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06-26-2020, 02:00 PM
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#1
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Rivet Master
1991 25' Airstream 250
Oxford
, Oxfordshire
Join Date: Jun 2007
Posts: 1,253
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1991 brake light/soft brakes
Hi all,
Last year, my 250 Classic developed a problem with the brakes which needs fixing as soon as possible.
We had a drivers side front wheel blow out on the first day of our vacation. It was pretty spectaular and terrifying in equal measure.
During the holiday, the brakes became softer and eventually the check brake light came on and we ended up getting towed back from the UK Port.
I've finally got round to looking at the issue today. I managed to remove the shroud and have a look about:
Findings to date:
The coach has the Hydroboost set up where it gets additional braking power via the power steering.
Brake set up is front disc/rear drums.
Brake set up is JB8
The master cylinder is full in both resevoirs
The power steering fluid is also full
I can't see any leaks, no sign of major brake fluid leakage.
There is a small amount of wetness (I can't see a drip) in the attached photo
The Master Cylinder was swapped out about five years ago.
The Hydroboost about two years ago. Both worked without issue following the installs.
I am unclear whether the 1991 with TBI set up and Hydroboost had a combination or proportioning valve. I can't see one on GM parts or the AC Delco site.
Can anyone give me any pointers as to the potential cause? I'm note sure whether the drivers side front wheel blowout caused the issue. It seems likely given the timing, but it could be a co-incidence.
Any thoughts on next steps would be greatly appreciated.
thanks
Nick
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06-26-2020, 07:18 PM
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#2
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Rivet Master
1984 31' Airstream310
Honokaa
, Hawaii
Join Date: Jun 2010
Posts: 993
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The pedal is softer as in it goes down further and you have to pump it to get it to come back up, or you just have to push harder?
A blowout could damage the line to the front left caliper, but you would see that leak.
The light on ours only come on when fluid is low, but ours are older. Double check the m/c reservoirs? I, along with others here, have gotten bum rebuilt master cylinders.
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06-26-2020, 08:22 PM
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#3
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Airstream Driver
1994 30' Excella
1992 35' Airstream 350
Austin
, Texas
Join Date: Feb 2002
Posts: 5,224
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Quote:
Originally Posted by Boom Sounds
Hi all,
Last year, my 250 Classic developed a problem with the brakes which needs fixing as soon as possible.
We had a drivers side front wheel blow out on the first day of our vacation. It was pretty spectaular and terrifying in equal measure.
During the holiday, the brakes became softer and eventually the check brake light came on and we ended up getting towed back from the UK Port.
I've finally got round to looking at the issue today. I managed to remove the shroud and have a look about:
Findings to date:
The coach has the Hydroboost set up where it gets additional braking power via the power steering.
Brake set up is front disc/rear drums.
Brake set up is JB8
The master cylinder is full in both resevoirs
The power steering fluid is also full
I can't see any leaks, no sign of major brake fluid leakage.
There is a small amount of wetness (I can't see a drip) in the attached photo
The Master Cylinder was swapped out about five years ago.
The Hydroboost about two years ago. Both worked without issue following the installs.
I am unclear whether the 1991 with TBI set up and Hydroboost had a combination or proportioning valve. I can't see one on GM parts or the AC Delco site.
Can anyone give me any pointers as to the potential cause? I'm note sure whether the drivers side front wheel blowout caused the issue. It seems likely given the timing, but it could be a co-incidence.
Any thoughts on next steps would be greatly appreciated.
thanks
Nick
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Nick, Like Steve (Waipio Rim) says, first thing to check is "pedal fading". (not sponginess) With the engine running press on the pedal wait a sec or 2 without letting off pressure and continue to push. If the pedal continues to go down, you can assume to have a faulty master cylinder seal. If it says in place firmly but feels spongy and hardens up when you pump it, you can assume air in the line. Now how air would have gotten in the system, would be the next question , especially with the tanks being full.
I still would look for any sign of moisture around all wheel cylinders
The wetness on that power steering line is almost to be expected. After rebuilding my lines and power steering pump, i find myself marveling at all the dry hoses, since i know it will not last.
__________________
1994 30' Excella Front Kitchen Trailer
1990 25' Excella Travel trailer
1992 350LE Classic Touring Coach
AIR #13
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06-27-2020, 12:07 AM
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#4
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Rivet Master
1991 25' Airstream 250
Oxford
, Oxfordshire
Join Date: Jun 2007
Posts: 1,253
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Thanks all. I’ll have another reccee today. The fluid levels in the MC are definitely OK. I was pumping the brakes just before I finally gave up and got towed. Even that became unworkable, the pedal was just too soft to continue safely. In terms of the Master Cylinder deal. I have a gut feel that it is a duff MC. We all know they fail and it’s conceivable that was replaced up to seven years and 20000 miles ago. If the seal has gone, would that explain the symptoms I am experiencing? I’m sorely tempted to just swap it out. It’s not an expensive fix and would give more certainty for the next few years.
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06-28-2020, 08:03 AM
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#5
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Rivet Master
1974 20' Argosy 20
Richmond
, Kentucky
Join Date: Jan 2003
Posts: 9,115
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Nick,
Replace the inexpensive stuff first, if that doesn't do it then you go after the big ticket items.
Many replacement master cylinders on the market now are rebuilt units and it's been my experience that rebuilt units don't last as long as original unit. It's just the nature of what we have to deal with when owning one of these old rigs.
Good luck.
Brad
__________________
Air forums # 1674
1974 20' Argosy Motor Home
1975 24' Argosy Motor Home
1974 31' Excella trailer (parting out, as of 4/1/2015 I have wheels & windows left to sell)
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06-28-2020, 08:55 AM
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#6
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Airstream Driver
1994 30' Excella
1992 35' Airstream 350
Austin
, Texas
Join Date: Feb 2002
Posts: 5,224
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Quote:
Originally Posted by bkahler
Nick,
..
Many replacement master cylinders on the market now are rebuilt units and it's been my experience that rebuilt units don't last as long as original unit. It's just the nature of what we have to deal with when owning one of these old rigs.
Good luck.
Brad
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Couldn't agree more!
This new unit is what I used on the 350
ACDELCO 174834 {#14009146} (Daily Driver) GM Original Equipment Info Rear Disc brakes; Hydraulic Power Brakes; mounted to booster Assembly, 1.336 DIA X 1.434 STROKE
__________________
1994 30' Excella Front Kitchen Trailer
1990 25' Excella Travel trailer
1992 350LE Classic Touring Coach
AIR #13
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06-28-2020, 11:22 AM
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#7
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Rivet Master
1991 25' Airstream 250
Oxford
, Oxfordshire
Join Date: Jun 2007
Posts: 1,253
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1991 brake light/soft brakes
Thanks guys. I checked my service records. I actually replaced the master cylinder four years ago. It was a rebuilt AC Delco unit. I have the JB8 rear drum set up on 16” rims. I used a ACDelco[emoji768] 18M230 - Professional[emoji769] Brake Master last time round. I did painstaking research to ensure it was a precise match for the stock unit. I also replaced the hydroboost. Tye MC is from their ‘professional’ range - read rebuilt junk prone to failure.....AC Delco no longer make the OEM version for the JB8 Motorhome set up. I’ve ordered the same rebuilt unit again (I’m probably mad) but wasn’t sure about the other options from other suppliers and whether they would marry up correctly with the hydroboost. Perhaps I would have been better to try a Dorman product. Any thoughts on Delco Professional (rebuilds) vs Dorman?
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