Re: [MBZ] Tight pistons rear caliper GMC 1500 No M/B
Phenolic is impervious to water, should not be the source of your problem. Aluminum however is not, could be the source of your problem if there was water in the brake fluid. I would want to take a close look at the surface condition of the inside bore of the caliper bodies. If indicated, a light honing using plenty of fluid to carry away the cuttings from the hone. Also check the Phenolic pistons surface condition for anything that has attached its self. Should be clean and smooth. Phenolic can be sanded, machined, or polished to a high finish. Hand fit the pistons back in their respective bore with coating of brake fluid for lube and continue to polish or hone till they slide smoothly. Check fit frequently, if you hone to much put it back ;).. Grant... AZ On Sat, Jun 25, 2011 at 10:03 PM, Barry Stark barryst...@verizon.netwrote: I did mike the piston. It was 54.7mmantwhich way I measured it so if it grew it did so exactly proportional. I didn't have an inside mike to be able to check the bore for accuracy. I suppose it may have been misshapen. If it was a fluke thin, wellboth pistons were tight in their bores. The calipers are aluminum. Maybe it was a real hot day when the bores were machined. :^) The piston is phenolic. Does that material swell with water? Barry Swelled plastic from water in the fluid or from excess pressure? Dia. check? ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] Tight pistons rear caliper GMC 1500 No M/B
Barry, et al. Some plastics do slowly take in water. Kelvin Hughes made plastic thru hull fittings for small boats that swelled and trapped the transducers in their bores. Also, Brocks Electronics (Seascan) used a plastic drive gear to turn the antenna via a toothed belt. When the plastic swelled in the sea air the belt no longer fitted between the teeth and stalled the rotation of the radar. Machining it down to 3 inches plus 20 thou cured that. So, some plastics do swell, whether modern phenolics do, God knows. Something to ponder, or search the web? Aluminum is ductile and will flow away from pressure, overheating can't be a good thing. Delete is you know where. Fred Moir Lynn MA Diesel preferred On 6/26/2011 1:03 AM, Barry Stark wrote: I did mike the piston. It was 54.7mmantwhich way I measured it so if it grew it did so exactly proportional. I didn't have an inside mike to be able to check the bore for accuracy. I suppose it may have been misshapen. If it was a fluke thin, wellboth pistons were tight in their bores. The calipers are aluminum. Maybe it was a real hot day when the bores were machined. :^) The piston is phenolic. Does that material swell with water? Barry ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
[MBZ] Tight pistons rear caliper GMC 1500 No M/B
I have a '99 Sierra 1500 and I noticed that I got pretty much all the use of the rear brake pads so I went to replace the pads. Caliper pistons were pretty far out so used a c clamp to retract them so the new pads would fit. Seemed like it took way too much pressure with the clamp to retract the pistons into the caliper. I figured a seized piston and popped one out. New style phenolic piston in an aluminum Caliper body. Bore and piston Don't look that bad. Cleaned both up, even took a little 600 paper to the bore and outer circumference of piston. Piston will only go half way into the bore then it stops. This is without the piston seal in its groove. Too little clearance piston to bore. What's going on here? Bore and piston look clean but piston is still very tight in the bore. AFAIK these are original parts from the factory. May be the reason the outer pad wore much faster than the inner pad. Any thoughts? Barry ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] Tight pistons rear caliper GMC 1500 No M/B
Barry Stark wrote: Any thoughts? Is there a parking brake in there? ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] Tight pistons rear caliper GMC 1500 No M/B
Is there any pattern on the face of the piston, like a cross? Sometimes rear calipers have pistons that are screwed back in vice pressed. Max -- Sent from my Android phone with K-9 Mail. Please excuse my brevity. Barry Stark barryst...@verizon.net wrote: I have a '99 Sierra 1500 and I noticed that I got pretty much all the use of the rear brake pads so I went to replace the pads. Caliper pistons were pretty far out so used a c clamp to retract them so the new pads would fit. Seemed like it took way too much pressure with the clamp to retract the pistons into the caliper. I figured a seized piston and popped one out. New style phenolic piston in an aluminum Caliper body. Bore and piston Don't look that bad. Cleaned both up, even took a little 600 paper to the bore and outer circumference of piston. Piston will only go half way into the bore then it stops. This is without the piston seal in its groove. Too little clearance piston to bore. What's going on here? Bore and piston look clean but piston is still very tight in the bore. AFAIK these are original parts from the factory. May be the reason the outer pad wore much faster than the inner pad. Any thoughts? Barry_ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] Tight pistons rear caliper GMC 1500 No M/B
Guy at work has pretty much the same truck, I think his is a 2000 or 2001. His eats rear brake calipers like they're going out of style. His mechanic says its because the rear brakes don't do much and discs are overkill for the application if you aren't carrying a lot of weight on a regular basis. He does regular panic stops to exercise the rear brakes and make the sticking not so frequent. Apparently GM has gone back to drums for rear brakes since then. Sorry I can't help your actual problem, if your calipers are original based on my friend's experience I'd say you've gotten excellent service. -Curt Date: Sat, 25 Jun 2011 00:34:19 -0700 From: Barry Stark barryst...@verizon.net To: 'Mercedes Discussion List' mercedes@okiebenz.com Subject: [MBZ] Tight pistons rear caliper GMC 1500 No M/B Message-ID: 01cc330a$4bc716d0$e3554470$@net Content-Type: text/plain; charset=us-ascii I have a '99 Sierra 1500 and I noticed that I got pretty much all the use of the rear brake pads so I went to replace the pads. Caliper pistons were pretty far out so used a c clamp to retract them so the new pads would fit. Seemed like it took way too much pressure with the clamp to retract the pistons into the caliper. I figured a seized piston and popped one out. New style phenolic piston in an aluminum Caliper body. Bore and piston Don't look that bad. Cleaned both up, even took a little 600 paper to the bore and outer circumference of piston. Piston will only go half way into the bore then it stops. This is without the piston seal in its groove. Too little clearance piston to bore. What's going on here? Bore and piston look clean but piston is still very tight in the bore. AFAIK these are original parts from the factory. May be the reason the outer pad wore much faster than the inner pad. Any thoughts? Barry ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] Tight pistons rear caliper GMC 1500 No M/B
Max, others - Thanks for all your comments folks. I still can't figure this out. I ended up getting a pair of rebuilts. Barry Subject: Re: [MBZ] Tight pistons rear caliper GMC 1500 No M/B Is there any pattern on the face of the piston, like a cross? Sometimes rear calipers have pistons that are screwed back in vice pressed. Max ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] Tight pistons rear caliper GMC 1500 No M/B
Swelled plastic from water in the fluid or from excess pressure? Dia. check? Fred Moir Lynn MA Diesel preferred On 6/25/2011 3:34 AM, Barry Stark wrote: I have a '99 Sierra 1500 and I noticed that I got pretty much all the use of the rear brake pads so I went to replace the pads. Caliper pistons were pretty far out so used a c clamp to retract them so the new pads would fit. Seemed like it took way too much pressure with the clamp to retract the pistons into the caliper. I figured a seized piston and popped one out. New style phenolic piston in an aluminum Caliper body. Bore and piston Don't look that bad. Cleaned both up, even took a little 600 paper to the bore and outer circumference of piston. Piston will only go half way into the bore then it stops. This is without the piston seal in its groove. Too little clearance piston to bore. What's going on here? Bore and piston look clean but piston is still very tight in the bore. AFAIK these are original parts from the factory. May be the reason the outer pad wore much faster than the inner pad. Any thoughts? Barry ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] Tight pistons rear caliper GMC 1500 No M/B
Probably the smart way to do it. The ability to stop is far more important than the ability to go... Max -- Sent from my Android phone with K-9 Mail. Please excuse my brevity. Barry Stark barryst...@verizon.net wrote: Max, others - Thanks for all your comments folks. I still can't figure this out. I ended up getting a pair of rebuilts. Barry Subject: Re: [MBZ] Tight pistons rear caliper GMC 1500 No M/B Is there any pattern on the face of the piston, like a cross? Sometimes rear calipers have pistons that are screwed back in vice pressed. Max_ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] Tight pistons rear caliper GMC 1500 No M/B
I did mike the piston. It was 54.7mmantwhich way I measured it so if it grew it did so exactly proportional. I didn't have an inside mike to be able to check the bore for accuracy. I suppose it may have been misshapen. If it was a fluke thin, wellboth pistons were tight in their bores. The calipers are aluminum. Maybe it was a real hot day when the bores were machined. :^) The piston is phenolic. Does that material swell with water? Barry Swelled plastic from water in the fluid or from excess pressure? Dia. check? ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
