brake callipers disassembly

[Monkey Wrench]

I haven't done this for while and never on a Porsche. I ordered some caliper seals and the dust boot for my early 85 944. it sat outside about 10-12 years or more and I can't easily turn the wheels, so I want to just sand (clean) the rotors and pads a little and free things up and make sure I'm not going to have a seized caliper later on.

I thought that since I just got it and it's an old car, rather than only bleeding, I'd just eject the caliper pistons and change the seals and I'm interested if the caliper pistons will be all rusted or not. are they chrome and susceptible to pitting?

If I remove the caliper, I should be able to eject the first one easily ( using the car's hydraulics) so there is a trick to not let that first one come right out and then it will try to eject the second one and then once both are mostly all the way out I can maybe fight it with my hands or grip it somehow and pull it the rest of the way out. if anyone knows how long they are that might be helpful to know when to stop.

once one of the pistons is out of course there is no more hydraulic pressure there are two circuits. i assume it has a dual circuit would dual circuit brakes "power" all 4 calipers?

i think these calipers only have 2 pistons per caliper but I might be wrong , I'm learning here.

Maybe in this case both can be ejected using the hydraulics.

I think then I should be able to change the caliper seals and the dust boots.
I have a bit of grease intended for brake parts, maybe I can put a smear of that grease on the calipers to lube them a little during assembly or I can use brake fluid.

is there anything else I should look for or will need? I did order the hoses 1 per wheel, but something I didn't consider is that if it has dual circuits it might have more hoses so maybe i need more than 1 per wheel.. I'm not near it now , that will or course become obvious. I think I will want to paint them, maybe I can treat them somehow to clean them up.

if it needs pads / rotors ill get to that later on.. I'd like to do this before I bleed the brakes. I ordered about a thousand dollars worth of stuff, fuel pump, filter. injector parts, rubber hoses, belts plugs, wires, cap and so on my plan for at first is for some basic maintenance that it never had.

I wanted to disassemble clean and lube the CV joints, now I learned more about rusty gas tanks and I might pull the tranny, to pull the tank and seal the tank up. I tried using POR 15 fuel tank repair kit on a couple of small gas cans at work and It seems like it would work fine, but I'll need to remove the tank and that means taking the CV joints out anyway I guess.. I did buy the 8 mm triple square bit for that.

[djnolan]

I think most models are single piston. The hard part is separating the caliper from the frame rail due to the tension spring. Dress the caliper slide rails with a small triangular file to remove burs and rust. Replace the brake hoses at the same time. Also convenient to do the front sway bar bushings and grease the wheel bearings. And bleed... Maybe struts, too?

on the rear there are shoes for the ebrake too.

[walfreyydo]

Ive always removed the caliper, drain them of fluid, and eject them using compressed air with a piece of wood or something to absorb the force when they come flying out. Not knowing how rusted and degraded your calipers are, Im not sure if this will work or not (if the pistons are badly seized).

Once out, the pistons should be inspected for any rust, pitting or damage that may interfere with a tight seal. Reassemble with lots of brake fluid for lube.

CV joints are attached to the axle shafts via a snap ring. The shafts can be reused and the joints can be replaced. If you have axle shafts with 33 splines, you can use EMPI VW vanagon joints (much cheaper and higher quality than alternatives) - Ive been using these joints for a few years now under autox conditions and they have held up. EMPI also makes these joints in chrome moly if you really want them to be bullet proof. I am not sure if an equivalent exists for the 31(?) spline shafts.

Also, I suspect having a good solid trans mount can save your axles from a lot of stress. When I first got my car, you could move the trans and it would sway around rather easily. One day I broke an CV joint cage, and not only did I replace with the EMPI joints, but I also did the trans mount urethane mod. Doing so made the trans much much more solid. Im still not sure if the joint breaking was due to the low quality axles previously installed (PO said they were from Rock Auto, yikes!) or due to the large amount of movement in the old worn out trans mount putting stress on the joints (especially during autox) but either way I havent had any issues since.

[Monkey Wrench]

I noticed that the cost of replacing the CV joint boots was pretty close to the price of complete axles and it's hard to judge the quality before ordering them. Perhaps the low price is due to low quality, have others here seen failures due to weak parts? The rock place also usually caries a variety of supplier's parts and a variety of price and quality but just for the axle parts there may be only one option available and it won't be OEM. I got Uro plug wires but the Bosche cap so it doesn't have those cheapo aluminum parts in there. if I had buckets of money Id go all OEM and spend several grand doing that, but Ill try to make reasonable choices along the way. I got the bosche fuel pump and I think it was a Mann filter, middle of the road in quality and price,

my first plan is to disassemble clean inspect , re-grease and feel for looseness. If Im taking out the axles maybe I can continue, pull the transaxle and get the gas tank out. Ill try to check the clutch measurement as described in the manual, I haven't driven it and the cost of clutch seems like it's around $1500 or so. I'm not sure if it's always necessary to do the pressure plate, I would need the throw-out bearing and clutch plate for sure. maybe I should have some bearings or seals if they will be easy to change then. axle shafts, maybe a seal or two in the transaxle?

I put in an order for about 1K and got a whole bunch of maintenance items that I thought would be a good start. Mainly things that could cause a breakdown or that I figured should be changed due to age. I plan to do all the belts , some ( most? ) hoses, all the fluids and a few other items before I try starting it. after 35 years things like taking the starter and alternator apart to clean and inspect replace bearings etc may be in order.

shocks and struts , I'll see, they wont cause a breakdown unless Its stuff like rust attacking the strut towers. I was lucky it's not very rusty. that inspires me. I can wait and see how it drives and make that a later project.

I assume a new polyurethane engine or trans mount, sway bar bushings etc might be cheaper , maybe more road noise?

the engine bay itself looks nice but everything is pretty dirty, Id like to clean the valve cover up just to make that look nice so I got a gasket. I got a new cap, wires, plugs fuel regulator and some parts to try to clean out the injectors. a new washer bottle or expansion tank might look nice but if it's intact that's fine for now. they seemed a bit expensive just for show. I have seen older expansion tanks go brittle and break though. the windshield washer bottle isnt; going to cause a breakdown.

my car doesn't; seem to have the issue with the fuel hoses running over top of the exhaust manifold. I think Ill leave that alone for now but Ill clean replace and purge all the fuel components that I re-use to make sure I dont have goop plugging the injectors on startup.

both side mirrors had fallen out and were gone and the rear view mirror detached. got the right glue for that. sun visor clips were turned to dust, I got those. It will need fresh tires as they are cracked Ill get those after when it's ready to drive. I paid 2K now I got about $1200 more in parts so far.. , not doing so bad but there is a limit to how much I can expense so i will take it in baby steps.

I figured some taking apart and greasing and things like that will help and not be too expensive. I'll be at it as I can over the summer in whatever spare time I can muster. I have no garage and it's cold out yet but I'm getting set up. I'm learning lots here and I have to thank you guys for all the great info.

mine is early 85, I don't think it has AC or power steering and I like simplicity so I'm happy about that. I'm not sure on the spline count. older style dash.

the tires on it are all p225 / 50 ZR 15 the rims all have 5 big spokes and the Porsche logo in the center. Beauty rings. they are not phone dials. I was expecting that the rear tires would be wider than the front but that doesn't seem the case. I think I have the sports seats and it has the rear bumper skirt thing that was on turbo models. It could be that some things were changed since new but it seems pretty original. I noticed some clear coat flaking, and I think the original paint may have not been clear-coat? someone repainted at least some or most of it but it looks pretty ok. I thought I might just try to wax or polish it by hand.. Ill have to learn about the right products. maybe I need a buffer or to learn more about using newer style paints. I have some experience with old style acrylic enamel. I'll just try to use a guards red spray can to see if I can fix the bumper caps as the used ones I got need some love.

I was looking into the pressure washer attachments that will add sand or grit to the water stream and wondering if maybe one of those might be ok for cleaning up parts. I've used muriatic acid and washing soda and water electrolysis before for rust and paint removal, I dont much like using muriatic acid. its pretty harsh stuff. it will take paint and clean thick parts that are iron , it will dissolve aluminum parts. I can do some spot treating with some of the autobody etches.

I'm looking for a cheap and not too hard way to make the aluminum parts look nice. some seem to use dry ice blasting bit it may take more equipment. maybe I can water blast walnut shells or something. the water blaster attachments are cheap and I have a gas powered pressure washer.

I have a little porta power hand pump that will actuate small hydraulic cylinders, maybe I can connect that to one of my used brake flex hoses and that might be a way to push the pistons out. If I need to use the car hydrauliics I'm limited because once the first one is out it's not going to push anything. air could work but I do see them leaving their holes abruptly that way.

I could fill my hand pump with brake fluid but that may be ok , I will be cleaning things up anyway and replacing the rubber seals. I made new caliper pistons before for my Volvo out of stainless , it has 3 per unit, and that worked nice but I wont do that if I dont need to it takes a bit of work to turn and polish new ones.. I haven't priced OEM ones yet.
I think so long as the bore is ok if there is a bit of rust on the pistons , well they dont really need to seal , the rubber seals do that. Ive seen others though, where the chrome was flaking off. in operation they dont travel far, but as the pads wear they do need to move properly. I was wondering if I should just bleed them and call that enough. i only saw one of the seals show up but it's only been three days, Pretty fast shippiing through fedex. one of the seals or the dust boot looked a bit crumpled up in it's plastic bag. Ill compare to others when they show up. perhaps they were stored a long time in some parts bin in a warehouse under some sort of load and being distorted. Maybe the seals were not good quality, Possible.

e-brake pads, they might not wear much if the PO didn't drive with the brake on but Ill see. Volvo's which I'm more familiar with used a similar system in their 240's and 740's with a separate drum style shoe. I've cooked them up in other cars before by forgetting to release it. in a perfect world they never see much wear because they are just used when parked.

[walfreyydo]

Alot to process in your response here so Im not sure what your questions are... Maybe try breaking your posts into smaller pieces and be more direct with your questions.

The EMPI CV joints I mentioned are high quality and much cheaper than other quality axle options. You can find them here (again, 33 spline only):
https://www.amazon.com/Empi-87-9917-Joint-Volkswagen-Vanagon/dp/B06WCZQYTK/ref=sr_1_1?crid=3KHO2O48FYBT7&keywords=EMPI+vanagon+cv+joint&qid=1677256652&sprefix=empi+vanagon+cv+joint%2Caps%2C126&sr=8-1&ufe=app_do%3Aamzn1.fos.304cacc1-b508-45fb-a37f-a2c47c48c32f

Budget axles (Rock Auto, Autozone, etc) are almost always not worth the money - they are cheap chinese reman axles and rarely hold up for a long time. On my other cars I prefer OEM used (re-packed and re-booted) over these other options.

The polyurethane DIY trans mount solution from what I have seen, has zero down sides. You would be smart to do some research on this and take a look at the different urethane mixes/rigidity options. I think I went with a 60% and it worked out well - I think this is what others recommend. No additional NVH but much better response in terms of drivetrain slack. I have noticed I can really feel the power response much better-huge difference, I guess my old trans mount was pretty bad.

If your fuel lines have not been replaced, especially the ones in the engine bay, its highly recommended you do so. They may look ok, but even a slight pin hole crack will spray fuel onto your hot manifold and poof, your car is gone. Many many 944s have been lost this way.

[Monkey Wrench]

thank you for the great info Tyler, sorry I did put too many subjects into one post, sorry for the confusion it created. Ill try to be more organized, I admit I can be a bit scattered sometimes.

I did find some good videos on assembly and in particular , making sure to retain balance by not changing parts relationships. My first plan of action will be to have a look, clean, grease and check for freeplay.

I know the engine mount is quite special and expensive for the OEM one, maybe there are other solutions that are a bit more economical. Ill have to find sources for the poly ones and compare. both poly and rubber can be formulated to different durometers, that's a measure of the rigidity basically. there is a tool with a little point and you depress it into the rubber and if the point goes deeper into the rubber, that's a softer rubber or lower durometer reading, it changes over time.

rubber hardens over time but oil can make them turn mushy too. any 35 year old chunk of rubber wiil have deteriorated somewhat just due to age, maybe poly is less susceptible to aging. rubber might work better at dampening vibrations. an example I'm familiar with it pool table cushions, the real rubber ones are made through a process of extrusion using heat and force. poly ones are basically molded and hardened by an oven to cure them. The rubber has better bounce characteristics, poly is cheaper. It's easily molded.
there are others such as nitrile ( a synthetic) and neoprene and probably many others.

I once worked in a factory where we stripped the old rubber from printing press rollers, cleaned up the cores ( steel shafts or pipes) put them in long pipes,( the molds) pumped in synthetic rubber. we had drums of different "durometers" of rubber so the formulation in that drum determined how hard it was.

We cooked that in a 400 degree oven for an hour per inch of thickness and then turned them using basically special lathes with wet belt sanders. The original rollers made of real rubber were better but may have swelled faster. the ends are attacked from the surface plus the end so they tend to swell faster than the middle and the swollen ends cause problems in that application. the main advantage of this type of "rubber" was price. a lot of machinery needs to be used to make more traditional "real" rubber parts. the poly may resist oil better than real rubber. one of the differences is that rubber is porous and it is "grippy" whereas synthetic rubber is more "slippy" probably the correct term is the measure of "coefficient of friction" how slippery a mount is probably has no bearing in the application. If its rubber used to drive something , like a belt, that's different. the high price of the OEM one is likely because they are using a rather expensive process and the parts would have limited numbers. tooling costs are probably reflected in the final price.


seeing those differences and knowing about the formulations is hard to determine from an internet picture. there is a lot of chemistry and science involved but some cheap plastic components that can be molded into shape cheaply can be a reasonable alternative, depending on their use. If you buy OEM, you probably get a good part, not some cheap plastic equivalent. I'm also not so closed as to suggest its the best alternative to always choose OEM for me when considering price and a rather tight budget.

I noted issues and resolved them in my 66 volvo, although a straight axle and different design, there are a lot of stresses put upon the axle and if it can start rotating as it puts power down to the road it also needs to be able to counter those forces and too much movement will cause bad handling and other issues. where i really noticed it in that car was in trying to drive at 5 miles an hour in traffic, in a state of accelerating and decelerating, the backlash is being punded in either direction sometimes frequently. every where there is play it ads.. you can liken that play to the swinging of a hammer, no swing, no damage, a lot of play more impact. like swinging a hammer further as compared to hammering in a restricted space. when you are putting power down to he road then there is no freeplay and less wear and movement.

that movement ads to any freeplay through all the links of the drive line and that sort of stacks together and adds up. I'm my case it was causing an uncomfortable driving experience, removing rear axle backlash helped but I think all these things are important. in hard driving it may also cause the shifter linkage to want to move about when shifting from full power to gearing down, or applying and releasing full power. obviously a track car has a lot different conditions than I will subject it to under normal road driving.
with the 944 it has a bit different linkage so maybe that comes into play within that subject.


fuel lines I'll get to., just cant; tackle all at once. I had a good conversation with a pro in this forum that can make them up nicely but I need to be able to afford them. Ive also seen some info on making them up from more common parts. Blue fittings , etc.

Ill count splines when I'm in there but I have a feeling my early 85 may be less robust than later versions. Ill learn more as I go. If I dig into comparing the correct part numbers it can probably be defined that way.

in my job I work on a lot of new equipment and old equipment and I often see bad bearings from Chinese factories that fail in short order. I always try to replace them with more recognizable brands NSK, FAG, etc, usually the bearing suppliers can offer a range in price and the cheapest ones are no bargain because ill be back in doing the same work again. If I have a machine apart and see "china" stamped into the bearing shields, I try to replace them then. I do believe there are parts that one is wise to stay away from.

The quality of boots and seals for a caliper. I got cheap aftermarket ones, uro brand, they may or may not be of the finest quality and the labor to change them all .. it's possible the best decision there is to use OEM and chuck or return the cheapo seals. I got sun visor clips, cheap, mine were turned to dust, I'm ok with those, happy to get something economical to replace them with.

i got a few hoses and belts, often I'll chose "Gates" brand. I see the name often and its familiar. I would not be surprised if a lot are made in China. probably still better than using 35 year old rad hoses etc. I noted there were some hose kits available with molded silicone, maybe they are better. they seemed more common for models newer than mine. some may like the bright colors. Ill try to keep mine fairly original.

[walfreyydo]

In terms of the fuel lines, I would prioritize the ones coming from the fender well to the fuel rail. These costed me approximately $150-$200 (cant remember) from a guy on the 944 Facebook groups (Devin Lyons). The lines to/from the dampener costed me another $100. Total price was about $250-300 (but well worth it). These were AN converted lines, not OEM.

The other lines running back to the tank can be left alone (unless they are leaking) for now.

There are a few DIY threads out there on Pelican and Rennlist on the late/early trans mount urethane mod. Super easy albeit potentially a bit messy if you are not liberal with the tape!

[Monkey Wrench]

Thanks Tyler. I'm learning here. Ill plan to look into both and read into some of those threads, but first I'd like to see the thing run. I got the pump, filter and an aftermarket pressure regulator and there are some hoses near the tank that leaked and need attention. I'm not planing to replace the dampener unless I need to as it's pricey. maybe I can use some regular fuel and vacuum lines, but some are molded and need to be. since the tank is dripping molasses like goo, I need to address that before starting. If that stuff got into the injectors they might be plugged too.
once I have fuel pressure Ill do the belts and I got a bunch of hoses , rad hoses, etc. I'll change what I bought and all that will help me get my hands in there and do some cleaning, mine is pretty dirty and corroded looking but I dont think much of anything was done in the way of maintenance or new parts. at first I thought I'd just do the bleeding and try , because the stuck wheels are not really telling me the calipers are actually seized. maybe disassembling them to look isn't' too bad.

i think what I'd like to do is get it going and then tackle other things and try to complete each step to the point where I have a running and driveable car, otherwise it can be a bit daunting if I get into too many directions in tandem.

I guess to get the tank out its' not just the transaxle but also the exhaust? every time I try working on any old exhaust I seem to be into a battle with it because of the way U bolts squeeze the pipe and because of rust. If I can drop more of the exhaust then maybe there are joints that dont need to come apart. some might be stainless. I noted that there is sort of a chrome cover where the exhaust exits the pipe and it looked like the cover is getting a but pushed away I think there is some rust causing expansion there. It might not be critical.

If I do that I can do some general cleaning. There was a great article about the top of the tank rusting out so it made me think maybe I should check into that, and if I can pull the tank I can fix that up but it looks like a project in itself to get it out. I was already thinking of trying to disassemble and then lube the CV joints so maybe those two should happen together.