mellonman Posted December 27, 2012 Share Posted December 27, 2012 hi all looking for some help about diesel vacuum pumps that are needed for braking / after a scary brake failure i started to check for problems with a peugeot 306 dturbo stage II, what i have is that i can pump the brakes up with the engine off but when i start it the pedle stays hard for a long time unless i rev the engine! if driving if i press once its fine and gets worse every time i press the pedle until i drive again i have checked all the vac pipes and one way valves and all seems fine but when i check to see how much vacuum the pump is pulling it seems very low hardly any suction when i put my finger over the hole but when i rev its fine also i took the pump off the crank and found that on the inside there are 2 holes with a reav valve sort of thing that had come displaced from what looks like its normal position. how much vacuum do these pumps generate at idle? ( should it have a good suck oooh errh at idle ) should i replace the pump its a pierburg type i know its a long shot but some of you guys might very well know Quote Link to comment Share on other sites More sharing options...
Benjy Posted December 27, 2012 Share Posted December 27, 2012 Should have a reasonable vacuum mate. When you say crank, I assume you mean cam? Quote Link to comment Share on other sites More sharing options...
absz Posted December 27, 2012 Share Posted December 27, 2012 You will normally have to rev the engine slighty at idle to feel the pedal creep down on MOST diesel engines. if you keep pumping the pedal at idle then it will loose the vaccum which is built up by the pump and pedal will go hard quite normal. Quote Link to comment Share on other sites More sharing options...
mellonman Posted December 28, 2012 Author Share Posted December 28, 2012 (edited) sorry yes i do mean cam lol. so when you say fair vacuum i take it that this amount would be enough to hold your finger there with a little force ? i mean i can hardly tell that there is anything there at all. IE, its enough to hold a small peace of paper BUT NOT enough to hold a peace of card . when i say rev i have to floor it really to make it work normally, So you can make the brake pedal hard even with it idling? these brakes are like press it once its good it has the stored vac come off slightly and the repress pedal you loose about 50% braking power then if you have to release and press again you loose about 80% braking power :o sorry for all the noob questions about this think i will get one from the brakers yard and change it as i dont think its right Edited December 28, 2012 by mellonman (see edit history) Quote Link to comment Share on other sites More sharing options...
Benjy Posted December 28, 2012 Share Posted December 28, 2012 No it should suck your finger. Not so much that it makes you jump thinking it's gonna pull your finger off, but you should know it's doing it. I'd get a new'un mate. Also check your oil level. The last few vac pumps i've replaced have been caused by oil starvation. Quote Link to comment Share on other sites More sharing options...
mellonman Posted December 28, 2012 Author Share Posted December 28, 2012 oil levels good mate , this pump is deffinatly shot then i would say then thanks for the help Ben i will update once i have a replacement Quote Link to comment Share on other sites More sharing options...
Benjy Posted December 28, 2012 Share Posted December 28, 2012 No worries dude Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted December 28, 2012 Share Posted December 28, 2012 Might also be the diaphragm on the servo, if its not the pump. Quote Link to comment Share on other sites More sharing options...
mellonman Posted December 28, 2012 Author Share Posted December 28, 2012 Might also be the diaphragm on the servo, if its not the pump. how do i go about checking that? when i blow down the vac pipe its solid as a rock and when i suck i can feel the diaphragm release, i cant hear any hissing from inside the car, i know the servo may be shot too but this pump does seem a high suspect at the mo and is easy to change Quote Link to comment Share on other sites More sharing options...
mellonman Posted December 29, 2012 Author Share Posted December 29, 2012 Well as I thought the vacuum pump was shot stopped for a new one and it's good as new Thanks for all the input guys great help Quote Link to comment Share on other sites More sharing options...
Benjy Posted December 29, 2012 Share Posted December 29, 2012 No worries dude. Glad to be of assistance Quote Link to comment Share on other sites More sharing options...
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