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Old 06-12-2020, 09:34 AM   #1
Mini-Skoolie
 
Join Date: Jul 2019
Location: Asheville, NC
Posts: 42
Year: 1988
Coachwork: GMC
Hydraulic brake SQUISH

Hey all, never dealt with a brake system issue before, fingers crossed this one is at least somewhat of an easy fix.

So I was testing my new tachometer last night. Just letting it warm up, testing the idle a bit, nothing crazy. However, when I turned the bus off, I noticed that the brake pedal was extremely squishy. It’s, of course normally extremely firm when the bus is off. (Can’t press it all the way down at all)

But this time I could press it all the way to the floor for some reason. Sounded “wet” when I pressed it down slowly. Surely a leak, right? Well there doesn’t seem to be any obvious leaks underneath.

Just seems to have depressurized completely. The reservoir tank is nearly completely empty. It was behaving absolutely normally until last night.

Again, totally new to dealing with brake issues. But what’s my plan of attack here? Brake issues definitely make me nervous.

All input is appreciated. Thanks!

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Old 06-12-2020, 09:55 AM   #2
Bus Crazy
 
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Join Date: Aug 2019
Location: Moved to Zealand!
Posts: 1,517
Year: 2002
Coachwork: Thomas
Chassis: Freightliner FS-65
Engine: 7.2L Cat 3126 turbo diesel
Rated Cap: 71 passenger 30,000 gvwr
If the res was full and now it ain't obviously it (the fluid) went somewhere...

1) where it went is problem one
2) running the res empty has NOW introduced air into your system making for an additional problem of it's own.

How long has the bus been sitting?

I'm guessing you have a vacuum booster/ power brakes?
Remove the line from the booster and see it it's wet inside? It should be dry.
If the booster is leaking it will suck (and burn) the brake fluid into the engine.
https://axleaddict.com/auto-repair/B...-Booster-Check


First top up the system and bleed the brakes. You need to get back to 'working' before you can get to testing...
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Old 06-12-2020, 11:05 AM   #3
Bus Crazy
 
Join Date: Feb 2019
Location: New Hampshire
Posts: 1,349
Year: 1990
Coachwork: Thomas 4 window w/lift
Chassis: G30~Chevy cutaway
Engine: 5.7/350 Chevy Vortec
Rated Cap: Just me and my "stuff"?
Could be a few things, (master cylinder, caliper(s), wheel cylinder(s) or brake line(s).
Refill your master cylinder reservoir. have someone pump the brake pedal while you lay underneath looking at all 4 wheels and the brake lines that feed the calipers or drums.

The fluid doesn't simply evaporate from the reservoir, there's a leak somewhere.

If the above is beyond your comfort level, you'll need to call in professional help.

Good luck, and let us know how this goes...
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Old 06-12-2020, 11:58 AM   #4
Bus Crazy
 
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Join Date: Oct 2017
Location: Virginia
Posts: 2,324
Year: 1971
Coachwork: Wayne
Chassis: International Loadstar 1700
Engine: 345 international V-8
Quote:
Originally Posted by banman View Post
If the res was full and now it ain't obviously it (the fluid) went somewhere...

1) where it went is problem one
2) running the res empty has NOW introduced air into your system making for an additional problem of it's own.

How long has the bus been sitting?

I'm guessing you have a vacuum booster/ power brakes?
Remove the line from the booster and see it it's wet inside? It should be dry.
If the booster is leaking it will suck (and burn) the brake fluid into the engine.
https://axleaddict.com/auto-repair/B...-Booster-Check


First top up the system and bleed the brakes. You need to get back to 'working' before you can get to testing...
Yup good advice.
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