924Board.org

[wdem]

Just acquired a 1979 924 with 4-lug wheels. Back brake cylinder was leaking, so rebuilt both back drum brakes. Went to refill/bleed the system and was going fine until the Front Right. Constantly blowing air. Skipped and was successful with the Front Left. Was using pump and release, method, so switched to Motive pressure bleeder -- same result when going around the car to all wheels. When all bleeder valves shut, Motive will hold the 10 pounds, and take over 10 minutes to drop to zero. When opening all locations, fluid flows - EXCEPT the Front Right where all the air escapes.

Figured it was the caliper, so pulled the line from the caliper, and pumped the Motive -- hard line simply spit air -- no fluid.

Read a bunch of posts and seems everyone says it is the master. That is fine, but the master has three outputs -- one to the Front Left, one to the Rear Right, and one to the tee splitting to the Front Right/Rear Left. If the Front Right is the problem, yet the Rear Left holds pressure and bleeds fine, how can it be the Master?

Thinking it is the line between the tee and the caliper, but that connection is really corroded, and worried about damaging the rear hard pipe.

Any suggestions? Is the line being the issue a crazy thought? I even squirted everything with soapy water to try and induce some bubbles -- nothing. Starting to wonder if this new purchase might turn into a garage decoration!

[924RACR]

That's a strange one.

We too have struggles every time we bleed the RF on our '79 - but it's been converted to 5-lug and so has a bit different line routing... and the problem is different, not blowing air.

I struggle to think that there's some failure whereby you are legitimately blowing so much air at the one corner, without other symptoms. Does the pedal now just drop to the floor? When you apply pressure - either with the Motiv or with a foot - does the RF brake lock up? Do you not have brake fluid leaking on the floor somewhere?

Seems like the only way you could have air coming out of not only the caliper but also the hose is that your MC reservoir is dry on that circuit and you are pushing air, not brake fluid, through.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Mclaren924]

Make sure the back reservoir is full of fluid as it only has a tiny little spill over at the very top of the shared divider where fluid can enter the rear. AKA you got to basically overflow the front to get the rear full. The brakes on these are always annoying as hell if air gets into it somehow. I've had to pull the reservoir and bleed each chamber manually with plastic tubes to get air bubbles un stuck. I would also recommend cracking open the Tee fitting and making sure its getting fluid past there, I've also had an air bubble trapped in there too. Lots of rust pen oil and have two good wrenches to evenly apply pressure to get the Tee off, even better if you have a mate hold the tee dead straight and you try taking off the line. Ultimately if it brakes, the tools and parts would be around 50-100$ and you could have new SS or Nickle copper brake lines in every corner.
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1980 931 "Salt" Bucket wannabe racer (Dreaming)
1979 924 Sebring "Pepper" -Sold
1977 924 Slicktop "Pennie"-Most likely parts
1979 3/5 gt clone 924- Shop Test Car

[wdem]

Thanks for the feedback. Was able to break the front caliper line from the tee (needed the torch to loosen). lines seem clean -- thinking the bleed on the rear left was a false reading.

Planning to look to replace the master, since no availability on rebuild kits.

Porsche replacement is $1100 and 2 months out. Hoping to source aftermarket. Any recommendations on brands that are good quality?

Also, since it is a 4-lug having issues validating the right part. I believe the proper Porsche P/N is 477-611-015A -- anyone able to help confirm? This will help find a proper aftermarket match.

[Mclaren924]

[wdem]

Looked at that post (with a bit of excitement) -- though after looking at the car again, the Master has a giant 20 stamped in the side, which I think indicates the smaller bore.

Need to find a solution to get this running at a reasonable price before Summer ends. It's a bit rough, but runs great -- now need it to stop. Still open to some suggestions. Plan to disconnect all the fittings, a complete systems drain, blowing out the hoses -- and then trying to charge again.