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> Brake issue: is it the master cylinder ?, first noticed this yesterday-
DRPHIL914
post Jun 24 2013, 09:47 AM
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75 914 2.0, have had the car 4 years, no braking issues- only put about 5,000 miles on it.

Ok, have not been driving the car much, last drive was a month ago, took it out for a spin last night, 30 minute drive. almost home , and i notice as i go into a corner and brake, i have to pump several times , first time pedal goes all the way down. this occurs again the next 2 stops before getting home.

- i check and fluid level is at 100%, and i can not find any leaking (IMG:style_emoticons/default/confused24.gif)

so seems like it must be a master cylinder issue, yes? any way to confirm besides just replacing the MC?

Thanks, Phil

Part 2 of this would be, if it is - what would be recommended?- i am getting ready to put on the 5 lug conversion and 5 lug fuchs, have not decided whether to upgrade the calipers while i am at it or not. Discussed ths with Eric, and since it is a casual cruiser with the occasional spirited twisting road drive, he recommended to stay will stock calipers , but a pad upgrade. - so no need to change to a 911 MC then, right?

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sean_v8_914
post Jun 24 2013, 10:09 AM
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yes
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stugray
post Jun 24 2013, 10:10 AM
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I had this happen to me on a 914.

After a long drive, you would press the brake and have nothing.
You would have to pump it to have brakes again.

It turned out (after two caliper rebuilds) that the flex lines were old and the liners begin to swell.
This blocks the flow from leaving the caliper when you release the pedal.
Then that brake gets so hot it boils the brake fluid in the stuck caliper.

Replace the flex lines and see what happens.

Stu
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sean_v8_914
post Jun 24 2013, 10:43 AM
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please do not "fix" the brakes. restore the brake system. please don't go cheap or be lazy when it comes to stopping.
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DRPHIL914
post Jun 24 2013, 11:00 AM
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Normally if t the flex lines swell, and i saw this on my truck, the caliper on that side will be slow to grab but then slow to let go, pulling to that side. I have not seen this, so my feeling is it is more likely a pressure/MC issue. however i will dig thru the receipts to see if those had been changed out by a P.O. and if not the lines will get changed at the same time as the MC.

so we will be fixed, or er.. ah... i mean "restored" (IMG:style_emoticons/default/biggrin.gif)
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mepstein
post Jun 24 2013, 12:08 PM
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New pads. New flex lines. New 17 mc. Money well spent
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stugray
post Jun 24 2013, 03:23 PM
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QUOTE
please do not "fix" the brakes. restore the brake system


So from now on we should not try to diagnose the problem... just tell them to call Eric for a full restoration?

The point of your post is lost on me.

A bad master cylinder does not give you bad brakes unless it is leaking (leaves evidence).
The problem I experienced (and fixed) had zero leakage, but the same symptoms as the OP... (IMG:style_emoticons/default/confused24.gif)

SO we should not try to "fix" the brakes when one component fails anymore? Just "call an expert"??

Stu
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SUNAB914
post Jun 24 2013, 03:34 PM
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Pull the pedal board and see if there is any leaking, report back.
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TheCabinetmaker
post Jun 24 2013, 03:41 PM
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Not so stu. A master cylinder can leak internally with no visible evidence.
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r_towle
post Jun 24 2013, 03:47 PM
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Have you checked the rear venting?
Set that right before you throw money at the system.
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stugray
post Jun 24 2013, 04:19 PM
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The symptom that solved it for me was:

Long drive on the highway with minimal braking: one front wheel (left) was hot to the touch. And there was evidence of the bearing grease leaking out.

This meant stuck caliper. That is why I first tried to rebuild the caliper.
While rebuilding the left caliper, I noticed that almost zero fluid leaked out of the line.
The right caliper just dripped and dripped.
One press on the pedal with the left caliper removed and I still had pressure?!? while just a dribble came out.

Replaced flex lines and problem was gone.

Now I know that a stuck caliper (piston) is less likely than a bad flex line.

Stu
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