when pulling compressors from the junkyard.

I also disconnected the high and low pressure lines at the back of the compressor. There was no need to bleed the system as it was all gone through the hole in the compressor.

I lifted the compressor to get better access to the wire and once it was loose, I removed the compressor. Next I removed the lines from the drier.

Removing the 13mm nut that holds the drier to the frame rail was the most difficult part of the removal process. I ended up using a shot 13mm socket on a swivel and lots of extensions. Access is difficult due to the high pressure hose that runs right across the top of the nut.

Once the old drier was out I began flushing the system. I flushed so that any particles form the failed compressor would be pushed back to the compressor connections. Some black and gray dust came out but no metal shavings as I feared might be there. I elected to reuse the expansion valve and not remove it. I back flushed through it. Once the flush ran clear, I used compressed air to dry the system.

I then began stripping the old drier. The low pressure switch and an adapter on the inlet side had to be swapped over to the new drier that was not exactly the same size and shape as the original. I used the new O rings provided to reassemble. I started the lines one but did not tighten them down. I then fought with the mounting nut and got the drier secured to the body. Then I finished tightening down the lines. I then reconnected the wire to the low pressure switch.

I filled the replacement compressor with PGA oil. I could not get all of it into the compressor before it started pumping out the discharge. I slowly rotated the compressor as I added oil to get it in. I added the remainder of the 8 oz bottle to the suction hose.

Next, I set the compressor in place. Again, I got the lines started onto the threads before putting bolts in the compressor. I also installed new O rings on the ends of the lines.

I put a dab of anti-seize on teach bolt before setting it in place. Once the compressor was in place, I tightened the lines on the back. I would like to say I reconnected the wire at this point, but I actually forgot until later when trouble shooting why the clutch was not pulling in.

I then connected my vacuum pump and began drawing a vacuum on the system. While waiting, I put the drive belt back in place and set the tension. I also had time for an oil change as well.

Once the system was vacuumed for 20 minutes, I checked to make sure it held vacuum. It did so I proceeded to put in the first can of R134. The Jeep compressor has a service valve. I set it about the middle point for both vacuum and installing the Freon. I use an old water faucet handle to turn the ¼ inch square valve stem.

A second can of Freon brought the pressures in line. I was careful to close the service valve and replace the caps as I disconnected my gauge set. It was nice to have cold air again. There was a big puddle of condensate on the garage floor by the time I had all the Freon installed.

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4.0 Engine rebuild – quick and dirty

Quick and Dirty Engine Rebuild
Jeep 4.0

Jennifer’s Jeep had a sudden severe clacking sound. With the head removed, there was no evidence of a problem. However with the oil pan off, parts of the piston skirt were found.

A quick internet search found several reports of broken piston skirts. Many of the pictures looked just like hers. The original idea was to replace just the one piston and put the engine back together. However, closer inspection of the other pistons revealed cracks in the same area of the skirts.

Due to the cost of replacement pistons, we elected to use pistons from an older engine we had in storage. The engine currently in her XJ is a 96 4.0 removed from a Grand Cherokee. The older engine was her original 92 model. The block was worn but the pistons were fine.

We noticed a major difference between the way the skirts were made on the older pistons. The older ones are much thicker. The older pistons use different rings so we had to order a ring set for the 92 engine.

We obtained a gasket set and a set of rod bearings as well. We elected to retain the original main bearings and not remove the crank or main caps.

We left the 92 pistons on their original rods and installed new rings and rod bearing inserts. The pistons ring grooves were carefully cleaned before the new rings were put in place.

We used a ridge reamer to cut the small ridge out of the top of the cylinders. The ring end gap was a few thousandths over spec but we felt was close enough; much lower than the gap on the original worn rings.

We used a cylinder hone to lightly scuff the cylinder walls. They looked smooth even in the hole with the broken piston.

We fitted a ring compressor over the piston and tapped it down into the cylinder bore. Rubber hose was placed over the rod bolts to help guide it over the crank and to protect the crank while driving the rod into place.

When the rod made contact with the crank, there was a notable change in the sound made when tapping the piston top. We would then move to user the Jeep and install the rod cap. While difficult, it was possible to find a position to place the crank so that the rod bolts could be accessed with torque wrench.

Once all six pistons were in place, we set the head back on. While the head was off, I installed the new valve seals that came with head kit. I used a KD tool valve spring compressor and carefully removed the retainers. I then pried off the old seals and tapped the new ones in place using a deep well socket as a driver. I then replaced the springs and keepers.

After start up, she drove about 500 miles before the first oil change. The engine seems to be running fine now. And it is much quieter.

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Jeep broken piston

After replacing he lifters and push rods in Jennifer’s Jeep, there was still a nasty clatter. The lifter tick was gone but the clatter meant something was bad wrong.

I dropped the oil pan and discovered pieces of aluminum in the sump. A quick inspection showed part of the number six piston was missing. A google image search turned up several pictures of broken pistons that look exactly like hers. So this is not a completely unheard of problem.

I pulled the head back off and pushed the piston out the top. It is broken right below the oil ring and the complete skirt is missing. However, the cylinder walls look fine. Hopefully the other pistons are OK and I can just put in one new pistons and some new rings and bearings and she will be good for several thousand more miles.

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Replacing the ABS module on a 2000 Passat

When she bought it, Jennifer’s Passat had a scary warning on the dash says “STOP brake.”

Since the brakes stopped the car fine she bought it hoping the fix would be simple. It turns out it was.

The folks at Cheap ABS.com were a big help. We followed their helpful instructions at http://cheap-abs.com/removal.html and easily removed the unit.

We found her car had a mix of T25 and T20 fasteners holding the inner fender in place. It also took a few seconds of study to see how to pull it out of the various things it slides behind after the fasteners were out. With the inner fender out of the way, the washer bottle was visible. However, even with all three screws out, the bottle would not move out of the way enough to get to the ABS unit comfortably. I had to unplug the wiring harness and remove the pump from the bottle, to get it out of the way. These just pull right off but are behind the bottle so it was hard to do the first time.

With the bottle out of the way. I set at disconnecting the two wiring harnesses. The disconnect tab was really hard to pull forward and I had to use a screwdriver to get a bit of leverage to start it moving. I was very careful not to break any of the small plastic mounting tabs. With the wire loose, we then removed the six torx screws holding the module to the pump body.

Jennifer then packed it carefully and shipped it off to Virginia. She was able to drive the car with the box gone just as she had been driving it with the defective module.

One week alter the repaired module returned and we again pulled the fender liner and washer bottle out. The repaired module slipped right in and the wires were easy to connect after I aligned the tabs correctly. It was much easier to manipulate the washer bottle and fender liner into place after having done it once already.

When starting the car, she was greeted by a friendly reminder to top up the washer fluid instead of the STOP message that had been tieing up the display for the last few months. The anti lock brakes work as expected and so does the traction control. Thanks to the folks ta Cheap ABS!

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Jeep Lifter replacement

Jennifer’s Jeep has had a loud lifter tick for a while. We finally decided to pull the head and replace all the lifters and push rods. We used the following procedure from Jim Alton to work with:

Mike,

Jen sent me a message and said her lifters need replacing. The head needs to come off unfortunately. Before going that deep, just to eliminate a longshot (but much easier fix), remove the pushrods and make sure they are straight. If any get bent slightly they will be too short and make noise. They have to come out to remove the head anyway, so its easy to check them before getting too deep.

Procedure for lifters (coming from my head…hopefully I don’t miss anything):

-Remove the valve cover.
-Remove the rocker arm bolts. I leave them right in the rocker arms and remove them as an assembly in pairs. Put them somewhere so you can keep them in order. Lined up on a clean bench or table, or even in a divided container like muffin pans.
-Remove the pushrods. Inspect them to make sure the ends aren’t worn. Roll them on a flat surface to check for straightness. If they are even slightly bent replace them. If any are more than slightly bent, this could be your problem- replace them and reassemble, and see if its quiet again. (just a very slim chance this is the problem…most likely, its lifters)

If the pushrods aren’t the problem-

Have new head bolts handy. They are supposed to be “one reuse allowed”, but I always install new. Most part’s stores will have them. They cost a little, but easier and cheaper than ending up with stretched bolts.

-Remove intake manifold. Remove remaining 3 fasteners to loosen exhaust manifold if you didn’t already. Pull the exhaust manifold away from the head slightly using a bungee cord or similar.
-Drain coolant, then remove upper radiator hose & both heater hoses from the engine.
-Remove belt
-Remove 4 bolts holding the A/C compressor top the mount. Don’t disconnect AC lines. Lift the compressor up, flipping it to the passenger side of the Jeep. It should sit over there upside down still attached to the hoses.
-Remove a couple bolts attaching the A/C bracket to the head. You don’t need to remove the whole bracket, just the bolts going into the head. Removing the whole bracket involves removing the alternator.
-If the head has never been off before there is a spot on the firewall that could keep the driver’s rear head bolt from being removed. Bending this over slightly will give clearance.
-Remove the head bolts.
-Lift the head from the engine- straight up, then out. Its HEAVY! This is old American engineering cast iron! Get someone to help if your back isn’t good, or use an engine crane.
-Use a pick to pull the lifters out. Some may be somewhat stuck. I have found letting them drop low, then a quick pull up helps get them past the dry ridge that builds up. You may have to try several times up and down.

Once they are out check the cam lobes for wear. Look for scarring, obvious wear signs. It would be best to have a dial indicator to check for lobe lift, to eliminate cam wear from a possible noise cause, though that would usually lead to a misfire code as well.

While the head is off anyway, I would use a straight edge to check for flatness. Check the length of the head in a couple places, then check corner to corner. If you can put anything larger than a .003″ feeler gauge between the straightedge and the head, the head is warped. Very rarely does this happen on a 4.0, especially earlier years. Also take the time to clean the oil return passages in the head. They are very small, and often have casting flash left making the holes even smaller. Gunk builds up and keeps the oil from draining back as well as it should. I feel this is one cause that leads to blowby in the earlier engines. Just make sure the passages (near where the pushrods go though) are clear.

If everything looks good, lube the new lifters and drop them in. Reverse the removal procedure.

-Clean the block surface and head. I use an air powered scuffing wheel, but a razor blade followed by a Scotch-brite pad will work also. Do the same for the intake & exhaust manifolds and their surface on the head. Clean coolant out of the cylinders and clean up the block as well as you can.
-Set the head gasket in place, then the head, being careful not to damage the head gasket.
-Torque the head bolts, then reassemble everything.
-At the end have 5 extra quarts of cheap oil ready (plus the 6 you will be using), and a filter. Drain & change just the oil before starting the engine, then start up, and run several minutes. Then change the oil & filter. While shops won’t spend the money to do this, I like to. Changing the oil right off gets the coolant out that ends up there during the head removal. Starting it up circulates the new oil and picks up more coolant that is in the block, as well as the material that dropped in while cleaning up the block and head. Changing it a second time gets rid of this. Overkill? Maybe…but it only costs a few dollars for cheap oil, and it makes me feel a lot better.

Jim