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gregburb
Samba Member
Joined: May 10, 2011
Posts: 66
Location: NH
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 Posted: Mon Apr 29, 2019 1:46 pm Post subject: Soft brake pedal, then fine |
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Before parking my van in garage for the winter I had an issue with the brake pedal going almost to floor. My heart would skip a beat, and I would apply brakes again. On second attempt they feel normal again. I took van out for first time this spring yesterday and the same thing happened. The brake fluid seemed full at reservoir under dash, and no puddles under steering wheel or van.
Should I try to bleed some air out, or is the MC done for?
Thanks, Greg |
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SCM
Samba Member
Joined: January 26, 2011
Posts: 3119
Location: Bozeman MT
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| Posted: Mon Apr 29, 2019 1:51 pm Post subject: Re: Soft brake pedal, then fine |
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| gregburb wrote: |
| Should I try to bleed some air out, |
Yes. That will either fix it or give you an idea if
| gregburb wrote: |
| the MC done for |
or something else is wrong. I think having rear brakes poorly adjusted can result in similar symptoms too.
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'91 Westfalia GL Automatic (GTA "Turbo" Rebuild w/Peloquin) and 2.3L GoWesty Engine |
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Igeo
Samba Member
Joined: September 25, 2018
Posts: 888
Location: Oakland, CA
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| Posted: Mon Apr 29, 2019 1:59 pm Post subject: Re: Soft brake pedal, then fine |
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It's possible that poorly adjusted rears could cause this. Does the pedal feel a lot higher when the parking brake is applied? I would bleed the system and adjust the rear shoes to a slight drag before condeming the master.
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1987 Westfalia 2.1 WBX Manual |
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dobryan
Samba Member
Joined: March 24, 2006
Posts: 16505
Location: Brookeville, MD
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Mellow Yellow 74
Samba Member
Joined: October 14, 2014
Posts: 1615
Location: Sydney, Australia
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| Posted: Mon Apr 29, 2019 2:28 pm Post subject: Re: Soft brake pedal, then fine |
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If you have replaced the rear wheel cylinders, some do not have the spring which makes both pistons operate simultaneously - when you put your foot on the brake, one cylinder moves then you need to push again to get the other one to move and apply pressure to both.
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1962 Karmann Ghia
1974 Deluxe Microbus
1985 Caravelle (Vanagon) |
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gregburb
Samba Member
Joined: May 10, 2011
Posts: 66
Location: NH
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| Posted: Mon Apr 29, 2019 3:44 pm Post subject: Re: Soft brake pedal, then fine |
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| Thanks for the info. Can someone explain the parking brake up check? Is that with engine running etc... |
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VicVan
Samba Member
Joined: July 01, 2015
Posts: 1845
Location: Vancouver Island, BC
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| Posted: Mon Apr 29, 2019 6:06 pm Post subject: Re: Soft brake pedal, then fine |
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| dobryan wrote: |
| I think it should not appear all at once if it is the rear brakes, unless something else is wrong too. It would appear kind of gradually over a period of time afaik. |
That's a good point, although the difference from one day to another will be so small you don't notice it. So you adapt a little bit, every day, without noticing. And then one day, you have to do a semi-emergency braking, which you don't do very often, and then the pedal hits the ground.
So what is mechanically gradual, appears to you as a instant change. Not saying that this is what is happening here, but watch out for perception.
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'90 Little Blue Truck, 2WD auto, FAS GenV 2.0 NA (AVH) |
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Igeo
Samba Member
Joined: September 25, 2018
Posts: 888
Location: Oakland, CA
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| Posted: Mon Apr 29, 2019 6:21 pm Post subject: Re: Soft brake pedal, then fine |
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| gregburb wrote: |
| Thanks for the info. Can someone explain the parking brake up check? Is that with engine running etc... |
When the parking brake is off, and the shoes are out of adjustment too, the wheel cylinders have to push much further to get the shoes to the drums, and the pedal will feel low. When the parking brake is applied, (and holding) the rear shoes are firmly contacting the drums and it follows that the wheel cylinders have no where to push so the pedal feels higher.
If you have to pull way up on the parking brake lever to set the brake, then it's likely that the rear brakes need adjustment. You should only need 3-4 clicks on the lever to set the parking brake.
It's true that the brakes would always feel low if the rears need adjusting, but if it were me, I would adjust the rear brakes and flush/bleed the system to get to a good diagnostic starting point with regard to the master.
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1987 Westfalia 2.1 WBX Manual |
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iceracer
Samba Member
Joined: February 28, 2006
Posts: 949
Location: Milwaukee, Wisconsin
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| Posted: Mon Apr 29, 2019 6:27 pm Post subject: Re: Soft brake pedal, then fine |
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I have the exact same issue. Last fall I adjusted the rears and the pedal came up higher and is firm however it still happens. I noticed it will only happen when the rpms are low such as when coasting to a stop instead of shifting down which makes me think it has to do with engine vacuum. There is a valve in the rear for the booster that can go bad however I have never run into a bad one on any van so far.
I believe my booster is fine because most of the time the brakes work properly.
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86 Syncro Wolfsburg edition
63 Beetle (The Iceracer) |
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candyman
Samba Trout Slayer
Joined: December 20, 2003
Posts: 2694
Location: Missoula MT
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| Posted: Mon Apr 29, 2019 6:45 pm Post subject: Re: Soft brake pedal, then fine |
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| This was how my MC showed signs of failure. I would consider replacing it. Sounds like a MC failing. But try bleeding and see if that works, but my money is on MC |
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dobryan
Samba Member
Joined: March 24, 2006
Posts: 16505
Location: Brookeville, MD
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Gizmoman
Samba Member
Joined: September 10, 2011
Posts: 1554
Location: Nevada
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| Posted: Tue Apr 30, 2019 7:27 am Post subject: Re: Soft brake pedal, then fine |
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| Mellow Yellow 74 wrote: |
| If you have replaced the rear wheel cylinders, some do not have the spring which makes both pistons operate simultaneously - when you put your foot on the brake, one cylinder moves then you need to push again to get the other one to move and apply pressure to both. |
Getting the slaves with the spring (as mentioned in the above quote) and adjusting the rears solved it for me.
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82 Vanagon Westy - AAZ 1.9 TD, HE200 Holset, WAIC, 27.75 dia tires, Electric power steering, 5-speed AAP w/.078 5th
Oversize spare carrier - stock location (no longer for sale). |
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