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Mushy Brakes After Caliper Rebuild

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

ferocity02
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Mushy Brakes After Caliper Rebuild

Post by ferocity02 » Mon Mar 23, 2020 2:15 pm

I am doing a brake overhaul on my 1998 S70 with 205k miles. As far as I know the calipers have never been rebuilt, so I am replacing caliper seals, dust boots, rotors, pads, and flushing/bleeding the system.

Pads = Akebono Euro Ceramic
Rotors = Zimmerman
Fluid = Pentosin Super DOT 4
Seals = ATE

Yesterday I got through the rears and the pedal is now very mushy. To bleed the system I pressurized the master cylinder reservoir to 10-20psi. I made sure it never went empty either, it never got below half. Some air bubbles came out of each caliper but not as many as expected. I flushed about 0.75L through the system with just the rear 2 calipers. I am using Pentosin Super DOT 4 fluid.

I'm thinking the traditional bleeding method (manually pressing the brake pedal, 2 man job) might work better since it could force the fluid through faster and perhaps dislodge some stuck bubbles. Thoughts? Also thinking that putting some miles on it and bleeding again will help.

Also, until I rebuild the front brakes, the rear pads are ceramic and the front are the dust-loving semi-metallic pads, not sure what brand. So the brake pedal has a 2-stage feel to it, where it will bit initially then nothing for a bit, then I think the rears start to bite.

ferocity02
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Re: Mushy Brakes After Caliper Rebuild

Post by ferocity02 » Sat Apr 04, 2020 3:07 pm

Update... I rebuilt the FR caliper and replaced the FL caliper with a reman ATE unit from Autozone. The FL caliper dust boot was dislodged, so the piston and totally rusted, meaning it would not be reusable with the new pads, it would leak around the piston seal. I did the power bleed method again.

After this the brakes were even mushier. I went out and bed the brakes doing a few 50-10 aggressive stops and then a few 65-10 very aggressive stops making sure not to come to a complete stop until the brakes were fully cooled. The rotors were blue and purple after this, luckily no warping.

The bedding process may have helped a little bit, but it was far from okay. If I smashed the pedal as far as I could the ABS would not activate, meaning I'm not getting full force from the brakes.

Today I dragged the wife out from quarantine and had her help bleed the brakes the good ol way, she would pump the pedal and I open and close the bleeder screw. Surprisingly a good amount of air came out of the rear calipers, barely any from the front. I believe this bleeding method is superior to others. Pressing the brake pedal puts significantly more pressure in the brake system, which in turn moves the fluid faster when the bleeder screw is open, which in turn helps dislodge the air bubbles.

After this the pedal is much better! The ABS will engage now. It still not quite as good at the Volvo pads, but that's the price you pay for a dust-less ceramic pad. These pads will probably last longer than the car. They are very quiet and smooth as well. So far I am happy with the Zimmermann Akebono combo.

scot850
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scot850

Re: Mushy Brakes After Caliper Rebuild

Post by scot850 » Sun Apr 05, 2020 8:46 pm

I am using Volvo rotors and Akebono pads. I find the brakes are weak when cold and way better (normal) when warm.

Neil.
2000 V70 R - still being an endless PITA
2006 XC70
2003 Toyota 4Runner V8 Limited
2015 Kia Sportage EX-L
1993 850 GLT -Sold
1998 V70 XC - Sold
1997 Volvo 850 SE NA - Went to niece in California - Sold
2000 V70 SE NA - New project and test bed - Sold

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RickHaleParker
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Re: Mushy Brakes After Caliper Rebuild

Post by RickHaleParker » Sun Apr 05, 2020 11:23 pm

ferocity02 wrote:
Sat Apr 04, 2020 3:07 pm
Today I dragged the wife out from quarantine and had her help bleed the brakes the good ol way, she would pump the pedal and I open and close the bleeder screw.
You miss an opportunity to buy more power tools.

Ask her if you can spend $20.00 on a hand-held vacuum brake bleeder so you never need to drag her like that again. :wink:
--------
Platform: P80 1998 C70, B5234T3, 16T, AW50-42, Bosch Motronic 4.4, Special Edition package, Plant: Uddevalla Sweden.
Platform: X40 (Nedcar) 2003 S40, B4204T3, 14T twin scroll AW55-50/51SN, Siemens EMS 2000. Plant: Born Netherlands.
Platform P2 2005 XC90 T6 Executive, B6294T, 4T65 AWD, Bosch Motronic 7.0, Plant Torslanda Sweden.
Platform P2 2004 S60R, B2524T4, AW50/51 AWD, Bosch Motronic 7.0, BorgWarner K24 turbocharger, Plant Ghent Belgium.

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