Rear Caliper Piston disassembly plus brake Qs, 1971 914-4 Frankenstein Options

[mikesjunk]

Ok so Frankenstein is running and driving. Stopping well that was a different story. So I'm getting into the rear brakes first. Watched the awesome video by PMB Performance to get the know how. But my pistons aren't like those in the video. My pushrod won't drop into the adjuster hole so you can screw the internals out. I did try a piece of drill rod in the hole but the inside piece just spins. I see the obvious snap ring on here but want to know if it's a booby trap. I don't want to pull the pin and the piston sends its guts to all four corners of my shop. (IMG:style_emoticons/default/smile.gif) So what is the way to get the internal piece out of this piston?

(IMG:http://www.914world.com/bbs2/uploads_offsite/www.mikesjunk.com-19423-1459563369.1.jpg)

And the next question is can the rear prop valve keep fluid from getting to the rears? I have the calipers off and thought I'd see if I could get fresh fluid flowing. Pulled a vacuum on one side and it held. So jumped in the car and pumped the brakes and zero fluid coming out the open rear lines. I was able to take the line to the prop valve off and it flows brake fluid via gravity so I'm pretty sure it's getting to the valve. Thoughts on the blockage? I hope this doesn't have to come off as it looks like a real fun time with the engine in the car.

[mepstein]

Did you replace the soft lines

[mikesjunk]

No soft lines yet. I've seen some of the posts about them, but I'd think I'd get something out of the lines when they are open. I gave the fittings a dose of PB blaster if I have to take them off. The top one looks to be fun to get to so I'm sure there will be twisted steel lines in the future.

[mepstein]

You don't need the twisted steel ones, just new rubber. Cut the old lines in half since they need replacement anyway and do an autopsy. Maybe they are completely swollen shut. Could be origional. Heat might be your friend at the fitting, just be aware of gas lines.

[mikesjunk]

What I meant by twisted steel is that in trying to remove the rubber ones I'm probably going to twist the steel ones. In all the years of working on old cars me and steel brake lines don't seem to get along. (IMG:style_emoticons/default/smile.gif) I was quite surprised I got them off the calipers without twisting them.

I see PMB has some reasonably priced steel lines so I might be proactive since I know my luck. But I'm guessing getting the drivers side off/on the prop valve is going to be a fun task.

I'm sure my sister is going to love getting my next bill on this beast. (IMG:style_emoticons/default/blink.gif)

[stugray]

I have rebuilt the brakes on a couple of 914s and have never had to actually remove the prop valve.
I dont think they fail all that often, and when they do I am guessing that it will seize and act like just a tee anyhow.

I have had the flex lines swell completely shut and not allow the pistons to retract when you release the pedal.
Then the brakes overheat and cook the piston seals.
So when you rebuild a caliper you should just automatically replace the flex lines.
I also have not yet ruined a rigid line when disassembling.

[mikesjunk]

Well looks like some hoses and maybe lines to do.

Any suggestions on the piston disassembly?

[Mark Henry]

Hose and steel lines that are stuck.
I've found that if you take vicegrips and apply pressure fairly hard, but not enough to crush them (maybe a few teeth marks) they will crack open without destroying them.

[mobymutt]

Well looks like some hoses and maybe lines to do.

Any suggestions on the piston disassembly?

Mine worked just like the video. Are you saying the adjuster screws won't screw into the back of the pistons?

[mikesjunk]

Moby,
My piston threads are smaller than the video but they thread in fine. The parking brake pushrod doesn't fit in the hole like in the video. So I put a piece of drill rod in the hole and threaded my adjuster in. When it hits the drill rod the piece with the internal thread spins(piece snap ring is around) so it doesn't keep threading down to apply the force to push in the insides out like the video.

So I'm at the point of trying to figure out how to keep it from spinning or to pull the snap ring off. Just wanting some feedback on what happens if I pull the snap ring.

Mark,
Usually breaking them free of the threads isn't a problem but breaking the nut free from the tube to keep it from twisting the tube versus spinning free is where my luck never works.

[mobymutt]

Moby,
My piston threads are smaller than the video but they thread in fine. The parking brake pushrod doesn't fit in the hole like in the video. So I put a piece of drill rod in the hole and threaded my adjuster in. When it hits the drill rod the piece with the internal thread spins(piece snap ring is around) so it doesn't keep threading down to apply the force to push in the insides out like the video.

So I'm at the point of trying to figure out how to keep it from spinning or to pull the snap ring off. Just wanting some feedback on what happens if I pull the snap ring.

Oh, I think I see. I'm not sure you want to take that snap ring off while the adjuster assembly in still inside the piston -- I took mine all apart while it was out, and I seem to recall it was quite fiddly.

But I've only done it once, maybe Eric can give you some real advice!

[mikesjunk]

So went out this morning and thought I'll try again. Picked up the first piston and no dice so thought try the 3 other. Next one bam internals came out. Next one bam out they came and the then 4th one bam. So that was really strange went back to the first one and bam out they came. So not sure why but guess the car gods gave me a break since I'm probably going to be twisting some brake lines here before the day is out. Did some more wire brushing and PB Blaster before I came in here for lunch. Those top hose fittings aren't going to be fun.

[mikesjunk]

Back out after lunch and success of the passengers side....no twisted tubes. As soon as I was able to break it free it started dripping fluid. Once I got the hose off I took my air compressor nozzle to it.....absolutely no flow. Call me a believer now this hose is crap. Off to the kids soccer game and then to tackle the drivers side.

I did pull the heater ducts off for better access. I plan to replace the slotted screws on this with real bolts. They are a pain.

[mikesjunk]

Ok so drivers side hose is off and no twisted lines. (IMG:style_emoticons/default/piratenanner.gif) So the only line that was an issue was the drivers from the hose to caliper. I got it off without twisting it by cutting the hose but the nut is pretty much stuck to the tube. So I'm now waiting an order from PMB for some hoses, tubes, misc. etc.

Hopefully some boxes show up this week and I'll have more projects next weekend.

[Eric_Shea]

Waiting on pedal pads. Shipping Tuesday (prolly).