The Jeep Guru – Page 93 – Jeep Performance Improvement Ideas

July 1, 2010October 25, 2011

How to remove a Jeep Cherokee Brake Caliper

There are two different brake calipers used on the Jeep Cherokee. The earlier Jeeps, 1990 and before, use two cylinders with 7mm hex key slots. The later, 1991 and newer, use two 13 MM blots to hold the caliper in place.

In either case, begin by lifting and securely supporting the Jeep.

Remove the wheel.

To improve access you can rotate the steering so that the brake caliper is facing out. However unless you have longer than stock brake lines, don’t turn it all the way or you will have trouble getting the caliper off the brake pads due to the brake line.

Remove the mounting bolts or cylinders using a 7MM hex bit or 13MM socket as needed for your year.

On the earlier models, the ones with he 7mm cylinders, the brake pads stay in place and the caliper slides off them. On the newer ones, the pads come off with the calipers.

In either case use a pry bar to rotate the top of the caliper back to slide it off. On the newer one, if there is a groove in the rotor you may have to push the pads back into the caliber slightly to get it to slide off. In severe cases, you may have to loosen the bleeder screw to get it to compress.

When replacing the earlier style it is a good idea to replace the Teflon sleeves that go around the cylinders when you replace that caliper. At least inspect them before reinstalling the caliper.

Sometimes the caliper can be stored by placing it over the lower control arm. In most cases it is best to use a wire to tie it up while the other brake parts are being serviced. Do not let it hang by the brake hose.

If new brake pads are being fitted, you will need to compress the piston back into the caliper before they are refitted. I use a large C clamp to push the piston in. Or you can use a caliper compressor tool.

To replace the caliper, slide it into place and carefully feel for the fit of the retaining bolts or cylinders. They should start easily by hand. If not remove the caliper to see why it is not aligned. These bolts can be easily cross threaded and a thread repair is not easy on the knuckle. So avoid cross threading by carefully aligning the caliper when reinstalling securing bolts or cylinders.

Reinstall the wheel and properly torque the lug nuts.

Before moving the vehicle, be sure to pump the brake pedal a few times to take up any slack that was generated by pressing the piston back in.

June 30, 2010June 29, 2010

How to repair a leaking valve cover on a Jeep 4.0

Repairing a valve cover leak — Jennifer and Hunter prepare to repair her Jeep's valve cover leak

The early Jeep 4.0 valve cover is sealed with RTV silicone. However after 1995, Jeep used a rubber coated metal gasket. Be sure to get the right seal before removing the valve cover to repair a leak. The proper silicone is oil resistant. You can get it from a Jeep Dealer or from some aftermarket suppliers such as Crown Automotive.

Begin by removing the cables going to the throttle body. These unclip from the throttle body and the bracket between the throttle body and the valve cover. Label them and lay them aside.

Remove the crankcase vent tubes.

Next, remove the hose supports and spark plug wire holders that may be attached to the longer studs of the valve cover retaining bolts.

Make a cardboard or Styrofoam template of the valve cover and use this template to keep track of the various types of bolts used to secure the cover. They need to be installed in the same holes they came out of.

Remove all the bolts. They are typically 11mm and you will need a deep well socket for the studs. On the Cherokee, there is one in the back near the firewall that can be difficult to access. I use a 3/8 drive socket mounted on a universal joint to access it.

With all the bolts out, carefully bump the cover with your hand or a rubber hammer to break the seal. Carefully lift it off the head taking care not to drop trash into the valve area.

Scrape off the old gasket material. If you are working the earlier RTV type seal, a Scotchbrite wheel on a drill can be helpful to clean the cover. I mount mine in my drill press to make it easier to handle.

Clean the head mounting surface as well.

For the gasket style, simply place the gasket on the head. Pay attention to the two locating dowels to make sure the gasket is properly aligned. For the RTV style, apply a thick even bead of silicone to the cover and let it sit for about five minutes before installing the cover.

Set the cover in place and make sure it is aligned properly. Make sure that none of the wires or other tabs are trapped between the cover and the head.

Using your template, put the bolts and studs back into the holes they came from. Tighten them snugly but not too tight. These are small bolts.

Replace the holders on the studs and put back any nuts that were removed.
Reconnect the cables to the throttle body.

Reconnect the crankcase vent lines.

Take a moment to check for any other lines that may have been knocked out of place. It is easy to pop out the line to the MAP sensor or the fuel pressure regulator while removing or replacing the valve cover.

The gasket style can be started immediately and checked for leaks. The RTV style needs to set at least half and hour before starting.

June 29, 2010

How to replace the AC compressor on a GMC 1500

How to replace the AC compressor on a GMC 1500, 2500 or 3500

Replacing the AC compressor on a GM 350 engine is not nearly as hard as it looks. The compressor is held to the engine by an aluminum cradle. The cradle does not have to be removed to replace the compressor. There are simply three bolts that hold the compressor to the cradle that have to be removed.

Note that this procedure only covers the physical swap of the compressor, not he associated tasks related to servicing the AC system after a compressor failure.

Begin by removing the freon from the system. If you want to have it reclaimed, take it to a shop that does this.

Remove the two electrical connections to the compressor.

Next remove the freon lines form the back of the compressor. The manifold is held in place by a single bolt. Mine was 15 MM.

Use a pry bar to move the belt tensioner and slide the belt off. I found the easiest pulley to get the belt off of was the smooth idler below the compressor.

With the freon lines out of the way, the bolts are much easier to access. There are nuts on the back and the bolt heads are held in place by a boss on the front. Mine were 9/16”.

With the nuts removed the bolts can be pushed out the front. However, it appears that they will not clear the clutch. However, there is a flat cut on each bolt. Rotate the flat to be next to the clutch and the bolts will slide out. A pry bar can be used to get just a little extra clearance if the bolt does not slide past easily.

On mine, one bolt also interfered with the fan shroud. I found that by removing the bolts that hold the shroud to the front header, the shroud could be moved enough to get the bolt out.

With the bolts all out, the compressor simply lifts out of the cradle.

With the compressor out, I had to swap a pressure switch that did not come with my replacement compressor. This switch is held in place with a snap ring.

Before attempting to slide the new compressor back into the cradle, take time to tap the bolt hole inserts all the way to the back of the cradle. This will make inserting the new compressor much easier. They will press back into the proper place when the nuts are tightened.

Slide the bolts back in by again aligning the flat spot on each bolt with the clutch and slide it in. Place the nuts on each bolt and tighten.

Reconnect the electrical connections to the compressor.

Secure the fan shroud.

Make sure the belt is routed correctly and use a pry bar to move the tensioner and slip the belt back in place.

Add the proper amount of oil and reattach the freon lines to the compressor.

You can now have the system serviced and the freon replaced.

June 24, 2010

Jeep Cherokee Fuel Injectors

How to change an injector or fix a leaking O ring

Begin by obtaining the proper sized O rings. These are available from your local Jeep dealer or from a Crown Distributor like me. It is important that you get the proper sized O rings as you don’t want fuel leaking down on the hot manifold.

You only need a few simple hand tools to replace an injector or change the O rings. On the 90 and earlier Cherokees, the fuel rail is held in place by four bolts with 13 MM heads. You will need a pick to remove the old O rings. I found a magnet handy for getting the bolts out once they were loosened.

Also, since you are going to be spilling fuel on a potentially hot manifold, be sure to have a big fire extinguisher on hand just in case.

Even if you are just replacing one injector, you have to remove the entire fuel rail. On this 1989 Cherokee, the rail is held in place by four bolts.

After the bolts are loose, I used a magnet to fish them out of the brackets.

With all the bolts loose, pull the fuel rail away from the manifold. This will pull the injectors out of the manifold. To service an injector, first remove the electrical connector. I use a pick to gently pry the clip back so it will pass the detente on the injector. Be careful not to loose the clip as they are expensive to replace.

Next remove the clip that holds the injector to the fuel rail. It just slides off. I use the pick again to help get it moving. Don’t loose these either as they are not available form Jeep separate from the fuel rail.

One it is unclipped, pull the injector out of the fuel rail. Sometimes it helps to twist it, to get it out.

I used the pick to pull the old O rings off the injector. Note: on the Jeep, the brown O ring goes on the manifold end and the black O ring goes on the Fuel rail end.

Insert the injector back into the fuel rail. I found it helpful to put a drop of oil on the O rings to get them back into the fuel rail. Again twisting it helps to get it in. Reinstall the clip that holds the injector to the rail. Make sure the slots are properly aligned. If they are not, you may not have the injector seated properly. The clip will slide on easily when the injector is properly seated.

Twist the injector to the proper position and reconnect the wire. Make sure the clip seats with a click in the detente.

Repeat with procedure with the remaining injectors.

One you are ready to reinstall the fuel rail, carefully align the lower part of the injectors with the manifold openings. Use the heel of both hands to press the fuel rail into place and seat the lower part of all the injectors.

One the injectors are seated, replace the bolts that hold the fuel rail in place. Look around for vacuum tubes that have been knocked out of place during the procedure. The MAP sensor line and the vacuum line to the fuel pressure regulator will likely be knocked loose by moving the fuel rail around. reconnect them before starting the engine.

Turn the key to on and listen for the fuel pump to run. Do not start the engine yet. Inspect for leaks first. If you see a leak, loosen the fuel rail and wiggle it around to seat the leaking injector. Again twisting the injector may help.

Once you have a seal, start the engine and check for leaks again. If you see any, shut off the engine immediately and reseat the leaking injector.

June 2, 2010June 2, 2010

Jeep Cherokee Harlan KY day 3

XJlist Spring Fling Harlan, Ky day 3

Saturday morning brought more rain as I added power steering fluid to Jenny’s Jeep and bled the air out of the system. Through the breaks in the drizzle, we had scrambled eggs made on Frosty’s grill.

Getting a slow start from camp we decided to make a leisurely run along the east ridge of the park to see the vista the group had found the night before. We headed up the other end of trail 15 out of Middle Fork. This trail starts of with a steep twisty climb before it follows the ridge out to the helicopter pad.

Just at the top of the hill, a place we spent way too much time at on our first trip to Harlan, there is now a very deep mud puddle.

Just as we were lining up to go through he puddle, Evan called on the radio that his Jeep was leaking transmission fluid and was not moving well. I pulled out a hospital cloth for him to lay on and he found that his control arm had hit the transmission lines and crimped both and punctured one of them.

It took a while, but we eventually gathered enough hose, clamps and tools for him to cut and splice the two damaged lines. We headed out again after he was repaired.

From there we made our way on to the Helicopter pad. We continued on the trail past the pad and drove up to the vista the guys had found the evening before. The view form there is spectacular! We enjoyed lunch there and posed the Jeeps for a group photo.

Next we made out way to Mason Jar. We decided to follow the new signs instead of the map thinking that they may have made a short cut to the entrance of Mason Jar that was not mapped. However, we were disappointed to find that the signs led us to the exit of Mason Jar. And Mason Jar is a one way trail!

Janice and several others decided to walk the short trail while some of us drove around to the entrance. At the entrance we saw a buggy on huge tires having a terrible time getting up the first obstacles. He would just sit there and use his big engine to dig out dirt at the bottom of the rocks. As we met the walkers, they told us of two wranglers that were broken down further up the trail.

Neal, Frosty and Josh elected to go ahead and run the trail while the rest of us decided to explore elsewhere. We loaded up every one into the back seats and cargo areas of our Jeeps and made the trip back to the exit of Mason Jar to pick up their Jeeps.

Form there, we went to Lions Den so that those who missed Thursday adventure could at least get a feel for what it was like. We watched a Wrangler on one ton axles crawl through but not without great difficulty.

From there we headed back to Middle fork to play on the hills there. We had just started up Running Board when the others caught up with us. Scott P made a run but ended up backing down.

We decided to head back to lower rock garden to play around more. After some time there we headed back to camp to enjoy the now famous steaks and potato boats around the camp fire.

Videos of this trip can be found on Youtube:

Rail Bed
Mud Puddle 1
Mud Puddle 2
Scott in the Lower Rock Garden
Josh on Killin Time 1
Josh on Killin Time 2
Haywire on Profanity