1978 911SC Brake Issue

[mfiazzo]

Hi All,

Thanks for reading my post. I went for a long ride on Sunday. Car was running great. I did notice the brake pedal intermittently would go down almost to the floor, the car stopped fine. I would pump the brake pedal a couple of times and the pedal would come back up to normal braking position.

When I got home, I did check the fluid. Fluid is fine. Do I have air in my lines? If so, how did it get there? Small leak somewhere?

Thanks for your help.

Mike

[BK911]

You could have air in the lines. You could also be dragging a caliper. Happened to me once and the dragged caliper boiled the brake fluid, causing a spongy pedal. Get a cheap infrared temperature gun and measure the temp on all the calipers after a short run. A dragging caliper will be hotter than the rest.

May be a good time to swap out all the rugger lines and bleed the system. If dragging a caliper, rebuild the calipers too.

[mrhaydndownes]

If you decide to replace the rubber lines, I'd recommend installing speed bleeders.

They are offered by our host, and have check valves in them so that you can bleed brakes by yourself.

Good luck

[cornernfool]

Personally, it sounds like a master cylinder going bad.

[The cap'n]

Yup. Bad M/cyl. Never hurts to replace the aging rubber lines with more of the same, especially if your brake fluid hasn't been changed every 2 years. Speed bleeders I hear are cool, but that's an individual preference kinda thing.

The Cap'n

[Trackrash]

Originally Posted by cornernfool

personally, it sounds like a master cylinder going bad.

+1

[TechnoViking]

I'm a tightwad, so here's how I'd go about it:

Bleed the brakes. It's free. You may have an air bubble in the line caused by boiling the brake fluid. If you still have problems, rebuild calipers. This is almost free. Buy the rebuild kit from Pelican.

Inspect the brake lines, replace the old rubber lines and tighten everything up.

If after all of that you still have issues, look at the master cylinder.

[mfiazzo]

Thanks all, I am going to take Vikings advice and try bleeding first. I have a vacuum brake bleeder any issue using it on a Porsche? Also what brake fluid should I use?

[theiceman]

how much is your time worth ?

put on a new M/C and four rubber lines , bleed and call it a day.

[cornernfool]

Or do it his way and replace all the front sheetmetal on that nice SC when the brake doesn't work in the first panic stop. It's the master, all the symtoms.

[The cap'n]

Originally Posted by cornernfool

Or do it his way and replace all the front sheetmetal on that nice SC when the brake doesn't work in the first panic stop. It's the master, all the symptoms.

The Cap'n chuckles in amusement and agreement at this reality based pearl of wisdom ............... Been there, seen it.

The Cap'n

[boyt911sc]

Originally Posted by mfiazzo

Thanks all, I am going to take Vikings advice and try bleeding first. I have a vacuum brake bleeder any issue using it on a Porsche? Also what brake fluid should I use?

Mike,

Do you have an air compressor at your place? I have a pressure brake bleeder you could use and if you don't have an air compressor (electric), I have the portable electric compressor too. A DOT 3 or 4 grade brake fluid would be sufficient. I also have a Motive Power bleeder but it is not as convenient and efficient as my home-made pressure bleeder. PM me if you need them.

Tony

[mfiazzo]

What size wrench do I use on the nipple? It seems like it is round with no flat sections on it. Am I missing something?

[The cap'n]

In the interest of potential liability, I think I'm gone from this discussion ...................

The Cap'n

[cornernfool]

Ya, your missing the master cylinder! Hope it's just a car you hit and not a kid.

[john walker's workshop]

don't forget to check wheel bearing free-play first. that causes the rotor to wobble and push the pads outward, resulting in a low pedal first pump.

[Targalid]

Mike,
It sure sounds like your master cylinder. As for the rounded fittings, that happens with age and abuse. You can probably loosen the rounded brake line fitting with a vice grip. Ultimately you will need to replace, or repair, the hard lines to the master cylinder. If I lived in Philly I would accept Tony's offer of help.

[emac]

Personally I wouldn't waste the time chasing all things mentioned. I say M/C is bleeding through itself.
Ernie

[BK911]

Originally Posted by mfiazzo

What size wrench do I use on the nipple? It seems like it is round with no flat sections on it. Am I missing something?

Take it to a shop.

[theiceman]

Originally Posted by boyt911sc

Mike,

Do you have an air compressor at your place? I have a pressure brake bleeder you could use and if you don't have an air compressor (electric), I have the portable electric compressor too. A DOT 3 or 4 grade brake fluid would be sufficient. I also have a Motive Power bleeder but it is not as convenient and efficient as my home-made pressure bleeder. PM me if you need them.

Tony

Tony what pressure do you use ? I made one from a garden sprayer bottle but could hook it to my compressor
.