benny Posted July 6, 2013 Share Posted July 6, 2013 Hi All, Helping a friend out with his project. Rears have been updated to r31 units everything else is factory. Bled the brakes up the other day and had a reasonable pedal(didn't road test but felt firm) went out today after finishing the clutch off and no brakes at all, pedal just goes to the floor. Have checked for fluid on the ground/leaks and cant see anything. Ideas? Master is new also. Benny Quote Link to comment Share on other sites More sharing options...
zzzzed Posted July 6, 2013 Share Posted July 6, 2013 Air lock? Quote Link to comment Share on other sites More sharing options...
benny Posted July 6, 2013 Author Share Posted July 6, 2013 air still in the lines? perhaps.... bled it quite thoroughly though. Quote Link to comment Share on other sites More sharing options...
dat2kman Posted July 6, 2013 Share Posted July 6, 2013 Unscrew caps on master cylinders, let us know what, or what isn't , in there. Peel back carpet inside footwell. Any mousture? Possibly master has crapped a seal, and leaked it all back into the Vac unit. Quote Link to comment Share on other sites More sharing options...
RLY240 Posted July 7, 2013 Share Posted July 7, 2013 Did you bleed the master cylinder? Quote Link to comment Share on other sites More sharing options...
nizm0zed Posted July 7, 2013 Share Posted July 7, 2013 Possibly master has crapped a seal, and leaked it all back into the Vac unit. Thats what i'd be thinking too... Also, has it been sitting for a few days leaking onto a porous ground surface? even concrete is porous. If so, it could have leaked out enough fluid via line fittings ect (look at the connections to the rear calipers you just changed) and soaked into the ground. Would only leave a stain but not necessarily a wet patch. Did you use new flare fittings on the lines or the existing ones when you changed the calipers over? Do the flare fittings match the calipers? Quote Link to comment Share on other sites More sharing options...
benny Posted July 7, 2013 Author Share Posted July 7, 2013 Unscrew caps on master cylinders, let us know what, or what isn't , in there. Peel back carpet inside footwell. Any mousture? Possibly master has crapped a seal, and leaked it all back into the Vac unit. fluid levels in master havent moved/changed. Did you bleed the master cylinder? now that I think about it i didn't bleed the master just the callipers. could this be the issue? Thats what i'd be thinking too... Also, has it been sitting for a few days leaking onto a porous ground surface? even concrete is porous. If so, it could have leaked out enough fluid via line fittings ect (look at the connections to the rear calipers you just changed) and soaked into the ground. Would only leave a stain but not necessarily a wet patch. Did you use new flare fittings on the lines or the existing ones when you changed the calipers over? Do the flare fittings match the calipers? Im 99% sure that there were no marks on the ground but will double check the actual callipers. Used old/existing flare fittings which im 99% sure are correct for the R31 calliper. Quote Link to comment Share on other sites More sharing options...
Moderators Zedman240® Posted July 8, 2013 Moderators Share Posted July 8, 2013 Always bleed the master first then caliper furthest and work to the caliper / drum with the shortest line. IIRC Quote Link to comment Share on other sites More sharing options...
benny Posted July 15, 2013 Author Share Posted July 15, 2013 UPDATE!!! bled the master (didn't seem to expel any air) had a firm pedal again. under vacuum it lost pedal again. there is a hose running from the booster straight to the rear of the efi manifold. Is there ment to be something inline? Ideas? Quote Link to comment Share on other sites More sharing options...
dazzed Posted July 15, 2013 Share Posted July 15, 2013 UPDATE!!! bled the master (didn't seem to expel any air) had a firm pedal again. under vacuum it lost pedal again. there is a hose running from the booster straight to the rear of the efi manifold. Is there ment to be something inline? Ideas? depending on the position of the rear callipers the callipers could be mounted on the wrong side with the bleeder valves at the lower part allowing a air pocket in the top of the piston if the callipers are mounted at the top in line with strut you will have to take the calliper off to bleed it .if thats not the problem you said a new master cylinder was fitted if the push rod in the booster came out upon removal of the master cylinder the compression rubber in the booster may have fallen into the bottom of the booster and you wont be able to retrieve it unless you split the booster or get another rubber from another booster and just leave the lost one in there it wont do anything, other than the push rod length in the booster is too long which means wrong master cylinder and if thats the case the the brake lines around wrong way fronts going to back an vice versa, I get this all the time Ben Quote Link to comment Share on other sites More sharing options...
dazzed Posted July 15, 2013 Share Posted July 15, 2013 UPDATE!!! bled the master (didn't seem to expel any air) had a firm pedal again. under vacuum it lost pedal again. there is a hose running from the booster straight to the rear of the efi manifold. Is there ment to be something inline? Ideas? there is a one way valve in line to stop vacuum leaking off but even if it wasnt there it would cause the pedal to sink but check make sure it is there as it should be. the valve is in line near the rh w.w washer jet, oh yeah what car is this we are talking about ? Quote Link to comment Share on other sites More sharing options...
benny Posted July 15, 2013 Author Share Posted July 15, 2013 hey daz.... thanks for the reply. it is missing the check valve but I was under the impression it shouldn't need it?? callipers are mounted at 9 o' clock so shouldn't have issues with bleeding. I didn't replace the master, im thinking at the moment that this is the best bet? Any gurus feel like coming over and having a look over the w/e?? Quote Link to comment Share on other sites More sharing options...
Wayne G Posted July 17, 2013 Share Posted July 17, 2013 did you bleed the fronts too? sounds like possibly a bad master, by-passing internally, therefore no external leak or fluid loss. line clamp to isolate all of the callipers and see what the pedal feels like and if it stays the same after a period of time. with all four callipers isolated from bled master, the pedal should be at the top and rock hard. just my 2c worth. Quote Link to comment Share on other sites More sharing options...
benny Posted July 17, 2013 Author Share Posted July 17, 2013 did you bleed the fronts too? sounds like possibly a bad master, by-passing internally, therefore no external leak or fluid loss. line clamp to isolate all of the callipers and see what the pedal feels like and if it stays the same after a period of time. with all four callipers isolated from bled master, the pedal should be at the top and rock hard. just my 2c worth. I will try this over the weekend and post back... thanks wayne Quote Link to comment Share on other sites More sharing options...
benny Posted August 18, 2013 Author Share Posted August 18, 2013 STILL STRUGGLING!! I rebled the rears todays by removing them an got a bit more air out. The problem still remains though..... can press the brake and it will seem to build up pressure, as soon as i stop pumping it loses pressure again?? Any more ideas?? Quote Link to comment Share on other sites More sharing options...
benny Posted August 18, 2013 Author Share Posted August 18, 2013 I should also note im able to pump up the pedal when car is off then once started the pedal sinks..... from what I've ready its most likely the master?? maybe still air in the lines?? i didnt rebleed the front today? Quote Link to comment Share on other sites More sharing options...
C.A.R. Posted August 18, 2013 Share Posted August 18, 2013 Was the MC rebuilt? I had similar symptoms & realized I had the accidentally reversed an O-ring in the MC. Quote Link to comment Share on other sites More sharing options...
MaygZ Posted August 18, 2013 Share Posted August 18, 2013 Benny Boy, are you losing fluid? Are the master cylinder levels going down? If the answer is yes, then you have an external leak. Find it and fix it. It could be anywhere in the system so after checking the likely spots (all the pistons, back of the master cylinder - into the vac unit) then check along all the lines and any pressure switches. If the answer is no (to lowering levels) then you have an internal leak. These are nearly always in the master cylinder where a cup has folded or split. This allows any pressure built up to leak back into the non-pressured side of the system. The only way to fix it is to remove it and replace the cups. With regard to the one-way valve in the manifold vacuum line from the manifold to the booster: the valve allows a constant vacuum to be maintained in the booster. Obviously manifold vacuum changes (quite a lot) depending on engine rpm and throttle opening. Without this valve your braking assistance will change a lot through the rev range (with a wide open throttle - stuck open or just wanting to dab them to balance the car) you will have no boost. They are a pretty universal thing so you should be able to source one from any vehicle that has a similar sized booster. They are easy to check - blow through one way - no blow through the other. MaygZ Quote Link to comment Share on other sites More sharing options...
benny Posted August 18, 2013 Author Share Posted August 18, 2013 Benny Boy, are you losing fluid? Are the master cylinder levels going down? If the answer is yes, then you have an external leak. Find it and fix it. It could be anywhere in the system so after checking the likely spots (all the pistons, back of the master cylinder - into the vac unit) then check along all the lines and any pressure switches. If the answer is no (to lowering levels) then you have an internal leak. These are nearly always in the master cylinder where a cup has folded or split. This allows any pressure built up to leak back into the non-pressured side of the system. The only way to fix it is to remove it and replace the cups. With regard to the one-way valve in the manifold vacuum line from the manifold to the booster: the valve allows a constant vacuum to be maintained in the booster. Obviously manifold vacuum changes (quite a lot) depending on engine rpm and throttle opening. Without this valve your braking assistance will change a lot through the rev range (with a wide open throttle - stuck open or just wanting to dab them to balance the car) you will have no boost. They are a pretty universal thing so you should be able to source one from any vehicle that has a similar sized booster. They are easy to check - blow through one way - no blow through the other. MaygZ Was the MC rebuilt?I had similar symptoms & realized I had the accidentally reversed an O-ring in the MC. I think the MC is new but not 100% sure.... fluid levels aren't changing and went over everything again and nipped everything up ( i found that the right hand front in the distribution block was leaking and not nipped up correctly but haven't bled the fronts again since). I have added the check valve and issue remains the same. I will try bleed the fronts up again but i dont think thats the issue. One last thing worth noting since the interior is all back in the BRAKE light in the centre facia is lit which i think is pressure related in the distro-block? I pulled the master off the booster and checked for leaks... there were none. did i mention i freakin hate brakes Quote Link to comment Share on other sites More sharing options...
MaygZ Posted August 18, 2013 Share Posted August 18, 2013 The fact that the master is new or just rebuilt doesn't mean the fault is not in there. If for example the pedal was pushed all the way to the floor (during the initial bleeding process) before the it was allowed to fill with fluid the friction could have easily turned a cup. Or if the initial bleed was a violent affair with severe and extreme pumping of the pedal (and I have seen very competent mechanics do just that) then same thing. I will say it again - if the fluid levels are not changing - you have an internal leak! MaygZ Quote Link to comment Share on other sites More sharing options...
benny Posted August 18, 2013 Author Share Posted August 18, 2013 ok.... thinking i will order another master and hope thats the issue!! appreciate your input lads!! Quote Link to comment Share on other sites More sharing options...
benny Posted August 19, 2013 Author Share Posted August 19, 2013 have just ordered a new master so will see how we go!! Quote Link to comment Share on other sites More sharing options...
PZG302 Posted August 19, 2013 Share Posted August 19, 2013 Before you pay the moneys take the time to bleed the brakes again. If air was getting in the system through the distribution block then good chance this is the problem. The front brakes need to move a heap more fluid volume than the rears, and it doesn't take much of an air gap to move the pedal a long way and have it at the floor. Easiest way to bleed all brakes if you have the time and can get the car up in the air on stands is the good old gravity bleed. Attach plastic hose over all teh bleed nipples, crack all so that they can now flow, take the top off the reservoir, and keep an eye on it over half an hour or so, also checking the fluid coming out of the brakes. You may need to tap the end of the tube on each nipple to get a suction effect going to get the fluid flowing out. This way doesn't give you dramas with pumping the pedal with not enough fluid in the system and gets all the air out of the system, and also gives you time to enjoy a beer or two. Quote Link to comment Share on other sites More sharing options...
Wayne G Posted August 20, 2013 Share Posted August 20, 2013 "I should also note im able to pump up the pedal when car is off then once started the pedal sinks..... from what I've ready its most likely the master?? maybe still air in the lines?? i didnt rebleed the front today?" This could be normal. The pedal will become hard and with minimal travel when there is no boost from the vacuum brake booster and then change feel when there is boost from the booster, when you start the engine. A fault is indicated if the pedal sinks after it has been pumped up with the engine still switched off. Quote Link to comment Share on other sites More sharing options...
benny Posted August 20, 2013 Author Share Posted August 20, 2013 Thanks Wayne.... The pedal stays solid after being pumped up with vehicle turned off. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.