Part 19: Thor Enhancement Actions and Brake Failure


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The Trip

We completed the addition of the turbocharger and intercooler.  Additionally, the windshield was replaced.  All of these actions were to be performed at Rob Pickering's shop in La Junta, CO.

Once the enhancement and maintenance actions were complete, we headed north toward Colorado Springs, then Denver.  But, when we got to Denver, we encountered a brake lockup that stuck us in the Jefferson County Fairgrounds parking lot for 3 nights.

The Photos

The photos below are what we saw.

The mounting frame for the intercooler was test-fit on the headboard to insure there were no interferences with the existing components.

Visible in the photo above is the intercooler radiator, intercooler, ducting and the new HX-35 Holset turbocharger.

Finishing touches are put on the assembly before it is torn down to be painted.

While the paint was drying, we added two additional circuits to the 12VDC breaker panel: radiator fan and intercooler water pump.

12VDC supply lines were placed into loom and run from inside the cab's cargo bubble along the air conditioning lines.

Electric fan was attached to radiator prior to installation in newly painted mounting frame.

The mounting frame was installed and the cab was lowered to perform a final check on fit and clearance.

Next up was the windshield.  We had suffered a large stone strike many months prior so Rob ordered the windshield for installation on our next visit.  The old rubber was actually in quite good shape for being 25 years old, but it was stuck on both the glass and the body.  Getting it loose was hard.  Above, Scott and Rob pry the glass loose.

The prying was not fully successful, so Rob resorted to using the pressure from his feet.

Persistence and effort finally prevailed and the old windshield was removed.  Next, the new gasket was checked to insure it would fit.

The gasket was installed on the new glass.

The glass was "roped-in" to the frame, but it was ever-so-slightly misaligned so it took quite awhile to fully seat.

In the end, the manlift was brought out to allow us to more firmly press on the windshield to get it installed.

We went through several rounds of tuning to get the fuel delivery adjusted to make better use of the new hardware.  The fuel delivery was increased, so care is required to insure that the exhaust gas temperature stays within reasonable limits.

We prepared to depart La Junta and then headed out toward Pueblo, CO.  Along the way, a line of thunderstorms crossed our path.

We spent the night in Colorado Springs at a convenient spot (AKA the KOA campground right next to the freeway).  Because of a variety of factors contributing to the extended maintenance period, we ended up there on the 3rd of July.  The place was packed but we got lucky and got a spot.  We had a delightful dinner at Walter's Bistro and then settled in for the night.  The morning of the 4th we broke camp and headed into Denver.  We reached top speeds of 65mph and exhaust temperatures peaked at 1300 degrees F on the 7350 foot Monument Grade (AKA Palmer Divide) north of Colorado Springs.  The truck was running well and I was pleased.  My fellow Unimogger Bob Ragain and his wife Kitty were in Denver visiting relatives and were watching our progress on our SPOT device.  We contacted them and met up for lunch and then continued north.

We decide to head toward Golden, CO to see if we could find a place to stay for the night.  Being the 4th, everyplace was full except the Jefferson County Fairgrounds which has a small set of RV spots.  We went to the place and checked in, then headed out to the store to get some supplies.

En route to the store, the brakes locked-up.  We managed to pull into a 7-11 parking lot for a closer look.  A call to Rob, who was in New Mexico for the long weekend, suggested that we should bleed the front brakes to release the pressure.  The design of the master cylinder on the brakes was such that the front circuit engages before the rear, so bleeding the front would likely remove the excessive pressure and allow us to go on our way.  Why, exactly, the pressure was there was a bit of a mystery until we considered the situation a bit more carefully later.

I jacked up the front axle in the parking lot and checked to see if the front wheel would rotate -- No.  While the rear axle could be locked as well, the infrared thermometer showed the front drums to be much hotter than the rear drums.  I bled the line on the front axle resulting in an explosion of brake fluid and an unpleasant popping sound from the rear of the truck.  Once the bleed nipple was closed, the front wheel could spin.  And, when the parking brake was released, the truck would roll backwards toward the street, but TOTALLY WITHOUT ANY BRAKES.  A measured re-application of the parking brake brought us to a halt.  I reasoned that I had somehow I introduced air into the front circuit when they were bled, but the rear circuit was non-functional as well.  In theory, aside from being actuated from the same booster, the circuits are independent.  The have separate reservoirs, separate lines, etc.  But, in this case, something had happened to both circuits.

We attempted to bleed the front circuit, but with no success.  Depressing the brake pedal did not result in much pressure in the lines but it DID migrate fluid from the front reservoir to the rear reservoir, strongly suggesting a seal issue in the master cylinder.  Finally, after many tries and the onset of both dusk and a rain squall, we decided that we could not spend the night in the 7-11 parking lot.  Since we had already paid for a place and it was only a mile or so away, we decided to risk a drive without any brakes.  We kept the speed below 20mph and use a careful application of the parking brake to stop at intersections.  The rain slick streets were scary, but we only skidded once.  Once we were safely back at the Fairgrounds RV area, we set up for the night and decided to attack the problem in the morning.

Kathleen had texted Bob about our predicament and he offered to come to us to help.  Next morning he and his son in law came to assist.  The short story is we were unable to repair the problem.  We pulled a vent plug on the booster and blew out a bunch of rust particles.  We built air pressure and attempted to bleed the brakes but noted that when the brake pedal was depressed, fluid moved from the front reservoir to the rear reservoir but no hydraulic pressure was achieved.

My current conjecture is that a particle of rust initially obstructed the booster's ability to vent air pressure when the brake pedal was released, thus causing a gradual buildup of hydraulic pressure and later a lock-up.  This happened on my mog several times.  The rapid release of hydraulic pressure during the road-side bleeding process likely caused damage to one or more seals in the master cylinder, thus resulting in inability to build hydraulic pressure in the brake lines and moving fluid from reservoir to reservoir.  There are other possibilities as well including the actuation cable being mis-adjusted.  But, at some level, the cause is moot.  The real issue is the ability to build and maintain hydraulic pressure in the brakes.

We stayed one night at a regular RV spot with power and water and then we were told that our site was reserved and we would have to move, but with no service brakes, you are not going far.  We ended up on the other side of the parking lot with no services.  But, we did have access to the restroom and showers so it was better than being in the parking lot of the 7-11.

Rob agreed to come to us with parts and some tools that I don't have.  With luck, we'll be rolling tomorrow back to La Junta to get the rust in the tanks addressed.

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Photos and Text Copyright Bill Caid 2014, all rights reserved.
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