300tdi vac pump

[harry]

does anyone know what vacuum the vac pump in a 300 tdi should pull?

i have just tested mine and am getting 22 in hg.

the reason i ask is that i suspect my vac is low causing a hard brake pedal, with the resultant lack of braking retardation, and an impossibly hard to push pedal.
the vehicle is a 95 disco 300 tdi.

[Outlaw]

No idea but i do have a s/h one from a disco if you need it. Bought it off Outkast back in March when i was having a couple issues but the problem's never returned.

[DRanged]

Harry
About 480 mbar when I tested the pump in the disco I wrecked. Cant find my conversion chart though. I do have a real nice 12v vac unit from a Hot Rod if you want to rig it up and try it?????

Justin

[mudder110]

sounds.like.vacum.pump.is.shot.any.oil.leaking.if. so.will.be.shot.
but.make.sure.you.replace.brake.booster.as.well.or .vac.pump.will.fail.
at.around.20oooks:)

[justinc]

does anyone know what vacuum the vac pump in a 300 tdi should pull?

i have just tested mine and am getting 22 in hg.

the reason i ask is that i suspect my vac is low causing a hard brake pedal, with the resultant lack of braking retardation, and an impossibly hard to push pedal.
the vehicle is a 95 disco 300 tdi.

Harry, 22inhg is OK, I'd be looking closely at the plastic line between the booster and the vac pump for leaks. Did you test it at the booster end?

A normal petrol vehicle will have that sort of reading at idle. Maybe 25 but you should be fine at 22.
These boosters have been known to pack it in on the second stage too, but only seem obvious under hard applications. Normal use they seem no diffrent usually.

JC

[harry]

thanks all for the replies.

oh dear, 480 mbar, what's that in inches of mercury?
when did vacuum go metric/

i will have to go and sit in a book for a while on that one or drop down and check my jigger with your gauge.

my pump isn't leaking, just didn't know what it's supposed to pull.

josh, look out, i might borrow yours for a swap test.

jc, thanks, i did test it at the booster end, and when i pulled the hose off at the booster just after shut down, the vacuum in the booster sucked in.
the line doesn't appear to have any leaks.
can you tell me more about the booster and 'second stage'?
although the booster appears to hold vac, the pedal is very hard, and any extra pushing, like trying to not run down the ricer in the on ramp merge lane, when you need to push harder, this car doesn't slow faster, like when you jab the boot on the pedal, and then want to push more, it doesn't slow any faster.

[bee utey]

thanks all for the replies.

oh dear, 480 mbar, what's that in inches of mercury?
when did vacuum go metric/



1 bar = 1000 mBar = 1 atmosphere's worth of pressure = 14.4 psi = 30 inches of Hg pressure. So 480/1000 times 30 is about 14 inHg; vacuum or pressure, works both ways so long as you know which end you are working from.:)

[justinc]

thanks all for the replies.

oh dear, 480 mbar, what's that in inches of mercury?
when did vacuum go metric/

i will have to go and sit in a book for a while on that one or drop down and check my jigger with your gauge.

my pump isn't leaking, just didn't know what it's supposed to pull.

josh, look out, i might borrow yours for a swap test.

jc, thanks, i did test it at the booster end, and when i pulled the hose off at the booster just after shut down, the vacuum in the booster sucked in.
the line doesn't appear to have any leaks.
can you tell me more about the booster and 'second stage'?
although the booster appears to hold vac, the pedal is very hard, and any extra pushing, like trying to not run down the ricer in the on ramp merge lane, when you need to push harder, this car doesn't slow faster, like when you jab the boot on the pedal, and then want to push more, it doesn't slow any faster.

Harry, they have a second diaphragm, if thaat is no good you can still have vac when you pull the hose off, its only the first stage you are hearing. AFAIK once you pull them apart there is no refitting them back together, it is however a very easy job to replace them. If you can borrow a known working example it would be a cinch to swap it in and try, obviously after you have discounted the pump for low output. BTW, when the engine is running, does the vacuum in the pipe pulse very harshly? or a smoother small pulse and strong vacuum? If harsh like ffft ffft ffft then the pump could well be unable to keep up, one of the valves is leaking internally.
Sorry, not sure to convert mbars to Inhg:(


JC

[harry]

thanks jc,

mumbles and wanders off to find a new booster.

look out gumboot!

i have suspected that all along, 95 car, so it's not unlikely to be sick.
the maint manual does have a good description and diagrams that make sense to the people that wrote them, but not to me.
this thing is an abs car also, so that had me lost for a while also, but i know the abs works.

i will check the pulsing tomorrow, i haven't noticed, but wasn't aware of this either.

[Ace]

I am having the same issues in mine to Harry. I have done the fix a couple of times now but its time to admit defeat and buy a new one I think.