Sticky Porsche Front Caliper

[1990C4S]

The front right caliper on my 89 cab has dragged for years. Sometimes it's minimal, but if I jack up the car I can feel way too much rotation resistance. If I pry the caliper open the drag goes away.

It is not a 'closed off' flex line, I replaced the lines with new braided SS hoses a year or two ago. It is not lack of lubrication on the top slider pins, they are fine. It is not old brake fluid, I have bled the brakes a half dozen times, the fluid is clean and clear.

What's left? New seals in the calipers? That's sort of the last thing I can think of.

[GH85Carrera]

Just spray it all down with WD 40!

When in doubt about the calipers, send them to PBM for a rebuild. They take them completely apart, plate them and rebuild them and they come back looking new.

I have rebuilt my calipers in the past, and after over 150,000 miles they looked terrible. PBM sent them back looking like new, and rebuilt.

[masraum]

I don't have an answer for you, but it sounds like "new seals in calipers" is the last thing left (assuming the likelihood of a problem with a hard line or the proportion valve is super low)

[911 Rod]

I would have started with rebuilding the calipers.

[Jeff Higgins]

Originally Posted by 911 Rod

I would have started with rebuilding the calipers.

Absolutely. This is the first thing to do when a caliper starts hanging, not the last. The caliper pistons and their bores in the caliper body corrode. Brake fluid is hydroscopic, meaning it attracts water, which is what leads to this corrosion.

And no, those are not "slider" pins that go through the tabs on the tops of the pad backing plates and into the caliper body. They only serve to keep the pads from falling out, the pads do not "slide" on them. There is a great deal of clearance between the slots in the pad backing plates and these pins, the pads rattle around pretty freely on those pins. There should never be any "lubrication" of any kind on those pins.

Rebuilding calipers is pretty darn easy and the rebuild kits are pretty darn cheap. The only real problem can be getting those pistons out of their bores. Most of us use compressed air through the bleeder port, some pump them up with a grease gun.

[jhynesrockmtn]

PMB is usually the answer on calipers. They have done several sets for me, both 911 and 914. You may have a bad seal or a bit of rust on that caliper. I would do them in pairs or send all 4 in.

https://pmbperformance.com/

[911 Rod]

Sort of funny story. My front wheel was locking up under very heavy braking. I was trying to figure out what was wrong with the brake when I realized it was perfect. It was the only one working!

[1990C4S]

Originally Posted by 911 Rod

I would have started with rebuilding the calipers.

I did them a few years ago, the car might have 2,000 miles since then. But it's the next thing to try. Again.

[Jeff Higgins]

When you rebuilt them, did you lube the pistons, bores, and square cross section bore seals with a suitable grease? Ate and PMB both supply what you need. It's also important to thoroughly remove any corrosion and pitting from both the pistons and the bores. PMB can also supply stainless steel pistons. My son and I just installed a set on the rear "L" calipers on his '68.

[gregpark]

PMB. I'll bet they have the caliper for an '89 already rebuilt and sitting on the shelf. Simple swap and a two day turn around time. I had to wait a month for mine to be re-built but they did it right

[porsche930dude]

Its almost always just the outer 1/8" or so of the bore that gets rusted before it gets to the seal. just have to sand it down. Never sand the piston. If it is bad you have to replace it. New seals and fluid and your good. Always use new fluid especially when you are filling the whole system like that. I used opened fluid once in my jeep and it killed the brake cylinders in a matter of months.

[Tidybuoy]

Originally Posted by GH85Carrera

When in doubt about the calipers, send them to PBM for a rebuild. They take them completely apart, plate them and rebuild them and they come back looking new.

I have rebuilt my calipers in the past, and after over 150,000 miles they looked terrible. PBM sent them back looking like new, and rebuilt.

PMB rebuilt my calipers and after that, I could push my '74 into the garage with just a finger. I had trouble sitting still at a red light without keeping a foot on the brake. Point is, all dragging stopped and the brakes worked and looked great. Very reasonable pricing too.

[1990C4S]

Originally Posted by Tidybuoy

PMB rebuilt my calipers and after that, I could push my '74 into the garage with just a finger. I had trouble sitting still at a red light without keeping a foot on the brake. Point is, all dragging stopped and the brakes worked and looked great. Very reasonable pricing too.

I was hoping to avoid a rebuild, shipping and parts are a problem for me. I will order parts and do them over the winter I guess, seems like I can't avoid it.

Thanks to everyone who gave the answer I didn't want, but needed.

[1990C4S]

Caliper has been repaired. It was very difficult to get one of the pistons out, I has to resort to the grease gun. No corrosion, just tight.

All cleaned up, no longer dragging.

Thank you for pointing me in the right direction.

[Tobra]

You knew what you needed to do, just not keen on doing it

[A930Rocket]

On the 911 or 930s, are the pistons coated with any kind of material? I’ve always used fine wet and dry sandpaper with brake fluid to smooth the pistons and bores.

[1990C4S]

There's no coating. I the bores are very difficult to clean, unless you separate the caliper, which I wanted to avoid.

The pistons are just ground to size, I cleaned mine up with steel wool. I was expecting to see some rust spots, but it was very clean.

[GH85Carrera]

Originally Posted by 1990C4S

There's no coating. I the bores are very difficult to clean, unless you separate the caliper, which I wanted to avoid.

The pistons are just ground to size, I cleaned mine up with steel wool. I was expecting to see some rust spots, but it was very clean.

I rebuilt mine once. The advice on the board was don't split the calipers as it is a difficult task to get the back together properly. My rebuild was good, but the old calipers were really getting ugly. I had PBM rebuild them, and they do split the calipers, the plate the calipers, and they come back looking and working like new.

The hardest part of rebuilding them is getting the piston angle rotated just right. PBM does it right.

[Bill Douglas]

I heard about this guy with a 911SC. He swapped out the front callipers for a new set and put them on upside down. In other words the right hand one on the left side. Couldn't figure out why he couldn't bleed them. Fool.