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novice brake questions
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B
Aug 25, 2012, 8:00:52 PM8/25/12
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'87 944
some general novice questions about brakes:
* is there a trick to getting the pins to line up the holes with the clip when installing them?.. or should they be able to rotate by grabbing the end? (mine are very corroded).
* I flared out the end of a pin (is very corroded). any trick to getting it out - even with bolt cutters? it seems it will not go through the caliper easily, and if it does I suppose it would damage it.
some general novice questions about brakes:
* is there a trick to getting the pins to line up the holes with the clip when installing them?.. or should they be able to rotate by grabbing the end? (mine are very corroded).
* I flared out the end of a pin (is very corroded). any trick to getting it out - even with bolt cutters? it seems it will not go through the caliper easily, and if it does I suppose it would damage it.
Bill
Aug 26, 2012, 3:33:43 AM8/26/12
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with kroil and let it sit for a bit. once you get it out, clean up with
a file.
non-corroded pins can be rotated pretty easily - just put a stiff wire
into the hole and turn it to the proper alignment
B
Aug 26, 2012, 10:53:21 PM8/26/12
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On Sunday, August 26, 2012 3:33:43 AM UTC-4, Bill wrote:
> use a punch and a hammer to drive the corroded pin out,
I went and bought a new punch. what a difference.
> use a punch and a hammer to drive the corroded pin out,
> once you get it out, clean up with a file.
which leads me to this nugget I discovered at the Pelican Parts or Rennlist forums: the pins turn out to be almost identical to the pins from a 1994 Toyota T-100 4WD, which are usually available at the local parts shop (unlike the 944 variety). the clip is not at all identical. there are small differences between the pins, but the diameter and length is the same - it goes clean through the caliper, and the clip fits the pin hole.
* I assume that the pins either are held by the large clips or else they need hatch clips or cotter pins - mine had only the clips.
> non-corroded pins can be rotated pretty easily - just put a stiff wire
> into the hole and turn it to the proper alignment
as for more novice brake questions: AFAIK the inner pad is removed first, then the outer. anyways, some trouble next:
The inner pad material in my case is partially corroded into orange dust/cracked mess. the pad budges, but that's it. I pressed the pad against the piston with channellocks, but they barely move. the brake fluid reservoir was open, so I figure no pressure is behind it. I tried a number of screwdrivers to pry the pad out, on top of various pliers, but this pad isn't moving much. perhaps there is a sticky backing, but I can't see. any suggestions appreciated how to get this out.
I am also suspecting the caliper went bad. the other pad looks like plenty of friction material is still there. what are the signs of a bad caliper, and how long a job is rebuilding one?
Bill
Aug 29, 2012, 12:00:53 AM8/29/12
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change fluid every other year at least. you will probably find that you
need to change both master cylinders, the clutch slave, and rebuild all
4 calipers.
unbolt caliper and pry the whole thing off the disk, then take it apart
and rebuild or replace.
B
Aug 29, 2012, 11:51:32 AM8/29/12
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* what parts of the installed caliper should move, e.g. by prying or pushing with any given tool?
* what type of lube should be used for rebuilding a caliper?
* I read that the piston can be removed using an air compressor or by hand (!?) - any other way?
* what type of lube should be used for rebuilding a caliper?
* I read that the piston can be removed using an air compressor or by hand (!?) - any other way?
Bill
Aug 29, 2012, 9:50:03 PM8/29/12
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and reading the Porsche manual?
B
Aug 30, 2012, 8:13:30 PM8/30/12
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On Wednesday, August 29, 2012 9:50:02 PM UTC-4, Bill wrote:
> I can keep answering questions, but have you actually tried downloading
> and reading the Porsche manual?
one thing I am confused about is in vol III, 46-3, step 5. there is an arrow in the picture to - IIUC - indicate motion of the mounting frame (part 5 in the diagram on 47-1). the caption on 46-3 reads:
> I can keep answering questions, but have you actually tried downloading
> and reading the Porsche manual?
"[press] out floating caliper frame until brake pad protrudes out of pin on floating caliper frame."
... however, reading it again just now, I think this might be for the "pin" - which I will have to look at on the caliper again, I guess some sort of tab that is in the pad. any clarification appreciated.
BTW, I found a bunch of stuff on caliper rebuilding at Rennlist, etc. but for 968's, and 911's, but they say it is very similar. one question that persists though is if just the pistons can be purchased anywhere - i.e. is the only way to get a new piston by buying a new caliper?
thanks again,
-Bryan
B
Sep 1, 2012, 6:42:54 PM9/1/12
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OK, I gave up on this job.
however, I mentioned Toyota pins, which I read about at the following link:
http://forums.rennlist.com/rennforums/924-931-944-951-968-forum/303662-brake-pad-pins-interchange-with-toyota-pickup.html
the thread claims they will "interchange". this is not true. The interest in these pins is that they are of course inexpensive, but readily available at a local store, and you do not have to buy a larger kit with all the clips and stuff for around $70.00 (for instance). I'd like to add to my previous comments about this.
while the diameter is the same as measured with an inexpensive caliper, and the
pins and retaining clip appear to assemble acceptably, that's where the similarities end.
there are at least three problems. (measurements are not accurate - only by "eye"):
1. the length is about 10mm longer, which means the holes for the clip
do not line up along the caliper edge. this leads to
the clip being bent out - or worse, you move the pin in.
either way, the pin is not sitting the way it needs to.
2. on the Porsche pins (from what I can tell on a corroded pin) have
for about 3mm long under the head, a raised (1mm or less) section.
this section appears to sit between the outboard pad and the inboard
caliper mounting frame edge. the Toyota pins do not. the consequence
of this is unclear to me.
3. the head edge on the Porsche pin is about 1-2mm larger diameter
than the Toyota pin. this edge sits on the mounting frame outboard
edge. the consequence of this is unclear.
-Bryan
however, I mentioned Toyota pins, which I read about at the following link:
http://forums.rennlist.com/rennforums/924-931-944-951-968-forum/303662-brake-pad-pins-interchange-with-toyota-pickup.html
the thread claims they will "interchange". this is not true. The interest in these pins is that they are of course inexpensive, but readily available at a local store, and you do not have to buy a larger kit with all the clips and stuff for around $70.00 (for instance). I'd like to add to my previous comments about this.
while the diameter is the same as measured with an inexpensive caliper, and the
pins and retaining clip appear to assemble acceptably, that's where the similarities end.
there are at least three problems. (measurements are not accurate - only by "eye"):
1. the length is about 10mm longer, which means the holes for the clip
do not line up along the caliper edge. this leads to
the clip being bent out - or worse, you move the pin in.
either way, the pin is not sitting the way it needs to.
2. on the Porsche pins (from what I can tell on a corroded pin) have
for about 3mm long under the head, a raised (1mm or less) section.
this section appears to sit between the outboard pad and the inboard
caliper mounting frame edge. the Toyota pins do not. the consequence
of this is unclear to me.
3. the head edge on the Porsche pin is about 1-2mm larger diameter
than the Toyota pin. this edge sits on the mounting frame outboard
edge. the consequence of this is unclear.
-Bryan
B
Oct 14, 2012, 12:38:32 PM10/14/12
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can the brake wear sensor wire harness be replaced without removing the fender (on the passenger side)?
... also, I assume the BWSWH is fried from the heat - any suggestions how to repair it - I figure I have to sit with the multimeter and chase down breaks in the wire.
-Bryan
p.s: thanks Bill for your helpful comments last month - I was out of internet contact for a while.
... also, I assume the BWSWH is fried from the heat - any suggestions how to repair it - I figure I have to sit with the multimeter and chase down breaks in the wire.
-Bryan
p.s: thanks Bill for your helpful comments last month - I was out of internet contact for a while.
.
Oct 14, 2012, 4:26:30 PM10/14/12
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specific plastic they used at the time - but I haven't seen the wires
actually go bad - why do you think the harness is bad? if you don't see
bare wires, you can just sleeve it and leave it alone. if memory
serves, there is a left and right harness that come together in a
connector on the right side in front of the battery. You certainly
don't need to remove the fender.
by the way, email me (using the address on my web site, wbnoble.com) - I
have about 1/3 of an original manual (the pages I removed when I updated
it years ago) for sale cheaply - these pages would really help you, I think.
B
Oct 14, 2012, 8:12:24 PM10/14/12
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On Sunday, October 14, 2012 4:26:33 PM UTC-4, . wrote:
> the rubber outer jacket of the harness fails with age due to the
> specific plastic they used at the time
can you recommend a replacement? I think 3M has some tape-based products.
> the rubber outer jacket of the harness fails with age due to the
> specific plastic they used at the time
> why do you think the harness is bad?
brake pad warning light remains lit even with new wear sensors.
they worked for many years. the wires always had some duct tape around them from the previous owner where they emerge from the fender into the engine compartment for an unknown reason. also the tubing (if there was any) is mostly crumbled off and gone.
> certainly don't need to remove the fender.
-Bryan
B
Oct 19, 2012, 2:57:01 PM10/19/12
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On Sunday, October 14, 2012 4:26:33 PM UTC-4, . wrote:
> why do you think the harness is bad?
I will investigate this later, but for sure the brake pad warning light can be off when the car is started, but will light after the car has moved a slight bit, and always by the time the car is moving along at normal speed.
I am wondering if this actually suggests that any of the other sensors are just faulty, instead of the harness wires jiggling around and cutting out.
can any of the wires be connected to bypass the light - i.e. turn it off while bypassing the warning function?
B
Oct 21, 2012, 12:58:20 PM10/21/12
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do the vibration damper plates need to be removed prior to removing the pads?
.
Oct 23, 2012, 2:43:49 AM10/23/12
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On 10/21/2012 9:58 AM, B wrote:
> do the vibration damper plates need to be removed prior to removing the pads?
>
now that you have a manual, the procedure is detailed in there - not
> do the vibration damper plates need to be removed prior to removing the pads?
>
sure what you mean by vibration damper plates - once you pull the two
rods out and compress the piston back into the caliper, you remove the
pad being pushed on by the piston, then slide the caliper and remove the
other one.
B
Oct 23, 2012, 8:58:43 AM10/23/12
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How high a PSI compressor might be needed to force some badly stuck pistons out?
.
Oct 23, 2012, 8:43:52 PM10/23/12
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On 10/23/2012 5:58 AM, B wrote:
> How high a PSI compressor might be needed to force some badly stuck pistons out?
>
my compressor runs at 160 psi - i think if the situation is as you
> How high a PSI compressor might be needed to force some badly stuck pistons out?
>
describe, I'd attach the caliper back to the brake system and pump the
brakes to force the piston out. if you are going to use air pressure,
put a thin piece of wood into the caliper so you don't damage it or the
piston when it breaks free. you can also use a hydraulic hand pump for
this purpose, or a spare brake master cylinder held in a bench vise.
B
Oct 26, 2012, 2:39:37 PM10/26/12
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what's the thread pitch and M# (or diameter) for the brake hose that connects to the caliper?...
.
Oct 26, 2012, 8:51:59 PM10/26/12
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On 10/26/2012 11:39 AM, B wrote:
> what's the thread pitch and M# (or diameter) for the brake hose that connects to the caliper?...
>
I don't know actually.... but I may have some of the connectors - I
> what's the thread pitch and M# (or diameter) for the brake hose that connects to the caliper?...
>
think they are standard, you could just take the caliper to an auto
parts store and buy a short length of tubing with the proper fitting.
B
Nov 7, 2012, 3:51:22 PM11/7/12
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OK, I have to ask:
Can brake cleaner go all over the caliper, including the seals? I.e. just "hose it down"?
Can brake cleaner go all over the caliper, including the seals? I.e. just "hose it down"?
B
Nov 9, 2012, 1:47:29 PM11/9/12
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IIUC:
I have noticed there are single-piston floating frame calipers that either have "Ate" or "Porsche" cast onto the edge. I do not know if there are others.
who actually made these calipers, and what is the difference - i.e. are they truly interchangable?
...
a different question:
IIUC the surface of the piston that contacts the brake pad is not a flat surface - there is a discontinuity. is this where the 20 degree angle tool is supposed to fit so the angle is correct?
I have noticed there are single-piston floating frame calipers that either have "Ate" or "Porsche" cast onto the edge. I do not know if there are others.
who actually made these calipers, and what is the difference - i.e. are they truly interchangable?
...
a different question:
IIUC the surface of the piston that contacts the brake pad is not a flat surface - there is a discontinuity. is this where the 20 degree angle tool is supposed to fit so the angle is correct?
.
Nov 22, 2012, 1:51:32 AM11/22/12
to
in the piston is what you align to 20 deg - I made a tool out of scrap
metal for this purpose. The reason for the angle is to reduce squeal
and grabbing.
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