single "click" sound when braking hard

[tbitz]

My '78 911SC started making a sound and I just can't figure where it is coming from.

When the car is moving, if I press on the breaks slowing inreasing pressure a point is reached when I hear a "click" sound coming from the right wheel. If the pressure is released I hear a "clack". The car must be moving to get this sound.

With the car stopped, I've tried pushing down on the bumper on all four corners, but no "click" sound. I've removed both front wheels, looking for a loose caliper, but everything is tight. Removed the pads and put them back in, still click.

What could it be?

Tony

[ClayMcguill]

Ummm..is it the dime you stopped on?

Seriously, check to make sure the caliper mounting bolts are torqued correctly, and the brake pad retaining pins are inserted all the way.

[tbitz]

I check the above and it looks good. Still can't figure it out.

Tony
'78 911SC

[nhromyak]

What was the last thing you did to the front end?

Did you install a Rack Spacer kit?, tie-rods, strut tower brace, do wheel-bearings?




------------------
Nick Hromyak
'85 Carrera 7 & 9 Fuchs
Havin' Fun in Sacramento

[tbitz]

Last thing I did was replace the front left rotor. Then flushed the fluid and I change the brake fluid to ATE Blue. I used a pressure bleeding technique.

Tony
'78 911SC

[Roland Kunz]

Hello

The right rotor come losse to remember you that working on brakes should allways made as a pair !!!!!!!!!

Never work unsymetric, at least if you ain´t have ABS or a good insurance.

If you are there then look at the pads and the retainers........just a tip.

Oh btw is your rim tourqued down ?

Grüsse

[tom964]

I have the same thing in my 91 C2. It just started happening at an autocross last week. I asked one of the tech people there and was told it was probably the rear brakes setting themselves because they are worn to near the limit. I don't quite follow, but I intend to replace the rear brake pads this weekend and check everything out. I'll post next week if I learn anything new.

[Eric Coffey]

Could it possibly be a bad/sticking caliper piston, or loose/delamintated pad backing plate? Just some suggestions, I could be way off.

-Eric

[tbitz]

I replaced one rotor just before putting it away for winter. Then I replaced the other rotor just after the car was taken out of winter storage.

The wheels are torqued to 96lb*ft.

I didn't look at the rear wheels because I assumed the sound was coming from the front. I'll have a look at the rear end tonght.

The pad look OK. They are not new, but they have about 1/2" of material left. Are there supposed to be any shims between the pads and the calipers?

Tony
'78 911SC

[tom964]

I posted above saying I had the same problem and was going to replace my rear pads this weekend. Did that, and the clicking is gone. I saw no problem with the calipers/pistons. I think that the wear in the brake pads created enough play so that the piston cap would separate from the pad and then hit against it when the brake was applied.

[tom964]

Oops. I forgot to mention that the metal plate on the back of the pad was also gone.

[tbitz]

tom964,

What do you mean the meatl plate on the back of the pad was gone?

Is there supposed to be a metal shim between the brake pad and the caliper piston?

I looked at my rear brakes, and they have about 3/8" thickness of braking material left on both. I am fairly sure that my "click" sound is coming from the front.



------------------
Tony
'78 911SC

[tom964]

Tony:
My sound was coming from the right rear,which is why I focused on the rear brakes.

What was missing was a thin plate on the back of the brake pad with the part number, etc. I think the only significance of it is that it increased the play between the piston and the pad. Maybe I'm completely off, but I think it was just this play that was causing the sound.

[Nifty]

I also have a '78 SC and have just been through a similar situation. I found that if you reversed slighlty then went forward and braked you would get this noise. But if you braked again nothing.

What I discovered was that the pads are slightly loose in the calipers. When you brake the rotors grab the pads and knock them against the bottom of the slot in the calipers.

I pulled mine apart and cleaned them out. With the retaining pins out and the pads backed off you can slightly move the pads up and down. The pads are almost new and the rotors are not warped. I can't imagine that this is a problem so I have just left them as they are.