89 911 - Dragging Calipers

1990C4S · 09-17-2021, 04:32 AM

I am 99% sure my front calipers are 'sticking' on my 89 911 cab. I still need to jack the car up and do a manual rotation test, but I can feel it dragging, and the car is very difficult to roll by hand on a flat surface.

I had this issue years ago, to the point where the brakes got very hot on a long-ish drive and I lost brake pressure briefly. I thought I had solved it by replacing my flex lines, but the problem appears to be back.

The car sits a lot, and only gets driven about a dozen times every summer.

Should I do a caliper rebuild now? I'm not sure hat causes the problem, and the internet searches haven't lead me anywhere useful.

hcoles · 09-17-2021, 04:51 AM

I had this on my 89. I replaced all the brake hoses. Now I don't have it.

hcoles · 09-17-2021, 04:55 AM

I should add more info. I wouldn't say I had "dragging". One of the fronts would squeal just a bit after coming to a stop and I let off of the brake pedal. Under normal rolling I don't think my brakes were dragging as the runout would push the pads back. Your issue sounds a bit different.

GH85Carrera · GH85Carrera's Garage

Yea, old hard brake hoses can be a real drag.

Replace the hoses if you don't know for sure when they were replaced last.

1990C4S · 09-17-2021, 04:58 AM

I replaced the 'old' factory lines with braided stainless three years ago...they might be the problem. But it seems unlikely to me. I could be wrong.

masraum · 09-17-2021, 05:14 AM

Presumably you flushed the fluid. It couldn't hurt to flush again (brake fluid being hydrophilic).

If you don't know the last time your calipers were rebuilt, that wouldn't be a bad idea since you know the flex hoses were relatively recently replaced.

vash · vash's Garage

I had that.

Brake lines. They swell on the inside so fluid can’t back out. - or something.

Geronimo '74 · 06:09 AM

Quote:

Originally Posted by 1990C4S

The car sits a lot, and only gets driven about a dozen times every summer.

Should I do a caliper rebuild now? I'm not sure hat causes the problem, and the internet searches haven't lead me anywhere useful.

I had the same issue.
Rebuilt calipers and fresh brakelines solved it.
How's your pedal feel? reduced travel?
If the car sits a lot, I'd check the calipers too, not just the brakelines.
Piece of mind and all that.

Also, this should be in 911 tech.

speeder · speeder's Garage

Quote:

Originally Posted by GH85Carrera

Yea, old hard brake hoses can be a real drag.

Replace the hoses if you don't know for sure when they were replaced last.

You can always know for sure when they were last replaced, (on any vehicle), because they have a date stamp on them in several places along the hose, as well as "DOT" and other markings.

Most cars on the road are running their original, factory hoses.

masraum · 09-17-2021, 07:25 AM

Quote:

Originally Posted by speeder

You can always know for sure when they were last replaced, (on any vehicle), because they have a date stamp on them in several places along the hose, as well as "DOT" and other markings.

Most cars on the road are running their original, factory hoses.

Wouldn't the date stamp on the lines be the date of manufacture?

And the OP said that he replaced his 3 years ago with braided steel lines, so may not see date stamp.

speeder · speeder's Garage

Quote:

Originally Posted by masraum

Wouldn't the date stamp on the lines be the date of manufacture?

And the OP said that he replaced his 3 years ago with braided steel lines, so may not see date stamp.

Yes, date stamp of manufacture. That's close enough for me. On original hoses, they will closely match the date the car was built. Easy to tell original hoses.

On braided steel lines, they have a clear or colored plastic sleeve on them with the markings, including date of manufacture, (month/year), and "DOT," etc.. Anyone running non-DOT lines on a street car is beyond ignorant and opening themselves up to massive legal exposure in the event of a catastrophic traffic accident. Always pay a few bucks more for DOT hoses.

speeder · speeder's Garage

Quote:

Originally Posted by vash

I had that.

Brake lines. They swell on the inside so fluid can’t back out. - or something.

Yep, the inside of the hose can swell over time to the point where it either doesn't let fluid past or even worse, turn into a *check valve* where it only allows it to pass or flow in one direction. It's fortunately rare but catastrophic if it occurs. I change the hoses on every older car I work on if they are more than about 12 years old.

hcoles · 09-17-2021, 09:08 AM

Quote:

Originally Posted by speeder

Yes, date stamp of manufacture. That's close enough for me. On original hoses, they will closely match the date the car was built. Easy to tell original hoses.

On braided steel lines, they have a clear or colored plastic sleeve on them with the markings, including date of manufacture, (month/year), and "DOT," etc.. Anyone running non-DOT lines on a street car is beyond ignorant and opening themselves up to massive legal exposure in the event of a catastrophic traffic accident. Always pay a few bucks more for DOT hoses.

DOT hoses are supposed to pass a whip test. Not an easy test to pass. I'm not sure how to confirm the hoses you might buy are certified. I get the OEM or ATE hoses and I'm then fairly certain the design will pass the test.

speeder · speeder's Garage

Quote:

Originally Posted by hcoles

DOT hoses are supposed to pass a whip test. Not an easy test to pass. I'm not sure how to confirm the hoses you might buy are certified. I get the OEM or ATE hoses and I'm then fairly certain the design will pass the test.

The initials *DOT* are stamped on the hoses, that's how you can tell. It's not an optional requirement. I'll see if I can dig one up and post a picture.

hcoles · 09-17-2021, 11:29 AM

This is an interesting thread....
"DOT approved" stainless brake lines?

1990C4S · 09-17-2021, 11:43 AM

Quote:

Originally Posted by Geronimo '74

I had the same issue.
Rebuilt calipers and fresh brakelines solved it.
How's your pedal feel? reduced travel?
If the car sits a lot, I'd check the calipers too, not just the brakelines.
Piece of mind and all that.

Also, this should be in 911 tech.

The pedal feels perfect.

I'm going to do an inspection this week. Might be time for hoses, a caliper rebuild, and a flush before winter.

Zeke · 09-17-2021, 12:30 PM

I've been here a long time and absorbed voluminous amounts of info. If you don't use it, it goes pretty deep in the brain and hard to recall. However, it seems to me that some SS Brake hoses made for similar problems. The advice from Grady Clay and others of that ilk (IIRC) was to go back to using OEM rubber hoses.

vash · vash's Garage

Quote:

Originally Posted by Zeke

I've been here a long time and absorbed voluminous amounts of info. If you don't use it, it goes pretty deep in the brain and hard to recall. However, it seems to me that some SS Brake hoses made for similar problems. The advice from Grady Clay and others of that ilk (IIRC) was to go back to using OEM rubber hoses.

your memory is fine.. that is exactly how i remember it.

red-beard · red-beard's Garage

Quote:

Originally Posted by vash

I had that.

Brake lines. They swell on the inside so fluid can’t back out. - or something.

This was a common issue on the 914's at the 30 year mark. Your 911 is a 30 year old.

And it is a poopy head!

red-beard · red-beard's Garage

Quote:

Originally Posted by speeder

Yep, the inside of the hose can swell over time to the point where it either doesn't let fluid past or even worse, turn into a *check valve* where it only allows it to pass or flow in one direction. It's fortunately rare but catastrophic if it occurs. I change the hoses on every older car I work on if they are more than about 12 years old.

Again, when I was playing with the 914s in the late 1990's, early 2000's, they were hitting 30 years old. This was a common problem. They acted like check valves.