Leave the emergency(parking) brake off?

[rbrand]

I had a brake caliper seize heading up Vancouver Island. I had it replaced at OK tire in Duncan. Excellent service had me out in an hour.
The fellow that I was dealing with said that if an Motorhome is left sitting for a extended period of time. It should be left with the parking brake off. This will help prevent the brake caliper from seizing up.

I've never heard of this.

What are your opinions?

[Chum_lee]

The last 4 German cars I've owned had brake systems manufactured by ATE/Teves. All the brake fluid reservoirs had fluid level sensors that were vented to the atmosphere. Humid or dry air was free to circulate throughout the space above the fluid level. IMO, that's where the moisture came from. The factory service manuals clearly said in bold letters "CHANGE BRAKE FLUID EVERY TWO YEARS" as does my Ford F53. It's your choice. Ever price an ABS unit?

Chum lee

[pnichols]

Matt ... from what you say above, DOT 4 is about the right compromise. I try to use that as much as possible.

[Matt_Colie]

klutchdust wrote:
I have wrenched my entire life. I have changed brake fluid only when the repair called for it, be it a broken line or whatever. My question is this,what has changed in the brake fluid industry that some feel the need to replace their fluid. One of my vehicles i owned for over 25 years, it stopped just fine and had no indication of fluid losing it's ability to work properly.
Recently a friend told me the quick lube stores are recommending it to customers.

OK Klutchdust,

I can tell you what changed. Vehicles changed. You have had the same vehicle for 25 years. Before that vehicle was built, the life of a passcar or light truck brake system was maybe 5 years (I one was lucky). The typical passcar was scrapped at something around 100K and a rare one made it to 15years. (They only had odo that went about that far.)

Not counting the antique coach which is a choice, the two passcars in the family are both seniors. The "new" one is 16yo and still under 200K. Mine is 22yo and is way over 200k (the odo broke 5 years back).

Brake fluids DOT 3 & 4 are both HIGHLY HYDROSCOPIC. It will soak up all the water it can get. A typical disk/drum system can even let some (a molecule at a time - but it adds up) in through the seals at the pistons. In long term testing, we found brake fluid with over 4% moisture in systems that had no other deficiency and had been properly maintained. There was still no corrosion to be found anywhere in the system.

The problem then gets to be the fact that the water depresses the boiling point. With DOT 3 fluid, this can get bad real fast.

What about DOT 5??
That has a very high boiling point and does not absorb any moisture.
Sounds good - Right? Problem:
Moisture can still come in through the seals. But, now it is not absorbed by the brake fluid. It can pool in the bottom of cylinders and corrode them.

As you can see, it is your call. I have access to an instrument that reads the moisture content of the brake fluid and if I find any, I flush the system.

Matt - retired Detroit engineer

[tatest]

Parking brake likely has nothing to do with your caliper seizing. The motorhome sitting with the brakes unused is the most likely cause.

My E-450 does not use the disk brakes for parking, there is a small drum brake on the tail of the transmission. My E-350 (and most light trucks with rear disk brakes) uses small drum parking brakes inside the rear disks.

I've had one car that mechanically tightened the rear calipers with a lever attached to the cable, but have not encountered one that used the hydraulics for parking.

[pnichols]

We once owned a 1969 Class C motorhome built on the GMC 3500 chassis that had the opposite issue: It had an automatic transmission - that for some reason by design - did not have a park gear at all. All it had was an emergency brake!

[ron_dittmer]

ernie1 wrote:
He had a 1989 Buick Riveria which had parking brakes that involved a mechanism that engaged the piston in the caliper each time it was set.

The Pontiac Fiero parking brake had that setup, and I worked on many of them. Strange but recently I ran into a foreign car, maybe a Honda, maybe a Toyota, with that same parking brake design. It is a bad design. The best parking brake is the mini cable-driven drum brake inside the rotor.

[ron_dittmer]

Moisture in brake fluid is visual. It almost always settles in calipers and wheels cylinders because water is heavier than oil. It looks a bit milky during the bleeding process. And "yes" water in the brake lines can do damage. But moisture is usually an issue with vehicles left outside in humid environments. Not in desert regions, and not if stored in a dry garage.

[ernie1]

Once upon a time I was working on the transmission of my 1974 Oldsmobile Cutlass Supreme and while I had the pan off gazed at this little round piece of metal that was maybe 3/8" in diameter and was shocked to learn that that was the parking pawl. REALLY?

Then there was the idiot who was stuck at the marina where he had loaded his boat back onto his trailer but couldn't get it out of park because he had rolled down the ramp and when the trailer was in the right position, slammed the shift lever into park without setting the parking brakes. What a fool.

Of course there was my neighbor who "never uses the parking brake". "What for?" This is the same person that complained long and loud that a brake job cost him +$800 (35 years ago) because the calipers had to be replaced each time (this happened twice). He had a 1989 Buick Riveria which had parking brakes that involved a mechanism that engaged the piston in the caliper each time it was set. Turns out if one doesn't use the parking brakes, the caliper piston corrodes in place and the brake pedal gets lower and lower.

[ScottG]

At the most, that parking pin is about the size of a carpenter pencil and usually much smaller. I have seen many broken.
It isn't meant to hold the MH or any type of vehicle especially on any kind of incline.

Also, you should set the parking brake FIRST and then put it in park so there's on load on the pawl and so it wont bind.

[rhagfo]

time2roll wrote:
I am amazed how many think the invention of the parking pawl was to make the parking brake obsolete. Most seem to think it is just a Federal mandated 'emergency brake' that no-one actually needs to use.

"Why does the transmission make that 'bang' when I pull it out of park on my sloped driveway"

X2!! :S
Using Just the transmission parking pawl, to hold a motor home on any surface is just crazy!
I have a manual TV and two automatic cars, I set the parking brake on all three every time!

I think at one time or another all the car makers have issues recalls for automatic transmission not fully engaging and popping out of park and rolling and causing damage, injury or even death.

[time2roll]

I am amazed how many think the invention of the parking pawl was to make the parking brake obsolete. Most seem to think it is just a Federal mandated 'emergency brake' that no-one actually needs to use.

"Why does the transmission make that 'bang' when I pull it out of park on my sloped driveway"

[Chum_lee]

time2roll wrote:


My test is to put transmission in neutral. If it starts to roll set the parking brake. After you verify the parking brake is holding the vehicle then put transmission into park.

BINGO!

Then, ALWAYS take the transmission out of park (to put it into drive or reverse) before you release the parking brake just prior to taking off.

Chum lee

[ScottG]

garyemunson wrote:
All that retracts disk pads is what little axial runout exists in the rotor.

The rubber seal for the pistons are designed to roll slightly and then roll back when pressure is release. That is what causes the pistons to return and allow the pads to retract.

[Sam_Spade]

Fulltimers wrote:

My car has over 160,000 miles on it and still has the original brake fluid.
What's the problem?

Well THAT swings the pendulum of obsessive behavior in the OTHER direction.

Are you really saying that during all of that 160k miles it has never needed any major brake work ? Really ??

I subscribe to "If it ain't broke, don't fix it." so I don't change brake fluid until some other major brake work needs to be done.

P.S. In 1972 my Dad bought a new GMC pickup. When I got it, about 2005, it had EVERYTHING ORIGINAL, including tires with low mileage. Just about the time I decided to catch up on the neglected maintenance, a friend let it run low on oil and it threw a rod.

Just because people occasionally get away with stupid stuff like that doesn't mean that it is a good idea.