Brakes locking up after replacing master cylinder.

[RrmyGuy]

I just replaced the master cylinder on my 2014 Edge Sport, because it was spongy, and there was no pedal until you pushed it almost to the floor. Now it keeps building pedal pressure as I drive it until the brakes eventually lock down. I can release pressure via a bleed valve, and it's good for awhile, but it starts building pressure again. Has anyone else had this happen? And what would cause it? Thanks in advance. 

[Cerberus]

Paging Ford2504x4, paging Ford2504x4..?

 

 

[RrmyGuy]

I just replaced a master cylinder. Brakes were working, just spongy. No issues with ABS, now they just lock up after a while. I can bleed the pressure from the either front bleed valve and drive it until it locks up over time. I think I just got a bad quality MC. I just wanted to see if anyone else had a similar issue. 

[WWWPerfA_ZN0W]

On 12/4/2023 at 7:56 PM, RrmyGuy said:

I just replaced a master cylinder. Brakes were working, just spongy. No issues with ABS, now they just lock up after a while. I can bleed the pressure from the either front bleed valve and drive it until it locks up over time. I think I just got a bad quality MC. I just wanted to see if anyone else had a similar issue. 

what brand mc did u install? if aftermarket, their seals are known to be no good and usually transferring the old seals over fixes issues.

 

otherwise you may need to bench bleed the mc.

 

note that this generation is at a point where the abs is starting to give way if fluids have not been regularly maintained. so it could still be the HCU acting up as it is the distribution box for the brakes. you have to bleed the abs separately from the main system to get air out of it using a service procedure available through forscan lite, high end scan tools, or the dealer.

[RrmyGuy]

I bought it from rockauto.com,  it's a centric brand master cylinder. It wasn't the cheapest, but it was listed as the favorite part. 

[WWWPerfA_ZN0W]

if you still have the old mc, see if you can swap the seals. otherwise maybe a dealer can provide new ones to you.

 

you can try getting air out of the abs with a few hard stops that activate abs either in forward or reverse. but follow it up with a main system bleed. good time to flush the fluid as well.

 

 

[Naut Owner]

I cannot vouch for the setup used on the Ford Edge, but this problem could possibly be associated with the booster throw rod extending to far into the master cylinder. It is starting to close the ports ready to supply fluid pressure to brake system. All may be ok initially, (when cold) but as vehicle warms up, the rod expands pushing further into the MC causing the brakes to apply. What may be happening, is that where you are bleeding from is relieving this pressure within the MC. Carefully match up your old cylinder to the new one. Check the rod between the booster and the rear piston of the MC. If you did not touch this rod adjustment, (if it has an adjustment) it is possible you could have a MC problem, whether it be the wrong application or a defective unit. If the rod has an adjustment, you would need to check how to adjust via FSM.

[1004ron]

On 12/6/2023 at 4:47 AM, RrmyGuy said:

I bought it from rockauto.com,  it's a centric brand master cylinder. It wasn't the cheapest, but it was listed as the favorite part. 

This is likely the same issue with the radiator cooling fans and their control module i.e. non-OEM replacements don't work.

 

If you've had the master cylinder off then you'll need equipment to perform the ABS bleed procedure.

Edited December 26, 2023 by 1004ron