Brake failure - help!
Thread Starter
Intermediate
Joined: Apr 2006
Posts: 35
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Brake failure - help!
Hi. Need some help. Have a 76 911 Targa which is suddenly having brake problems.
I took the car out three days ago and the brakes were working fine, after driving for a while (approx 30mins) the brake pedal suddenly went to the floor and the brake warning light came on.
I was far from anywhere so I drove on slowly with minimal brakes use and then suddenly after about 15 minutes the brakes were back again.
Tried a short 10 minute run the next day the brakes worked fine.
Today I took another test, a longer run, and had exactly the same failure again. After running fine for while suddenly the pedal goes to the floor, I lay off the brakes for a while and then they are suddenly back again.
Anyone have an idea what is causing this and at which part of the brake system I should look at?
I took the car out three days ago and the brakes were working fine, after driving for a while (approx 30mins) the brake pedal suddenly went to the floor and the brake warning light came on.
I was far from anywhere so I drove on slowly with minimal brakes use and then suddenly after about 15 minutes the brakes were back again.
Tried a short 10 minute run the next day the brakes worked fine.
Today I took another test, a longer run, and had exactly the same failure again. After running fine for while suddenly the pedal goes to the floor, I lay off the brakes for a while and then they are suddenly back again.
Anyone have an idea what is causing this and at which part of the brake system I should look at?
I haddah Google dat
Rennlist Member
Rennlist Member
Joined: Nov 2008
Posts: 11,501
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From: Fresno, CA
Does your '76 have a brake booster (vacuum operated assist servo) on the master cylinder? When this happens, did you check the brake fluid level? How about now, is the level low?
Rennlist Member
Joined: Oct 2004
Posts: 20,607
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From: Bakersfield, CA, for now...
rusnak; no booster on a '76. zach is either low on fluid, or his master cylinder is dying. The car does have a dual circuit hydraulic system, so he better figure out what's wrong before he has to use a telephone pole to stop the car. Those handbrake shoes will only last so long!
Team Owner
Joined: Aug 2005
Posts: 28,418
Likes: 1,612
From: Cambridge Ontario Canada
i would say put a master cylinder in it, 4 new flexible lines since the system will be open anyway .. remove the reservoir , wash it out with warm soapy water and rinse it with rubbing alcohol or dry it over a dehumidifyer and of course put some good quality fluid in , flush it all and be on his way ..
Thread Starter
Intermediate
Joined: Apr 2006
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Thanks for all the great replies guys. Yes am not planning to drive it until I have had a good look and shifted what needs to be shifted. Two trips with my heart in my throat is enough for me 
Seemd to me like something was getting hot after I drove for a while and then when I laid off the brakes it had time to cool off, hence the return of the brake function.
Is that an incorrect assumption, or is that also a symptom of MC failure?
Seemd to me like something was getting hot after I drove for a while and then when I laid off the brakes it had time to cool off, hence the return of the brake function.
Is that an incorrect assumption, or is that also a symptom of MC failure?
Rennlist Member
Joined: Oct 2004
Posts: 20,607
Likes: 16
From: Bakersfield, CA, for now...
Heat can be easily diagnosed by touching all four wheels, and checking for a difference in temp. However, you didn't report any other symptoms (dragging/scraping noises, pulling to one side, etc., so I didn't go there). Also, as others have posted, replacing your four flex hoses, when you do the m/cyl, is critical if their history is unknown.
Pro
Joined: Sep 2011
Posts: 559
Likes: 0
From: Sparks, NV
I would agree with Peter's sentiment.
Swap the Master Cylinder with a new one (or perhaps an upgrade)
Change out the flex hoses.
And perform a complete flush with new fluid.
Swap the Master Cylinder with a new one (or perhaps an upgrade)
Change out the flex hoses.
And perform a complete flush with new fluid.
