Brake issue immediately after start

[Ross Del Duca]

I searched around and haven't seen anyone else mention this. I've had 3 instances where, immediately after starting and driving for about half a block, on my first brake application, the pedal is incredibly stiff and the truck doesn't stop. After panicking and pressing REALLY hard, the ABS activates and the truck stops. This has only occurred immediately after starting up.

Definitely going to make an appointment but.... anyone else heard of this?

Sponsored

 

[Lunchbox88]

I searched around and haven't seen anyone else mention this. I've had 3 instances where, immediately after starting and driving for about half a block, on my first brake application, the pedal is incredibly stiff and the truck doesn't stop. After panicking and pressing REALLY hard, the ABS activates and the truck stops. This has only occurred immediately after starting up.

Definitely going to make an appointment but.... anyone else heard of this?

Havent seen this brought up before. Definitely abnormal behavior and should be looked at by the dealer. Based on your description, sounds like it could be fairly dangerous. As to the cause, Im not really sure. Does the braking feel return to normal after the ABS activates?

 

[P. A. Schilke]

I searched around and haven't seen anyone else mention this. I've had 3 instances where, immediately after starting and driving for about half a block, on my first brake application, the pedal is incredibly stiff and the truck doesn't stop. After panicking and pressing REALLY hard, the ABS activates and the truck stops. This has only occurred immediately after starting up.

Definitely going to make an appointment but.... anyone else heard of this?

Hi Ross,

Have not heard of this before, but definitely needs attention of the dealership service department. Do you start and go quickly or do you let it idle for a few minutes? Here is the deal with turbo engines...when under boost there is no vacuum and it sounds like your vacuum booster is loosing vacuum overnight and not recharged before your first brake application. One of the ways the system gets vacuum while being boosted is with a little venturi that pulls a vacuum by using boost pressurized air flowing through it. The venturi causes a pressure drop which results in vacuum...so something in this system is not working properly and needs a diagnosis. Usually there is a switching valve that switches vacuum source depending if there is boost pressure or not..It maybe this valve is not switching. This is just a SWAG....

best,
Phil Schilke
Ranger Vehicle Engineering
Ford Motor Co. Retired

 

[Ross Del Duca]

Havent seen this brought up before. Definitely abnormal behavior and should be looked at by the dealer. Based on your description, sounds like it could be fairly dangerous. As to the cause, Im not really sure. Does the braking feel return to normal after the ABS activates?

It does return to normal after that. Immediately actually.

 

[Ross Del Duca]

Here is the deal with turbo engines...when under boost there is no vacuum and it sounds like

Oh.... you know what - that is EXACTLY what it feels like. Like the vacuum booster has failed. I wasn't sure if these rangers were drive by wire or not.

 

[P. A. Schilke]

Oh.... you know what - that is EXACTLY what it feels like. Like the vacuum booster has failed. I wasn't sure if these rangers were drive by wire or not.

Hi Ross,

This is from the shop manual.....

Component Test- Brake Booster

1. Disconnect the brake booster vacuum sensor/check valve from the brake booster and connect a suitable vacuum/pressure tester to the booster side of the vacuum sensor/check valve.

1. Apply the parking brake, start the engine and place the transmission in NEUTRAL.
   • Allow the engine to reach normal operating temperature.

1. Verify that vacuum is available at the vacuum sensor/check valve with engine running at normal idle speed.
   • The vacuum gauge should read between 51-74 kPa (15-22 in-Hg).
   • If specified vacuum is available, stop the engine, connect the vacuum sensor/check valve and continue with Step 5.
   • If specified vacuum is not available, continue with Step 4.

1. Disconnect the vacuum sensor/check valve from the vacuum hose and verify that the specified vacuum is available at the hose with the engine at idle speed and the transmission in NEUTRAL.
   • If specified vacuum is available, stop the engine, install a new check valve and continue with Step 5.
   • For vehicles equipped with a brake vacuum pump, if specified vacuum is not available, inspect the vacuum hose and install new as necessary. If the vacuum hose is OK, install a new vacuum pump.
   • For vehicles not equipped with a brake vacuum pump, if specified vacuum is not available, stop the engine, connect the vacuum hose to the check valve and diagnose the no/low vacuum condition. Carry out the Intake Manifold Vacuum Test.
     REFER to: Engine (303-00 Engine System - General Information, Diagnosis and Testing).

1. Apply the brake pedal several times to exhaust all vacuum from the system.

1. Apply the brake pedal and hold it in the applied position. Start the engine and verify that the brake pedal moves downward after the engine starts.
   • If the brake pedal moves, the brake booster is operating correctly.
   • If the brake pedal does not move, install a new brake booster.
     REFER to: Brake Booster (206-07 Power Brake Actuation, Removal and Installation).

1. Operate the engine a minimum of 20 seconds at idle. Stop the engine and let the vehicle stand for 10 minutes, then apply the brake pedal. The brake pedal feel should be the same as that noted with the engine operating.
   • If the brake pedal feels hard (no power assist), install a new brake booster vacuum sensor/check valve and retest.
   • If condition still exists, install a new brake booster.
     REFER to: Brake Booster (206-07 Power Brake Actuation, Removal and Installation).
   • If the brake pedal feels the same as noted with the engine operating, the vacuum sensor/check valve is functioning properly

Best,
Phil Schilke
Ranger Vehicle Engineering
Ford Motor Co. Retired

 

[Ross Del Duca]

Hi Ross,

This is from the shop manual.....

Component Test- Brake Booster

Thanks! Got it back from Ford service and the not-surprising response from them was "We can't reproduce the problem." Given that it seems to happen once every 2 to 3 weeks on a daily driven vehicle that was pretty much what I expected.

You've given me some new things to try on my own. I appreciate it!

Sponsored