04 LS430: While changing my rear brake pads, I removed the old pads, compressed the outer piston, and I put the new outer pad in first (driver side). It compressed easily, and the inner extended.

Now the inner piston refuses to go back in so I can put the new pad in. Any ideas why?

• It extended easily, so I doubt it is seized.
• On the outer, I just used a large flat blade to push it in. Tried the same on the inner, no luck.
• Cracked the brake line loose and tried compressing it. Little fluid came out, piston barely budged.

The inner piston is now fully extended, with no pad between it and the rotor. Maybe I should have left the pad in it while I compressed the other side so it would go out so far, I removed both pads before compressing. Could it be extended too far to push back in?

 

Probably just needs a little more force. Try some channel locks:

https://www.amazon.ca/CHANNELLOCK-44.../dp/B00004SBCU

These worked for me. Remove the pads on both sides. Use the channel locks on the pistons, alternating sides.
You'll see if you compress one side, the other side will pop out a bit. But if you keep alternating squeezing the pistons they'll pop out less and less. Eventually you'll get them both in. Takes a reasonable amount of force.

 

I use "C" clamps on each side to avoid the back and forth. Be sure to open the brake fluid reservoir too.

 

Yes good call on opening the brake fluid reservoir.

 

Res was opened, double checked to make sure that the cap hadn't fallen back on and sealed.

I'd inserted an old pad and tried leveraging against it with a make-shift cheater bar, the pad BENT and the piston didnt budge. I was worried I was applying too much pressure at that point, but the piston may not have had even pressure applied this way. Grabbing 2, clamps now and trying again.

 

Be careful, if the piston traveled too far, it may be out of the caliber and now won't go back in because it's not aligned into the piston cylinder.

 

I have one of these tools, and it's great for brake jobs and only around $30. Does a good job evenly compressing the calipers.






If you've already opened up the bleeder screw and it still won't go back in with a good deal of force, I'm not sure what's going on. The only thing I can think of is the pressure isn't being evenly applied or it somehow popped out of place.

 

It was indeed out of place due to un even pressure being applied. I had to remove the caliper (line attached), get a C Clamp, and place it over the center of the piston and caliper. Issue resolved, thanks everyone.

My other issue was that the Wagner ThermoQuiet ceramic pads forced the shims to sit slightly upwards and the retainer pin had trouble aligning through... Pain in my ****.I notched the wholes a tad bit just so I could get the pin through.

 

The Wagner's have an integrated teflon shim, so that's probably why it was an issue. You don't put the factory one on there, just leave it off.

It should probably be fine though.

 

Leave both the shims off? I may go back and investigate that. In Hindsight, I was worried the pads wouldn't move to and way from the rotor smoothly, and may be stuck contacting the rotor due to friction on the pin but every DIY had the shims being re-used so I followed suit. Hooray for re-work.

 

On my back ones I recently replaced, they had an integrated shim that was built into the pad (Wagner ThermoQuiet). I believe on the included sheet that came with the pads, it has generic instructions that it doesn't need shims.

I "learned" this because on a different application with the same brand pads I did a while ago, I couldn't get the factory shims to fit properly and then found out it was integrated into the pads already.

I'm not sure though it's a problem that you put the shims back on, as long as it wasn't catching on anything and it fit, it might just serve as a bit extra squeal/noise protection.

 

I'll just monitor them for a while to for premature wear. Im pretty sure there's some additional friction there