Car repair – Page 30 – The Jeep Guru

January 5, 2012January 5, 2012

Jeep Cherokee Thermostat Replacement

On the last few cold mornings, I noticed the heater in my Jeep Cherokee was not putting out heat like I wanted. I also noted that the temperature gauge was not reading as high as normal.

I knew that the thermostat must be opening too soon. The only cure is to swap it out.

I picked up a Stant Supersat at Advance Auto. I used the order online – pick up at the store option to save a couple of bucks.

My Jeep is equipped with a K&N air filter and intake tube so I don’t have an air box in the way any more. I loosened the power steering pump and moved the drive belt out of the way of the thermostat housing. I have done it without loosening the belt but it is much easier with out the belt in the way.

The later model XJs have the belt routed where it is not in the way. However, on an earlier XJ like my 91 the belt interferes with getting the bolts started back in the housing. I previously wrote about changing a thermostat on a 99 XJ.

I popped off the radiator and heater hose. I disconnected the temperature sender wire.

I then removed the two 1/2 inch head bolts and popped the housing off the block. I set up a pan under the Jeep to catch the antifreeze. I also laid out newspaper to soak up the splatters as anti freeze is very slippery on the floor.

I cleaned up the bolts and the housing using the wire wheel on my bench grinder. I then use a scraper and a scotch brite wheel in my drill to clean the block face.

I noticed that the new thermostat did not have a bleed hole in it, so I drilled a small hole in the flange. It is hard to bleed all the air out of a 4.0 if there is no hole in the thermostat. Most of the ones I have bought lately have a hole but this one did not. So, I made one.

Getting the new thermostat to stay in the block while setting the housing is always tricky. I knocked mine out the first time and only noticed it when the antifreeze started to run out as I was filling the system.

I put a dab of Permatex on the flange to get the thermostat to hang in place long enough for me to slip the thermostat housing in place over it. I used additional Permatex to make the gasket stick to the housing. I held the housing in place with one hand while I started the bolts with the other hand. I was able to get it all in correctly on the second try.

I tightened the bolts and left the hoses off until I filled the system. I then reattached the hoses and filled the radiator completely with anti freeze. I then put back the temperature sender wire.

I put the belt back on and started the engine. I checked for leaks and made sure the engine came up to the proper temperature. I let it cool and topped off the radiator with coolant. I enjoyed having a nice warm heater again this morning.

Stant Superstat Super Premium Thermostat, 195 Degrees Fahrenheit – 45209

January 3, 2012January 3, 2012

Jeep Cherokee Power Steering Hose Replacement

I have replaced several power steering hoses on various Jeep Cherokees. It has gotten to be a pretty straight forward job. See this previous post on how to replace a power steering hose.

Janice’s 1999 Cherokee had been emitting a puff of smoke each time she turned her XJ to full lock. Although there was little sign of a leak on the hose, our experience with the Green Jeep catching fire due to a power steering hose leak made me extra cautious.

I got a new hose and then pulled the electric fan and the air box to make room. I tried using the various 18mm wrenches I had to get the hose loose from the steering box. I have always been successful in the past using an open end wrench. However, this one refused to budge.

I picked up a set of crow foot flare nut wrenches from my local NAPA store. They have a great set of tools in a nice case for around $20. Unfortunately I forgot that the bottom is an 18mm and the top is a 5/8 inch. I bought only the SAE set. The store was closed for the holiday by the time I figured out I also need the metric set.

Jennifer rescued me by searching until she found a set at O’Reilly’s. It is still a nice set for about the same price as the NAPA set but does not have the nice case.

I used the 18 metric crow foot flare nut wrench to break loose the lower line. It took a lot of torque but it eventually broke free. Janice and Jennifer were able to finish taking it out using the 18mm stubby wrench.

I used the 5/8 crow foot to pop loose the upper hose. It was not nearly as tight. I showed them how to put on the O rings on each end of the hose and let them get the lines threaded into place. The lower one always seems to be difficult and takes some patience to get it started.

After the new line was installed, I had them add some fluid and jack up the front of the Jeep. They turned the wheel from lock to lock to bleed the air out of the line. After that, they started the engine and repeated the process.

Once most of the air was out, she turned the wheel to one of the locks and listened for the pressure relief to open. There was a noticeable change in sound as the last of the air purged.

I rechecked the level of fluid in the power steering reservoir and checked for leaks again. Now we all feel much safer driving the Jeep.

Powercraft Power Steering Pressure Hose – 80290

January 2, 2012January 11, 2012

Fabricating a Gas Tank Skid Plate for a Jeep Cherokee

The fuel tank on Jennifer’s XJ has taken quite a beating from off road driving. In fact the fuel pump pickup is no longer the lowest point in the tank making the effective size of the tank much smaller than its original 20 gallons. She will need a new tank to cure this problem but in the mean time, I decided to fabricate a skid plate to prevent further damage and to be ready when she can get a replacement tank.

I began by making a mock up out of foam construction board. The pieces I had had once been a sales display. It provided several large sheets of ¼” poster board with a foam liner. The material is stiff, lightweight and easy to cut and draw on.

I looked at several skid plates commercially available and I did not like the way they mounted. I wanted something that attached to the unibody frame rails one either side of the tank. Of all the ones I looked at, only the Mopar plate mounted like that.

I began with two pieces of 3x3x1/4 angle. I cut them to extend from the front of the trailer hitch to the front of the tank. I shaped the upper flange to match the shape or the curved frame rail section. I drilled holes in the angle face and then made corresponding holes in the Jeep. I tapped the sheet metal for 5/16 bolts. I used the existing exhaust hanger bolts on the passenger side as well.

Using the template I made from foam, I cut two side plates form 3/16 scrap. These extend the angle down to level with the lowest point on the tank. They are angle d at the rear so that I could mount a plate angled up behind the gas tank to protect the rear of the tank and not take away departure angle. I ended the rear late below the trailer hitch cross bar.

I then welded the extensions to the vertical parts of the mounting angle. I bolted the side pate to the Jeep temporarily and confirmed the measurements of the two main plates. I put one large plate under the main part of the tank and second plate going up at an angle at the rear of the tank. The fabricated angle between the two plates adds a lot of strength.

I tack welded the bottom plate to the side plates. I then took the assembly down and finished welding the bottom to the sides. I then welded the back plate to the assembly. I made a series of short welds along the long seam to avoid warping the metal.

Once the welds were finished I ground the edges smooth and painted it black.

Putting the entire assembly back up took some help as it was now too heavy to balance on one hand. Jennifer assisted me by balancing it on the under lift stand. She also helped move the exhaust pie out of the way while I started the bolts. Only one of the 5/16 – 18 bolts stripped in the thin frame rail. The others tightened down well. I drilled and tapped a new hole to replace the one that stripped.

I plan to replace the tapped holes with nut rivets in the future if these do not hold. The skid plate is very sturdy and neatens up the appearance of the rear of the Jeep. I think I will have to make another one for my Jeep now.

December 28, 2011December 28, 2011

How to Replace the Rear Brake Hose on a Jeep Cherokee

The brake fluid for the rear brakes on a Jeep Cherokee passes through a metal line from the master cylinder to a point above the rear axle. There it makes it way to the axle by a rubber hose. This hose can be damaged if the axle over travels either by having longer shocks or by having the shocks disconnected.

To disconnect the hose, first remove the metal line from the joint. The joint is right above the sway bar if you still have one. Use a 3/8 line breaking wrench. It may be necessary to heat the joint to break it free if it is rusted. Be careful not to twist the metal line as it goes al the way to the master cylinder and can be difficult to replace if you damage it.

Once the metal line is loose, remove the retaining clip. If the swap bar is still in place access is difficult. If the bracket is rusted, the impact of a hammer will be needed to break it free. Some penetrating oil may help as well. Once the clip moves some, it can be pried off with a screw driver.

Once the clip is removed, pull the line out of the hex opening in the bracket. Next, remove the two metal lines that go from the junction block to either side of the axle. These also require a 3/8 line breaking wrench.

Once the two lines are disconnected, remove the bolt that holds the junction block to the axle. On the later models this bolt is hollow and is also the vent. You can leave the vent tube attached and just let it wind up as you unscrew it. The bolt uses a 9/16 wrench.

Clean the mounting surface and set the curved side of the new block against the axle. Attach it with the bolt. Carefully align the two metal lines and attach then to the block.

If the vehicle is lifted by the body, it may be necessary to raise the axle slightly so that the new hose will have some slack for the next step. I use my under lift screw jack to lift it a couple of inches.

Fit the end of the hose in the hex hole in the bracket. Make sure it is seated against the clip on the hose. Slip the C clip in the slot and tap it in place. You can now release the axle to make sure the hose is not too tight at full droop. If the shock does not limit the travel enough, you may need to limit the travel with a strap or get a longer hose.

Reconnect the metal line to the hose fitting. Refill the master cylinder and bleed the brakes before driving. It will take quite a bit of fluid passed through to purge all the air from the new line.

December 27, 2011December 27, 2011

How to Replace Rear Brake Shoes on a Jeep Cherokee

While many people swap in disk brakes, the rear drum brakes on the Jeep Cherokee work pretty well when they work correctly. They self adjust each time they are applied in reverse. The shoes will generally last at least 100,000 miles.

Begin by lifting the Jeep and removing the rear wheel. Next remove the brake drum. If it has never been off before, there will be one or two spring clips on the lug studs. Grab these with pliers and break them away or try to unscrew them from the studs.

Pull on the drum to remove it. If it hangs on the shoes, remove the rubber cap on the backing plate and use a brake spoon to release some of the tension on the shoes. Rotate the adjuster up to release.

If the drum hangs on the hub, try hitting the face of the drum with a hammer. This will often break loose the rust weld at the center. Penetrating oil may help as well. In severe cases you may need a drum removal tool.

Once the drum is removed, inspect the brakes. There should be two overlapping springs at the top, an adjuster cable running from the top to the bottom of the rear shoe, retaining springs on each shoe and a smaller spring connecting the two shoes at the bottom.

The adjusted lever should lightly contact the wheel on the adjuster screw. The screw should turn freely when the adjuster lever is moved away from it.

If any of the springs as broken or missing, you will need a spring kit with the new shoes. If the cable or the adjuster is not working properly, you will also need a small parts kit.

To remove the shoes, I start with the retaining clips. Press in on the cup using either a brake tool or a pair of vise grips. Reach behind the backing plate and rotate the pin until it lines up with the slot in the cup. Release the spring to separate it from the pin. Use the same procedure on the other shoe.

Next remove the two large springs at the top. Use either a spring tool or a pair of vise grips to release one spring at a time. Note that the spring on the rear shoe also holds the cable pivot in place. Note the arrangement so you can put it back later.

The two shoes can now be slipped down around the axle and the lower spring can be removed as well as the adjuster. Pay attention to how the hand brake lever engages the rear shoe so you can put that back later. Also note the orientation of the adjuster screw. I like to lay all the parts out on the floor in a sort of exploded view so that I can reference it upon reassembly.

The mounting pin for the new shoes will likely not be installed. To put it in, note which side it is mounted on the old shoe. Use a vise to press the pin into the hole in the new shoe.

Put a small dab of grease on the backing plate in the places where the shoes contact. Also inspect the wheel cylinder and replace it as necessary before installing the new shoes.

Set a shoe in place and set the retaining spring over the hole. Insert the pin from the rear and align it with the slot in the cup. Compress the spring and rotate the pin to lock into the cup. Then release the spring to hold it in place. Do the same with other shoe. Note that the front and rear shoes are different. Make sure you have them in the correct place. Also make sure they properly engage the wheel cylinder. Slip the bar in place between the shoes in the upper slots.

Put the loop of the cable over the anchor pin. Hook the spring for the front shoe in the hole and use a spring tool to hook the spring over the anchor pin. Carefully place the cable pivot into the hole in the rear shoe. Hook the spring to hold it in place. Use the tool to secure the spring to the anchor. Inspect the pivot to make sure it is properly engage in the hole and is flat against the shoe. Adjust as needed.

Use pliers to install the lower spring between the shoes. Rotate the adjuster screw to fully closed. Stretch the spring and slip the adjuster screw in place between the screws. Clip the adjuster lever to the pin in the rear shoe. Install the spring on the lever. Tip the lever up and attach the adjuster cable making sure it is routed properly around the pivot.

When properly fitted, the lever will be against the cog wheel o the screw. It if hangs above or below the wheel, adjust the pivot under the spring. Adjust the screw until the drum will go on with just a slight drag. Install the drum and make a final adjustment of the screw through the access hole in the backing plate.

Repeat the procedure on the opposite side. Keep in mind however that the other side is reversed and even the screw threads on the adjuster screw are opposite.