E450 brake problems

[Uk lexi]

Hi!
Ii am uk based and have owned a FR lexington since 2007
It's a e450 super duty with a V10 6.8 triton
Having problems with the braking system
Having lost a lot of brake fluid and not finding any signs as to where it has gone. everywhere is dry from the brake pedal to the rotors, pipes etc no signs
I have depleted the vacuum system and the brake pedal is staying hard. is it possible for the brake assist ( servo ) to be passing fluid if so where would it go. ?? And what short term damage would it cause
Any help would be greatly appreciated
John

[TitanMike]

Originally Posted by Uk lexi

Hi!

Ii am uk based and have owned a FR lexington since 2007

It's a e450 super duty with a V10 6.8 triton

Having problems with the braking system

Having lost a lot of brake fluid and not finding any signs as to where it has gone. everywhere is dry from the brake pedal to the rotors, pipes etc no signs

I have depleted the vacuum system and the brake pedal is staying hard. is it possible for the brake assist ( servo ) to be passing fluid if so where would it go. ?? And what short term damage would it cause

Any help would be greatly appreciated

John

When brake fluid disappears with no visible signs it is usually a leak in the master cylinder where it joins the vacuum booster.

Two ways to diagnose. The hard way is to remove the master cylinder and look at it's rear where operating rod sticks out.

Another is far easier. Take a sheet of newsprint and roll it into a long, tight piece about the size of a long thick pipe cleaner.

Once you have this done remove the vacuum check valve on the booster can. It is the fitting where vacuum hose is attached and almost all check valves have a barbed tube that is pushed into a rubber grommet. With the check valve out use the tightly rolled newsprint as if it was a dipstick and probe ihe inside of the booster can's lower regions.

There should be NO brake fluid in this can and if the end of the newsprint comes out wet, master cylinder needs replacement.

Newsprint is preferred over regular paper as it will suck up liquids immediately and there will be no question if it's wet.

Good luck but based on your description that's the only place left for the fluid to go.

Sent from my SM-N950U1 using Forest River Forums mobile app

[Uk lexi]

Hi thanks for the information will try and sort it out with your recommendation..
Thanks john

[TitanMike]

Originally Posted by Uk lexi

Hi thanks for the information will try and sort it out with your recommendation..
Thanks john

Good luck and if you solve your problem come back and let us all know what you found.

Others with the same issue or question will benefit.

[2021rvers]

If it has a vacuum booster could be getting sucked in from the rear piston seal on the master cyl. If you remove all the vacuum from the booster wether you have a bad master cyl or not your pedal will be rock hard. Remove bolts from master cyl and pull it forward if it's wet there's your problem.

[TitanMike]

Originally Posted by 2021rvers

If it has a vacuum booster could be getting sucked in from the rear piston seal on the master cyl. If you remove all the vacuum from the booster wether you have a bad master cyl or not your pedal will be rock hard. Remove bolts from master cyl and pull it forward if it's wet there's your problem.

True, this also works but often the brake lines connected to the Master Cylinder, being rigid and usually with no "slack" make the "paper dipstick through the vacuum port" a lot quicker and easier.

In most cases where one has absolutely found zero leaks at calipers, wheel cylinders, flexible lines, proportioning/failure indicating valves, ABS controllers, and every inch of the steel brake lines, they just plan on replacing the master cylinder. Removing it usually just confirms it's bad.

Also, another indicator that the M/C is leaking into the booster is when divided M/C reservoir's rear portion is where the loss of brake fluid occurs.

[Larry-NC]

Originally Posted by 2021rvers

If it has a vacuum booster could be getting sucked in from the rear piston seal on the master cyl. If you remove all the vacuum from the booster wether you have a bad master cyl or not your pedal will be rock hard. Remove bolts from master cyl and pull it forward if it's wet there's your problem.

True, but Post #2, posted 23 hours before yours, shows an easier way to detect the same problem.