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Old 01-30-2011, 03:56 PM   #1
POOLSHARK
 
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Default 311 lwb Brake problems

I have a 2006 311CDI LWB sprinter camper van. Had it parked up for six weeks Nov/Dec 2010 when I went to move it i found a brake problem.

symptoms:

Tngine off brake pedal is as you would expect solid and quite firm.
Engine on Brake pedal slowly goes all the way to the floor when pressure applied.
The system is not loosing fluid and Master cylinder Res level is not dropping.
If I brake quickly it will still stop as normal so the "leak" is very small.

Actions taken;

I have checked and there is definitely no leaks from any caliper, brake pipe or anywhere else.

I have bled all brake lines just in case but no change in the fault.

My thoughts
Its either the Master cylinder or the ABS pump. as these are the only two components that can cause this fault. i.e let fluid back into Res and not out onto the grass.
The van has the uprated brake master cylinder i.e. the 25mm bore version TRW25. . Have stripped and checked master cylinder all looks good.

I have ordered a replacement master cylinder (so no seal kit is available for the 25mm bore unit) Which I will fit as soon as it arrives.


so in the mean time any ideas before i spend 600 + vat on a new ABS pump.??


Sorry for the long thread am trying to avoid the easy answers to stuff i already tried
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Old 01-30-2011, 06:08 PM   #2
bc339
 
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Default Re: 311 lwb Brake problems

Dr. A has a procedure for mushy brakes - it may help. Here's his write up from the Spongy Brakes thread:

Quote:
Originally Posted by mechreclined
One of my regular accts. just brought me an 06 2500 with spongy brakes.Tell me what you think.

Here is a reprint of my previous post that may help:

"I receive a lot of mail and phone calls on the subject of ('02-'06) Sprinter brake pedal feel, especially a perceived "abnormal sinking pedal".

Many first time Sprinter owners or those who drive other vehicles (more often than their Sprinters) are alarmed by a brake pedal feel that they are convinced is abnormal.

Here's how to tell if your Sprinter brake pedal action is "normal" OR in need of immediate service attention:

Engine running, push lightly on the brake pedal. Mushy and sinking seemingly endlessly toward floor? This may be NORMAL.

Engage Park and handbrake. Shut off the engine and then step on brake pedal 4 or 5 times. This releases the vacuum from the booster servo and reservoir-you should hear a loud hiss when pressing pedal each time until the vacuum is expended.

Engine still OFF, ALL vacuum expended, now step on brake pedal and exert a steady force. Pedal should move a relatively short distance (compared to before) and stop hard without further sinking- REGARDLESS of how long you exert foot pressure. This is the TRUE test of the brake master cylinder. If pedal slowly sinks to floor during this test- you have a problem.

Now step on pedal again and exert steady pressure while starting engine. With engine now running- the pedal should begin sinking steadily toward floor. This is NORMAL and indicates the engine's vacuum pump and the brake servo are working properly.

Take foot off the brake pedal and run the engine for a few seconds at 1500 rpm to build vacuum. Go back to idle speed, step on the brake pedal slowly-see the difference and the much greater sink distance compared to engine "off" and vacuum released?

Still convinced it's excessive pedal travel? Try this test-Engine running, move Sprinter to a downward sloping driveway, place in neutral and SLOWLY creep down hill. Gently apply brake pedal pressure and note how little pedal travel is needed to stop and hold the vehicle-now push harder-see how much pedal travel remains?

This long, soft, pedal travel is a normal characteristic of the Sprinters vacuum booster design when engine is running."

Doktor A

P.S. This is for the NAFTA T1N's, hopefully a similar setup on yours.
Hope this is some use.
Bruce
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Last edited by bc339; 01-30-2011 at 06:10 PM. Reason: Add
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Old 01-31-2011, 02:24 AM   #3
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Default Re: 311 lwb Brake problems

I believe he has a 2006 NCV not a Tin.
Richard
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Old 01-31-2011, 02:32 AM   #4
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Default Re: 311 lwb Brake problems

Yep, the 2006 caught me off guard.
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