Boston Driver’s Notebook 6/9/12

8 06 2012

The Five Month Brake Job -Part 1

I was coming back from a white Christmas at nephew Aaron and Echo’s house when I first heard the noise.  Echo came from what used to be known as a “mixed marriage,” as well as what used to be called a “broken home.”  As a result, she generally entertained her black family one year and her white family the next.  The white Christmases were much more restrained than the black Christmases, which were way more entertaining.

Clyde the Barrow

Getting back to the noise, it was a little ‘thunk’ when I applied the brakes, coming from the rear passenger-side wheel. 

Uneasy, I decided to pull the wheel the following Sunday.

What followed was a Shackletonesque slog into the heart of winter, and many long and pointless hours were wasted.  All of which I will now report in exhaustive detail.

It had been a very temperate autumn and winter, so far.  The Sunday when I went outside to check the brakes was another story, cold and windy.    I went back inside and put on another layer.  I put a sheet of reflectix (bubble wrap and mylar insulation) that I had scavenged from the curb on trash day down on the ground, and pulled off the brake drum.

There’s no Reflectix like Trash Day Reflectix

The drum came off filled with oozy oil, which clearly would increase the lag time before the shoe applied friction.  It was just what it soundled like, a delayed grab, followed by a ‘thunk’ as the brake finally engaged.

It should not look like this

I made an assumption at this point that the wheel cylinder had failed, and the seals therein were leaking.

When your foot presses the brake pedal, a mechanical linkage depresses a piston which displaces the brake fluid within the master cylinder.  That displaced fluid transfers the force via the brake lines to the slave cylinders, also known as the wheel cylinders, in the rear wheels.

More wisdom from the machine shop wall:  “An assumption is the mother of every (foul) up.”



The blank-faced girl in the imitation parts store kept returning with brake pads for the front disc brakes, rather than the brake shoes I requested for the rear drum brakes.  Keeping in mind the shortness of daylight, and tiring of such sport, I went over to the other imitation parts store, where I was able to purchase the imitation parts that would fit my blue Toyota truck, Clyde Barrow.  I returned home with four brake shoes, two brake hardware kits, two wheel cylinders and two new small bottles of brake fluid.  It was already mid-morning, and I had a decent amount of work to do before the short winter  day came to an end.


Brakes Have Such As Shoes?

The job went along with surprising ease, until the fateful moment when I had that thought that all I needed to do now was to bleed the brakes, and then could move on with my life.  As soon as the thought crossed my mind, I knew something bad would happen to punish me for such flights of optimism.

Angel of Retribution

There are various methods of bleeding brakes, the most basic of which consists of having an assistant pump up the brakes and then hold down the pedal, as the wheel cylinder bleeder is opened and the air and aerated fluid is forced out.

The more sophisticated method is to connect a rubber line to the bleeder and dunk the free end in a bottle of brake fluid.  This allows the air to flow out of the bleeder valve, but prevents air from being drawn back in as the brake pedal is released.


One-Person Brake Bleeding                                                                                                    Fluid in the jar keeps air from being drawn back into the system.

After bleeding the rear brake system several times, including the LSPV, the Load-Sensing Proportioning Valve circuit that my little Toyota truck had in common with big, real trucks, I had a lower brake pedal than before.  As the name implies, the LSPV uses a sensor to determine the deflection of the rear springs, and increases the proportion of braking performed by the rear wheels.

Load Sensing Proportioning Valve LSPV
Increases rear braking as load is applied to truck bed
A snorkledepth photo

I was using the jar method, pictured above, to bleed the brakes, and I quickly determined that the shallow threads in the cheap castings of the wheel cylinders were allowing air to be pulled in around the bleeder valves.  I figured this out after removing one of the wheel cylinders and checking out the bleeder.  There was almost no thread in the bleeder valve hole.

This is Not Ideal

This wouldn’t have been an issue for the Usual Driveway Mechanic (UDM) who has an assistant pump up the brake pedal, and then maintain pressure as the UDM opens and closes the bleeder valve.  In the solo method I was using, a vacuum is created inside the system as the pedal is released between pumps.

Fluid Forced In- Pistons Forced Outward

At this point, I removed both sets of brakes shoes and both wheel cylinders.  I cleaned up the original castings, and rebuilt them using the new pistons and seals from the crappy new wheel cylinders.  I noticed that the original pistons were made of a brass alloy, where the new pistons were made of rough cast iron.  I saved the old pistons, then spiked the new castings into the trash can, getting a small amount of value from them thereby.

Quoting Charlie Paradise, I said, “We’ll just store these in the trash.”

Charles of Paradise @ Walden Pond

It was getting dark as I finished replacing the wheel cylinders and shoes once again.

The temperature was falling like it wouldn’t ever warm up again, as I tried to bleed the brakes, but there seemed to be nothing but air in the lines.

Enough for One Day
Jackstands are under frame, and jack is under differential.

The next morning I should have gone to work, but my truck was not going anywhere.  All that day and the next, I poured brake fluid through the master cylinder and bled it from the back brakes: passenger side  wheel cylinder, driver’s side wheel cylinder, and the ever-popular load sensing proportioning valve bleeder.  The volume of air in the lines had absolutely vapor-locked the rear brakes, and I pictured a thin trickle of brake fluid sneaking past the atmospheres of air malingering in the cold steel lines.  All the while, I’d been using the tubing-into-bottle method of solitary bleeding.

This Much Air in the Braking System

Wednesday promised to be the coldest day of the season so far, with highs in the twenties, so I thought I’d call a friend to try the two-person bleeding method, where one person pumps up the pedal.

then the ground mechanic opens the bleeder valve while the cab mechanic keeps pressure on the pedal until the bleeder is closed off again, so as not to draw in more air as the pedal is released.  I was hoping the pressures built up in the system while it was pumped up would be enough to make the difference and expel some of the air.

It Got this Warm

The friend arrived with a stack of chemical boot warmers and a thermos of hot coffee.  I was putting myself on the hook for a return favor of the highest degree, on the order of helping to move a glass piano or being in a wedding party.  The cab of the truck was cold enough, and he had to keep a window rolled down a bit to hear my instructions.  As cold as it was in the cab, it was much colder on the ground, and the wrenches burned my fingers as ice cold hydraulic fluid ran down my wrists.

I’m sure used brake fluid causes birth defects in the State of California.  Luckily I had already been born, and was freezing my butt off in Massachusetts.

I alternated the three bleeding sites for the morning hours.

A Friend Indeed

A Friend In Deed

The front and rear brakes are two separate closed systems, so that a leak in one set of brakes will not compromise the other set.  Before about 1967, there was a single master cylinder, and if there is a leak anywhere, there instantly are no brakes.

I’ve been on that ride, and it’s a once in a lifetime experience.   Twice in a lifetime for me.

And that’s not counting the black ice.

“People may or may not live. The crazy never die.”
Hunter S. Thompson photo: Annie Liebowitz

I could tell the front brakes were OK because the pedal would go half-way down and then stop.  If the front bleeders had been opened, the pedal would have traveled to the floor.  Since it was a heavy flow day, I bled the front system again with about the same height pedal at the end of the day.  Halfway empty or full depending upon your philosophical bent.

A More Modern Approach to the Dual Braking Split
It used to be front/rear back in the 80’s

After lunch, I bled the master cylinder fittings, and every other fitting between the master cylinder and the rear brakes.   There was a junction at the firewall, which shouldn’t have been there, but had been pieced in later by a brake hack.  There were also two junction blocks; one that split the front brakes and fed the back brakes, and one that split the rear brakes from the LSPV.  Air bled freely from all the connections.

Finally the friend had begun to grumble like the Huns at the Battle of Stalingrad, and we declared the two-person method DOA.

He promised to return the next day with a vacuum pump, the final method yet to be tried.

Make Your Own Vac. Pump @                                                                                                                Brake Fluid Pumps are My Bag, Baby.

I called in missing at work again, and the friend came by with the vacuum pump.  After a couple of hours of vacuuming, there was the hint of a brake pedal which got a bit higher each time, until finally we were in business.  I had saved $50 on my inexpensive parts, but it had cost me a week of work.

What are popularly called “opportunity costs.”

The next day the pedal was a bit mushy, but definitely there.  I applied the pedal on the way home from my one-day work week, and heard the slight clunking noise again.  I smiled at the sublime nature of life and the myth of Sysiphus and what not.

Rolling Stones. The Hard Way.                                           photo:

The Five Month Brake Job, Part Two

I lived with the clunking for a couple of months until I had to panic stop for a texting suicidal jay-walker, which brought home the fact that I was braking with three wheels only.

FAILboat photo

I pulled off the passenger side wheel that had the clunk, and the drum was full of brake fluid again.  I suspected the new seal from the cheapy chineesy wheel cylinder which I had used to rebuild the original casting after extracting it from the cheesy cylinder casting, which you may recall had been stored in the trash.  I assumed I had either nicked the new cheap seal, or it had never been any good to begin with.  I was underemployed that week, so I parked the truck and ordered a pair of original equipment wheel cylinders, supplied by the Aisin corporation to the Toyota corporation.

Made in the Middle Kingdom

When the slave cylinders arrived, I was glad to see they were made in the USA.  It wasn’t just patriotism that swelled my heart, it was also the knowledge that we make reliable parts here.  Mexico is getting better, and Japan has had it together for a good while.

China and India are lagging behind on quality.  It’s also nice to know that no jailed orphans have been harmed in the manufacture of the part, before their fingers wore out and their organs were harvested.

Fei Tsui Leopards

The Chinese are capable of the highest grade of handwork, as their jade carvings will attest.  Right now though,  China is the best expression of lassaiz-faire winner-take-all capitalism on the planet.

Slash and burn, keep moving, take no prisoners… Ask no questions, tell no lies.

Scorched earth and production for use.  You may want to wait a few days before you breathe much air.

Feed the baby some melamine and forget about it…  It doesn’t build long-term customer satisfaction.

Original Equipment. What I’m Talkin’ About

In less time than it took to write that rant, the parts arrived, and I replaced the wheel cylinder, which involves unhooking the main tensioning spring connecting the two shoes to each other.  It takes a large set of vicegrips and a serious pull.  If it doesn’t lift off the post on the first or second try, you have to rest up, if you’re like me.  Re-assembly is a similarly good time.

Let Me Just Deliver these Fridges, and I’ll Get that Mainspring for You

That’s the heavy lifting component of replacing the brake shoes, and since I had some brake shoes in stock, I got rid of the fluid-soaked brake shoes, that were only a month old.

A friend had given me a new set of brake shoes when I had been driving my old truck, the Death Tuna.  They had been too modernistic for the 1986 Death Tuna, but fit nicely on the 1988 Blue Barrow.  Sometimes it pays not to store parts in the trash.  I somehow remembered that I had them, at the right moment, and was able to locate them in the basement of perdition.

Death Tuna, RIP

When the clunk returned the next week, I was not dismayed.  If you have no taste for the bitterness of endless failure, you should just lease a new BMW.  Rehab is for quitters, as the saying goes.

My new feeling was that it was a rear axle seal that was allowing gear oil from the differential past to contaminate the brake shoes.  I had sniffed the contaminated brake drum, and it hadn’t smelled of gear oil, which is that smell that automotive repair facilities smell like.  But it had been cold out, and I may have missed it.  PV=nRT  with temperature antithetic to vapor pressure.

All this knowledge was not enriching me.

Katie C. photo

The seals wear out as a result of the bearings wearing out, so you always replace both seals and bearings.

So it was on to the axle bearings, but that would have to wait for another day.



One response

30 03 2014

Hi i am kavin, its my first time to commenting anywhere,
when i read this paragraph i thought i could
also create comment due to this sensible article.

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