Servo help wanted

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steve2286w

steve2286w

Well-Known Member
Posts
4,632
Location
monkeyangerland
HI my series 3 diesel landy failed MOT last week , on servo and a few other things,
I guess he tested servo by pressing brake pedal and starting engine expecting pedal to go down further as you would expect.

new servo fitted tonite tested as above and still the pedal does not creep down further, the pipes to vacuum tank and inlet manifold do not seem to leak (when left a few mins can be disconected and hissing heard as vacuum relaeased),

it needs to go to retest in next 2 days any suggestions on what else i can try to prove its working or not, any other reasons what stop pedal moving down
I read on forum the lack of vacuum on S3 deisels but did expect a wee bit of help from new servo
 
If it has a Vacuum tank the pedal WILL NOT be sucked down just by starting the engine UNLESS FIRST the brake pedal is repeatedly pumped to get rid of the stored vacuum in the tank, AND when you do it will take a good few seconds after starting the engine to build up enough vacuum to suck the pedal down, and when it does it won't feel like a lot as the vacuum won't have built up much.

Instant solution worth trying .... bypass the vacuum tank.
Connect the tube from the vacuum pump(or manifold nipple if a petrol engine) direct to the servo. Then it will react quickly like a normal car - because normal cars don't have vacuum tanks

Later take the tank off and empty it out of crap and rusty oily water.

let us know if you do this and if it helps.

CharlesY
 
Cheers CharlesY
bypassed vacuum tank but nothing felt on pedal when starting up, will clean out Vacuum tank later, when last on road the brakes stopped me but being a newby dont know what good series brakes feels like just want to get it through test, will google poogut too!
steve
 
steve2286w said:
Cheers CharlesY
bypassed vacuum tank but nothing felt on pedal when starting up, will clean out Vacuum tank later, when last on road the brakes stopped me but being a newby dont know what good series brakes feels like just want to get it through test, will google poogut too!
steve
Click to expand...


The servo itself holds vacuum for two or three shoves of the pedal.

The test is this:

stop engine.

pump brake pedal 5 or 6 times - it will feel hard after 3 or 4 shoves.

press brake pedal, and hold it pressed and be prepared for your foot to go down in a second.

with NO FOOT ON THROTTLE turn key to start engine into tickover speed.

in a second or so if the servo is working the pedal will feel as if it is being helped down but only if you "follow it down" with your foot.

make sure there's a Hell of a good suck into the inlet manifold nipple thing, and then at the hose end that fits to the servo. Hoses can choke.

Let us know!

Charles.
 
Hi Thanks for all suggestions, checked suck on pipe from manifold and very little, so cant imagine it being enough to move servo and pedal the butterfly spindle in manifold was loose in hole, i sealed this leak up and remade all rubber pipe ends and clamped jubillee clips still no movement on pedal,
when it goes for test tomorrow, will explain its not the servo thats inefficetive but the lack of vacuum and hope tester sees reason
 
You should check up on this. The vacuum in the manifold should be as good as that produced by the Puggy pump. If it isn't, there's a problem, probably a faulty manifold vacuum hose connector - it may have a one-way ball-valve or flap, and I reckon it's jiggered or blocked somehow.

If it isn't that, then the vacuum in the whole manifold is lousy, and that usually means the engine is sick as a parrot.

CharlesY
 
:) :)
Checked and cleaned one way ball valve in manifold, while investigating realised butterfly valve was open 2-3mm at tickover due to idle speed being controlled by hand throttle which reduces vacuum.
used slow running screw on pump ( which dosent open valve) to bring revs up to tickover and backed off hand throttle to about mid position.
greased up ends of butterfly spindle, and dum dum sealed around manifold adaptor
the suck on the pipe was much better and the pedal sinks like a stone, MOT tomorrow
Thanks for all your help,
steve
 
steve2286w said:
:) :)
Checked and cleaned one way ball valve in manifold, while investigating realised butterfly valve was open 2-3mm at tickover due to idle speed being controlled by hand throttle which reduces vacuum.
used slow running screw on pump ( which dosent open valve) to bring revs up to tickover and backed off hand throttle to about mid position.
greased up ends of butterfly spindle, and dum dum sealed around manifold adaptor
the suck on the pipe was much better and the pedal sinks like a stone, MOT tomorrow
Thanks for all your help,
steve
Click to expand...

Well well ..... ain't that just dandy now?

Nothing like a bit of suck to make a fellow feel good, eh HybridGirl .... ?

CharlesY
 
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