Rear caliper bolt size

5rivers · Post by **5rivers** » 25 Sep 2020, 06:25

I finally got the rear wheels up in the air after a few weeks of rear brake grinding!!! The problem I am having is that I cannot figure out the right size socket/wrench to use to remove the caliper bolts. A 13mm sort of grabs but then slips. A 12mm is too small. A 1/2 inch wrench grabs better than the 13mm socket but then slips. Now the corners are starting to flatten out. I have even applied heat to the bolt and caliper, but the bolt does not want to budge. One rear passenger side bolt is almost rounded, the driver's side is starting to get there! I was able to remove the outer pad on each side but the inner pad seems to be wedded to the caliper!
Any ideas/clues on what I could try next?

Post by **abscate** » 25 Sep 2020, 06:47

If the calipers are being replaced, try multiple heat cycles. You might melt seals doing this but if it needs to come off I’m guessing it’s seized anyway

60 seconds propane, then 5 minutes cool. Repeat at least 3x

Go around and heat up all four bolts. You finish bolt four just in time to come back to bolt 1

After last cool, hit with PBBlaster or equivalent.

Try a six point socket or one of the grabber sockets from Lowes if it starts slipping

Post by **ZionXIX** » 25 Sep 2020, 18:58

6 point sockets are the way to go. Sometimes you can hammer a 12 point socket of a slightly smaller size but you sacrifice the socket.

850oldschool · Post by **850oldschool** » 25 Sep 2020, 19:12

Die grinder is the right size wrench.

Post by **abscate** » 25 Sep 2020, 19:18

You have to drill a caliper bolt out, unfortunately

Just taking the head off won’t help.

New bolts and aluminum, or , even better, Nickel anti seize is important on caliper work in the Northeast

5rivers · Post by **5rivers** » 25 Sep 2020, 20:19

Yes, indeed! North County weather really does a number on bolts!!

This will be the first time I have tackled these bolts since I got the car, now just over 2 years ago. And believe it or not, the PO took the V70 for maintenance and repair to a reputable Volvo indie garage in Central NY!

850oldschool · Post by **850oldschool** » 25 Sep 2020, 21:45

I ground the head off one back in April. The heat and vibration helped the penetrating oil do it’s job and the stub came out with a vise grip. I used the Harbor Freight electric die grinder, which is like a giant monster Dremel and uses 1/4” shank bits. The pneumatic ones are cheaper but you need a big air compressor.

Why the heck is it always the one on the passenger side? And yes, anti seize on every bolt you install!

Post by **mkc1** » 26 Sep 2020, 20:06

Grip Tite Sockets and a long pipe worked well for me.

Post by **abscate** » 28 Sep 2020, 05:11

K...heat it up for 60 seconds with propane, then 100 raps with a small hammer. Light Taps likes small woodpecker. Repeat every day for a few days