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busman78 Samba Member
Joined: August 17, 2004 Posts: 4518 Location: Oklahoma City, OK
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Posted: Sun Apr 18, 2010 1:43 pm Post subject: Brake Booster Test with Mityvac |
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Purchased a Mityvac, discovered that all the plastic hose connections to the metal tube and at the booster were leaking, replace all of that line with DOT booster line. Now my question is, when I evacuate the entire line including the booster with the Mityvac from the end of the hose that would attach to the intake how long should a vacuum be holding? I have brough it up to 17hg, and that takes a lot of pumping with the vac tool, it holds for a few minutes then slowly drops to 15hg, after 40 minutes there is still 5hg holding, is that a leak or normal? |
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busdaddy Samba Member
Joined: February 12, 2004 Posts: 51057 Location: Surrey B.C. Canada, but thinking of Ukraine
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Posted: Sun Apr 18, 2010 2:04 pm Post subject: |
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That's a leak, a small one, but still a leak, it should hold a vacuum for weeks or months. _________________ Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!
Слава Україні! |
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WestyPop Samba Member
Joined: February 08, 2005 Posts: 1732 Location: SoCal
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Posted: Sun Apr 18, 2010 2:05 pm Post subject: |
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Sounds like something is leaking. Good commentary here... http://www.thesamba.com/vw/forum/viewtopic.php?p=3626103
I'd have to agree with the assessment by SGKent "... I would replace a booster that doesn't hold vacuum for at least over night (assuming the valve and hoses are good and not leaking.)"
Such a booster is definitely on its way out, and could leave you, or another driver of your bus, seemingly without braking power at the most inopportune moment. Don't buy a booster from a place that forces you to buy its 'rebuilt' master cylinder with the booster, as a package. Those MCs are usually crap.
Your call. _________________ Never underestimate the power of stupid people in large groups.
______________________________________
J.R.
68 Westy
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busman78 Samba Member
Joined: August 17, 2004 Posts: 4518 Location: Oklahoma City, OK
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Posted: Sun Apr 18, 2010 2:29 pm Post subject: |
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Cool, thanks, I have a spare I can send to H&R for rebuild then swap out on return. |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Sun Apr 18, 2010 4:29 pm Post subject: |
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Quote: |
it should hold a vacuum for weeks or months. |
keep looking at your connections. Our bus sat in a field for 10 months and still had a vacuum. _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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busman78 Samba Member
Joined: August 17, 2004 Posts: 4518 Location: Oklahoma City, OK
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Posted: Sun Apr 18, 2010 4:41 pm Post subject: |
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Good idea, I may vac pump just the can and let it sit, and then do the lines if the can holds. |
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patayres Samba Member
Joined: March 20, 2009 Posts: 991 Location: Bend, Orygun
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Posted: Mon Apr 19, 2010 8:29 am Post subject: |
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Have you tested how the Mityvac itself holds vacuum? I've had one go bad and it caused me to chase leaks that didn't exist. _________________ 1975 Westfalia Helsinki - 1800 EFI w/ Pertronix
1965 Singlecab - 1600dp
yuthi'so'coro |
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busman78 Samba Member
Joined: August 17, 2004 Posts: 4518 Location: Oklahoma City, OK
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Posted: Mon Apr 19, 2010 8:36 am Post subject: |
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No, but a good idea. Will do.
Update: Tested the tester and it bleeds out at about the same rate as it did while testing the entire booster system. Bummer. Need to make a phone call to Mityvac. |
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busman78 Samba Member
Joined: August 17, 2004 Posts: 4518 Location: Oklahoma City, OK
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Posted: Sun Apr 25, 2010 11:38 am Post subject: |
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Update: Got the replacement Mityvac Friday, tested it and it holds vac, Yes! Tested the bus from the line at the engine all the way to the booster including the can. 15hg held for over forty minutes with no drop. even hit the brakes, lost about 4hg and vac held held steady.
Really is a cool tool. |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Sun Apr 25, 2010 12:41 pm Post subject: |
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busman78 wrote: |
Update: Got the replacement Mityvac Friday, tested it and it holds vac, Yes! Tested the bus from the line at the engine all the way to the booster including the can. 15hg held for over forty minutes with no drop. even hit the brakes, lost about 4hg and vac held held steady.
Really is a cool tool. |
Awesome! Great job and glad it was just the tool. Great suggestion by patayres to test the tool. _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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busman78 Samba Member
Joined: August 17, 2004 Posts: 4518 Location: Oklahoma City, OK
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Posted: Sun Apr 25, 2010 2:11 pm Post subject: |
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You bet, last thing I would of thought of is a new tool not working, not only was Lincoln (maker of Mityvac) helpful, but the company I bought it from had the replacement sent the day before I returned the broken one and they paid for the return shipping. |
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patayres Samba Member
Joined: March 20, 2009 Posts: 991 Location: Bend, Orygun
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Posted: Mon Apr 26, 2010 9:21 am Post subject: |
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Nice. Glad you got it figured out. _________________ 1975 Westfalia Helsinki - 1800 EFI w/ Pertronix
1965 Singlecab - 1600dp
yuthi'so'coro |
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