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Old 12-22-2004, 08:34 AM   #1
Rivet Master
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1978 31' Sovereign
Texas Airstream Harbor , Zavalla, in the Deep East Texas Piney Woods on Lake Sam Rayburn
Join Date: Jan 2003
Posts: 2,435
Images: 292
Chevy Chassis Brake System

Just to give all of you P-3X S&M dudes (you all know who you are) a "heads up" on one more thing to watch out for...

When driving back from the Blanco Rally, I just pulled into my street when the "Brake" idiot light came on.

I still had brakes - just a bit hard to apply.

Jacked up the front end, installed the safety jacks, and took off the two front wheels (I'm getting pretty good at this by now) - found the "front" reservoir bone-dry and found the leak to be the curb side brake bleeder - upon inspection there is a circular "cut" (3/4 of the way around) on the bottom of the failed bleed valve - almost as if I over-torqued the valve and the seat cut into the valve.....don't know for sure the mechanics of the actual failure. I use a wrench about 6" long for all of the brake bleeding work, so it's hard to imagine that my carpel tunnel affected wrists could screw up ANYTHING with only a 6" wrench.

Replaced the bleed valve with a new one, bled the fronts, re-set the combination proportioning valve, replaced and torqued the front wheels, and hit the back streets for a test drive. BTW, the test route navigated the 345 to the local Mega Lo Mart where I took on a considerable number of gallons of 87 Octane at $1.449 per gallon. Don’t think I will ever see gasoline at that price again.

Interesting thing - the proportioning valve - it actually performs 3 functions:
a.) metering valve
b.) warning switch
c.) proportioning

…. and I did not think I had one! It (the valve) is hidden within the front crossmember - took a lot of touchy-feely to determine that it was actually there - the reason I was looking for it was I KNEW there were no electrical connections to the master cylinder, and yet I had the idiot light come on - so I knew there was a brake/electrical interface that I was not aware of.

I had assumed previously that the two pressure outlets from the master cylinder went only to the front and rear systems respectively - learned something new….one of my “Christmas gifts” to myself came in handy – a genuine paper set of 1986 Chevy Light Truck Service/Repair Manuals…off of e-bay. Most of the time understanding what the manuals are trying to say is a bit of a chore for me, but this time it was explained simply enough (interpretation – there were a LOT of pictures and diagrams) that I was able to follow along.


"Suck it up, spend the bucks, do it right the first time."

WBCCI # 1113
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Trailer '78 31' Sovereign

Living Large at an Airstream Park on the Largest Lake Totally Contained in Texas
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Old 12-22-2004, 01:51 PM   #2
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1986 34.5' Airstream 345
Louisville , Kentucky
Join Date: Feb 2003
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Now that we know you own the manuals you better ask a moderator to increase the number of messages allowed in your PM inbox.
Steven Webster
1986 Airstream 345 Classic Motorhome
AIR 1760
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