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Are you driving around with your brakes on.... and do not know it!


Dollytrolley

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Hi all,

 

Recently we picked up a "Project RV Hauler" in the form of a older converted FL Century /M11/ 10 sp that was pretty long of tooth.

 

The old truck was bought as one of three identical FL Centurys by a central WA wheat rancher in 1997 and he had the three trucks haul wheat for about 10 years and then retired the trucks with +1,000,000 miles each. One of the ranchers best friends had just retired and was trying to travel around with a heavy 5th and complained that it was costing a lot to keep the not-so-super-pickup running with the heavy RV load. The old wheat rancher joked "heck what you need is one of my old wheat haulers hitched up to the 5th RV and you'll be amazed how good life can be".......so.......

 

The rancher agreed to sell one of the old FL's on the condition that it was referbished into decent operational condition such as a Cummins remain M11, new rad/ aftercooler/ new clutch, new brakes/ drums/ remain tranny, U-joints, bats, A/C, seats and new tires, and the thousand of "other misc" items that pop-up.

 

What was not included was any cosmetics to speak of so what came out of the shop on purchase day was a lot of pretty new major components hiding under a rather dull exterior.

 

For eight years and about 15,000 miles the FL idled back between cental WA and Yuma, AZ every year with a couple of side trip as well with NO problems whatsoever.

 

Recently health issues have prompted the RV owner to retire from RV travel so he chose to pass the old FL on to me for the next adventures in our retirement.

 

Prior to picking up the old FL I crawled around under the old truck and made a mental note that the brake lining at the back axle was worn TWICE as much as the powerdivider lining. The powerdivider lining was virtually new thickness.

As with many tandem trucks this FL has spring brakes on the back axle only so, IF the complete tandem axle sets were redrummed AND re-shoed at the same one might expect nearly identical brake lining wear on all rear axle positions UNLESS the spring brake was dragging at times without the operator not knowing.......

 

In my childhood, our family had wat too many heavy trucks, Dozers, Log Loaders, Dumps, Lowboys, Service trucks , etc so from about the age of 11 to my mid twenties I was buried in too much rolling stock so to speak.

 

Grumps ( my stepfathers nickname) was a pretty hard-boiled machinery operator that kept a sharp eve on everything mechanical and was hugely critical of brakes so if he were to look at this current FL he would say fix the spring brake NOW before this truck moves another mile.

 

Whenever Grumps would see a worn-out set of spring brake shoes he would joke that the operator would never have enough money to reline his brakes because he was spending all of his money on fuel while driving around with the brakes on just enough to not notice the drag too much.

 

As a kid I would just pass Grumps remarks as just being Grumps, but now that I am a Grumps myself, well.... thing look a bit different these days.

 

So here is the rub...... the FL owner stated that the truck averaged about 8mpg towing or bobtailed it seem not to matter much and having it dialed back to 370 hp seemed not to change the mileage. Most of my Cummins experiance was from the pre-electronic engine age so I was not too alarmed at *mpg but I thought in the back of my mind that it seemed that the truck should have better mileage.

 

Shortly after I brought it to our Yuma location I went out one morning to take the bride for a "spin around the block" but as soon as I released the parking brake I started losing air pressure and before we were out of the driveway the springbrake deployed and we were one again "PARKED".

 

In the end I replaced the spring brake exhaust valve and now the spring brake fully retracts and does not drag at all.

 

Guess what...... from Yuma to Quartsite to Tonapah to Wickenburg towing our 30 ft Dolly-Box / toybox we averaged 13.53 MPG and it would have been likely better if I had used the cruise control more.

 

The loss of more that 50% of the spring brake lining in about 15,000 miles points to a long history of spring brake wear and it obviously takes a lot of diesel to drive around with the brakes on......

 

With tandems with one axle only spring brakes, it is fairly obvious when you compare linings of the spring brake to the non-spring brake linings. On trucks with single back axles it takes more attention to brake matters.

 

Leaking spring brake lines, cans, valves, etc can sneak up on you and drag the spring brake and you really do not know it and if the cruise control is on it's no problem the cruise control just pours more diesel into the engine to keep us rolling along........

 

How many of us are driving around with the brakes on????

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Hi Stan,

 

Indeed a few IR temp shots of the entire brake system drums on a regular basis might not hurt and IF the weather was cold it would likely make it easy to catch the heat-rise of a dragging brake.

 

It seems that many of the HDT owners seem to make a habit of running away from cold weather, so the higher outside temps makes tires and rear-gear sets stay fairly warm and might "mask" some of the brake dragging temps IF the brake drag was light or intermitent at times.

 

I've somewhat been involved with pesky aircraft for the last 40 years, so getting back into trucks inn my advancing years is fairly taxing on my old ramdom access memory so ..... it takes me some time to connect the truck dots so to speak.

 

Like I said, "Grumps" was pretty picky about brakes ( loads of around 300,000 lbs on steep one-lane mtn roads make you "picky" (or dead)), so he insisted that when I ever warmed up a truck to change oil, I had to turn off ALL noise (even the radio) in the shop and then crawl arould ALL over the truck to find and FIX EVERY air leak NO MATTER HOW SMALL THE LEAK WAS........ what a pain Grumps was...... but his brakes worked well.

 

Please folks don't get me wrong, don't assume that your spring brakes are about to become a smoking mass of lost $$$, infact I would guess that the vast population of RV HDT's are very well kept, lightly-used "pets" with very good brakes.

 

Perhaps it is good to keep a thought in the back of your mind that the ole spring brake is just held away from the brake drum by a fairly large amount of system air pressure and ANYTHING that lowers your system air pressure risks having the spring start it's fail-safe job applying the brakes.... thats the blessing and....... at times.... the curse of airbrakes.

 

Happy travels,

Mike, Carol and Dolly the paint-horse

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Hey Mike - And welcome to the forums (liked your first post also by the way).

 

For the $30 or so that a Harbor Fright IR scanner costs, many of us use them at every stop. A quick walk around and compare temps, call it 30 seconds (and it helps the knees to move some) is not a big deal. I keep one by the seat, climb down, walk around, truck and trailer by the way, put it back behind the seat and walk to ??wherever we are going. It also causes me to look at the lights (turn the running and flashers on).

 

Prior to travelling, I used to check lights, fluids, etc. every Sunday morning. Now, with the more intermittent use, the truck can sit for a while. So about 2 weeks before moving, I start checking the truck out. And then every stop.

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Good morning Bill,

 

Thanks for the welcome, I have been viewing the forum for quite some time and have enjoyed the comments.

 

Indeed the use of a IR gun to monitor temps and obtain "baseline temps" can be a good way to understand many conditions that occur on various systems. Now that "I take the time to smell the roses" regarding truck maint, I like you, can spend considerable time inspecting and puttering away on the "project".

 

It sounds like your rig is a "pampered pet" that I mentioned in my previous post, and this can indeed be best described as a daily education at times.

 

After pondering your post regarding the IR gun use I wondered how many "super-pickup owners" might migrate over to the Dark Side if they shot the "super-pickup" with the IR gun and find that the temp display indicating "OVERTEMP RANGE"..... I suppose smoking engines, trannies, and brakes on a pickup tell the owner enough about high temps that he doesn't need a IR gun reading......

 

Your post does bring up a excellent point about HDT haulers, and I suppose larger trailers, and that is, that at times the large capacity of the larger equipment can somewhat mask events that will make smaller units to start boil smoke and flames..... the larger capacity "reserves"of larger equipment

can shoulder excess conditions and still carry on down the road.... at times....

 

The use of heavy trucks to haul light loads is a fairly new concept for me to wrap my mind around for likely different reasons that most of the forum members......I grew up in a family where ALL of the trucks HAD to haul HEAVY loads and at times EXTREAME loads over very rough mountain roads or

"pig-trails" often in very bad weather as well. Once these trucks got to paved roads the driver got out and re-cinched the loads and then hit the road at the same speeds as the long-haul trucks The family trucks were never abused by intent, but often the needs of the jobs taxed the trucks to the limits.

 

To me, at times I look at our current "HDT adventure" and pinch myself and ask........ "is this somewhat like waterskiing behind a 6,000 HP tug boat" ..... you know......... no shortage of power...... and a heck of a wake.........

 

Happy travels,

 

Mike, Carol, & Dolly the paint-horse

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Brian - power is one of the "problems" of these trucks. We were bringing my buddies new trailer home, he was driving, and he had hooked the emergency brake cable on the trailer on a turn. I run my cable different and its' movement is "contained". Anyway, I noticed smoke from the wheels, we stopped and ran back with the fire extinguisher. He may not have had the feel yet, but he just couldn't tell that they were dragging. Running gear was OK, smoked the linings and the next week, we replaced the linings and regreased the bearings.

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Brian & Bill hello,

 

Indeed at times when things start to smoke it really gets our attention.

 

In my recent spring brake adventure the valve failure stopped the truck in the driveway before anything could even get warm to the touch.

 

There was some quirks in the spring brake adventure that could have made things pretty hot and maybe a bit exciting, depending where the spring brake deployed. Since I really had nowhere to go with the truck I started troubleshooting the spring brake in the truck parking spot in the driveway.

I reset the parking brake a few times but everytime whenever I released the parking brake the truck would lose air pressure exhausting out of the service brake exhaust port. Once I deployed the service brake BEFORE I released the parking brake and guess what..... the park brake released and the truck did NOT lose any air pressure out of the service brake exhaust port. I could easily move the truck so I pulled foreward stopped with the service brake took my foot off the service brake and then set the park brake and the park brake deployed fine. Next I released the park brake and guess what....... the truck started losing air fast out of the service brake exhaust port......and of course as the air pressured lowered the spring brake went into fail-safe mode and the truck was unable to move.

 

Next I tried the trick of resetting the parking brake while I also stepped on the service brake peddle but this time reduced flow of air pressure leaked out of the service exhaust port. With the smaller amount of leakage and keeping the engine at about 1200 RPM the park was somewhat dragging but I could move the truck with some drag from the parkingg brake being felt.

 

I played with the parking brake / service combo deployment and a few times the park brake released cleanly but most times the parking brake remained dragging or nearly locked up.

 

Here is my theory for what it is worth...... when the service brake is deplloyed BEFORE releasing the parking brake the service brake air flow travels up the balance line to the park brake valve and as such it opens the check valve into the park brake valve to counterpressure and releive potential overstress on the park / spring brake. It seems that the check valve was late-stage-progressive-failure and whenever the service brake flow thru the check valve the seemed to function or partly function as intended. Since the check valve was intermitent in operation it was not very easy to troubleshoot until more logic could be brought it shine some light on the problem.

 

Here is the hair-puller.......at times even mechanical items with a intermitent nature and so in this casse you might be driving a fairly long leg of a trip and SOMETIMES when you use the service the spring stays released and then SOMETIMES when you deloy the service brake the check valve unseats and then the spring brake starts dragging for 30 miles and then you deploy the service brake again and this time the check valve functions properly and the spring retracts and then the brake cools off after 30 miles and when you stop your brakes are cool....... but..... your spring brake linings are just a bit thinner each time the brake drags.....AND..... if the brake drums are cool when you stop you do not know that the spring was dragging for 30 miles.....

 

Way back in my childhood, when I attended airbrake class I recall that the "prof" would lecture us "kids" that .....Airbrake systems are pnuematic-logic systems, and that if we ever hoped to master airbrakes WE students had to THINK and apply LOGIC to retain proper system operation. Wow I hate to say it but once the old-guy was right on the mark. These days most logic systems are electronic and many time we are presented with fault codes to troubleshoot the electronic systems. Airbrake systems tend to not provide printed fault codes but if we apply logic and get some seasoned help the system trouble shooting tends to work well in the end. I notice that the newest trucks with advanced ABS might provide actual fault codes I am not educated enough to comment on these systems.

 

Whew..... all I know at this point is, that the new spring brake valve seems to make my life much better for the last few hundred miles.

 

Happy travels,

 

Mike, Carol. & Dolly the paint-horse

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