I have a 2007 F150 SuperCrew lowered. Since new, the brakes have been what I consider on the "soft" side. When I first start to brake, the peddle has more travel than what I feel it should. With a second pump of the brakes, the peddle travel is reduced by 40%. I have a motive power bleeder that I've used on my older rigs. Can I use this just as I do them? Are there any special bleeding requirements on this truck that are different from anything else? With all the computerized crap these days, I didn't want to just go about bleeding the brakes like I have on any other rig I've owned the past 30 years and find out I've spazzed the whole ECU and whatever else out.

So, to bleed normal.... or is there other stuff to watch out for?

Thanks in advance............

Don

 

Bleeding is normal... the pressure bleed should be fine. You won't damage anything (they bleed at 150 PSI at the OEM plant...) although I wouldn't recommend going anywhere near that high for any extended amount of time. I think most pressure bleed systems use about 30 PSI to push the fluid through the system so that will work just fine.

The reason the second pump feels stiffer (assuming you are doing a fairly quick double pump) is that you are "supercharging" the brake system. When you release the brake pedal, it takes a little while (roughly 0.5 to 1 second) for the brake fluid to travel back to the master cylinder. So every time you release you replenish a small amount of brake fluid over the master cylinder seals to make up for this fluid that is still at the wheels. Then (providing you don't hit the brakes again right away) the fluid makes its way back to the master cylinder and pushes back into the reservoir.

When you hit the brake pedal right away a second time, there is still some extra fluid in the system so the pedal feels stiffer. This alone does not indicate that you have a bad bleed... if there was air in the system it would still feel soft. But there could also be some air in there so it won't hurt to bleed if you think they are too soft.

BTW - I am a master cylinder engineer. (and before someone comes in and flames me, I'm not saying this to brag, or put other peoples ideas down, or anything like that... its just good sometimes to know that the information is based on facts and as opposed to something that my brother's neighbor's cousin told me )

 

some people have had luck extending the pushrod from the peddle to the master cylinder. Search for soft brake peddle solved or something like that

 

Thanks to both of you.... I'll proceed with the bleed just to make me feel better if nothing else.

I appreciate all the good info!!!!

Don

 

I bled my brakes, but still had the same problem. The answer was in this thread.... I turned my rod out 1/2 turn and the breaks are excellent.... no more excessive travel upon first application of the brakes... I no longer have to pump twice everytime I come to a stop!

https://www.f150online.com/forums/sh...t=bleed+brakes