Coastcard Posted July 18, 2009 Share Posted July 18, 2009 My brakes work fantastically for about 2 or 3 times while I am manoevering out of the drive (i.e. press brake pedal and almost hit the windscreen good) and after this it takes a heck of a lot of pedal power to get the thing to stop in a sensible distance. As a background, calipers are refurbed, new cylinders on rear drums, new copper pipes and recently changed the master cylinder with a new O ring as I thought this was the only thing left, but no change (if anything slightly worse). My thoughts were servo, but I have tested it by pumping pedal until hard and then starting engine. Pedal drops 1" as specified. It is not losing fluid, I think I have bled them OK ('cos it is similar symptom before and after m/c changed which involved a re-bleed). Did a search and there was a post with a similar problem, but unfortunately without the resolution. Anyone got any ideas? It just seems strange they work fantastically for a few pushes then go bad. Quote Link to comment Share on other sites More sharing options...
BogMonster Posted July 18, 2009 Share Posted July 18, 2009 What engine? 300Tdis have a habit of splitting the servo unit (check the can, close to the top of the two mounting bolts) this loses vacuum and gets progressively worse and you will find the emergency braking effort is way down as well, it happens to all of them even my 06 has already had a new servo! Need to get a new one, don't bother with genuine get an OEM version which is Lucas. Quote Link to comment Share on other sites More sharing options...
Coastcard Posted July 18, 2009 Author Share Posted July 18, 2009 Thanks Bogmonster. It's a V8 (Flapper efi). Are Lucas still in existence? Quote Link to comment Share on other sites More sharing options...
Coastcard Posted July 18, 2009 Author Share Posted July 18, 2009 Done some more checking. - Servo is not split by the mounting bolts. - Thought the suction hose could be closing under higher revs. This is OK. The initial stopping OK could be a red herring - due to low speed. As the vehicle does not get used much, maybe the pads need bedding in? Can they go off? Quote Link to comment Share on other sites More sharing options...
Briarston Posted July 18, 2009 Share Posted July 18, 2009 Done some more checking.- Servo is not split by the mounting bolts. - Thought the suction hose could be closing under higher revs. This is OK. The initial stopping OK could be a red herring - due to low speed. As the vehicle does not get used much, maybe the pads need bedding in? Can they go off? You say the vehicle is not used very much. It could be a light coating of rust on the discs that gives you extra friction until it has been polished off by the first few brake applications. This fits with the symptoms you describe. Quote Link to comment Share on other sites More sharing options...
reads90 Posted July 18, 2009 Share Posted July 18, 2009 Had the same problem in my 90 But that was a 300 TDi . Was pretty bad in traffic. Would work great first couple of times and then not work . On the 300 TDi it was the Vacum pump. Can't remeber what they have on the V8 that does the same thing . But i found this out after replacing the servo, master cylinder Quote Link to comment Share on other sites More sharing options...
jbs Posted July 18, 2009 Share Posted July 18, 2009 have a look at your wheel bearings as mine sometimes does this-what happens is-as the wheel rotates and is "off balance" so to speak this makes the brake disk(as it wobbles) push the brake pads/calliper pistons outwards when the wheel bearings are loose as the wheel rotates, the only way i can get a decent pedal is to pump the pedal to make the pistons go back to how it should be, as soon as it starts i know i have to adjust the damn things And before anyone says anything if i find it's started doing this i rectify it toot sweet as not to do so would be daft and dangerous to not only me but everyone else on the roads too Quote Link to comment Share on other sites More sharing options...
Coastcard Posted July 19, 2009 Author Share Posted July 19, 2009 Thanks for the suggestions guys. - Disks not too bad on the rust front. - V8 efi's use plenum suction, so just a pipe straight to servo. - Wheel bearings all new. I feel a trip to Chi 4x4 coming up. Quote Link to comment Share on other sites More sharing options...
ajh Posted July 19, 2009 Share Posted July 19, 2009 I am just going to fit hydroboost and be done with it (and get all that open space back where the booster was), messing around with vaccume boosters is just a nightmare and the double-diaphragm booster does not fit. Quote Link to comment Share on other sites More sharing options...
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