| Do we have to bench bleed it? [message #370210] |
Wed, 27 July 2022 11:22  |
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wally
Messages: 643
Registered: August 2004
Location: Omaha Nebraska
Karma: 5
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I helping a GMCer get his brakes fixed. He had a hold down spring break and chew up the shoes and drum. While the drum was off getting turned the brake pedal must have got pressed or something and the rear fluid went away ( master front reservoir empty). Can we use a pressure bleeder straight away or do we need to remove and bench bleed the master. Front brakes are intact and work. Trying to save some work..not having joy with the pump the pedal bleed routine.
Wally Anderson
Omaha NE
75 Glenbrook
[Updated on: Wed, 27 July 2022 11:32] Report message to a moderator |
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| Re: Do we have to bench bleed it? [message #370211 is a reply to message #370210] |
Wed, 27 July 2022 11:36  |
Tom Katzenberger
Messages: 399
Registered: June 2019
Location: Kingsville, MD
Karma: 4
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WallY,
I have had that happen a couple of times in the last several months while upgrading the system from original MC to the P30 and then to 2 stage MC. I was successful in bleeding the MC and system both times. I used a Harbor Freight Holt vacuum bleeder and blead from the calipers while keeping the MC full.
I hope this helps.
Take care,
Tom K.
Tom & Oki Katzenberger,
Kingsville, Maryland,
1977 23' Birchaven, 455 C.I.D., Micro Level, Howell EBL-EFI Spark Control, Macerator, York Air Compressor, 6 Wheel Disc, Quadra Bag, Onan W/Bovee Ignition
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| Re: Do we have to bench bleed it? [message #370213 is a reply to message #370210] |
Wed, 27 July 2022 19:13 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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The pressure bleeder works well for me. I have installed 2 masters without bench bleeding. (Side of road where bench bleeding was not practical)
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: Do we have to bench bleed it? [message #370216 is a reply to message #370213] |
Wed, 27 July 2022 21:37 |
boybach
Messages: 566
Registered: December 2020
Location: Vancouver Island
Karma: 4
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lqqkatjon wrote on Wed, 27 July 2022 17:13The pressure bleeder works well for me. I have installed 2 masters without bench bleeding. (Side of road where bench bleeding was not practical)
What does this pressure bleeder look like and where do you attach it? I have a mightyvac that I usually use to bleed brakes but I guess that's no good for the GMC?
Larry
Larry - Victoria BC -
1977 ex-Palm Beach "Ol' Leaky" 40,000 miles, PO said everything working but forgot the word NOT. Atwood helium fridge, water heater & furnace. SS exhaust system, Onan, Iota Converter, R134A, New fuel lines & heat exchange hoses
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| Re: Do we have to bench bleed it? [message #370219 is a reply to message #370218] |
Thu, 28 July 2022 09:24 |
boybach
Messages: 566
Registered: December 2020
Location: Vancouver Island
Karma: 4
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Thanks Bruce
Larry
Larry - Victoria BC -
1977 ex-Palm Beach "Ol' Leaky" 40,000 miles, PO said everything working but forgot the word NOT. Atwood helium fridge, water heater & furnace. SS exhaust system, Onan, Iota Converter, R134A, New fuel lines & heat exchange hoses
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| Re: Do we have to bench bleed it? [message #370223 is a reply to message #370216] |
Thu, 28 July 2022 13:55 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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Senior Member |
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I use Jim Hupy's plate with a motive bleeder because I had the motive one before I knew Jim had one. The motive plate works, but is too big and hard to clamp tight. Jim's plate fits perfectly.
here is Jim's info and he has photos to show how you hook it up:
http://www.gmcmotorhomemarketplace.com/jhupy/
his bleeder has worked flawless for me on many GMC's, many times. 15-20 minute process and most of that is spent trying not to spill fluid and getting hoses and bleeders loose.
Bench bleeding a master on the side of the road is not so much of a problem of not having the "kit"(witch can be hard to find, not always in stock.. I now keep one on hand). but more trying to hang onto the master. at home it goes in the vice.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: Do we have to bench bleed it? [message #370224 is a reply to message #370223] |
Thu, 28 July 2022 14:19 |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
Karma: 0
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One reason to bench bleed is that some Master Cylinders are mounted at an angle. this angle will trap air. mounting it to a vice will hold it level and let air out.
Other than that. there's no magic to bench bleeding
Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
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| Re: Do we have to bench bleed it? [message #370349 is a reply to message #370210] |
Thu, 11 August 2022 11:12 |
rgogan
Messages: 82
Registered: February 2004
Location: Milwaukee, WI
Karma: 0
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I had the same brake failure happen to me on a recent trip. Backed up several times in a gas station and heard a loud clunk in the back. Drove over 100 mi without any noticeable problem but when I stopped at a gas station, the braking was poor and the passenger side drum was smoking. Pulled the drum off and all the friction material was gone from the shoes and half of the springs, adjuster screws etc. had been worn down from dragging on the drum. The wheel cylinder piston had popped out and the rear brake fluid had leaked out.
Didn't have immediate replacements available but removed all the drum brake components except for the drum and put a 3/8" union 24 pitch onto the brake flare nut and capped it with a flair nut plug. Refilled the master cylinder and bled all the rear brakes. Test drive actually produced better braking and pedal position with only 5 brakes than I ever had before. The non functional brake was the rear most of the passenger side which is not responsible for much braking anyway.
A word of caution about this temporary fix. I actually drove over a thousand miles with this situation, but shortly before arriving home, I found poor braking performance again. Pulled the drum off and found that from vibration, my flare nut plug had unscrewed from the union and I had lost all rear hydraulics again. If anyone were to do this, it would require putting a rubber tube around the union to pad it from brake base plate vibrations. The vibrations were significant enough that the flats on the brass union were actually worn down.
In retrospect, I don't think that I ever properly bled the brakes in the past and hence had poor performance. Now I followed the manual and put a clamp on the combiner brake valve to prevent it shutting off the hydraulics to the rear brakes when pedal or pressure bleeding. BIG IMPROVEMENT
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