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05-26-2022, 08:55 PM
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#1
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Senior Member
Join Date: Mar 2013
Location: The Evergreen State
Posts: 493
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76 Dodge M500 Motorhome Brake Issues
Hello:
I'm getting rid of my 76 King's Highway RV which has been sitting at least 8 years. The guy taking it got it started and it move front and back but has no brakes. He tried bleeding the brakes, but no fluid comes out on all 4 bleeder screws, and yes master cylinder has fluid. So, he figured it was the master cylinder and pick one up at NAPA. After installed the new master cylinder, same thing, no fluid comes out on all 4 bleeder screws.
The guys on a buget and instead of just throwing this and that on this RV I thought I asked here for anyone that had an experience like this or someone with brake knowledge that can put us in the right direction. In other words, your advice is very much appreciated.
Thank you in advance!!
__________________
1996 34'J Fleetwood Bounder, Chevy 454 TBI P-32, Bank PowerPack, Ultra Power Chip, BellCranks, Rear Trac Bar, Silver Safe-T-Plus and 04 CR-V Toad, Roadmaster Base Plate and All Terain Tow Bar, SMI Stay-In-Play DUO.
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05-27-2022, 05:35 PM
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#2
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Senior Member
Join Date: Mar 2015
Location: Craigmont, Idaho
Posts: 172
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Have you checked to make sure the bleeder screw holes are open. They do tend to plug. Small drill bit run through them and some air will usually open them back up.
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1976 Dodge 440 Monaco body built by Caribou Manufacturing in Junction City Oregon
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05-27-2022, 06:41 PM
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#3
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Senior Member
Join Date: Aug 2013
Location: Cincinnati, OH
Posts: 849
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Under brake pedal pressure there are several hundred psi of fluid pressure. Make sure the bleeder is open enough.
Is the brake pedal going to the floor? Did you bench bleed the new master cylinder?
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2017 Renegade Verona 36 VSB
2005 Kenworth Showhauler truck conversion. sold .
I used to have a handle on life, but it broke
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05-28-2022, 01:25 AM
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#4
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Senior Member
Join Date: Mar 2013
Location: The Evergreen State
Posts: 493
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Quote:
Originally Posted by ihc1470
Have you checked to make sure the bleeder screw holes are open. They do tend to plug. Small drill bit run through them and some air will usually open them back up.
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Yes, the bleeders screws are open.
Thanks
__________________
1996 34'J Fleetwood Bounder, Chevy 454 TBI P-32, Bank PowerPack, Ultra Power Chip, BellCranks, Rear Trac Bar, Silver Safe-T-Plus and 04 CR-V Toad, Roadmaster Base Plate and All Terain Tow Bar, SMI Stay-In-Play DUO.
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05-28-2022, 01:29 AM
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#5
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Senior Member
Join Date: Mar 2013
Location: The Evergreen State
Posts: 493
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Quote:
Originally Posted by 38Chevy454
Under brake pedal pressure there are several hundred psi of fluid pressure. Make sure the bleeder is open enough.
Is the brake pedal going to the floor? Did you bench bleed the new master cylinder?
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Yes, bleeders are open.
Yes, pedal goes to the floor.
Yes, bench bleed the master cylinder before installed.
Thanks!
__________________
1996 34'J Fleetwood Bounder, Chevy 454 TBI P-32, Bank PowerPack, Ultra Power Chip, BellCranks, Rear Trac Bar, Silver Safe-T-Plus and 04 CR-V Toad, Roadmaster Base Plate and All Terain Tow Bar, SMI Stay-In-Play DUO.
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05-28-2022, 05:15 AM
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#6
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Senior Member
Join Date: Jul 2014
Posts: 30,383
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Looking at M500 chassis online, one site shows a hydroboost unit in it.
Do you have 2 rear axles, if yes, then one axle is controlled by the hydroboost. When they fail, they can suck the brake fluid into the engine and burn it.
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05-28-2022, 05:24 AM
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#7
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Senior Member
Join Date: Apr 2016
Posts: 258
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Assuming no leaks along the length of the brake lines themselves, remove the lines from the master cylinder and one at a time remove the other end of each lie from the calipers or wheel cylinders and blast air through them. Its not unheard of for the metal lines to rust up and clog. If air blasts through the lines, then the next step is to remove the bleed screws completely from the calipers and cylinders and blast air through them to see if it comes out the line connection. Be sure to leave the caliper and pads mounted and only remove the bleed screw and brake line or else you'll pop the piston out and then you're rebuilding it. Same thing applies for the rear wheel cylinders.
Frankly if this new owner is preparing to drive anywhere more than a few slow miles, they would be better served to just replace all the hard and rubber lines and be done with it. If there is so much blockage within the brake system that fluid won't pass, there is a leak & complete failure coming very soon especially when the extreme heat and pressure builds up from a couple of stops. Sorry this person is short on cash but going cheap and lazy with brakes on a large heavy vehicle like an RV is not a good idea.
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05-28-2022, 07:49 AM
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#8
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Senior Member
Join Date: Aug 2021
Location: Maine
Posts: 118
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When the master is bench bled then it should be ready to pump fluid. If you start pumping it while on the vehicle the brake fluid level should go down in the reservoir and start filling the lines. If that isn't happening, then I would crack a brake line at the master to verify that it is trying to push fluid. It should be able to push fluid somewhere. If there is a proportioning valve in the system it should at least push fluid to the front or rear.
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1986 Itasca Sunflyer 22 ft P32 chassis with 454 engine
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05-28-2022, 10:42 AM
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#9
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Senior Member
Join Date: Mar 2013
Location: The Evergreen State
Posts: 493
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Quote:
Originally Posted by twinboat
Looking at M500 chassis online, one site shows a hydroboost unit in it.
Do you have 2 rear axles, if yes, then one axle is controlled by the hydroboost. When they fail, they can suck the brake fluid into the engine and burn it.
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No, 1 rear axle. Thanks!
Quote:
Originally Posted by Tidy Tabby
Assuming no leaks along the length of the brake lines themselves, remove the lines from the master cylinder and one at a time remove the other end of each lie from the calipers or wheel cylinders and blast air through them. Its not unheard of for the metal lines to rust up and clog. If air blasts through the lines, then the next step is to remove the bleed screws completely from the calipers and cylinders and blast air through them to see if it comes out the line connection. Be sure to leave the caliper and pads mounted and only remove the bleed screw and brake line or else you'll pop the piston out and then you're rebuilding it. Same thing applies for the rear wheel cylinders.
Frankly if this new owner is preparing to drive anywhere more than a few slow miles, they would be better served to just replace all the hard and rubber lines and be done with it. If there is so much blockage within the brake system that fluid won't pass, there is a leak & complete failure coming very soon especially when the extreme heat and pressure builds up from a couple of stops. Sorry this person is short on cash but going cheap and lazy with brakes on a large heavy vehicle like an RV is not a good idea.
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Fluid is coming out the master cylinder lines. Going to tell him to blast air through the lines. I do understand brakes are important in a RV, but not to sure the new owners does, but he's not leaving here until it is fix. Thanks!
Quote:
Originally Posted by cadillac_al
When the master is bench bled then it should be ready to pump fluid. If you start pumping it while on the vehicle the brake fluid level should go down in the reservoir and start filling the lines. If that isn't happening, then I would crack a brake line at the master to verify that it is trying to push fluid. It should be able to push fluid somewhere. If there is a proportioning valve in the system it should at least push fluid to the front or rear.
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So, if the proportioning valve is not operating it should still allow fluid to the bleeders? Thanks!
__________________
1996 34'J Fleetwood Bounder, Chevy 454 TBI P-32, Bank PowerPack, Ultra Power Chip, BellCranks, Rear Trac Bar, Silver Safe-T-Plus and 04 CR-V Toad, Roadmaster Base Plate and All Terain Tow Bar, SMI Stay-In-Play DUO.
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05-28-2022, 12:45 PM
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#10
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Senior Member
Join Date: Jul 2014
Posts: 30,383
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Does it have a big brake booster behind the master cylinder ?
If not, it may still have a hydro boost down the chassis rail.
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05-28-2022, 05:10 PM
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#11
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Senior Member
Join Date: Feb 2020
Location: NY State
Posts: 1,705
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You have gotten some good advice. I will add that I have seen bleeder screws with clogged ports on vehicles that have sat for extended periods. The cure is to remove one at at time, hold your finger over the hole, and have someone pump the brakes. If you get fluid, drill out the port, *gently* just to clear the existing holes. I use a hand chuck, but you can use s power drill.
Rinse and repeat for the other three corners. You can get new bleeder screws, of course, but drilling them out is a lot faster and slightly less expensive.
__________________
John
1976 Southwind 28', '96 Winnie 34WK,
2006 Tiffin Allegro Bus 40QDP
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05-28-2022, 05:17 PM
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#12
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Senior Member
Join Date: Oct 2018
Posts: 268
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1976 vintage ID be replacing/rebuilding wheel cylinders and/or calipers. The pistons could be frozen
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2013 F150 5.0
2005 keystone zeppelin 241
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05-29-2022, 04:35 PM
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#13
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Senior Member
Join Date: Mar 2013
Location: The Evergreen State
Posts: 493
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Finally got the brakes working. Originally, he said the bleeder screws looks good. Today he brought someone that knows what he was doing, and he clean/open all breeders screws and the brakes bleeded fine and got brakes.
Thank you all for your help!!!
__________________
1996 34'J Fleetwood Bounder, Chevy 454 TBI P-32, Bank PowerPack, Ultra Power Chip, BellCranks, Rear Trac Bar, Silver Safe-T-Plus and 04 CR-V Toad, Roadmaster Base Plate and All Terain Tow Bar, SMI Stay-In-Play DUO.
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