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 > Leave the emergency(parking) brake off?

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ron.dittmer

North-East Illinois

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Posted: 09/08/17 07:42pm Link  |  Quote  |  Print  |  Notify Moderator

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.


2007 Phoenix Cruiser model 2350, with 2006 Jeep Liberty in-tow


ron.dittmer

North-East Illinois

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Posted: 09/08/17 07:47pm Link  |  Quote  |  Print  |  Notify Moderator

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.

pnichols

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Posted: 09/08/17 10:36pm Link  |  Quote  |  Print  |  Notify Moderator

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!

* This post was edited 09/08/17 10:44pm by pnichols *


Phil, 2005 E450 Itasca 324V Spirit

tatest

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Posted: 09/09/17 06:09pm Link  |  Quote  |  Print  |  Notify Moderator

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.


Tom Test
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Matt_Colie

Southeast Michigan

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Posted: 09/10/17 08:23am Link  |  Quote  |  Print  |  Notify Moderator

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


Matt & Mary Colie
A sailor, his bride and their black dogs going to see some dry places that have Geocaches in a coach made the year we married.


pnichols

Santa Cruz Mountains

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Posted: 09/10/17 09:13am Link  |  Quote  |  Print  |  Notify Moderator

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

Chum lee

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Posted: 09/14/17 11:56am Link  |  Quote  |  Print  |  Notify Moderator

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

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