Brake pedal on E350 sinking to the floor!!

[dgt62]

Hi All,
I have a 1995 C class RV on a E350 chassis I have just replaced the two front brake hoses with NEW ones I have bled the brakes and have a good pedal but when you keep your foot on it it goes slowly to the floor, there are no fluid leaks so I though that the master cylinder was shot I replaced it with a NEW cylinder that came from the States, bled the brakes again and it is still doing the same thing the pedal is still going slowly to the floor can anyone help with this one??

Dave.

 

[Terry]

Hi Dave you must have a leaky slave cylinder/or pipe as well somwhere:thumb:
terry

 

[dgt62]

Hi Terry,
Many thanks but I have checked all that every thing dry as a bone.
Cheers Dave.

 

[Tony Santara]

Hi Dave
Check all your fittings/unions to your brake pipes and mastercylinder again it sounds like it might be still drawing air into the system if that doesn't work you may have to use an "air pressure bleed kit" to get rid of an air trap

 

[wildcamper]

Hi dgt62
I had the same thing and as Tony said your better with an air bleed kit, Also does yours have the double bleed screw on each side ?

If it has a double caliper like mine did, Then you may have to clamp one of the feed pipes while you bleed it, Then clamp the other.

It sounds like you have got air in the system, If you use the easy bleed, it does do a much better job than the old fashioned way.

Hope you get sorted :thumb:

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[Digger Driver]

You could also try clamping off your flexi hoses one at a time to try locate the problem!

 

[Sundowners]

Do you have to top up the fluid??
Nigel

 

[DEL374]

Brakes

Hi All,
I have a 1995 C class RV on a E350 chassis I have just replaced the two front brake hoses with NEW ones I have bled the brakes and have a good pedal but when you keep your foot on it it goes slowly to the floor, there are no fluid leaks so I though that the master cylinder was shot I replaced it with a NEW cylinder that came from the States, bled the brakes again and it is still doing the same thing the pedal is still going slowly to the floor can anyone help with this one??

Dave.

Have a look at the rear flexis make sure they are not swelling up when the brake is pressed ,make sure pads are free in calipers you can buy a vacuum brake bleeder from machine mart (we use one in my garage for repairing customers cars) then if you still have trouble it looks like master cyclinder.DEL374

 

[dgt62]

Hi All,
Many thanks for all your replys I will have another go at them ASAP and keep you posted I hope it is only air and not the master cylinder again as the one that I put on is NEW and don't want to send to the States for another one.
Cheers Dave.

 

[pudseykeith]

hi Dave. If the pedal is spongey and if you can pump up the brake pedal to give you some resistance the chances are the problem is air in the systme.
But if when you press the pedel it is hard, but then slowly creaps to the floor under sustained presure it will be the master cylinder. [ brake fluid slowly leeking past the master cylinder seals. If the master cylinder is a reconditiond one its not unknown that it could have been assembled wrongly. If you decide to open it up get a qualified machanic to do it. cleanliness is paramount
Brake calipers when the piston are pumped out when parcialy worn brake pads are used cane retain trapped air. a good weese is to remove the pads, open the bleed screw, [BS ] and then push the pistons fully into the caliper, thighten the BS then pump out the pistons in the caliper, carefull not to pump the piston right ot of the caliper , then open the bleed screw again and push the piston back fully into the caliper so displacing the trapped air. Repeat the exersize untill there is no air being detected in the flow of fluid. Repeet on the other wheel on the same axel. If the caliper has two piston you will need to push both piston in at the same time.

If a bleed screw is jamed or brocken in, back of the brake pipe nut that is closest to the caliper and use this loosened nut instead of the bleed screw and repeet as described. When backing of this nut be carefull not to twist of the end of the brake pipe. Care and patiants may be needed and there is a posability that the pipe will be damage if it is badly corroded in due to age. oh:

Hope this helps, Pudseykeith. :thumb:

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[dgt62]

Hi Keith,
Mumber two that you said, hard pedal them sinks when you keep you foot pushed down on it the cylinder is a New one and not a recon., you see as I said before all I done was replace the two front hoses and also I forgot to say oh: I replaced the main brake pipe that runs from the front to the back a I am now starting to thing that the New cylinder is faulty.
Dave.

 

[American Dream]

Hi Keith,
Mumber two that you said, hard pedal them sinks when you keep you foot pushed down on it the cylinder is a New one and not a recon., you see as I said before all I done was replace the two front hoses and also I forgot to say oh: I replaced the main brake pipe that runs from the front to the back a I am now starting to thing that the New cylinder is faulty.
Dave.

Hi Dave,

Is it a dual Circuit Master Cylinder?If Dual Circuit, are you getting a brake fail warning lamp in the Dashboard?

Is it possible to put 1 / 2 short pipes on the cylinder and cap/clamp them off and try the Pressure test again to prove?

Just a thought.

You really don't want to incur the cost of shipping back to the USA if the cylinder proves to be ok after all.

 

[wildcamper]

Hi did you bleed the back brakes aswell ???

 

[Steptoe]

Hi, all the above comments are useful and valid, but for the cause it helps to go back to the beginning!

I'm guessing you changed your front flexible pipes because of cracking rather than because you were experiencing the pedal problem? If so the pedal problem was caused by doing the job! It is easy to check whether there is a fluid leak from either end of these pipes, (visual) or air in the system ( pedal will 'pump up' as has already been suggested)

The worst case senario is that the action of bleeding the brakes with the pedal has damaged the seals in the master cylinder (pedal right to floor puts the seals into contact with a unaccustomed bit of the master cylinder bore) and of course this can happen equally on a reconditioned cylinder though not on a brand new one (don't know which your replacement one was?)

Geo once gave me an excellent bit of advice re. brake bleeding and that was to gravity bleed without touching the brake pedal, where is he when you need him

As other posters have suggested, check & check again for leaks, bleed without pumping pedal, then ond only then try another master cylinder.

PS have a look at the rear wheel cylinders, IME these leak at the drop of a hat and may well have given up as a result of the unaccustomed pressure

Edit....Memo to self: read page 2 before posting & note that NEW cylinder has been fitted

 

[pudseykeith]

Hi Dave. The sugestion made by American Dream is a sound one. If you have a brake pipe flairing tool, make a pipe about 6 inch long ,complete with a pipe nut. Flaten the other end and screw it into the master cylinder. I f it is a tandam Cylinder Repeet on the other exit . Dont tighten the pipes fully,just off nip, fill the cylinder with brake fluid. Get 'Daves little helper' to slowly press the peddle. When air stops seeping past the brake pipe nuts tighten them up as presure is being applied. This will issolate the master cyl from the brake system. Then put sustained presure on the brake pedle. If it sinks it is a problem with the master cylinder.
If this test proove that the cylinder is sound when you start to bleed the brakes again, start by backing of the pipes that exit the cylinder first and bleed until air stops being expelled and tighten each as they bleed clear. If the pedle goes to the board before they are clear of air tighten the nut up BEFORE the pedle is SLOWLY SLOWLY DRAWN BACK. When its fully back repeet the prosses until no air is expeled. Master cylinder fluid reservoys dont hold a large amount of fluid and can soon run out so keep it full. If it draws air you will have to start the procces all over again. If you did a good job of bleeding the first time you could find that the job is then sound. If in dought repeat the procces at the next pipe nut down the line.
I hope this helps, Pudseykeith. [ Ramberling fred rumpole ]

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[Mitch]

E350 Brakes

Hi , same problem here with a '95 E350, but I'm also getting an ABS warning light.

I'll go through the brake system logically this weekend and bleed, but any idea's on the ABS would be apreciated

Cheers, Mitch

 

[American Dream]

Hi , same problem here with a '95 E350, but I'm also getting an ABS warning light.

I'll go through the brake system logically this weekend and bleed, but any idea's on the ABS would be apreciated

Cheers, Mitch

I had that on my vehicle.Turned out to be a faulty sensor.

Not an easy one to find unless you have access to a diagnostics Unit.

Assuming the visual comes up with no leaks, and the bleeding does not fix it, you might find it quicker to get a garage to interrogate the unit.

I guess Geo will be able to offer some firm advice.:thumb:

 

[dgt62]

Hi All,
Problem solved ! Air Air and more Air but first let me thank you all for your replys
it is good to know that there is lots of helpful people here that you can turn to for some help many many thanks I had to bleed the brakes five times I also did not know that with ABS and the engine running your pedal will travel with your foot on it until it gets about 3ins from the floor and with the engine off a good hard pedal .
Dave

 

[Tony Santara]

Hi All,
Problem solved ! Air Air and more Air but first let me thank you all for your replys
it is good to know that there is lots of helpful people here that you can turn to for some help many many thanks I had to bleed the brakes five times I also did not know that with ABS and the engine running your pedal will travel with your foot on it until it gets about 3ins from the floor and with the engine off a good hard pedal .
Dave

Well done Dave :thumb:
It's suprising how much air you can get in such a small bore pipe
Good job you didn't whip the the master cylinder off to the states again
We're all learning all the time

 

[American Dream]

Hi All,
Problem solved ! Air Air and more Air but first let me thank you all for your replys
it is good to know that there is lots of helpful people here that you can turn to for some help many many thanks I had to bleed the brakes five times I also did not know that with ABS and the engine running your pedal will travel with your foot on it until it gets about 3ins from the floor and with the engine off a good hard pedal .
Dave

Nice one Dave.

Glad you're sorted.:thumb:

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[pudseykeith]

Well done Dave, pleased it sorted.

Pudseykeith