Brake Booster - 2018 2.3L Ecoboost

[Rick369]

I have a 2018 2.3L Ecoboost Convertible with 28,000 miles. I returned to my home in Wisconsin in March and the Mustang sat in my garage in Florida for 2 1/2 weeks. I returned to Florida in early April and removed the battery maintainer. The battery was fully charged. I went to start it and the brake peddle was as hard as a rock and wouldn’t move. I finally got the brake peddle to move after applying a lot of force with my foot and the car started. I was concerned and made an appointment with my local Ford dealer in Florida. Took the car in and the technician said the brake booster was leaking and needed to be replaced. The dealership is waiting for the new brake booster to arrive. I currently have a free 2019 Escape loaner.

Anyone else have a leaking brake booster replaced on their S550 Mustang?

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[BoostedCanadianPoney]

i leave my car sitting for a few weeks without driving and no battery tender. never had issues. I was wondering did you do anything else other than a battery tender before the issue ?

 

[Rick369]

Nothing but the battery maintainer which I always do when the car will be sitting for more than a week without being started.

 

[Cobra Jet]

I have a 2018 2.3L Ecoboost Convertible with 28,000 miles. I returned to my home in Wisconsin in March and the Mustang sat in my garage in Florida for 2 1/2 weeks. I returned to Florida in early April and removed the battery maintainer. The battery was fully charged. I went to start it and the brake peddle was as hard as a rock and wouldn’t move. I finally got the brake peddle to move after applying a lot of force with my foot and the car started. I was concerned and made an appointment with my local Ford dealer in Florida. Took the car in and the technician said the brake booster was leaking and needed to be replaced. The dealership is waiting for the new brake booster to arrive. I currently have a free 2019 Escape loaner.

Anyone else have a leaking brake booster replaced on their S550 Mustang?

No offense, but if excessive force was applied to the brake pedal, which would then be applied to the booster, it’s very possible by that force seals were damaged.

If the booster was leaking down prior to that day, you would have a spongy pedal, there would be fluid found under the car too (especially if the car was sitting for a bit). Even if the booster were not leaking fluid, but had a vacuum leak the pedal wouldn’t be difficult to press down.

I can’t find it, but there were other threads on here with other members having the same issue across the platforms such as what you had experienced, it’s not EB, GT or V6 specific... maybe someone else will have better luck finding those threads.

 

[Rick369]

No fluid leakage under the car in my garage. Floor is bone dry. Brake pedal was not spongy before I parked it for 2 1/2 weeks or when I drove it to the dealership to have it checked out. Braking and brake pedal movement seemed normal.

 

[Niz55]

Could be your check valve.

 

[Rick369]

Local Ford dealership finally received the new brake booster today. It was on backorder with Ford for 1 week. The service advisor said the brake booster they received from Ford had a new part number and not the same as the defective one they removed. I have no idea if this is true. The part number of the brake booster assembly on the work order that they installed is JR3Z2005A. There was also quantity of 2 PM20 brake fluid.

Here is the work order information.

Performed brake booster component test as per workshop manual system chart. Brake booster needs to be replaced. Removed wiper arms, cawl assembly, cawl extension, master cylinder to access brake booster. Removed and replaced brake booster. Performed manual brake system bleed. Bench bleed master cylinder. Hook up IDS and perform ABS service bleed. Road test vehicle. Ok to return to customer.

 

[Niz55]

Brakes feel good now?

 

[Late Starter]

I had the same symptoms when the car only had 3,000 miles. Rather than having the dealer putz around with it, I replaced the check valve and still had the problem. Thought it was the booster, but I decided to try another check valve and solved the problem. By the way, the only time a booster will leak fluid is if the master cylinder leaks into it.

 

[Rick369]

Brakes feel good now?

So far good. Brake pedal seems to have a much better feel to it now than before the brake booster was replaced.

 

[Rick369]

Update:
It has been 1 month since my brake booster was replaced. I have not experienced any hard brake pedal feel while starting the Mustang since the brake booster was replaced. On a number of occasions the Mustang has sat for 3-4 days without being started. Looks like the Ford dealership technician diagnosed the problem correctly.

 

[gamecoc430]

I have the same exact problem. Sometimes it's when the car sits for a few days, other times it may only sit for a few hours. I just couldn't start mine when placing a foot on the brake pedal and pushing the start button. Everything worked - instrument panel, radio, seat moved into position, but car would not crank over. If I used my FOB to do a remote start (while sitting in the driver's seat) it would crank. Dealer said they had no idea what was wrong, but to bring it in the next time it happened. Duh, if it won't start how am I supposed to bring it in? Finally after many, many times of having this problem I would try pushing REAL hard on the brake pedal it would start. Brakes have always worked great, no leakage as far as I can tell, but I'll be talking it in shortly for service and have them look at the booster. Thanks for posting your problem, and fix, as well.

Bob A.

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