Spongy Brakes after Caliper Replacement (Miata)

Hi everyone,

I tried my luck on Miata.net, but so far I'm not having much luck. This is a bit more of a technical crowd, so I'm hoping you can help me.

The car is a non-ABS 1994 Miata. I replaced both rear calipers along with rotors and pads in the front and rear. I bled the brakes (furthest corner to nearest) using a Motive Power Bleeder twice with 1 liter of fluid each. The fluid coming out is clear and without bubbles on all corners. After the 1st round of bleeding, the brakes were terrible. After the 2nd round, they were better, but not great - I still can't lock the brakes even if I stab the pedal. I think the pedal is going all the way to the floor. I did adjust the rear calipers to the new pads if that makes any difference.

Prior to all this work, the pedal was firm. I found one guy who mentioned that you should push the brake in a few times during the power bleed to loosen bubbles. Any other thoughts?

I assume this is an OEM to OEM replacement? Given that, either you've got a spontaneous failure of a master cylinder (highly unlikely) a failing/ballooning brake line (possible, though not likely) or you've still got bubbles somewhere.

Bleed, then bleed again.

I new a guy with a Dodge truck, replaced both front calipers. No pedal after bleed. Did all the usual throwing parts at it. Master cyl etc.

Turns out he installed the calipers on the wrong side and had the bleed screws at the bottom. Switched calipers, problem solved.

I'm not saying this is your problem, but.

Power bleeders can introduce bubbles. Either do a gravity bleed or get someone pumping in the driver's seat.

Keith Tanner wrote: Power bleeders can introduce bubbles. Either do a gravity bleed or get someone pumping in the driver's seat.

This^

I've also seen cheap pads cause a soft pedal. Might be the case if you bought loaded calipers. I'm sure the pads that come on those are from the bottom of the parts barrel.

I, too, own a Motive Power Bleeder and have never once been able to get it to fully bleed anything without pushing bubbles into the system. Always end up having to finish the job manually. Have yet to figure out what I'm doing wrong but so far the damn thing is basically a waste of $50. Get a buddy or gravity bleed it.

Thanks guys - this was very helpful.

To answer your questions, the rotors and calipers are OE replacements and are installed in the correct orientation. The pads are Porterfield R4S.

It sounds like I'll have to do it the old fashioned way to get a good bleed. Bummer. I'm traveling for work right now for the next couple weeks, but I'll post an update when I get back.

I installed speed bleeders on my calipers and have had good luck. It's the old fashioned push through by pumping the pedal, but I can do this myself.

http://www.speedbleeder.com/main.htm

I always have found that it helps to get some heat into the system and then bleed again. So it may be better when you get off the road.

Keith Tanner wrote: Power bleeders can introduce bubbles. Either do a gravity bleed or get someone pumping in the driver's seat.

Yup. I'll use a power bleeder to flush fluid, then follow it up with the old two-man bleed. IF the calipers are installed correctly and are tight, you have air in the system.
Another thing, new pads and rotors can feel very uninspiring until they get heat in them once and de-gas. I bed brakes in when I do them for someone else so I don't get the car back the next day with "I don't think the car stops as well".

Parking Brake Adjust

Jump to 2:00 in video. Does the parking brake hold the car? There is an adjustment for the parking brake under a plug on each rear caliper. If you don't turn the allen screw in enough you will have a soft pedal and no parking brake.

+1 for speed bleeders, I put them on my car too. Allows easy quick bleeding with no special tools and the total cost is just a few dollars.