Porsche 356C Brakes

[Doug McDonnell]

Eric From comment #15 "After a few minutes I noticed that the brake pedal was not returning after being pressed , it was staying partially down and causing pressure." The brake pedal will only act this way if 1.the pedal assembly bushing for brake is bad Causing binding 2. The Brakepedal assembly arm is positioned so that the spring isn't applying correct force or 3. Spring is bad. The hoses, calipers, master cylinder etc are all separated from the pedal cluster. Tom Keating Am I correct ?

[Tom Keating]

Doug, You are pretty much correct. I get the feeling the brake pedal is the culprit. The spring may not be seated correctly or just plain weak. If the 1mm is set with the pedal buffer not present it may also not help setting it. "Usually" the bushing is not bad but factory grease may still be in it which does not help. I recommended to Eric that he take apart the set & redo the brake part of it. Also clean up the clutch cross shaft. That has to come out to work on the brake pedal. I did send Eric the correct length of the brake rod in case he may have incorrect one. Tom

[Eric McKinley]

I removed the pedal assembly and tore it apart and gave it a good clean and re-grease.
The large spring appears to be strong, the pedal returns to the start after every press when bolted to the bench and tested, I will replace the spring anyway.
I had replaced the rubber buffers previously.
The actuating rod length was way out, 140mm as opposed to what it should be, 130mm, how would you know that you have the correct clearance (1mm)
The other half of the actuating rod which enters the M/C was the correct length, I think Tom mentioned this should be 65mm, I would have to check, however it was the correct length that Tom said it should be, I also gave this a good polish.
I placed everything back in the car to see if it makes any difference to the pedal, I have more forward motion now when I press the pedal, before the brake pedal was very solid with very little movement forward, I think the 10mm difference in the rod length has made some improvement to the feel of the pedal, I have yet to drive the car yet to test it.

I have the wheels currently off the car and the car on stands, when I turn the hub by hand it makes a shhh sound, I get a rotation before it stops, the callipers are rubbing lightly on the discs on all four wheels, is this normal, I am guessing that after driving the car for a period this will wear down slightly and no longer happen.

[David Jones]

Eric, if you push on the brake pedal with your hand you should be able to feel when the rod contacts the piston plunger. The 1mm slop is amplified by the leverage ratio, but can be felt when you push the pedal down with your hand.
As soon as the wheels turn the brake rotors will push the pads back because they are never perfectly parallel, what you feel is normal.

[Eric McKinley]

Update on this.

I reduced the actuating rod to the correct length of 130mm as mentioned earlier, however due to the weather was unable to test until today.

I took the car for a drive today, everything worked well, no smell of burning brakes, the wheels were not hot to the touch after driving, see it appears reducing the rod by 10mm worked.

Thanks for all the help guys.

[Michael Moss]

If you dis assemble your master cylinder make sure the valve at the end of the spring has a hole in . This allows the line pressure to release so the calipers can retract. I read in a Girling manual its the flexing of the square o rings that actually retract the caliper pistons.

[Al Zim]

I was brought to task early in this post regarding my evaluation of your situation. I still is somewhat of a mystery what is happening to your brakes! Start from the beginning and carefully look at everything. We do in house caliper building because our supplier did not properly clean he inside of the caliper when they were rebuilt. Not stopping is a serious situation!

[Eric McKinley]

Thanks Al, I appreciate everyones input, different takes are helpful.

I think I got to the bottom of the brakes, I am no expert in brakes however I had them rebuilt by the guys that rebuild Roger Brays brakes, they came back looking like new.

It appears it was my fault, I did not measure the actuating rod, I didnt realise how important it was, 10mm can make a huge difference to it working properly and having all 4 brakes rubbing, and heating the wheels to the point were you cant place your hand on them because they are too hot.

[Doug McDonnell]

Dual master cylinder takes a different length rod than the original single master cylinder. That may have been most of your problem.

[Eric McKinley]

Thanks Doug,

I didn't fit a dual system, may do it down the road though.

[Eric McKinley]

I took the car out for another drive today, drives really well.

I have encountered another issue, I was expecting problem after problem during the shakedown so this is coming as no surprise.

I drove for about an hour and parked up, when I tried to restart my journey and place the car into reverse, there was resistance getting it into gear, grinding when being placed into gear, concerning as I do not want to cause damage to the gearbox.

I waited for a moment and it slipped into gear, however it happened again a short time later.

Any ideas what may be the issue.

[David Jones]

Adjust the clutch cable, it has probably stretched just enough to allow the 1st motion shaft to keep spinning. No synchro in reverse to slow it to a stop.

[Eric McKinley]

Thanks David, that sounds like an easy fix.

Would you have a picture of the location I should adjust it, should I be making the cable slightly tighter.

Its been a while since I placed the clutch cable and I have forgotten all the adjustment areas.

[David Jones]

Eric I would adjust the bowden cable at the trans bracket, a half to one turn should suffice. It is more difficult to adjust it at the clutch lever arm end and taking up the floorboard to do it at the front is even more hassle.

[Geoff Fleming]

Adjust the clutch after the car has been driven a bit of a distance rather than doing it 'cold'.