questions about my car. Stuck calipers, headlights etc Options

[dabird]

I'm 5 days in as a 914 owner and I have a couple of questions.

1. My headlights have a mind of their own when you turn them on off. The just continue to flip up and down for about 30 seconds before finally settling in the up or down position. sometimes the do it together. sometime only one side. My first thought is a ground issue but maybe someone else has had the same issue and knows the cause?

2. My biggest issue with the car is the rear calipers are dragging. I was told the parking brake was stuck when I got the car but it appears that pistons are stuck dragging against the rear rotors. The cables for the parking brake are moving the levers but you cannot get the car to budge in neutral with the parking brake on or off. I plan on getting rebuilds from PMB but after hearing that a lot of 914's are rolling around with inoperable rear brakes, I'm wondering if i can back the pistons off with the adjusters and be able to drive the car in the meantime?

3. I've found someone near me parting a 72. I'm interested in a few parts and I'm wondering how much difference there is between the two? Will the front valance from a 72 fit on a 74? I'm assuming all the lenses (turns, tails etc) are the same?

Here she is tucked safely in her new home

[dabird]

I was thinking about my brakes while driving to work today. Since my pistons are dragging against the rotors it makes sense that the cause could likely be internal swelling of the soft brake lines. I'm thinking a way to test for this would be to open the bleeder and that should release the pressure and allow the pistons to slide back....does that seem like it would work?

[Mblizzard]

I was thinking about my brakes while driving to work today. Since my pistons are dragging against the rotors it makes sense that the cause could likely be internal swelling of the soft brake lines. I'm thinking a way to test for this would be to open the bleeder and that should release the pressure and allow the pistons to slide back....does that seem like it would work?

This is a new concept to me regarding lines swelling which I have a hard time visualizing. If you think of brake fluid as an uncompressible fluid it basically performs like a rod that transfers the force you put on the pedal to the piston in the caliper. You get a force multiplication by the fact that the psi you put on the pedal is increased by the surface area of the piston.

Others may have more experience with this but unless the lines have completely swelled shut, I would find it hard to see that the rubber wall could hold back sufficient pressure to keep the piston pressed against the rotor indefinitely. I would think that the pressure would have to return to an equilibrium point after a certain amount of time and the pistons would move back. If that was not happening then opening the bleeder screw would release the pressure if it was present. Worth a try.

But I bet if you do it that wont be the problem. There is a procedure for setting the clearance on the pads but as stated earlier if the pistons are stuck they are stuck.

I would get a bunch of brake fluid and flush the system noting the condition of the fluid that comes out. If it is dirty and full of grit then you can be pretty sure internal corrosion is your problem.

[stugray]

I was thinking about my brakes while driving to work today. Since my pistons are dragging against the rotors it makes sense that the cause could likely be internal swelling of the soft brake lines. I'm thinking a way to test for this would be to open the bleeder and that should release the pressure and allow the pistons to slide back....does that seem like it would work?

This is a new concept to me regarding lines swelling which I have a hard time visualizing. If you think of brake fluid as an uncompressible fluid it basically performs like a rod that transfers the force you put on the pedal to the piston in the caliper. You get a force multiplication by the fact that the psi you put on the pedal is increased by the surface area of the piston.

Others may have more experience with this but unless the lines have completely swelled shut, I would find it hard to see that the rubber wall could hold back sufficient pressure to keep the piston pressed against the rotor indefinitely. I would think that the pressure would have to return to an equilibrium point after a certain amount of time and the pistons would move back. If that was not happening then opening the bleeder screw would release the pressure if it was present. Worth a try.

But I bet if you do it that wont be the problem. There is a procedure for setting the clearance on the pads but as stated earlier if the pistons are stuck they are stuck.

I would get a bunch of brake fluid and flush the system noting the condition of the fluid that comes out. If it is dirty and full of grit then you can be pretty sure internal corrosion is your problem.

The calipers work by having a tiny amount of "kickback" that is provided by the elastomer gaskets on the piston.
Under normal operation the pressure pushes the piston towards the rotor, and when you let off, the force of that rubber elastomer pulls the piston back the few thousandths that keeps the pads from dragging on the rotor.
It does not take much back pressure to keep the piston from pulling back.
The symptom of my problem was that after a long highway drive, you would go to use the brakes and they would go to the floor until you pumped them.
I finally checked and found after a long drive that one of the front wheels was really hot.
The brake was dragging and after a long time, it would boil the brake fluid creating a "gas pocket".
I rebuilt the front calipers three times to try to solve the problem and couldnt figure it out until I tried to purge the lines by pumping them with no calipers installed.
The side that was dragging would barely trickle out while the other side would shoot fluid 10 feet.

I replaced the lines and the problem went away.