[4g63t]

Brake pedal goes to the floor when engine running. When cars off I can build some pressure - but pedal never goes firm and still sinks to the floor slowly.

Bought the car with this low pedal brake problem. I’ve replaced the following;

New Driver caliper
New Driver caliper brake hose
New Master cylinder
New (used from junkyard) brake booster
New rear passenger wheel cylinder
New brake line from said wheel cylinder

Bench bled the new master cylinder before installing to booster

Then went ahead and replaced all 6 lines from the proportioning valve going to front calipers, master and rears, (spliced into the rears)

Since have attempted to bleed the brakes multiple times, starting from the furthest making my way to the MC. Fluid comes out from all four corners - pedal never gets firm

Don’t see any leaks from my new fittings. Brake fluid level doesn’t drop any.

Took the car on a test drive. Pedal goes straight to the floor when pressure is applied. Car stops but requires pedal to get pumped.

What’s going on here? Air pocket in the lines somewhere?

Any advice is appreciated. This has me going crazy

 

[DjkevinNYC]

Brake pedal goes to the floor when engine running. When cars off I can build some pressure - but pedal never goes firm and still sinks to the floor slowly.

Bought the car with this low pedal brake problem. I’ve replaced the following;

New Driver caliper
New Driver caliper brake hose
New Master cylinder
New (used from junkyard) brake booster
New rear passenger wheel cylinder
New brake line from said wheel cylinder

Bench bled the new master cylinder before installing to booster

Then went ahead and replaced all 6 lines from the proportioning valve going to front calipers, master and rears, (spliced into the rears)

Since have attempted to bleed the brakes multiple times, starting from the furthest making my way to the MC. Fluid comes out from all four corners - pedal never gets firm

Don’t see any leaks from my new fittings. Brake fluid level doesn’t drop any.

Took the car on a test drive. Pedal goes straight to the floor when pressure is applied. Car stops but requires pedal to get pumped.

What’s going on here? Air pocket in the lines somewhere?

Any advice is appreciated. This has me going crazy

I currently have the same issue any updates ?

 

[Blues_hawk]

The symptom sounds like a master cylinder(mc) seal is bad. If you don't have a puddle(a leak) this is the only thing I can think of to help. Nothing throws off a repair job like a bad new part.
This can happen even when installing a new or rebuilt Mc if the pedal is pushed too far to the floor and occasionally the seal is even bad out of the box. The seal on the shaft gets forced out of the machined sleeve and hits the rough cast metal at the end tearing the seal, sometimes while bleeding other times while priming. You have to be careful not to press hard at the end of the stroke during both procedures. Once it's pumped up and clear of air they're actually pretty tough. They're little prima donnas like that.
For troubleshooting: Air in the system or bad fluid does not act the same way. It acts springy or spongy and does not bleed down when held.

Hope this helps solve your mystery.

 

[aznnp77]

By "Brake Booster" did you mean master brake cylinder?

I dunno why you would buy all that stuff I still have the original wheel cylinders on my car, and it has 317K miles on them.

When I get a brake pedal that goes to the floor it's after changing some brake related thing and introducing air into the system. Bleeding the brakes usually makes it better, and it really goes away after day or so of driving in rush hour.

However, if it never gets any better, try a master brake cylinder I guess. I don't think it's that difficult to replace, but I've never done it on my car. I replaced one once on my Dad's corolla. The brake pedal would get soft randomly when coming to a stop. It did solve the problem. I got a NAPA one for like $80, but a random aftermarket one on ebay woulda been like $40-50. But for brakes I didn't wanna mess around with a random part. Either go used OEM or with a higher quality aftermarket part.