Changed out the thermostats and flushed coolant on UPGRAYYED (our 2002 LB7) the weekend before last. While I was in there, I also swapped out the MPROP (fuel pressure sensor), which I suspected was either leaking or failed and was causing the idle lope with which we’ve been dealing for the last year.

That was the culprit: failed MPROP. With that replaced, her idle both in gear and neutral is now silky smooth. There’s also no smoke on the highway. I’m actually somewhat surprised that it’s possible for a diesel to be so smooth.

Then Monday happened.

Fast forward a week and a day to this morning: Just after I started the truck to head off to work, I lost brakes and steering.

Aside from a brief moment of surprise when the thing lurched into reverse, my thought was something along the lines of, “Odd… I was nowhere near that stuff last weekend.”

Segue:

Why brakes and steering? The Duramax — and several other trucks — use a hydro-boost mechanism rather than a vacuum booster to actuate the brakes. The hydraulic power is supplied to the hydro-boost by the power steering pump.

If the pump fails: no brakes and no steering

Differential:

For neither brakes nor steering:

• insufficient power steering fluid
• loose serpentine or belt failure
• power steering pump failure
• clogged high-pressure from pump
• failed hydro-boost
• engine not running

Okay, I added that last one, but I’m sure it’s in somebody’s troubleshooting manual someplace.

Troubleshooting:

• Shut off the motor and check power steering has fluid. It’s full, although a bit dark: Good.
• Check the serpentine, which, too, looks fine; snug: Good.
• Start it back up and observe that it’s turning the steering pump’s pulley: Good.
• With the engine running, remove the cap from the power steering reservoir to observe fluid movement: No sloshing. No movement. Not good.

Diagnosis:

At a minimum, that’s a failed pump. Could it be something else? Sure, but without any pressure coming out of the pump, there’s no way to know whether the hydro boost is okay or not.

We’re now $170 poorer and at least a few days awaiting delivery of the new unit.

Fortunately, it’s a reasonably straightforward driveway task for a home mechanic.

A micro fifth-wheel and a VW Beetle from 1974:

Pretty neat, but I’d wager you’ll not see anything like that these days.

When we bought UPGRAYEDD, we knew that there would be a few things here and there to repair. One thing that we learned the day we took possession is that the engine has a behavior that we didn’t see during the test drives: when stationary, in gear, at idle, when above regular operating temperature: it lopes.

Noticeably and very annoyingly.

We hadn’t noticed it during the test drives because we bought it during the winter and it never had a chance to actually reach regular operating temperature.

Put it in neutral and the lope stops. Give it just a touch of throttle and the lope stops. Let it start rolling and after a couple of lopes to get moving, the lope stops.

Hmm.

Doing idle-speed maneuvering to position a trailer in a campsite or the driveway? It’s feels like a medium-sized gorilla is hopping on the hitch.

I’ve been suspecting all kinds of potential problems:

• An air leak after the MAF.
• Gummed up vacuum lines or even a failing vacuum pump.
• Bad injectors — and let’s not have -that- discussion again.
• Potential problem with the torque convertor, which is about as expensive as it sounds.
• Fuel system sucking air — diesels do -not- tolerate air leaks in fuel systems.
• Bad fuel pump or pressure regulator.

So, yesterday, I set to systematically working through the fuel and vacuum systems to see if I can identify a root cause. Here’s what I found:

• Yes, there was an air leak after the MAF, and the MAF was loose. Repaired both, but no change. Pass.
• Vacuum lines are clear, no leaks, all actuators are functioning smoothly. Pass.
• It has 8 new injectors, now with about 1200 miles on them. Pass. Also, no evidence of high-pressure internal fuel leaks. Pass.
• Torque convertor shows no signs of mechanical failure. It’s well-balanced and perfectly smooth in park, neutral, and while in motion. Pass.
• Fuel system: water/fuel separator was damaged and installed incorrectly. It would have been allowing air ingress. It needs a replacement, but I don’t have one right now. I did reinstall it correctly on a new fuel filter. No change in behavior. Pass.
• Fuel pump & pressure regulator (FPR/MPROP). You know, that the vacuum-side of the fuel system didn’t seem to resolve it and that at high power, there are no stumbles, I think the fuel pump is probably fine, too. Going to hold off on the high-pressure side for awhile.

…to be continued…

We’re chomping at the bit to get out for a camping trip. We’ve reserved a site at St. Vrain next weekend as our first trip of the season. The overnight in the driveway, tonight, doesn’t count, does it?

This week, I installed some seat covers, transferred the brake controller from Twuck, and tested the wiring harness. I also installed and adjusted a new shank for the Eaz-Lift hitch as the hitch needed to be lowered about three inches.

This morning, we took the trailer for a little drive to see how it behaves behind UPGRAYEDD, then decided to take it for a little longer drive up the interstate and ended up stopping for lunch while we were out.

When we got home, I did a few more tweaks to the Eaz-Lift and put the WD bars on. I really prefer to have the weight shifted a bit further forward than where it was. I’m sure it’ll take a few adjustments to get it the way I like it.

Next on the list was to prep the trailer for the season. Typically, that’s just a matter of opening everything up, sanitizing the potable system, running the appliances, and checking and repairing anything that was left from last season.

I’ll also need to remove the old bumper sticker that I had made for the trailer as it doesn’t really seem fitting anymore because UPGRAYEDD is two feet longer than the trailer.

So, what’s the sticker?

Of course, when we upgrade to the Heritage Glen T300BH that we like, we’ll need to come up with another humorous sticker.