cdkcorvette7

Here's the situation... I had to panic stop tonight to avoid running into someone that pulled out into traffic. Immediately after that the pedal went soft and the brakes won't engage until the pedal is 90% of the way to the floor.

Got home, checked for leaks and couldn't find any. Pulled codes and found none. Went to bleed brakes (two-person method) and the rear brakes will not bleed, but the front ones will. Also, with the rear bleeder screws open, the brake pedal will not go to the floor, but it will with the front bleeder screws open. Anybody have any suggestions as to what I should look at next?

Jnape

A long shot is it went into ICE mode. What were the road surface conditions like at the time. If it (ABS) goes into the ICE mode, your braking performance is 10% or less of normal.

cdkcorvette7

Road was bone dry. The strangest part to me is that I can't get air or fluid out of the rear bleeder screws but I get all fluid (no air) from the front.

cdkcorvette7

Bump

Bill Dearborn

Sounds like the ABS Modulator isn't allowing any fluid flow to the rear brakes. This may not throw a code. A person on the C6 forums just had something similar happen and it took quite a while to debug the issue. Ended up replacing the BPMV.

Bill

cdkcorvette7

I was kind of afraid of that. I'm starting to think that module may be going bad... Today, after the car sat in a hot parking lot for about three hours the problem mysteriously vanished and the brake pedal became very firm and very high, then later after some driving the softness and long travel returned, although not as extreme as it was before.

Any suggestions as to how I might confirm it's the bpmv before I spend a chitload of money on a replacement? I hate just throwing parts at a problem without isolating it first...

Got uid0

any chance that you just need to change the pads?

My rears gave no indication that they were worn out before it was too late.

ajg1915

Get with someone that has a Tech2 and do the automated brake bleed procedure.

That will let you know if the pump is shot.

Old Horsepower

Just a guess here. But it could just be in the master cylinder. The piston in there that moves when you step on brakes works front and back brakes as separate systems. It could be the seal for the rear went bad when you made the hard stop. Would also explain why you can't bleed rear. A rebuild kit or a new master cylinder might be all you need.

cdkcorvette7

I took one of the rear calipers off to check it out while I was trying to bleed the rear brakes and the pads looked good...

Hmmm... surely I know SOMEBODY that has one of those... I know a shop is going to charge me at least $200 for that. Probably a limb and a promise to sign over my first-born child if I took it to a dealer.

I'm going to check that out tonight... I'd much rather replace the master cylinder than the BPMV and what you said about the seal blowing out under a heavy load (panic stop) makes sense to me. Thanks!

ajg1915

I have a Tech2 and I'm sure some of the shops around your way do too.

It's a really easy procedure to perform and should take less than an hour.

Just put it on a lift, take off the tires and run the procedure.

Heck of a lot better than a pump and cost of installation. Where is Oak Hill, VA ? Is it close to Washington, DC ?

cdkcorvette7

I'm about 20 minutes outside of DC. I know a lot of the shops around here have them... I'm just trying to figure out if I know a person that has one. Either way I want to get this done today... it's driving me CRAZY.

ajg1915

My brother lives in the DC Area and might be coming up this weekend, I could send hom home with mine.

I've only seen one brake master cylinder go bad on a C5 and it totally failed, (i.e. No Pedal at all). Luckily it happened right in front of my house ( I live on a dead end street).

Ended up replacing it and running the automated bleed procedure.

Have you tried the gravity method. Crack open your rear bleeders with the car jacked up ( higher in the front) and see if you're getting any fluid.

cdkcorvette7

That is awesome of you to offer, but I will be out of town this weekend and a good part of next week, so I'm going to get this done today. This forum probably has the coolest members of any of the forums I read.

I had the car level with all four wheels off when I tried bleeding the brakes; I could try it again with the front higher later today. When I cracked the bleeder screws there was some fluid present, but there was not enough pressure when the brake pedal was depressed to cause any to shoot out...

Also, when I drove the car again this morning the problem had "magically" disappeared again. Right now the brake pedal is very firm and very high. Maybe I have a poltergeist living in my engine bay screwing around with the brake lines while I'm not looking

ajg1915

Maybe you have an air pocket. You could try re-bleeding them again.

Then take the car out and stomp on the brake pedal to activate ABS and try bleeding again. You may have some air bubbles in the ABS Block, that can only be bleed out via activation or the automated bleed procedure.

cdkcorvette7

I've been looking for a reason to try out the new HPS pads

lucky131969

Ice mode?

rustyguns

your braking system is messed up bad... the fact you cannot bleed rear calipers is terrifying ! take it to a good mechanic.

fyi this is NOT ICE MODE ! believe me i know!

cdkcorvette7

Never really considered ice mode to be a possibility. I'm going to try to troubleshoot/repair myself first.

rustyguns

ice mode is not a possibility.

Your rear brake system is screwed up!