Intermittent Brake Failure
 

The brake pedal on my wife's 2011 town and country intermittently goes to the floor when braking!!! This began some time after a local shop replaced the left rear caliper. I replaced the master cylinder and used a pressurized bleeder to bleed the system and thought I had it fixed till the problem returned again this week. I took the car for a test drive exercising the brakes under rough road conditions and activating the anti lock function at least a half a dozen times. The brakes worked perfectly. Brake fluid level is normal, no obvious leaks, all pads have very little wear.
Is there some extra step required when bleeding that is involves manually activating the anti lock brake module?
Any comments or suggestions would be appreciated. I'm about ready to take it to the dealer and pay big bucks.....

It can only be master cylinder if it goes to the floor. Air in system would make it spongy. Unless you have a leak but this would show on the ground..

Does this happen all the time or only when the engine is running?

Vonhufinvule. The brake failure was while driving.
goggs. It is not likely that the replacement master cylinder that I installed was defective.
I bit the bullet and took the vehicle to the dealer. Hopefully they will pin point the problem and I'll post what they find. Stay tuned.

Hi the reason I was asking is that I've seen a couple of Jeeps with an issue whereby after work was done to the system they developed a fault that resembled a bad master cylinder. However, what it was, is the ABS pump. They both had to be connected to a diagnostic computer and the ABS cycled.

What appeared to be happening was flued was simply being redirected from the pump back the the master cylinder reservoir.

Anyway, hopefully its something simple.

The saga continues... The Dealer couldn't find anything wrong but recommend that they change the master cylinder, which I replaced about 6 months ago, and the two rear brake calipers because they were known to give trouble. I said no thanks. I can throw parts at it a lot cheaper than them. So I ordered a shop manual cd from Faxon for $194 and an ABS modulator from mymoparparts.com for $229. If anyone has tips or cautions about changing the modulator please share. Thanks!

Finally got the shop manual from Faxon. (When they say two weeks to deliver they mean it.)

So the shop manual installation procedure states the following:

"The base brake's hydraulic system must be bled anytime air enters the hydraulic system. The ABS must always be bled anytime it is suspected that the HCU (Hydraulic Control Unit) has ingested air.
Brake systems with ABS must be bled as two independent braking systems. The non-ABS portion of the brake system with ABS is to be bled the same as any non-ABS system.
The ABS portion of the brake system must be bled separately. Use the following procedure to properly bleed the brake hydraulic system including the ABS."

Included in the instructions is this step:

"Using the scan tool, select ECU VIEW, followed by ABS MISCELLANEOUS FUNCTIONS to access bleeding. Follow the instructions displayed. When finished, disconnect the scan tool and proceed."

Two questions, 1. Will any of the non-OEM scan tools be able to read these instruction and perform required operations? and 2. Can someone share what those instructions are with the intent to perform the bleed procedure without the scanner?

As always any thoughts or comments would be depreciated.

correction, 'thoughts and comments would be appreciated.'

The Scan tool is cabel of running the ABS pump manualy , some times air can get stuck in ABS pump assemby . I doubt any non OEM Scan tool can do this , I haven't seen any.

You can bleed the system random and might be lucky to get the air out.