Weak Brakes, Weak brake booster or what?

[The_Handier_Man1]

From: Jupp318  (Original Message)
Sent: 3/13/2004 1:35 PM

Hi Guys,

Having replaced all the brake pipes last year I have recently gone to use my Winnie and found that the braking effeort is severely down on that when I parked it.  The big Brake red light has come on, so I have quickly bled the brakes and the light still hasn't gone out.  I have checked the vacuum pipe to the booster and that seems OK.  I have removed the air filter from the floor by the drivers seat to check that there is some airflow from it, which there is.  I do not however get a whoosh sound when I depress the brake pedal.  Sue tells me there is a difference in pedal "feel" if I disconnect the vacuum pipe (pedal is much harder to depress).

Can anyone suggest what may have happened here, as I am now at a loss for what to do next.  I don't want to go to the expense of importing another booster only to find out that isn't the problem.  As always any tips will be most gratefully received.

Many Thanks

Ian....



From: denison
Sent: 3/13/2004 3:38 PM

I assume your winny is on the M300 chassis, but I don't know its year, whether it has disc brakes on the front axle, or drums. If it had disc brakes in front I might think the caliper had sucked in some air from sitting, and to continue bleeding. If it has drum brakes on the front I still think bleeding is needed. When I replaced my master cylinder years ago I had to bleed it before I installed it - called bench bleeding. It came with the fittings for the outlet ports, each with a little hose long enough to feed the brake fluid back into the top of the reservoir. Clamped in the vise I pumepd that m. cylinder a lot to get the air bubbles out, cause the instructions said that if I didn't do it, I would never get the entire system properly air-free. After installing it I had to bleed the rest of the brakes, which on mine meant first bleeding the fittings on the dual hydrovac boosters mounted inside the frame rails. Then I bled the wheel cylinders, in no particular order. It is vital not to let the master cylinder empty out while bleeding, since that means you get to start over again. Refilling that m. cylinder is a miserable job. It takes me about a quart of fluid to completely bleed mine - till the fluid comes out clean. The red light coming on means one side of your brake system is displacing more fluid than the other. If the red light comes on but the pedal is acting normal, then it could be you have one side of your dual brake system with a stuck wheel cylinder, that isn't moving back to the relaxed position.. This could be from a stuck brake shoe, or one brake that is very far out of adjustment. It could be from a clogged up brake hose, between frame and axle. On our vacation in 2002 I had a leaky wheel cylinder on my rear axle; which I disconnected from the brake system, capping off the brake line with a fitting. The only hard part was finding such a cap-fitting, and dealing with the red ants. It meant I had 3/4ths of my brakes working. Each time I put on the brakes the red light came on, but we drove home 2000 miles from Tamaulipas, Mexico to Northern Virginia that way, and I could not tell any difference in braking. It would be a lot of work, but you could put on the brakes with a wheel in the air, and see if the brakes came on with the pedal down, and released whent he pedal was let up. A stuck shoe or wheel cylinder would show up this way. 



From: Minniewinnie4
Sent: 3/14/2004 4:35 AM

Ian I had the same problem with my brake warning light staying on , the
manual advises there is an imbalance between the daul braking system. With
this info I carried out a complete brake over haul wheel cylinders, master
cylinder brake pipes etc etc only to find there was nothing wrong with the
system. I disconnected the warning light sensor wire from the balance valve
only to find the problem was with the Parking brake switch was sticking.

This also happend last week again after the Winnie had been standing for two
months.
Not saying this is your problem but its worth looking at.

By the way we have Scotties Speed Shop in Southampton who does do American
spares and Pual is very helpful I have known him for 30 yrs and has always
delt with American cars. Tel 020232322
Regards Joe.



From: Jupp318
Sent: 3/14/2004 4:52 AM

Dave & Joe,

  Thanks for the reply's.  I am just about to go over to Winny and try bleeding once again.  The reason I don't think that this is electrical is because the brakes are awful.  Last year when Winny was tested she took the brake tester guages off the clock!.  Now the brakes will slow her down but with an awful lot of pedal pressure from me.  This is why I'm suspecting the booster.  If I had ever pulled one apart I might understand how they work better, and then I might be able to work out what has gone wrong.  As I say last year I had to be careful when using the brakes because they were so good.  I'll let you know what occurs later.

Cheers Ian...



From: UluzYarx
Sent: 3/14/2004 10:18 AM

Hi Ian,

Have you checked that your wheel pistons - pucks are moving?

If not, duck oil and a collection of powerful expletives will free them, with a lot of wiggling.
I use a hyperdermic needle to introduce duck oil through the rubber dust seal in some circumstances.

The manufacturers will confirm that Duck Oil is suitable if you wish to contact them.



From: Jupp318
Sent: 3/14/2004 4:37 PM

Chaps,

  Bleeding washed out due to rain!.  I did do some tests to work out if the booster is working, and I think it is.  I pumped the pedal a few times with the engine off and held pressure on the pedal and started the engine.  As soon as the engine fired the pedal went down further.  Hopefully if the weather is better tomorrow I'll get a chance to do the bleeding.  BTW Joe I couldn't find the Emergency brake switch.  Chassis BTW RM300.

Cheers Ian...



From: Jupp318
Sent: 3/15/2004 3:33 PM

Hi Chaps,

  We have brakes!.  I should have started with the basics like is there any fluid in the reservoir, which there wasn't!.  Really embarrasing I can assure you.  My main concern now is where did all the fluid go.  I'm most confident that my plumbing doesn't leak especially as the Winny had it's annual test afterwards.  I'm still a bit wary of the booster/Master cylinder as I have heard tales of boosters filling up with fluid leaked from the MC.  I'm sure all will become obvious in time.

My thanks to one and all, especially Dave Denison for information emailled to me.

Cheers for now

Ian...



From: denison
Sent: 3/15/2004 8:05 PM

The fluid could have leaked out at the front of the master cylinder, or at any of the wheel cylnders/calipers, and if it leaked out slowly enough while sitting, you might not find any trace of it - especially after a blowing rainstorm. Also it can leak from the hydraulic piston of the booster into the vacuum chambers. In which case the inside of the large rubber vacuum hose between the manifold and the boosters will be coated on the inside. A small amount of leakage here is probably very common, though still indicates an old booster that needs rebuilt. $$$$! If you can pull the hose off at the booster to check without destroying the hose, you might see the brake fluid slime in it. Checking at the engine end is harder, because the brake fluid would mix with the intake manifold fuel spray and general water condensate.
Something to try when you arent pressed for time - is to use a large C clamp, and force the pistons in the brake calipers back into the bore, then push it back out with the pedal, and work it back and forth a few times. You will probably have to unbolt the caliper from the hub and remove the pads to be able to do this. Each time you press the piston back in, loosen the bleed screw to let the old dark brake fluid be squeezed out. You will of course have to keep refilling the master cylinder reservoirs as you pump the pistons back out again. This will help to clean and lubricate the caliper seals. 



From: Jupp318
Sent: 3/21/2004 8:44 AM

Hi All,

  Thanks for the continued posts.  I'll bring you up to date.  I loosened the two nuts holding the MC to the booster and moved the MC by hand and no fluid appeared.  I re tightened the two nuts and went under winnie looking at the inside of the wheels, unfortunately I discovered brake fluid running down the left tyre.

  The good thing is that I now know what the real problem is.  If my grasp on my parts catalog is correct I either need a service kit 3549-081 or a new cylinder 3633-321.  I will be ringing ATP tomorrow but in the mean time can anyone give me an idea of the availability of these parts and the cost. I'm in two minds whether to get 2 service kits, or to get the service kits + wheel cylinders.  I can then replace the wheel cylinders and refurbish the old ones to use as spares.

Many thanks for the words of wisdom Rick!

Cheers Ian...



From: DaveVa78Chieftain
Sent: 3/21/2004 10:17 AM

Ian,
When I worked on my brakes, I went ahead and replaced the wheel cylinders.  Here in the states, NAPA carried them and they were only $12 a piece so, for that price, it made more sense to just replace them.  From the parts listings I saw, the one thing that helps dramatically, is knowing what size the cups are (bore diameter of the cylinder).   There seems to be a lot listings grouped together and that info really helps narrow it down to what you need.

Dave



From: Jupp318
Sent: 3/21/2004 2:44 PM

Thanks Dave,

  From looking at the service manual, again if I'm reading it correctly the slave cylinder bore is 1".  As you say, if the cylinders are that cheap I might buy four, two to fit and two for spares.  I definately think I will gradually replace everything to do with brakes.  After the wheel cylinders I only have the MC, Booster and front calipers to go oh and rotors of course.

Thanks again

Ian...



From: jhuey
Sent: 3/21/2004 8:42 PM

Keep bleeding, then bleed some more. once all the air is out and braking effort is normal, if the brake light is still on you might need to center up the switch in the master cylinder. Most dual master cylinders (any vehicle made after 1964/1965) have a switch integral in the master cylinder (or some type of pressure switch) to let you know when one side of your braking system has leaked out and is not functioning. To center it up, have someone put even pressure (not real hard) on the pedal while observing the light and release pressure on ether the front or the rear systems by normal bleeding or on the master cylinder (I've had more luck on the master cylinder, but remember don't let up on the pedal or air will leak back in and you start over again). Sometimes the normal bleeding sequence trips the switch, everything works great but the light stays on.
Joe



From: Jupp318
Sent: 3/23/2004 6:14 PM

Hi All,

  Latest installment is, I have torn down the rear axle.  I have proved without a doubt that the L/H Wheel cylinder has been leaking. I have ordered my list of parts from Alretta Truck Parts after NAPA assured me that they could not help.  My main concern now is that there appeared to be swarf on the half shafts when I pulled them out, and there also seemed to be some in the axle tube.  Would this be normal?, I am going to try and clean things out as much as possible including draining the oil.  Is there anything else I ought to look at whilst it's in bits?.

In my opinion the cause of the problem is probably water in the brake fluid as there is plenty of rust in the cylinder.  The seals actually look fine  with nice sharp edges, I think the problem is the fact the bores were rusty that stopped them sealing, but don't worry I won't try repairing them, they are beyond that!.

Cheers for now

Ian...



From: denison
Sent: 3/25/2004 6:33 PM

I think you have the situation pretty well covered.
I hope what is on your axle shaft is not what I found on the internet when I looked up swarf! It was a new word to me. My late machinist friend referred to the no-longer-clean liquid circulating onto the cutting tool or grinding wheel as "mud".
Anyway, you can expect to find a slimy coating of the heavy differential oil on the axle, and inside the axle housing. If there was much condensation mixed with it the stuff could look almost like bad chocolate pudding. But there shouldn't be much in the way of metal particles. There could be some tiny rust flakes in what you wiped off the axle, as the condensation would cause rust on the interior of the axle housing, but they should be very small. That is also a sign of sitting unused for long periods. When you drain the fluid from the differential you hope that it comes out with tiny flakes of rust only; if you catch the oil in a clear plastic container, there should only be a black slime in the bottom at most, not any sparkly pieces - of the bevel and pinion gear teeth for instance. Again if it was in a pretty wet situation, or had been driven in deep water, you could have some chocolate pudding sort of stuff. The hypoid oil for differentials, will mix with water just enough to cause that pudding like sludge. I use 80 or 90 weight hypoid oil in mine. Hypoid oil has additives for the very high contact pressure type of use. For capturing tiny metal shavings I like the drain plugs that have a little magnet embedded in them, though mine doesn't have one and has lasted over 30 years anyway.
The water in your wheel cylinder is also in the other wheel cylinders and brake calipers. Hopefully not so much in the boosters. Bleeding is the easiest way to get it out. Taking the cylinders and caliper apart and honing out the rust is a more sure way of getting the water out. The water accumulation is normal, since the fluid is hygroscopic; It LIKES to absorb and fully mix with water, so there will never be a little block of ice to interfere with your brakes, no matter how cold the weather. And this is why you should bleed the whole brake system about once a year. The rebuild kits for the wheel cylinders I needed were fairly cheap, at $8, but the wheel cylinders were more like $85 each. I would advise doing the other side of the winnebago as well, and before very long.
When you reassemble the wheel bearings you put grease on them, but that 80W oil migrating out the axle shaft is what keeps the bearings lubricated over the long run. Hence the need to keep the diff. fluid up at the right level.
Keep us posted on your progress. Posting pictures is good too!



From: Jupp318
Sent: 3/26/2004 5:56 AM

Hi Dave,

  Thanks for your reply, I think you've hit the nail on the head suggesting rust particles being the swarf.  In the UK Swarf means the waste material usually from a machining process i.e. turning or milling.  Part of the instruction to remove the half shafts was to give the axle a sharp tap with a hammer, this may well of led to rust falling from the axle housing.  I do know that at one point in it's life my Winnie was laid up for 10 years or more.  After all it has only done 36,000 miles so far!.

  As for bleeding regularly to remove all the moisture from the fluid, I would suggest a full service to include removal and stripping down the wheel cylinders and calipers if you don't know what maintenence regime has been undertaken previously.  As I have previously said, last year I undertook replumbing the braking system.  This did of course mean that I effectively changed the brake fluid by bleeding the new pipework through such that there was no more cloudy fluid coming out.  But when I took the wheel cyclinder apart the state of the fluid was terrible.  This leads me to think that if the system hasn't been regularly bled there could be an accumulation of moisture in the cylinder or caliper and that the only way to be sure of getting rid of the bad fluid would be to take the caliper/cylinder apart.

  The cylinder had obviously been assembled using the Red Rubber (Brake) Grease, but this had dried onto the pistons in a laquer type deposit.  This would be another reason to rebuild the caliper/cylinder maybe every 5 years or so.  I have read a spec for the DOT4 brake fluid where it is recommended a change of fluid every 18 months.

As suggested I will take some photo's, this work hasn't proved as daunting as I first thought, especially taking into consideration the help I have received from Mr Rosenberg at Alretta Truck Parts.  His help has made this job far less stressful as it would otherwise have been.  As Lefty said, he would be quite willing to pay the extra dollar for the peace of mind.

Cheers for now

Ian...



From: Jupp318
Sent: 3/28/2004 11:37 AM

Hi again Dave,

As suggested I have added some pics to my album.  You will be able to see the state that the so called "Good" cylinder was in.  The fluid on the bench is as it came out of the cylinder as I took it apart.  Remember that I got the brakes to work just 2 weeks ago by bleeding.  You can also see the "laquer" on one of the pistons.  I think as soon as I have the back axle all assembled and working I will see about a couple of caliper service kits just to make sure.

If you would like to see any other pics, please suggest what you would like to see and I'll see what I can do.

Hopefully Winnie will be all back together so I can take her to the Surrey Street Rodders "Wheels Day" on Good Friday at Rushmoor Arena.

Cheers Ian...



From: denison
Sent: 3/29/2004 6:08 AM

Ian: Your pictures were well done. And that wheel cylinder is about typical for a vehicle that sits unused so much of its life. The less the brakes are used the faster the fluid seems to absorb water. There is a firm here in Virginia (www.whitepost.com) that modifies wheel and master cylinders for the antique car collecting folks, whose cars dont even travel as much as our RVs. They bore out the wheel cylinder to take a brass sleeve, then put in the new rubber cups. Its usually substantially more expensive than a new wheel cylinder would be (if you can get one), but probably only needs doing once in a lifetime. Which is how long they guarantee it.
My rule of thumb; If I have to hammer the pistons out of the bore, I should definitely replace the wheel cylinder. 



From: Jupp318
Sent: 4/18/2004 1:20 PM

Hi Guys,

  The job is finished, I have brakes again.  Alretta Truck Parts did the business and supplied the parts at what I would consider a very reasonable price.  I can post the part numbers if anyone would like, it may make life easier for anyone else with the same brakes as me and with the same problem.

I will add some pictures shortly as this may help those without a manual.  One trick I developed during this exercise, (mainly due to the time it took USPS to get the parts to me) was to wash the wheel bearings and re-grease them ready for use. the trick being to then wrap them in cling-film to stop any dust etc sticking to the grease.

I would like to publicly thank Mr Geoff Rosenberg for his help and service in getting me the parts. The service I received for him made this little problem exactly that, a little problem. Also as always I thank the CWM members for their assistance, good advise as always.

Cheers Ian...



From: Liv42dayOK
Sent: 4/18/2004 8:47 PM

Good to hear you're back up and running, Ian!  - Sob