| Author | Message | ||
     Pedro Gomes Frequent User Username: portamno Post Number: 59 Registered: 2-2018 |
Hi! I am Back...After all the issues of back auto suspension, and possible overheating and other stuff resolved, I took my car out for a fun drive. Well, Brake pedal felt kind of spongy....Then, the low pressure light came on when I braked...Then it went out, only to come back again. Repeatedly. Took the car to the mechanic,figure needed to top off with LHM mineral oil. Went for a drive. Same stuff happened again, and there was a leak...in fact 2 leaks. First is because I overfilled the system (thru those 2 filling tubes, next to each other and covered with plastic plugs, on top of the engine, left side...I did not know that there are 2 bleeding tubes if you overfill. To check second leak, We put the car up, but stupidly enough, I forgot to take a picture. When one stands under the car, facing foward towards the engine, on the bottom of the car on the left side just before the engine there is a black rectangular box, and on the bottom surface it was quite wet with new LHM oil on it. The mechanic (not the one that usually works in the car) advised me that that's the location of the brake pump, which is "protected" by that box...Is this true? Also, that I should change the brake accumulators as the car was stopped for 4 years, and before that I never replaced them. Can you please help me on this new issue? I obviously will not drive the car, as this would extremely dangerous. Best Regards Pedro | ||
| Omar M. Shams Grand Master Username: omar Post Number: 1646 Registered: 4-2009 |
Dear Pedro, There are two hydraulic pumps on your car and both of them are on top of the engine in the centre of the block. One at the front of the engine and one at the back of the engine. The two pumps are not enclosed in any box. The reservoirs both have overflow pipes to ensure owners do not overfill the system. If the pedal feels spongy and you have a leak and both have happened at the same time - see if you can find out what is actually leaking. Does the pedal go hard after a pressing the pedal a few times? Are both reservoirs full? can you see from the sight glasses? I am wondering if you have a bleeding issue and there is a giant slug of air in the system from when you took the spheres off last time. | ||
| Pedro Gomes Frequent User Username: portamno Post Number: 60 Registered: 2-2018 |
Dear Omar: Thank you for your reply, as always. The pedal went spongy after just 2 pumps....I have never replaced the brake accumulator spheres, so I BET they need to be replaced. But that rectangular box under the car, on the left side, just before the engine, it showed LHM leakage under it...there's a lever that connects to the box on one side, and to the brake pedal on the other...What is inside that box? Today, I will take a picture of the box, so perhaps you can identify it. The mechanic told me that's where the brake pum is located. He is obviously wrong. I did overfill both reservoirs...There was puddle in the garage, as I did not know they had overflow tubes.... Best Regards Pedro | ||
| Jeff Young Grand Master Username: jeyjey Post Number: 379 Registered: 10-2010 |
Is the box directly under the driver's footwell? If so that's what's known as the "rat trap". It's a cover over all the valves for the braking system. The pedal shouldn't go hard/spongy like a normal system. All it does is open valves; it's not actually pushing against the brake fluid (the accumulators do that). Do you just mean that the light comes on or that the brakes don't seem to be as effective? (Or is the '92 system significantly different from earlier systems? I thought the pre-Arnage ABS just modulated the existing system?) | ||
| Robert J. Sprauer Frequent User Username: wraithman Post Number: 58 Registered: 11-2017 |
Pedro, If your mechanic says "that's where the pumps are" in reference to the "rat trap cover" I would highly suggest you find another mechanic. He is obviously not familiar with these cars and it will cost you dearly in the long run. RR techs see this all the time and a good percentage of their work is correcting poor work due to previous attempts to repair a condition. | ||
| Pedro Gomes Frequent User Username: portamno Post Number: 61 Registered: 2-2018 |
Dear Jeff: Thank you for your comments. Here are some pictures of that "rectangular box"....It's indeed under the driver's seat, and I saw some LHM fluid that seemed to be leaking from there...If it's the "Rat trap" to cover those valves, could they be leaking? The light goes on after just one pump, and the pedal goes all the way down, and the brakes hardly operate....I am quite sure I need 2 new brake accumulators, the 2 brake pumps don't seem to be leaking, what else should I check for...Those valves? Do you have part numbers for those, or where I can find them? Best Regards Pedro   | ||
| Pedro Gomes Frequent User Username: portamno Post Number: 62 Registered: 2-2018 |
Dear Robert: Thank you for your comment, as always. You are right of course. But that comment did not come from the "master mechanic" but from his helper, which today told me that the master pump should be there... The problem in Portugal is that Bentley Portugal is a DISGRACE....They don't even work in these early 90's car anymore. I even sent a letter to Crewe regarding this "denial" and the only thing I got back was that " they are not supposed to say that, we shall investigate"...My main mechanic is not familiar with Bentley, but he is extremely careful before he does anything....Thru your help here at the forum, and a lot of manuals I have gathered, including Tetis, we have been able to just about fix everything. But now I have major brake failure, and from what I have been able to study, it is those 2 accumulator break spheres that need to be replaced. The question is...What else should I look for? I have absolutely no leaks in any of the four wheels calipers, or along any high pressure brake tubing....However, as Robert pointed out, that rat trap is protecting valves, and those could be leaking...Do you have part numbers, or where I can find them? I have tried to use Tetis, but so far, have not been able to locate that rat trap and the equipment inside.... Best Regards Pedro | ||
| Jeff Young Grand Master Username: jeyjey Post Number: 380 Registered: 10-2010 |
Yep, that's the rat-trap. Inside will be something like this (although this picture isn't necessarily from the same model year): http://www.flyingspares.com/shop/media/catalog/category/Distribution_G_Valve.jpg The valves can all be re-built with new seals. You can also get already re-built ones from somewhere like FlyingSpares (you send in yours in exchange and they rebuild that for the next customer). The light going on and off quickly does indeed suggest accumulators (or perhaps accumulator valves). If it were the pumps the light would be slow to go back off. There are tests you can do to pinpoint the faulty component. Have a look at the last 3 PDFs here: http://rrtechnical.info/sz/sz87/gh.htm | ||
| Pedro Gomes Frequent User Username: portamno Post Number: 63 Registered: 2-2018 |
Hi Jeff: Thank you so much for your comment. In the meantime, the mechanic has taken the rat-trap, and here's 2 pictures of what he found...Can you identify them? That diagram from flying spares seem to be the right thing... One has a handwritten note on it, stating MC105IN, I think...and a date. I looked for that piece number on the net, and it shows on Amazon UK as "master cylinder....But looking at flying spares they dont have it...It's leaking for sure. He even taped it, buy I dont think I can send the video here. Thank you also for the "RR technical" bur it does not cover my car, as it's a 92.... Best Regards Pedro   . | ||
| Jeff Young Grand Master Username: jeyjey Post Number: 381 Registered: 10-2010 |
Those are the distribution valves. There are two of them, stacked on top of each other. (The hand-written note is actually on the side frame, not on one of the valves.) If they're leaking where the green pipes attach they might just need tightening. If they're leaking from the plungers (top of the first picture), then they need rebuilding. I think the rrtechinfo stuff is correct for your car. You just need to look for any updates in the later years, but if nothing is there than the earlier SZ documentation still applies. They didn't update everything for each model year. | ||
| Mark Luft Prolific User Username: bentleyman1993 Post Number: 215 Registered: 10-2016 |
Pedro, the rat trap is designed to seep a little fluid for lubrication. Do you just have a drop or two on the ground? if so, leave it alone. There is not a British car around that doesn't mark its territory.  | ||
| Robert J. Sprauer Frequent User Username: wraithman Post Number: 60 Registered: 11-2017 |
The brake distribution valves are precisely machined especially at the plunger and designed to drip on a regular basis to provide lubrication at the shaft.. They rarely go bad and are expensive. When either one goes bad you may notice either front or rear brakes locking early which is not your issue.Remember these are "brake distribution valves".Your hydraulic pressure failure is most likely in the accumulators. Each accumulator has a regulator to add pressure when needed, and it starts at the pumps located on top of the engine block. The hydraulic system may seem complicated at first glance but after working on these for over 30 yrs they are straight forward and easy to diagnose. Someone with no experience will be guessing at the solution and ultimately cost you money. | ||
| Omar M. Shams Grand Master Username: omar Post Number: 1652 Registered: 4-2009 |
Dear Pedro, It is good practice to have all 4 green spheres replaced at the same time as they often deteriorate together. You have changed the back ones, so now change the brake accumulators. They may have failed given their age. When you do that, bleed the whole system thoroughly and all will be well again. Mark Luft and Robert Sprauer are right about the distribution valves weeping. They are designed to do that. You will see oil coming out of there but at the rate of one drop per day or even less. The Rat Trap has been a red herring in your investigations. I would leave all that alone and focus on two things only namely changing the accumulators and bleeding the system. | ||
| Pedro Gomes Frequent User Username: portamno Post Number: 64 Registered: 2-2018 |
Dear Jeff; Dear Mark; Dear Robert; Dear Omar: Those comments of yours regarding that a certain amount of dripping is actually "designed to happen" has MADE MY DAY! And that comment from Mark regarding that "English cars mark their territory" just made me laugh, as it could not be truer...I have an XJ40 93, and a Mark II 68, and dont they "mark the territory"? Of course they do! But my Bentley was leaking a lot of oil...That has been taken care of, all the seals and gaskets etc, have been replaced, the engine was actually taken out of the car....Regarding leakage of LHM fluid, when the car was stopped for 4 years, there was leakage coming out out of one of the back shock absorbers, but that fixed itself. It was a dried out seal. Never saw any "dots" of LHM fluid in my garage....It was only when we raised the car to find out where the leakage came from that I came across some fluid (you can see it clearly on the top picture) and that raised a discussion with the Mechanic, which then proceeded to open the rat-trap, as now, thanks to you, i know what that is...And the main leakage came of course from me overfilling the system, not knowing that there are 2 small overfill tubes...Located very close to the rat trap.I just thought that the system was almost empty of LHM fluid, not noticing the enormous mess under the car.... So I am going to follow your advice and get those 2 accumulator spheres from flying spares...The assistants there know me by my voice alone...." How´s the weather in Portugal Peter?" then bleed the system carefully. And hopefully that will be the end of this matter Hoping no others pop up. Then will take the car for an extended drive, the car needs to run! WARMEST REGARDS TO ALL Pedro | ||
| David Gore Moderator Username: david_gore Post Number: 3002 Registered: 4-2003 |
Pedro, All hydraulic valve banks are designed to function without seals due to the high working pressures. The tolerances for the valve body and the pistons are very fine and the very slight fluid leakage in service is intentional to provide essential lubrication of the bore and piston to minimise wear. The normal leakage should show as a drop on the exterior of each cylinder piston and an occasional drop on the ground/floor from the rat trap cover. When I overhauled DRH14434, the hydraulic system and automatic transmission were major items and I let the registration expire for a few years while the car was off the road. The car had to have a major mechanical inspection for re-registration and the inspector asked for the rat trap cover to be removed and immediately defected the car for the fluid "leaks" from the valve body. To fix this problem, I had to copy the relevant section of TSD2476 which detailed the leak was intentional for lubrication and forward this to our vehicle registration authority to get an exemption for the fluid leak so the car could be passed for registration. The actual leakage was less than a tablespoon a year onto the floor of the garage. . | ||
| Pedro Gomes Frequent User Username: portamno Post Number: 65 Registered: 2-2018 |
Dear David: Thank you for your comments. My car has already had the yearly inspection, just a couple of months ago. Then everything was working OK....But just like yours, my car did not run for at least 4 years, as I could not find an able mechanic....It came to the point that I was going to send the car to England to get it overhauled.... Finally, i got an "honest" mechanic, that while not knowing anything about Bentley's, has been very careful before he does anything. Thank you for the tips regarding the relevant section on TSD2476. Tomorrow I shall order the Accumulator spheres, and in the meantime, will try to look very closely at how much leakage is actually coming out from those valves. Also, THANK YOU for the precious information that hydraulic valve banks are designed to function without seals due to the high working pressures. My mechanic had been suggesting that I should order a seal kit, which of course I have not been able to find...Now I understand why! Best Regards Pedro | ||
| gordon le feuvre Prolific User Username: triumph Post Number: 266 Registered: 7-2012 |
Pedro, Live on island that has lots cars that stand around. The distribution valves will ALWAYS weep when car not used. Take off cover, clean off and then road test. Only then take view on amount of weepage. The distribution valve has no internal seal and the piston is lubricated by brake system oil travelling up shaft. Mineral oil cars are more prone to leakage than Shadow range. I regularly take down "rat trap" on services of cars I look after, just to clean off mineral that has collected in tray. The very first Shadow bulletin on hydraulics was about NOT changing distribution valves because they weep- that was 1966- | ||
| gordon le feuvre Prolific User Username: triumph Post Number: 267 Registered: 7-2012 |
Pedro, as Omar says change spheres. Sysmtoms of loss of nitrogen in sphere is on starting engine light will go out as normal, but when brakes used after only one/ two pumps light will be on. That means no pressure in that system and brakes will feel far less effective. The two on rear suspension will make ride hard/bouncy at rear if no nitrogen | ||
| Pedro Gomes Frequent User Username: portamno Post Number: 66 Registered: 2-2018 |
DEAR ALL! Situation FIXED!!! Yesterday the 2 brake spheres were installed, brakes bled, the system is working like new!! Thank you ALL for your inputs. Again, anything you need from Portugal, please let me know! My address is: lofotenfish.portugal@sapo.pt Yesterday I drove the car 150 kms, just to test all systems. The more I drove, the better the car behaved...The cruise control was not working right, shiffiting too often at 110 kms/ hour, but then it stabilized. I ran into traffic, well with the new Thermostat the temperature did increase, but nowhere near the right hand of the white bar. And when traffic got lighter, it slowly moves towards the center...The actual position is about 3 mm right of the dead center of the white bar. This has been a long process... As far as removing the spheres, it can be a very hard job. However, as the mechanic had a very hard time to change to change the suspension spheres, about 2 months ago, enclosed please find a picture of the tool he got which made changing the spheres a "1-2-3" job. WARMEST REGARDS TO ALL Pedro  | ||
| Omar M. Shams Grand Master Username: omar Post Number: 1655 Registered: 4-2009 |
Well done Pedro. Come and have a cup of tea with me in Dubai one day. You will be most welcome. I can show you all my Bentleys too. | ||
| Pedro Gomes Frequent User Username: portamno Post Number: 67 Registered: 2-2018 |
Dear Omar: Thank you. One day perhaps...I have a partner that goes to Dubai all the time. I would love to see your collection. In the meantime, if you come to Portugal, I can show you around....Only have one Bentley, but I have other cars. Warm regards Pedro |
