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| General Discussion -> Mechanic's Corner | Message format |
woodlandfarms |
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Regular  | So I am having a big brake issue. Wondering if anyone can share some ideas. The front right brake locked up when braking, backs did not appear to do anything. So last week I jacked the FMC up, adjusted the brakes. I am no expert but I think I did fine. Now after this both front wheels lock up. Progress, but what is going on with the rear. So today me and my friend bled the entire brake system using a pressure bleeder. Flushed out a mix of oils (in the 90s the PO had gone silicone (DOT5) but someone since then mixed DOT3 back in. So we did a clean blead, going back to DOT 3 for the moment. Air came out, some purple, and a lot of dark black oil until we hit DOT3 brown. Got in the coach, brakes were tighter, no more pumping, but the front brakes locked up and the back seem to be doing nothing. We tried to disconnect the front booster, see if the back was working, but that just locked up the front wheel worse. So I guess two questions, any immediate thoughts? And has anyone had to replace a bad booster (I am thinking the rear) and what were the symptoms? Let me add we are on gravel here. But the front brakes seem very gung ho to lock up. | ||
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| hemi354az |
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Extreme Veteran  Location: Scottsdale, Aridzona | Hey Carl, Please tell yes how you adjusted the front and rear brakes . . . till they just touch ? And then X number of clicks ? Up or Down ? Did you install new wheel cylinders and copper washers ? New hoses ? You might have to break open each steel line and flush it out with alcohol several times to get each segment completely clean. DOT 5 and DOT 3 mixed form a GOOOO. Can't "flush" DOT5 with DOT 3, or the other way around. Big PITA but alcohol flush is only way to get clean tubes. Same alcohol flush, flush, flush for the MC and the Diff Pref Switch. Then you have to Bench Bleed the MC with the Brake Fluid of your choice. How did you CENTER the Press Diff Switch ? For RVs and other vehicles that "sit" a lot . . . DOT 5 is preferred. That is why the US Army developed it. Bleed rear H-Vac first, then front H-Vac, then LR, RR, LF, RF . . . into a jar that has fluid level above fluid filled tube sticking into it to start with, so no air gets sucked back when you close the bleed valve. There are flare nut wrenches that have a standoff bend that gets the handle part "away" from the backing plate, that have a slot cut in them that allow the "box" to slip over the bleed tube, that make that "wrenching" a lot easier. Or use a crows foot. Example - https://www.ebay.com/itm/SAE-4pc-Double-Head-Offset-Flexible-Flare-N... There really are "NO PUMP" FMC BRAKES out there. That is the way they sold them ! Adjust and Bleed are the way to get them. Brake ON! Lou #120 Edited by hemi354az 2019-05-27 1:29 PM | ||
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| hemi354az |
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Extreme Veteran Location: Scottsdale, Aridzona | Hey Carl, Got BRAKES ? Lou #120 Edited by hemi354az 2019-05-31 4:41 PM | ||
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| woodlandfarms |
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Regular | Hey All Sorry about the long response, I got caught up with work and am now back to the brake issue. Thanks for all the info everyone, lots to digest. One thing I was looking to get an answer from here, is this the old style booster or new style booster? And if it is the old, does anyone have a quick link to the new style booster? http://www.fmcowners.com/mbbs22/photos/show-album.asp?albumid=193&p... http://www.fmcowners.com/mbbs22/photos/show-album.asp?albumid=193&p... | ||
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| BigRabbitMan |
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Expert   Location: Cottage Grove, OR | Your coach was originally equipped with the small boosters and small master cylinder. It was a matched system. Late coaches were equipped with large boosters and large master cylinder. Also a matched system. Less pedal pressure is required with the large system. Now might be a good time to convert your coach by going to the large system. That would be both large boosters and large master cylinder. The large boosters are available through Auto Zone. The masters are available from multiple parts houses. Search this site for the part numbers. | ||
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| BigRabbitMan |
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Expert Location: Cottage Grove, OR | By the way, they are not new or old styles. One system is just larger than the other. I expect that feedback from the first 500 or so coach owners prompted the change. | ||
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| woodlandfarms |
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Regular | Stephen, thanks for the response. So in the Previous Owners notes he says 'Replaced Master with larger master and rebuilt boosters" I am enclosing also a picture of the master cylinder. I was not aware they system had to be matching, so can you tell by these pictures wether this is original or the upgrade? http://www.fmcowners.com/mbbs22/photos/show-album.asp?albumid=193&p... | ||
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| BigRabbitMan |
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Expert Location: Cottage Grove, OR | That looks like mine which is a large master, but I have not seen the small master. | ||
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| hemi354az |
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Extreme Veteran Location: Scottsdale, Aridzona | Hello again Carl, Your small (in size) pictures look like the large Hydro-Vac and matching Master Cylinder. The large H-Vac rear can is 35.5 inches in circumference right next to the band clamp. Measure yours with a Tailors Tape to verify. We are all indebted to Randy Bradshaw for his clever work and PERSISTENCE in determining just exactly what Master Cylinder is used with the larger Hydro-Vacs. Seems that some well known FMC "Experts" were using the wrong one . . . All that work and pictures are available on the other FMC Yahoo WebSite - https://groups.yahoo.com/neo/groups/FMCMotorCoach/info?guccounter=1 Please enter "Randy Bradshaw" in the Search Box to get started about the "discovery". Damn goodwork for a Hospital Administrator. Here is a Picture of the SMALL and LARGE H-vacs side by side - https://groups.yahoo.com/neo/groups/FMCMotorCoach/photos/albums/1729... All the Service Brake stuff is in Section 9 of the FMC Parts Book . . . including the Coach numbers for the two different size MC/H-Vac matched sets used. Looking at the applicable Coach numbers, the first 663 FMCs had first design then #664 thru #750 had the second design (also tubing changes to MC and Brake Pressure Differential Switch), then FMC made #751 thru #1012 with the first design, then went back to the second design for #1013 to the end. So, only 126 FMCs initially had the second design larger MC/H-Vac brake components. The Parts Book also notes that FMCs 750 to 1012 should use the larger H-Vac if the H-Vac is "replaced" but does not say anything about the Master Cylinder being changed as well to the "matching" MC. Could there have been some "supplier delivery" issue during the production run ? Before you continue with the Brakes on FMC #86 . . . please review: http://www.fmcowners.com/mbbs22/forums/thread-view.asp?tid=1031&pos... and http://www.fmcowners.com/mbbs22/forums/thread-view.asp?tid=914&post... You never did answer about wheel cylinders or brake hoses . . . or adjustment method. Lou #120 Edited by hemi354az 2019-06-14 8:12 PM | ||
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| LCAC_Man |
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Elite Veteran Location: Oceanside, CA | For the large system: https://www.napaonline.com/en/p/NMAM2134 | ||
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| woodlandfarms |
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Regular | Hey Lou, slowly digging through this website for info. I have to say it really sucks with a mac, trying to search for results and photos to accompany them. Anyway, gues it keeps me on my toes. So, this is all that Ihave done in regards to the brakes. First of all the symptoms. Passenger (right) front tire locks up when braked depressed, brakes need to be pumped to get to lock up (3 pumps). Doing a heat exam, (place hand on brakes after multiple hard stops) the other brakes appear to be activating, but not as strongly as the front right. 1st, I pulled out some brake fluid from the MC and tested it to determine if it was DOT3 or DOT5. It tested as DOT3 2nd, I reviewed all the plumbing I could see. The only squak was that the rear booster vacuum hose was pinched. Not sure how that happened (not under my guard) but there was that nice rubber hose pinched up betwee the frame rail and the cruise control. Brake hoses to the tires appeard in order, no sign of dry rot. Next, I jacked up each wheel and began doing the brake pad adjustment. I spun the tire, and starting with the lower star adjustor pushed it out (moving the star from the inside of the wheel toward the outside of the wheel). Once I felt the drag, I backed the adjusting star off by 3 clicks. I have seen the suggestion of 3 and the suggestion of 6. I made a choice. In doing this the front passenger brake needed little adjustment, while the driver front was pretty far off. The rears, however, took a lot of turning to get them to contact. A lot. At that point I lowered the RV and drove it again. While the front now locked up at equal times, the rears showed no improvement. Also, the braking still required 3 pumps. Next, my friend and I did the poor mans brake bleed. I pushed, the pedal, he opened the various bleed ports, but did NOT bleed the boosters, this was only to double check oil was moving through the system. On each stroke we got oil from all the slave cylinders. Next, I use a professional brake pressure pot. Took some messing around to get the plate to properly sit on the MC but we got it. I have to say as a side not this is the way to do brake oil swaps, man it made it easy. So as I had tested for a DOT3 grade oil, we used that in the pressure pot. We started with the rear booster, and that is when we had a small amount of purple (DOT5) oil come out. We moved then to the rear driver slaves, then to the rear passenger slaves. Bleeding where the hose comes in first, then moving to the other cylinder. Air was indicated on all rear lines. We then moved to the front, and started with the booster, then moved to the Driver side and then the passenger side front. We drove the RV again, and this time we had a near no pump response (brakes worked when depressed). But the front tires continued to lock up, and the rears only got slightly warm. So now I am trying to figure out how to test the booster. I know I need to check to make sure I have a vacuum,. Not sure how I prove that the booster is working, any suggestions? One note, when I got the front tires up on the RV, I felt a bit of play in the bearing. I don't think that is a feature, and of course I need to explore that issue now. | ||
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| hemi354az |
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Extreme Veteran Location: Scottsdale, Aridzona | Well . . . obviously you did not read either of the two entries I listed at the bottom of Message #6528 above. You are NOT ADJUSTING THE BRAKE SHOES CORRECTLY. You are NOT centering the brake shoes with the adjusters. You must do all four wheels the SAME, as stated in Message #5013. Or you can do what the FMC Service Manual says in Section 9.3, d, (1), (2), and (3). My description and the FMC Manual are the exact same with respect to CENTERING THE SHOES IN THE DRUM. Have you examined the wheel cylinders . . . they might need replacement. Since you got DOT 5 out of the rear . . . and you want to run DOT 3 . . . you MUST FLUSH ALL THE HARD LINES, the brake pressure differential switch and CENTER IT, and the H-Vacs, the wheel cylinders and hoses, and flush then bench bleed the MC. You must get all traces of DOT 5 out of the System flushing with alcohol. Then REFILL with DOT 3 and BLEED, BLEED, BLEED EVERYTHING, IAW Section 9-4 of the FMC Service Manual. The Vacuum hose from the "manifold" above the curb side cylinder head has one tee (from intake manifold) and two check valves (white nylon/plastic, 90º type, Ford #C3TZ-2365-A) going to each H-vac. That hose must be stiff enough to NOT COLLAPSE with 20+ In Hg vacuum. The hose from the check valves to the H-Vacs must also be stiff and NOT COLLAPSE. What you have is probably 45 years old and CRACKED someplace. All of this will be a lot of work, but if you flush the DOT 5 out of the system, CENTER the brake shoes, then adjust, then BLEED . . . you CAN HAVE REGULAR NO PUMP BRAKES on you FMC just as it was sold. Lou #120 Edited by hemi354az 2019-06-16 2:02 AM | ||
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| woodlandfarms |
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Regular | Thanks Lou, No, didn't read the instructions you posted as I had already done the work. Appreciate the knowledge, as I have to go over everything again I will take up these new directives. Nope, as noted, I have not taken out hte wheel cylinders yet I would prefer DOT5 and will flush and replace as you mentioned. I went with 3 on this first pass as it was what was in the master cylinder. I did not want to mix, figured that while the notes from the OP stated he had gone to 5, someone along the way dumped in some 3, and I was correct. Thanks for the info on the check valves and hoses, will get on that shortly. At ths point, the plan is to confirm my vacuum, and my rear booster are within specs. Once that is checked off the list the wheels and drums will come off and a full brake inspection will ensue. | ||
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| hemi354az |
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Extreme Veteran Location: Scottsdale, Aridzona | Morning Carl, NOW YOUR BRAKIN' ! FMCs are rare enough that most (Truck) Brake Shops won't get involved . . . or the "outcome" is uncertain even after big $$$ changes hand. Most current FMC Owner's will sooner or later experience the "Pride of Ownership" of a 45 year old 15,000 pound antique. I doubt that many of them ever thought that the would become "practical experts" about the FMC Brake System, much less learning how to get a FMC off the ground, or that a "brake spoon" is not really a kitchen utensil. Wise choice to completely flush and use DOT 5 ! Figure 9-5 in the FMC Service manual is worth printing and taking it "under the Coach" to remind you that there are LH and RH threads on the adjusters, or even go "all out" and print 4 of Fig 9-5 and mark each up with arrows and which wheel, LF, RF, LR, RR, that sheet applies to. The idea that you have to adjust the brakes till the wheel barely turns and then back off X clicks where it still is touching, and do it exactly the same at each corner only becomes understood after you have done it "right" the first time. Then you understand how many brake jobs get screwed up, pull left or right, lock up on front or rear or one corner, and also know that if one position is not braking the same as the others . . . that there is something "else" that is causing it . . . but it ain't the adjustment. Shoes can be relined at shops that do that . . . including some FARM EQUIPMENT Shops. Don't strip the LH or RH thread adjuster . . . they are rare and disappearing. You already know about the return springs. Wheel cylinders are also drying up . . . Part #WC28851. Rebuild kit Part #WK159. You need EIGHT ! Some have had stainless steel sleeves put in old wheel cylinders, which works but is $$$. This may be the time to put in NEW brake hoses and also two get longer ones for the rears so that the supply goes in the BOTTOM wheel cylinder (just like the fronts, and as shown in the Parts Book). Stephan has picture(s?) of how he routed his rear hoses . Extra clamp is necessary ! (http://www.fmcowners.com/mbbs22/photos/photo-thumbnails.asp?albumid=151) Hydrovacs ? You are making sure they work . . . If you switch to DOT 5 and put in new wheel cylinders and hoses, and if your recently installed MC can get completely flushed of the DOT 3 and then Bench bled (past tense of bleed ?) with DOT 5 and you get all the DOT 3 out of the H-Vacs and metal lines . . . then the only thing left would be shoe lining. If they get relined . . . then your Brakes should last another 45 years ! Yes, A LOT OF WORK ! But no one else will do as good a job as you will on your OWN FMC. NO PUMPING ! Just apply the BRAKES. Brake ON ! Lou #120 Edited by hemi354az 2019-06-16 1:00 PM | ||
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| hemi354az |
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Extreme Veteran Location: Scottsdale, Aridzona | Hey Carl, Please forgive me for "You already know about the return springs". I got cornfused with Michael Payesko's FMC #128. Please see - http://www.fmcowners.com/mbbs22/forums/thread-view.asp?tid=1115&pos... - for more discussion about FMC Brakes. Lou #120 | ||
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| woodlandfarms |
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Regular | So bringing this old article back up. Basically life got in the way and now with the corona issue I can tackle my brake issue. First I had to buy a nut buddy to get the lug nuts off. Wow did that work like a charm. So I got to the rear brakes and while the wife sat in the seat and pumped I watched the brakes. Well. It turns out someone decided to tighten down the retaining nuts so that the brake pads couldn’t move. In the interim I found a leaky brake cylinder so I think I will replace all 4. Also moving the brake lines down. Question for the group. I found rear drum info (Ford 500) but I can’t find any info on the front drums. Any thoughts ? | ||
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| LCAC_Man |
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Elite Veteran Location: Oceanside, CA | the entire drum brake assy is the same at all four corners..any brake part that works on the rears will work on the fronts.. | ||
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| woodlandfarms |
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Regular | So the drums are the same? I have not pulled my front off but the drums but are you sure they are the same? I thought the rears had a different spacing for dualies. | ||
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| LCAC_Man |
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Elite Veteran Location: Oceanside, CA | i'm sure | ||
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| dkarnath |
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Elite Veteran Location: Medford, OR | All four corners are the same | ||
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| woodlandfarms |
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Regular | Thanks guys. So moving on to the new issues. Turns out my brake cylinders are rusted... Three of the four rear are so bad I had to use a hammer to pound out the piston on one side. I know the machine has been sitting probably since 2008 in the PNW so this is not completely surprising, just frustrating. This said, I am of the ilk to replace (already ordered two from Crapa but now I need at least two more). Does anyone have experience with the rebuild kits? My neigbor who is a truck mechanic has a brake cylinder hone and said I should jsut rebuild but the pistons look pretty cruddy as well. So a bunch more questions. First, I found a lot of rust and oil between the piston and the outer boot. Is there a way to prevent water from getting in here? There was oil in this space , I assume that there is not supposed to be any? I am having an issue getting one of the connectors to the metal tube that feeds the second piston off. If I cannot get it free do you guys just have new ones built and if so by whom? Finally, I am tearing down the old cylinders, and the bleed valves are rough but probably useable. The thing is that they all have pipe tape on them. Is this normal for this sized cylinder? My car does not have any pipe tape on these threads. Edited by woodlandfarms 2020-04-06 9:23 PM | ||
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| hemi354az |
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Extreme Veteran Location: Scottsdale, Aridzona | Now you know why the US Army paid lots of money to develop, test, and change all their vehicles to DOT 5. You get one chance to do this RIGHT . . . get EIGHT NEW wheel cylinders - https://www.rockauto.com/en/parts/raybestos,WC28851,wheel+cylind... You may find one or more cheaper on the NETS NO TAPE, SEALER of any kind on BRAKES. Soak inside transfer tube B-nut with KROIL OVERNIGHT - https://www.galesburgelectric.com/kano-kroil-kroil-penetrating-oil-8... or http://www.kanolabs.com/index.html Get a TUBE NUT WRENCH to loosen and tighten the nut on each end of the transfer tube. No known source for those tubes. Local Civil Airport FBO Acft Mech might make you one or two however. YOU MUST FLUSH: MC, Diff Pressure Switch, Hydrovacs, and ALL TUBES/hoses with cheap Drugstore rubbing alcohol till NOTHING ELSE COMES OUT, then Fill with DOT 5 Silicone Brake Fluid. Best price I found on Nets for DOT 5 was Case of 12 oz bottles, which are easier to handle. DO NOT GET THE Silicone Brake Fluid IN YOUR EYES ! You CAN DO THIS ! You too will soon have NEW BRAKES on your 45 year old Antique Road Show. Brake ON ! Lou #120 | ||
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| woodlandfarms |
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Regular | Thanks Lou. So to be clear, your judgement is that the nature of DOT3 (being Hygroscopic) is what caused the brakes cylinders to rust up. That the oil seeped between the piston and the protective cap and due to that it rusted the brakes. I am just asking to make sure I don't need to seal these brake cylinders better. Also, going to be interesting to see if in this time of Covid I can get any rubbing alcohol. | ||
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| hemi354az |
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Extreme Veteran Location: Scottsdale, Aridzona | YES. Well known for YEARS !!!! ??? What oil ? What is the source of oil INSIDE the brake drum ? That is leaked brakefluid/water/grime. Your NEW wheel cylinders should come with new "RUBBER BOOTS. If they do not . . . here is WK195 rebuild kit with NEW BOOTS for $5 - https://www.carid.com/raybestos/element3-rear-drum-brake-wheel-cylin... Or look and pick alternate Part #s here - https://www.rockauto.com/en/moreinfo.php?pk=10882384&jsn=7 In the good old days . . . before OSHA . . . mechanics would rub "Red Grease" on the boots, inside and out, and the cups, on rebuilds. Kept the rubber soft, pliable. Then, for some reason, OSHA outlawed Red Grease. Still made and used in England and Europe by Castrol and Lucas/Girling I think, but you cannot source it here in the USA. Don't know why . . . But, but, but . . . I recently found the real stuff REPACKAGED - https://www.amazon.com/GENUINE-Corrosion-Oxidation-Resistant-TS-2-34... Get a jar while you can ! Every auto mechanic and airplane mechanic I knew growing up had a jar in his toolbox, and used it on any and every thing rubber . . . including O-rings. Someone "borrowed" my Genuine Girling Red Grease jar about 15 years ago . . . and I was lucky and happy to finally find some more. Yes, I am aware that Rubbing Alcohol is NOW more expensive than fine smooooooth Blended Canadian Whiskey like VO, and highly overrated paint stripper like Jack Daniels. Maybe visit a brake place and ask what they use to FLUSH old fluid. But you MUST get all that DOT 3 out of everything. DOT 5 is really the only brake fluid for a motor home, Deuce and a Half, Tank, Rocket Launcher, or other vehicle that does not get used very often . . . or have it's brake fluid Flushed and Replaced every several years. This is a lot of messy work . . . but once done . . . it is done for a looooooooooooong time and/or maaaaaaaaaaaaany miles . . . safely. FYI - The Wheel Mounting STUDS are longer on the rears (Part #MWC 81614) than the fronts (Part #MWC 06605) . . . Group 8 in the Parts Manual. Everything else is the SAME Front and Rear. Press ON ! Lou #120 Edited by hemi354az 2020-04-07 2:13 AM | ||
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| 5Dollar |
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Veteran Location: Bethune, SC | I use denatured alcohol that is used by painters. Henry | ||
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