| Author | Message | ||
     davide frada New User Username: davidef Post Number: 7 Registered: 11-2008 |
hello again i have assembled and installed the accumulator valve and was rather pleased to note the clack had gone... but as was the case after i installed the rebuilt accumulator, it returned after some use... now, though, it is coming from the rat trap area. one can feel the valves throb in time with the clack, which goes away when the brake is depressed. i haven't yet checked whether the fluid is pulsing from the accumulator bleeder. are there any circumstances in which components within the rat trap are known to clack? davide | ||
| Paul Yorke Prolific User Username: paul_yorke Post Number: 258 Registered: 6-2006 |
Davide, I the brake valves will not normally clack in themselves. It's usually the fluid going to them that is clacking. There is a flow chart or the test procedure for the accumulators, have you found and followed that? TEST 1: if you don't have access to a pressure gauge, I would run at fast idle for 5 mins then turn off and immediately bleed the accumulators. You should have about 1/3 to 1/2 pint in each one. Are you getting less fluid? If you have already filled with R363 The fluid can be reused if you you are scrupulously clean. TEST 2 I'd run again, wait 30 mins then bleed them both again. Is there a difference in quantities? (you can do the accumulators one at a time) TEST 3: You will then need to take the steel braided flex hose off each accumulator and put bleed nipples in them. Carry out test 1 & 2 and see if there are any differences. The next checks will require extra fluid (and preferably two people) TEST 4: clamp and remove the rubber return hoses from the accumulators. fit a hose to the accumulator return pipes and feed them into a bottle. (accumulators should be de-pressurised now) get assistant to start the engine while you watch for fluid. There should be no fluid coming out until the accumulator reaches break pressure (2400 psi ish) then should spurt. Turn off engine and fluid should trickle and stop completely, just about immediately. Let us know what you find. | ||
| davide frada New User Username: davidef Post Number: 8 Registered: 11-2008 |
Paul, thanks for your thoughts - very much appreciated. as i have some visitors staying with me, i won't be able to explore your suggestions for another few days, but yesterday, with the benefit of a few moments to spare, i opened up #2 circuit accumulator bleeder to find absolutely zero pressure. the first circuit seemed to hold quite a bit of pressure, having sat overnight. i wasn't able to measure the quantity of fluid expelled. i proceeded to start the car, let it idle for 10 minutes, and opened #2 bleed nipple. as expected, the fluid pulsed, not having the benefit of accumulated pressure. the accumulator was rebuilt a few weeks ago by a well regarded specialist, albeit with a NOS ebay sourced kit. i pulled apart the valve myself, and found nothing untoward, though the central piston/valve seemed a little stiff in action. having never examined such a device, i'm unsure how stiff is too stiff, or whether it should be a looser fit. upon purchase, the rear brake pump was seized. i managed to free it up, lapped in the valves, and it seemed to perform quite satisfactorily - i would imagine even a marginal pump would, after 10 minutes idling, be capable of generating accumulator charge, at lease sufficient enough to allow for the smooth passage of fluid. what do you think? | ||
| Paul Yorke Prolific User Username: paul_yorke Post Number: 259 Registered: 6-2006 |
Davide, You have guests now, ideal! get them working for their keep. lol  Go for test 3 on accumulator 2. You need to find out if the pressure is going through the flex pipe to the car's hydraulic system or through the rubber accumulator return pipe. Good luck! | ||
| davide frada New User Username: davidef Post Number: 10 Registered: 11-2008 |
Paul, thanks for your input. given the aim is to see where the pressure is going, i clamped the return line and slipped it off, running another length into a bottle. i didn't run the car long, 30 seconds perhaps, as it had been driven for 15 minutes immediately before the test. there was no sign of fluid at all, so it seems safe to say the fluid is passing through the hydraulic system (the second front calipers can be bled, albeit at a reduced pressure as compared to #1 circuit). based on this, would i be correct in saying that i am still no closer to determining whether the accumulator or valve is at fault? given how much difficulty was encountered separating the accumulator from the valve, i don't think swapping accumulators from one circuit to the other is viable. again, thanks for input - i'm very much looking forward to being able to drive the car properly. | ||
| Paul Yorke Prolific User Username: paul_yorke Post Number: 261 Registered: 6-2006 |
Davide, "so it seems safe to say the fluid is passing through the hydraulic system" Nope, you've narrowed it down to the pump not building up enough pressure OR it's going through the hydraulic system. You now need to block off the flex pipe outlet on the accumulator and see if fluid now pumps out of the accumulator return hose at high pressure. (use a bleed nipple from a calliper if you don't have a spare ) If it does, then it's most likely the hydraulic system. If it doesn't , then pump pressure is too low.  If only you had access to a gauge "based on this, would i be correct in saying that i am still no closer to determining whether the accumulator or valve is at fault?" Not yet, if it was either, the fluid should come straight out of the return hose. Perhaps you should have let it run for longer. The accumulator stores fluid in the range of 1000 psi to 2500 psi. The return hose should only let fluid through when it's over 2000 psi. So far you haven't got fluid from the return hose - which is why you need the extra tests. If the valve is faulty and is opening between 30 psi and maybe 900 psi, even a perfect accumulator would not be able to store any fluid. If the accumulator was gone, the pressure will reach 2000 psi but there will be no quantity. (A 1cc spurt at 2000 psi, then pump output.) :/ Good luck with it. Happy new year to all. | ||
| davide frada Experienced User Username: davidef Post Number: 15 Registered: 11-2008 |
hi Paul and others, i've finally had a chance to have another play with the Shadow. i took it for a 15 minute drive, the clack finally making itself heard. upon return i cracked the bleeder to find zero pressure when switched off, and pulsing fluid when running. if, as you suggested, i block off the output (to the flex pipe) with a bleed nipple and plumb the return to a container, the accumulator charges up, the light extinguishes itself, and some (not a lot) fluid makes its way out of the return. if i open the BLEEDER nipple, fluid will drain and the light comes back on again, as expected. any thoughts would be much appreciated. regards davide | ||
| Paul Yorke Prolific User Username: paul_yorke Post Number: 277 Registered: 6-2006 |
Hi Davide, With the output blocked. When you bled the accumulator, how much fluid did you get out? How long did it take for the lights to go out? When you say you didn't get much fluid from the return was that when the engine was running, or off. | ||
| davide frada Experienced User Username: davidef Post Number: 16 Registered: 11-2008 |
hi Paul, some more info... i managed to obtain approx 200mL when bleeding the charged (light out + 60 secs)accumulator. it took about 38 secs for the light to go out, at a normal idle. i only managed to get a dribble from the return line. weak pump? davide | ||
| Bill Coburn Moderator Username: bill_coburn Post Number: 1075 Registered: 4-2003 |
Davide/Paul. Can I interfere here. Davide for our sake go get yourself a pressure gauge. Simply go to a place that makes up and services hoses etc. They will supply you with a pressure gauge 0 - 3000 psi a length of soft copper tubing and the end fitted with a conventional nipple that you can get from any decent brake shop. The lot should set you back about $40 and it will always be there when you need it. You can plug in to bleed nipples at the wheels or apertures on the distribution valves or even pop in a junction in a line to see what is happening. otherwise we are simply running the old game of twenty and out? | ||
| davide frada Experienced User Username: davidef Post Number: 17 Registered: 11-2008 |
thanks, Bill, for your useful and friendly suggestion. as the valve and accumulator appeared to be functioning normally when separated from the brake and suspension system, i decided to disable the ride level system with some bleeder nipples to see what it'd do. the brakes are now excellent, and the system appears to work as it should. it would seem, then, that perhaps a ride level valve is bypassing, not allowing the system to pressurise. comments? | ||
| Bill Coburn Moderator Username: bill_coburn Post Number: 1082 Registered: 4-2003 |
I have never seen it happen but if the suspension solenoid on the back of the rear cross member sticks on high levelling, the levelling valves go beserk as the rear wheels bounce along the road. To test the solenoid disconnect the two wires and put a feed across them and you should get a clear click. If not whip it out, get a kit and overhaul it. Its unactivated state is of course on low levelling. Cars differ as to what switches the thing but a safe test would be (I think) put the car in drive turn the ignition on and then test for power at the solenoid. If there is, the wiring is up to you know what and the valve is being held on all the time when the ignition is on. Whenever I do one of these guess pieces I often think I should quote odds as to being right or wrong. Problem then is to find a bookie! Paul might care to demolish my amateur prognostications! | ||
| Paul Yorke Prolific User Username: paul_yorke Post Number: 284 Registered: 6-2006 |
Bill, I'd usually go for a HCV being faulty or assembled incorrectly. Maybe pipes swapped? Some sort of internal leak from High pressure to the return. If the accumulators are weak the possibly a solenoid valve stuck on fast may deplete the accumulator quickly, but I've never noticed it happening. Often you slip the car into neutral to listen for noises without the engine revving. You can go for quite a while like that with no lights or brake pulsing etc. (if you occasionally get hydraulic noises from a Shadow rear suspension, this often cures it for a while). NB, you can't block the return pipe to isolate a valve etc. because it can blow out the output connector from the HCV. Davide , I assume you have the colour diagram showing pipe pressures etc. Good luck on this one. |
