Safety – Page 3 – The Jeep Guru

January 2, 2014

Jeep Cherokee XJ Dash Fire

I was using Jennifer’s XJ to move my race car back into the shop. Just as I had cut loose the tow strap I noticed a glow in floor board. At first, I thought her under dash interior lights were trying to come on, but I knew they normally don’t work.

I leaned over to see what was going on and saw flaming drops of plastic falling into the floor. I quickly drove closer to the shop door and ran inside to get some water. I told Jennifer her Jeep was on fire and ran back out to splash water on the floor. Since the fire was actually inside the HVAC duct, the water did not help at all. Jennifer tried more water but that was not helping either.

I then got the fire extinguisher out of the race car and pointed the nozzle under the dash. A quick blast had it all out. However, now everything was covered in pale yellow powder.

Once the excitement was over, the cleanup and diagnosis began. The fire was located in the HVAC duct and the blower wheel had melted. The most likely ignition source was the resister pack.

She had been having trouble recently with blower motor fuse blowing. I had traced the problem to the Tan colored wire and after installing a replacement control switch, I had disconnected that wire. However, I disconnected it only at the switch. I did not remove it from the resister pack. At the time I did not realize that if it shorted, it could back feed from the resister and get the resister very hot.

She got a new blower motor and we used an old fan wheel we had in stock. Removing it from the old motor was quite a chore and had we known how hard it would be we would have simply bought a new wheel with motor. To get the old blower off, we first removed the clip. Then we used a heat gun to soften the hub and used a screwdriver to pry it apart until it would slide off the shaft. However, this operation made the shaft too loose on the new motor. We solved that by heating it again with the hot air gun while the spring clamp was in place. When it cooled it was tight.

When we tried to fit the assembly into place however, we found part of the side of the duct work had melted and interfered with blower wheel. Again, we used the heat gun to reshape the inside of the duct work so that the fan would clear. It still rubs a little and sometime makes a squeak, but it fits and moves air. Later the entire duct will be swapped out; but that is a job for another day or two.

To seal the hole that had melted in the duct, we used metal duct tape. Working from the foot well and through the blower motor opening we made two layers of tape to seal the hole. Once it was all in place we installed a replacement resister pack from another donor vehicle. This time’ I disconnected the tan wore on both ends. Access to the shorted area will have to wait until we pull the dash to replace the HVAC duct.

For now, she has heat and air so the Jeep is serviceable. However, even after much vacuuming, powder from the fire extinguisher still continues to blow out of the vents from time to time.

I also gave her a new fire extinguisher to keep in her Jeep from now on.

July 30, 2013

Trailer Brake upgrade

After hauling our Chump Car racer to Charlotte, I felt he current brakes were inadequate. They are over 20 years old but have new magnets and drums. Still he same old shoes however. When they were new, they would lock the wheels easily. Now even with full voltage applied, they will not quite lock even withe trailer empty.

My first upgrade was to install a new brake controller. I got one with a “boost” feature that really helped liven up the old brakes. However, the instructions boldly said not to use the boost feature to compensate for weak brakes.

I was about to buy new brake shoes when I discovered that for just three dollars more, I could get a whole new backing plate with a new magnet and new shoes installed. I then decided that since I was getting new plates, I could just put them on the other axle that does not have brakes. Then I would have four brakes instead of two. I just needed to add new drums to the order. I also discovered that the non braked axle did not have the mounting flange installed so I had to buy that as well. So my brake relining job quickly escalated.

When the big box arrived, I began by pulling the rear wheels up on ramps allowing the front axle to hang free. I removed the wheels and the hubs. I then pulled the rusty U bolts and removed the axle from the trailer. This step allowed me to carry the axle to the welding table instead of trying to bring the welder to the trailer.

I found the mounting tab fit nicely into a ridge on the spindle like it was mode for it. I test fit he backing plate and drum to confirm that was the right place. I had to clean some rust off the spindle surface to make it fit right and to get a good weld. I put a bead around the back on each flange. I made sure it was lined up square with the spring perch. I used masking tape over ht bearing surface of the spindle to protect it while grinding and welding.

I then reinstalled the axle. I bought new U bolts but they did not fit so I ended up reusing the old ones. I chased the threads with a die first.

My first glitch came when I discovered the brake plates did not come with nuts. They were 7/16 – 20 so not something I had in stock. I made it to Home Depot at 8:58pm to buy some.

The baking plates fit perfectly on the mountings flanges. I then greased and installed the new bearings that came with the new drums. I then discovered the new drums did not come withe a new castle nut washer or key. I reused the old nut and washer and used a new key from stock. I had trouble getting one of the new caps on so I reused one old cap.

Next came wiring. I was not looking forward to crawling under the trailer to run wires. So I spent a few minutes figuring a way to put the trailer on my car lift. It fits between the post with only an inch to spare. The arms can’t swing under the frame because they hit the tires. I ended up using some pipe to span the gap between arms and lifted the trailer that way. I did not try to thread the wire inside the axle tube although there are holes for this purpose. I just taped it to the outside of the axle tube.

I ran new blue wire from the new magnets to the front of the trailer and used a sheet metal screw to secure the ground side to the trailer frame. I know the instructions say to run a separate ground wire; but the old brakes have been wired this way for over 20 years and they get plenty of current to the magnets. I spliced into the other brake wire right at the connector. I may add a switch here later as the front wheels often don’t touch when towing the trailer empty.

A quick test pull showed that the new brakes give me a lot of confidence when towing. It feels much safer now knowing I actually have reserve stopping power and am not using all the brakes just to make a normal stop.

February 8, 2013

Spare axle storage in an XJ

After watching several fellow Jeepers break axle shafts in their Dana 30 front ends and having broken two myself I like to carry spares and the tools to swap them out. I think our record time for swapping an axle shaft on the trail is 14 minutes.

However, I have had trouble finding a good place to store the spares. They are heavy and tend to bang around if not secured. They would be a severe hazard if unsecured in a roll over.

I found both short and long shafts will fin inside a length of 4” PVC pipe that can lie cross wise in the rear floor up against the roll cage main hoop in my Cherokee. I don’t have a back seat in mine.

To make the storage pipe, I bought a 10 foot length of PVC sewer pipe. It is about half the price of regular PVC pipe. I also got two caps. The caps for sewer pipe are about a third the cost of pressure caps.

I cut the pipe with a hand saw just long enough to accommodate the two axles overlapped in the tube. It just barely fits between the sides of the XJ. I did not make a separate hold down bracket as I sat the spare tire on top of the tube and secured the tire with two ratchet straps. I don’t think it is going anywhere.

I then used the rest of the pipe to make a sleeve to keep my HI Lift, and axe together. For about $15 I have cleaned up the storage area of my Jeep and hopefully reduced the things that could hit me in the head in an incident.

February 22, 2012

Warped Brake Rotors on Jeeps and How to Prevent Them

When I picked up my new brake rotors for my Jeep the guy at the parts counter advised me to carefully clean the brake rotors of oils including oil from my fingers to prevent warping. This was new to me and got me thinking about warped brake rotors and reminded me that I have not had to deal with a warped rotor in a long time.

The first thing I learned years ago was that the pulsing sensation we called a warped brake rotor is not actually warping. You can put a dial indicator on the face of the rotor and spin it around and it will read very little run out when it is making a pounding sound when the brakes are applied. You can measure it all the way around and you will find very little difference in thickness either.

The real cause of the shudder is a chemical change in the metal of the surface of the rotor. You can sometimes see it but most of the time you can’t. Turning the rotor cuts off that surface layer making the rotor run smooth again adding to the warping myth.

The rotor surface chemically interacts with the brake pads under the heat of braking. Most of this interaction occurs during the bedding in process of the brake pads. Many high performance and racing pads have a critical bedding in process to establish the correct chemical bonding between the two materials. Usually this involves making controlled braking maneuvers at predetermined speeds to generate the heat needed for the reaction to take place. It is important not to come to a complete stop during the process so that the interface layer is kept consistent around the rotor face.

This leads to why rotors “warp” and how to avoid it. The interface layer is constantly maintained as the rotor face and the brake pad material wears away. A new layer is constantly formed with each use of the brakes.

If you come to a complete stop with the brakes hot, the reaction will continue under the pads where the heat cannot dissipate. If it is held there too long, it will create a bond that is a bit stronger or weaker than the area next to it on the rotor. As the rotor develops these uneven spots where the coefficient of friction is grater that the surrounding rotor face, the brakes will give the characteristic chatter that we call a warped rotor. The pulsing in the pedal will feel like the rotor is pushing the pads away from the surface.

I tried a lot of things before I finally got away from “warped” rotors. I tried the expensive rotors. I tried the cross drilled and slotted rotors. I tried various pad materials.

The thing that I found that helps more than anything is a simple driving technique. Some people call it the Limousine stop. I call it a creeping stop. If I suspect that my brakes are hot when coming to a stop, I will aim to stop a bit short and then just before the Jeep stops and is ready to rock back, I let off the brakes and let it creep forward about a half turn of the wheel. If I have to stay stopped like at traffic light, I will creep forward again another quarter turn of the wheel to help even out the heat buildup in the rotor.

There are times where it may not be possible to make such a stop. For example in an emergency or if you have to spot unexpectedly. You may also have to hold the brake longer than you wish thereby creating a hot spot. If this occurs, I repeat the performance pad bed in process and create a new interface layer. Depending on how bad the hot spot is, it may take several repetitions of heat cycling the pads to get them smooth again.

Since I have made this style of stop a habit, I have not had any more trouble with warped brake rotors. I can’t remember the last time I replaced rotor on one of my Jeeps due to chatter.

February 20, 2012

Remembering Y2K

As we count down the days to the end of the Mayan calendar, I am thinking back to the last potential apocalypse. I still remember all the hoopla that surrounded the change from 1999 to 2000. It seems many people were convinced that all the computers in the world were going to crash and we would be returned to the dark ages because the computers would not know what year it was.

At first I thought the whole idea was just silly. I had no idea anyone had taken the issue seriously. This is until I got a directive from my company that I had to certify each and every item in the plant to be Y2K compliant. Even in my relatively small plant employing just under 200 people, there were a lot of individual items that had to be certified.

Considering the relative importance of the situation, I first assigned the task to my co-op engineer. As he began to collect the data, and report back his findings to me, I began to realize that there were in fact many people who took the issue very seriously. Some companies were paying big bucks to have their equipment certified.

In order to not take resources away from solving real problems, he and I developed a checklist to quickly verify that the equipment would not self destruct at the stroke of midnight on December 31, 1999.

Naturally our first step was to see if the device even had a clock and even knew or cared what day it was in the first place. We also developed a form letter to send to manufacturers to get a document that added credibility to our own assessment.

Once we realized that not only did our own upper management actually task the situation seriously, but other companies were also taking the issue seriously we began looking into selling our services outside the company. Unfortunately by the time we realized people would actually pay us to do the work, most of the big contracts had already be let to people faster on the uptake than us.

So we just resumed our own process of certifying all the equipment we had and depended on. Naturally most of the stuff we looked at did not have a clock and could quickly be eliminated from the high priority list.

For most things with a clock, it was a simple matter to set the clock to a date past 1/1/2000 and see what happened. Only after we had tested most things on our list did we get stern warning from corporate not to test in this manner unless specifically told to by the manufacturer. Luckily we had completed most of our testing by the time they told us to quit.

One system of particular interest was the phone system. It did have a very important function of keeping the date and time of each voice message. About a week after we had run our clock forward and back again with no ill effects noted we received a dire warning from the manufacturer not to perform such a test. The assured us that it would indeed self destruct.

Sensing this was a scheme to cause us to hire one of their technicians to test for us, I called our sales rep and told her we had already done the test and nothing bad had happened. She informed me we were very fortunate that it had not crashed but was sad that we did not need their tech to test it for us.

Once we had complied huge notebooks of documentation for the equipment in the plant, we began thinking of how to best present the data to management and the auditors. Yes, they actually had auditors to make sure we actually did the certifications and did them correctly.

We first ranked items by criticality. The highest priority items were placed in the first notebook. These were items that would have the most impact on the operation should they fail on 12/31/1999. Of course these were items that might shut down production or make the facility uninhabitable for some reason.

My co-op engineer examined the data and decided in order to quickly point out how thorough we had been we would sort the data in inverse alphabetical order. After all our most important piece of equipment was made by Zerand and there was no point making them flip through the huge notebook looking for the Z’s.

The most rewarding consequence of the inverse alpha sort pattern was that it put the Zurn company at the top of the list. Zurn made the automatic flushers for our toilets and of course we ranked these as critical since no one wants to inhabit a building if the flushers are not working. The added benefit was the not so subtle hint as to where we thought all the data we had worked months to gather really belonged.

The managers go the last laugh on us however as they required us to be on site at the stroke of midnight on 12/31/1999 just to make sure we had not missed anything. We got to ring in the new millennium with a group of engineers and maintenance workers rather than our families. But, they did give us written authorization to have an actual Champaign toast at midnight.