Air in brake lines..

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j par

j par

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I seem to get- consistently get air in my front brake lines..?? Gravity bleed the front and the pedal comes back up... Fine for a couple of drives and then let it set for a little bit and mushy pedal again...
The proportioning valve is the obvious first culprit as I always seem to have a drip of fluid hanging off of it...
With what happened to me with a customer's car yesterday I have suspicions about the master cylinder as well... ??..
 
j par said:
I seem to get- consistently get air in my front brake lines..?? Gravity bleed the front and the pedal comes back up... Fine for a couple of drives and then let it set for a little bit and mushy pedal again...
The proportioning valve is the obvious first culprit as I always seem to have a drip of fluid hanging off of it...
With what happened to me with a customer's car yesterday I have suspicions about the master cylinder as well... ??..
Click to expand...
I think you diagnosed it. Prop valve if it's dripping. Master if it is dripping or is damp as well.
 
j par said:
I seem to get- consistently get air in my front brake lines..?? Gravity bleed the front and the pedal comes back up... Fine for a couple of drives and then let it set for a little bit and mushy pedal again...
The proportioning valve is the obvious first culprit as I always seem to have a drip of fluid hanging off of it...
With what happened to me with a customer's car yesterday I have suspicions about the master cylinder as well... ??..
Click to expand...

Just a FYI, if your valve leaks fluid out it will leak air in easier.
 
TrailBeast said:
Just a FYI, if your valve leaks fluid out it will leak air in easier.
Click to expand...
I'm hoping I can just tighten the lines a little better. I'm in fear I'll have to get New lines and would rather do that with the engine out of the way...
 
Used/old fluid will retain minute air bubbles that will eventually manifest as a squishy pedal.. if you are still having issues after you tighten up the lines, it's possible a fluid change is in order. Also, gravity bleed may not get all of the air out.. I would go as far as saying it rarely does.
 
lilfontleroy said:
Used/old fluid will retain minute air bubbles that will eventually manifest as a squishy pedal.. if you are still having issues after you tighten up the lines, it's possible a fluid change is in order. Also, gravity bleed may not get all of the air out.. I would go as far as saying it rarely does.
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The fluid is pretty good it doesn't get used very much at all. And I have a tendency to bleed the brakes more often than most so it gets recirculated pretty well. And again I gravity bleed them and the brakes are fine. I use it a couple times and then let it set for a while and the brakes are not fine...
 
Reminds me a of a customers car. GTO the judge. Kept comming back with air in the system. Finally discovered a tiny crack in a caliper casting. Never saw fluid wetness there. It was the little rust spot that gave it away.
 
Rear drums are adjusted? Mine kept doing what you describe, took them apart and the adjuster was laying on bottom of the backing plate/drum. But yea leaks are no bueno.
 
So again it seems to be the problem is with the front brakes. I had my wife do the old pump pump hold...(the breaks funny guys).. I started on the passenger side and sure enough lots of air and foamy brake fluid for came out clear..
Driver side some bubbles for nothing play passenger side. What should the brakes were hard again... also I'm kind of suspicious of that line catching a lot of heat being as it is routed right behind the hot engine...
 
j par said:
The fluid is pretty good it doesn't get used very much at all. And I have a tendency to bleed the brakes more often than most so it gets recirculated pretty well. And again I gravity bleed them and the brakes are fine. I use it a couple times and then let it set for a while and the brakes are not fine...
Click to expand...

It doesn't matter how much the fluid gets used, it matters how old it is. Brake fluid absorbs water from the air. The older it gets the more water it has. Even more true if you have a brake system that is pulling air from somewhere, that air has moisture in it.

j par said:
So again it seems to be the problem is with the front brakes. I had my wife do the old pump pump hold...(the breaks funny guys).. I started on the passenger side and sure enough lots of air and foamy brake fluid for came out clear..
Driver side some bubbles for nothing play passenger side. What should the brakes were hard again... also I'm kind of suspicious of that line catching a lot of heat being as it is routed right behind the hot engine...
Click to expand...

The heat shouldn't be that big of an issue unless it's touching something. Decent brake fluid should withstand temperatures upward of 500°. Just the Summit Dot4 I use has a boiling temp of 572°. Below that you shouldn't be getting air bubbles unless you have a leak, or water contamination. If the fluid is old and has absorbed water, well, suddenly heat is an issue.
 
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