F-150’s Single Cup Seal Master Cylinder is Leaking

Ford switched to a single-seal-cup master cylinder design for the 2013 F-150 and it didn’t take long for owners to start complaining about spongy brake pedals and a sudden inability to stop their trucks.

The new master cylinders are known for allowing brake fluid to leak back into the booster, limiting braking performance. Despite a bump in complaints, a federal investigation, multiple lawsuits, and even a recall for the 2013 and 2014 model years, Ford has continued to use the same defective master cylinder through the 2018 model year.

The Master Cylinder’s Role

So you want to stop your truck, great! When you apply force to the brake pedal it is amplified by a power brake booster (because you’re strong, but not that strong). The resulting force is used to move a pushrod into the master cylinder.

When the pushrod enters the master cylinder the wonders of engineering and science take over. Springs, pistons, and fluid dynamics all work together to generate hydraulic pressure that can be distributed to the brakes.

Maintaining pressure inside the master cylinder is essential to brake performance. For that, rubber seals are used to keep pressurized brake fluid from leaking out.

If the pressure is broken or leaks develop, the brake pedal will feel spongy and sometimes even continue to the floor after you’re done stepping on it.

Hitachi’s master cylinder design just isn’t working

Ford started using a master cylinder provided by Hitachi1. for the the 2013 F-150. Previously the part had been supplied by Bosch.

Hitachi’s design uses a single cup seal to keep pressurized brake fluid in place, compared to a more conventional design using two cup seals.

With double the load on the rubberized seal, it is essential that is seated properly. Hitachi’s design seats the seal in a machined groove, and it didn’t take long for Ford and Hitachi to realize that the seal is “rolling” in place and allowing brake fluid to escape.

In September 2015, Alejandro Rojas at Hitachi allegedly sent an email to colleagues saying:

“[We] have a big brake issue at Ford’s Dearborn Truck Plant. The issue is a leak in the master cylinder. There are between 20-25 vehicles that have failed.”_

A year later, an engineer at Ford’s Kansas City Assembly plant sent an email titled Master Cylinder reservoir seal partially not seated.

”Are you already aware of what looks like rolled seals on master cylinder assemblies that Dearborn Truck Plant found? If that is indeed the defect, this is something we have seen in the past.”

There certainly has been a spike in brake-related complaints. While most of the 2011 and 2012 complaints sent to CarComplaints.com are about a noisy and sometimes faulty vacuum pump, the number of overall complaints jumped for the 2013 model year, with at least 20 reports of brake failure.

The Master Cylinder Recalls

Following a preliminary investigation by the National Highway Traffic Safety Administration (NHTSA), Ford issued a recall for loss of the front brakes for the 2013-2014 F-150 with 3.5-liter engines.

Ford cited risks of compromised primary cup seals and loss of brake fluid back into the brake booster.

Lawsuits say the recall didn’t go far enough Master cylinder lawsuit points out internal communications

In September of 2018, Ford was sued for concealing master cylinder defects and not recalling enough trucks.

A second lawsuit was filed in October 2018 seeking financial compensation for any California based F-150 owner who paid for out-of-pocket-repairs. The lawsuit also called for a recall expansion.


  1. According to a lawsuit against Ford. We’re still looking for confirmation that the same master cylinder wasn’t used in previous model years. 

Vehicles That Might Have This Problem

Model Generation Years PainRank
F-150 12th Gen 2009–2014 59.75
13th Gen 2015–2019 36.82

Story Timeline

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