an odd issue

helpimcrap · 20 Jan 2010 at 18:13

Right, car is a 1997 R reg ford galaxy.

MOT is coming up and we've been told brake servo is required as it doesn't work 'great' when engine is off. i thought brake servos were vacuum operated and if the car wasn't running a vacuum wasn't created and hence they don't work well when car isn't turned on.

having checked here it seems it's only required when the engine is running? or am i reading it wrong? every car i've had i'm sure the brakes have never been anywhere near strong when not running. and when towing a car i've always had to allow extra as the servo isn't running (as the cars not running) and sometimes really struggled to stop.

http://www.motuk.co.uk/manual_360.htm

Lashout_UK · 20 Jan 2010 at 18:24

The brake servo/booster stores vacuum, so that when the engine isn't running you've got a few attempts at using the brakes with vacuum assistance - so if the engine cuts out then you can stop the car safely.

Presumably the servo/booster assembly has a leak somewhere (or a weak diaphragm) so isn't holding vacuum with the engine off, so the brakes have very little (or no) assistance - and thus it needs replacing.

Is the lack of assistance noticeable with the engine running? Maybe that's why they've picked up on it? Testing the correct operation of the servo is part of the MOT but I don't know to what extent.

helpimcrap · 20 Jan 2010 at 18:31

it makes kinda a little sense. but i don't recall having a car it has actually been an issue on and it's never worked. :confused:

Lashout_UK · 20 Jan 2010 at 18:33

Well, presumably their booster systems were working properly?

You can easily feel the difference - kill your engine and pump the brakes several times to deplete the vacuum.

The pedal will go from usable and relatively easy to push, to firm and hard (fnaar) with a few ...strokes

The amount of assistance from the stored vacuum is much less than that with the engine running (maybe why you've not noticed it before, if that's what you're saying?), but still makes a considerable difference to the required pedal effort.

helpimcrap · 20 Jan 2010 at 20:05

just been out and tried it.

got up to 20mph, switched car off - tried brakes. they worked great and i'd say were servo assisted the first 4 or 5 times. after that they were rock hard and got harder from the first one but were a lot stronger than the 5th one. :confused:

Aero · 20 Jan 2010 at 21:58

helpimcrap said:
just been out and tried it.

got up to 20mph, switched car off - tried brakes. they worked great and i'd say were servo assisted the first 4 or 5 times. after that they were rock hard and got harder from the first one but were a lot stronger than the 5th one.

I'm not quite sure he meant do it whilst moving

Lopéz · 20 Jan 2010 at 22:05

helpimcrap said:
Right, car is a 1997 R reg ford galaxy.

MOT is coming up and we've been told brake servo is required as it doesn't work 'great' when engine is off. i thought brake servos were vacuum operated and if the car wasn't running a vacuum wasn't created and hence they don't work well when car isn't turned on.

having checked here it seems it's only required when the engine is running? or am i reading it wrong? every car i've had i'm sure the brakes have never been anywhere near strong when not running. and when towing a car i've always had to allow extra as the servo isn't running (as the cars not running) and sometimes really struggled to stop.

http://www.motuk.co.uk/manual_360.htm

You are completely correct.

The MOT test to see if a servo is working goes as follows:

Pump brake pedal a few times with engine off. Start engine keeping pressure on brake pedal. If pedal drops slightly when engine starts, servo is working.

helpimcrap · 21 Jan 2010 at 18:14

Lopéz said:
You are completely correct.

The MOT test to see if a servo is working goes as follows:

Pump brake pedal a few times with engine off. Start engine keeping pressure on brake pedal. If pedal drops slightly when engine starts, servo is working.

cheers for that. completely baffled me. asked a few mates but they weren't sure either. is the MOT guy having one over on us?

checked and you have to buy one from ford for the model - £400 with a discount!

just wiper blades and tyres besides that.

Biohazard · 21 Jan 2010 at 18:27

£400?

Aero · 21 Jan 2010 at 18:27

Just out of curiosity where are you taking your car for is MOT?

helpimcrap · 22 Jan 2010 at 12:41

Aero said:
Just out of curiosity where are you taking your car for is MOT?

got no idea - it was taken to a garage by the mechanic. been told it isn't an issue by someone who deals with cars a lot so hopefully this can be resolved.