Caliper question

[supton]

Originally Posted By: MaximaGuy
I hear you my friend, it is hard for a daily commute ride to go down.

BTW, those screw in pistons are the biggest PITA, it never goes back in neatly like those hollow pistons.

http://forum.mazda6club.com/suspension-brakes/229713-how-do-i-depress-caliper-piston-back.html

The hollow ones are a gem to push back.


Yep...

On my VW, each time I needed to do rear brakes, I wound up needing to have calipers replaced (wind in pistons). One side would be hard to twist in. If I had owned it for another 5 years (or got another) I'd plan on just replacing calipers ($100 each?) when brake time rolled around.

 

[supton]

Originally Posted By: Gokhan
That road salt seems to be a pain. My 31-year-old pistons looked brand-new.


Yes it is... However my wife has had about enough of this summer, and can't wait for fall. Once it gets past 70F the both of us start to think it's getting warm.

 

[Ducked]

Originally Posted By: supton
Originally Posted By: Gokhan
Oh my God, is that rust all over the piston? I wonder what happened. My 31-year-old cylinders didn't have any rust or pits at all. Bad brake fluid?


Not sure but I'm pretty sure it was road salt.


I'm fairly sure it wasn't, because that bit of the piston is behind the seal in normal operation. If the road salt could get in, the brake fluid would get out.

In my case I'm pretty sure it was bad brake fluid.

You'll probably have to replace, but you're close enough that you may as well clean it up and see what it looks like. Mine looked arguably worse than that at first pop but they cleaned up (with aluminium foil) quite well. See pictures in the thread linked above.

 

[supton]

Well, dawned on me that the banjo bolt is directly behind the piston--so a suitable drift ought to be able to drive out the piston. I shot the piston with some penetrating oil, pushed it back in (go figure, it loosened up), then attempted to drift out. Gets most of the way, then the drift bent over. Piston might be coming out sideways and have gotten cocked; ran out of time today. Will try spraying with oil again and driving back in, then drifting out again.

 

[Gokhan]

Originally Posted By: supton
Well, dawned on me that the banjo bolt is directly behind the piston--so a suitable drift ought to be able to drive out the piston. I shot the piston with some penetrating oil, pushed it back in (go figure, it loosened up), then attempted to drift out. Gets most of the way, then the drift bent over. Piston might be coming out sideways and have gotten cocked; ran out of time today. Will try spraying with oil again and driving back in, then drifting out again.

Did you try turning the piston while pulling it out? This will not only loosen it more but will make sure that it's coming straight.

 

[supton]

I've tried grabbing it a couple of times to turn, but no luck. Tomorrow I'll drift it back in, find a spot where it is "loose" and see if I can get to where it will can be turned. Then try drifting out again.

Kinda hard to turn it while hammering on it.

 

[Gokhan]

It sounds like there is a rust spot and it's tilting when you are pulling it. Compressed air could work better because you would get equal pressure distribution. Or try pulling it from various points in the circle until it comes out without tilting.

 

[Ducked]

Originally Posted By: Gokhan
It sounds like there is a rust spot and it's tilting when you are pulling it. Compressed air could work better because you would get equal pressure distribution. Or try pulling it from various points in the circle until it comes out without tilting.


In the thread I link to above, the use of water pump pliers (channel-lock pliers in N America, apparently) is suggested, I'd guess because they are cranked so they give more leverage for turning.

I didn't try this because I couldn't find mine and (after trying compressed air) just put the caliper back on and blew the piston out with the brake pedal, but if you have a pair handy it might be worth a try.

 

[supton]

Figured out it out. When it was still on the truck and I stood on the pedal, the piston came out cocked, somehow. Trying to drift it out through the banjo bolt resulted in the same thing, only with buggered up threads on the banjo bolt. The right way: grab the piston with vice grips, grab the caliper in a vice, and wiggle&work out the piston.

And the answer to my question, long ago, yes, the piston should spin in the caliper, but a fair amount of leverage is required.

Anyhow, at this point I'd need to figure out what size tap to get, to clean up the threads on the banjo bolt before proceeding. Or just return this caliper and order a new OEM one, along with a set of pads while I'm at it.

 

[Ducked]

Originally Posted By: supton

Anyhow, at this point I'd need to figure out what size tap to get, to clean up the threads on the banjo bolt before proceeding. Or just return this caliper and order a new OEM one, along with a set of pads while I'm at it.


Depends how knackered and corroded it is. Not having seen it, I'd probably bet on the second option.

 

[supton]

It's corroded--but it's a substantial chunk of cast iron, so it's in no way compromised. Photos I previously took:

 

[Gokhan]

Or rebuild the rebuilt caliper.

 

[supton]

Originally Posted By: Gokhan
Or rebuild the rebuilt caliper.

True, true. Get the rebuild kit, try that. I did a dry run at it with the old caliper, and the dust boot was a pain to get back on, not sure I'm in a rush to try that (although it's possible that the rubber reacted poorly to the penetrating oil).

Sometimes I wonder if I should not just take a few days off from work whenever stuff like this happens, just so I can pay someone else to do this.

 

[Warstud]

Just go to one of the auto parts stores and get a reman caliper and put it on and be done with it $40-50

 

[supton]

Originally Posted By: Warstud
Just go to one of the auto parts stores and get a reman caliper and put it on and be done with it $40-50


Umm... I did... only it was $95 or so. And it drags. So it needs replacing, again. Since I really don't have time to mess with this until next weekend, I can easily mailorder an OEM for $225 plus another what, $60? for pads and a rebuild kit for the next time this happens.

Which is what I would have done had I any forewarning as to the impending failure. Unfortunately it seems you just can't plan for failures.

 

[Gokhan]

I hear your pain. Yes, sometimes it's better to take it to a shop. They will buy whatever rebuilt part they think is good.

I would have both sides replaced so that you don't deal with this again a few months later.

You can still mail-order both the OEM pistons and OEM rebuild kit and do both sides in a couple of weekends. It can't be that difficult and will cost only about $60. If it fails, then you go to a shop.

 

[Ducked]

Sorry, I meant the piston, which wasn't what you were referring to.

External corrosion of the caliper isn't of course an issue (I refinished mine but it wasn't necessary).

By all accounts (and first principles) internal corrosion of the caliper has to be very bad before it's a show-stopper, so it probably isn't an issue either.

I wonder if mix-and-match would be worthwhile? IF the reman and cleaned-up-original parts are interchangeable, could you put together a "best set"?