| Author |
Message |
matthew henricks
Samba Member
Joined: January 02, 2002
Posts: 1219
Location: So. Cal
|
 Posted: Mon May 01, 2017 4:57 pm Post subject: Single vs. Dual Circuit Master Cylinder behavior. |
 |
|
Is it normal for a Dual MC set-up to feel different from a single MC system?
Installed a system in my 65 a few years back and noticed over time it just feels different. When i brake the peddle travels 80% to the floor and then engages. The brakes feel solid but alot of travel.
I am using a bay window MC with a volvo reservoir. The MC has a 1/2" mount spacer and the push rod has no play when engaging the MC. The front MC circuit goes to the rear brakes. The rear MC circuit goes to the front brakes.
Wheels are adjusted right and no air in line. All parts are in good shape
This does not seam normal.
In the below pictures the second one is at rest. Third is the initial stroke which does not apply any pressure to the breaks. The last one is where all the breaking takes place.
|
|
| Back to top |
|
 |
glideking
Samba Member
Joined: February 02, 2013
Posts: 990
Location: California
|
|
| Back to top |
|
|
glideking
Samba Member
Joined: February 02, 2013
Posts: 990
Location: California
|
|
| Back to top |
|
|
David Raistrick
Samba Member
Joined: January 26, 2004
Posts: 539
Location: Geneva, Florida
|
| Posted: Mon May 01, 2017 7:24 pm Post subject: Re: Single vs. Dual Circuit Master Cylinder behavior. |
|
|
| matthew henricks wrote: |
| Is it normal for a Dual MC set-up to feel different from a single MC system? |
No. There should be no feel difference.
| Quote: |
Installed a system in my 65 a few years back and noticed over time it just feels different. When i brake the peddle travels 80% to the floor and then engages. The brakes feel solid but alot of travel.
|
80% travel means a PROBLEM. You've driven it for years like that? Scary.
80% travel means one of many things:
Very out of adjustment shoes. (gotta adjust all 4 corners, too).
Air in the system.
A leak in the system (on a single circuit the pedal will hit the floor with a leak - with a dual circuit you'll lose half+, so 80% travel might be about right).
A misconfigured master cyl with no free play and the "top" circuit isn't returning enough to recharge with fluid and reset the valve.
| Quote: |
the push rod has no play when engaging the MC.
|
And there's one of your major problems. You need to either shim that MC further away, buy a correctly fitting MC (or MC/adapter combo), or adjust or cut your pushrod.
That free play is IMPORTANT.
_________________
...david - '66 SO-44 #231 |
|
| Back to top |
|
|
matthew henricks
Samba Member
Joined: January 02, 2002
Posts: 1219
Location: So. Cal
|
| Posted: Mon May 01, 2017 9:12 pm Post subject: Re: Single vs. Dual Circuit Master Cylinder behavior. |
|
|
Thank you guys.
I am betting the problem then is no play in the pushrod and therefor no fluid is getting into the MC.
All four corners are adjusted. No leaks anywhere and the E-brake works fine. I do see that my brake spring is not in the right spot (Thanks Kurt) but the peddle does return all the way up easily.
The bus is rarely driven. She's a garage queen.
I will report back my findings. |
|
| Back to top |
|
|
60freak
Samba Member
Joined: October 08, 2002
Posts: 861
Location: Indiana
|
| Posted: Tue May 02, 2017 5:02 am Post subject: Re: Single vs. Dual Circuit Master Cylinder behavior. |
|
|
| Isn't there a possibility that certain bay MC's that will create several problems in a split (residual valves, piston bore & stroke?) I don't think you can just pop on a bay MC with the spacer and rock n roll. I know a friend did just that and had same issues as the OP plus the pedal was hard to push as well once the braking action occured. Using a '67 MC solved the issues he was having. Just a thought: is the correct MC installed? |
|
| Back to top |
|
|
easy e
Samba Member
Joined: May 28, 2008
Posts: 3931
Location: 1 hr north of Santa Barbara
|
| Posted: Tue May 02, 2017 5:21 am Post subject: Re: Single vs. Dual Circuit Master Cylinder behavior. |
|
|
| 60freak wrote: |
| Just a thought: is the correct MC installed? |
He said it was Bay + spacer... so, "correct" isn't in the picture.
But, good point about residual or check valve(s).
_________________
aka: Evan
Spreadsheet for Bus RPM, based on gearing & tire size (Excel format)
Searchable, click-navigable 1958 Bus Parts List |
|
| Back to top |
|
|
matthew henricks
Samba Member
Joined: January 02, 2002
Posts: 1219
Location: So. Cal
|
| Posted: Tue May 02, 2017 7:29 am Post subject: Re: Single vs. Dual Circuit Master Cylinder behavior. |
|
|
I cannot locate the original receipt for the MC but the part number was recommended on this forum. A 67 unit was out of reach.
Not sure how to tell after the fact which MC i have. Will look for a number tonight. |
|
| Back to top |
|
|
Eric&Barb
Samba Member
Joined: September 19, 2004
Posts: 24764
Location: Olympia Wash Rinse & Repeat
|
| Posted: Tue May 02, 2017 8:04 am Post subject: Re: Single vs. Dual Circuit Master Cylinder behavior. |
|
|
From the shape of the MC, it looks like it is a 1971-79 Bus type. It does sound like one of the two circuits in the MC has failed.
_________________
In Stereo, Where Available! |
|
| Back to top |
|
|
OB Bus
Samba Member
Joined: February 09, 2003
Posts: 2541
Location: Ocean Beach in Beautiful BLUE California
|
| Posted: Tue May 02, 2017 9:01 am Post subject: Re: Single vs. Dual Circuit Master Cylinder behavior. |
|
|
| matthew henricks wrote: |
I cannot locate the original receipt for the MC but the part number was recommended on this forum. A 67 unit was out of reach.
Not sure how to tell after the fact which MC i have. Will look for a number tonight. |
A number of vendors (EIS?) sell the Chinese built 67 dual circuit master. I have not heard of any problems with them. Price is quite reasonable.
_________________
Larry in OB
Stop dead photo links! Post your photos to The Samba Gallery!
69 Westfalia and 2002 Eurovan Camper. |
|
| Back to top |
|
|
matthew henricks
Samba Member
Joined: January 02, 2002
Posts: 1219
Location: So. Cal
|
| Posted: Wed May 03, 2017 7:36 am Post subject: Re: Single vs. Dual Circuit Master Cylinder behavior. |
|
|
Last night i pulled the MC and shortened the push rod. I then re-installed it and properly adjusted it so there was a 1/32 gap at peddle rest.
I did not fix the spring yet but after pressing the peddle down about 20 times i feel a marginal improvement.
I am going to re-check the wheel adjustment again next.
I looked for a part number on the MC. It is an EIS unit but all i found were casting numbers on it. "PAS 85112" and a large sideways "25".
Is there anything else at the MC end that i should check out? Anything about how the brake lines connect to the MC?
Thank you for the guidance. |
|
| Back to top |
|
|
Eric&Barb
Samba Member
Joined: September 19, 2004
Posts: 24764
Location: Olympia Wash Rinse & Repeat
|
| Posted: Wed May 03, 2017 7:42 am Post subject: Re: Single vs. Dual Circuit Master Cylinder behavior. |
|
|
| matthew henricks wrote: |
| Is there anything else at the MC end that i should check out? Anything about how the brake lines connect to the MC? |
Be smart to check everything. All too easy to mix up the LF brake line with the one line going to the rears.
_________________
In Stereo, Where Available! |
|
| Back to top |
|
|
matthew henricks
Samba Member
Joined: January 02, 2002
Posts: 1219
Location: So. Cal
|
| Posted: Wed May 03, 2017 8:46 am Post subject: Re: Single vs. Dual Circuit Master Cylinder behavior. |
|
|
Found the MC part number i used.
211 611 021 A
Oh. The bus is not for sure parked till this is fixed.
Matthew
Last edited by matthew henricks on Wed May 03, 2017 4:05 pm; edited 1 time in total |
|
| Back to top |
|
|
Nubby
Samba Member
Joined: August 28, 2010
Posts: 605
Location: Down by the river
|
| Posted: Wed May 03, 2017 11:56 am Post subject: Re: Single vs. Dual Circuit Master Cylinder behavior. |
|
|
| If I am replacing the brake system in my 62 with a 67 complete setup, do I still need the adapter? |
|
| Back to top |
|
|
60freak
Samba Member
Joined: October 08, 2002
Posts: 861
Location: Indiana
|
| Posted: Wed May 03, 2017 12:07 pm Post subject: Re: Single vs. Dual Circuit Master Cylinder behavior. |
|
|
| Nubby wrote: |
| If I am replacing the brake system in my 62 with a 67 complete setup, do I still need the adapter? |
No you do not need the the adapter, however you will need a "T" fitting for the front brake line and one short section of brake line (approx 8" or so) to tee the L & R front brake lines together. |
|
| Back to top |
|
|
matthew henricks
Samba Member
Joined: January 02, 2002
Posts: 1219
Location: So. Cal
|
| Posted: Thu May 04, 2017 2:22 pm Post subject: Re: Single vs. Dual Circuit Master Cylinder behavior. |
|
|
Before i go any further can anyone confirm that MC part number
211 611 021 A is one that will work?
Thanks |
|
| Back to top |
|
|
Eric&Barb
Samba Member
Joined: September 19, 2004
Posts: 24764
Location: Olympia Wash Rinse & Repeat
|
| Posted: Thu May 04, 2017 2:52 pm Post subject: Re: Single vs. Dual Circuit Master Cylinder behavior. |
|
|
| matthew henricks wrote: |
Before i go any further can anyone confirm that MC part number
211 611 021 A is one that will work?
Thanks |
If is originally fitted to 1971-79 Bus, then yes.
Just did a WWW search for "VW 211 611 021 A" and it shows up being sold for such.
_________________
In Stereo, Where Available! |
|
| Back to top |
|
|
60freak
Samba Member
Joined: October 08, 2002
Posts: 861
Location: Indiana
|
| Posted: Fri May 05, 2017 4:34 am Post subject: Re: Single vs. Dual Circuit Master Cylinder behavior. |
|
|
| matthew henricks wrote: |
Before i go any further can anyone confirm that MC part number
211 611 021 A is one that will work?
Thanks |
I personally would not use that MC, it is designed to have a "booster" most likely you are gonna be stomping hard on the pedal to stop decent. I would only use a '67 master or possibly an early bay. I'm pretty sure the late model bay MC has some differences that can cause issues, like piston bore and stroke, as well as the residual valves. If you plan to swap the brake booster in the bus as well, then yeah I would say the late model MC is what to use. Just do it right, get a '67 MC, they repop them for reasonably good prices. I picked my last one up for $100 or so brand new. |
|
| Back to top |
|
|
Eric&Barb
Samba Member
Joined: September 19, 2004
Posts: 24764
Location: Olympia Wash Rinse & Repeat
|
| Posted: Fri May 05, 2017 7:18 am Post subject: Re: Single vs. Dual Circuit Master Cylinder behavior. |
|
|
Well so far no problem for us with the 1971-79 Bus MC over about 150,000 miles. It should be a little harder to lock the brakes than the 1967 MC, but at same time that gives you a bit more control not to lock the brakes which is something you want to avoid.
Sure if you have a bad leg get the vacuum booster to help!
_________________
In Stereo, Where Available! |
|
| Back to top |
|
|
matthew henricks
Samba Member
Joined: January 02, 2002
Posts: 1219
Location: So. Cal
|
| Posted: Fri May 05, 2017 7:36 am Post subject: Re: Single vs. Dual Circuit Master Cylinder behavior. |
|
|
Thanks guys. I am looking at my options. I suspect i am going to find a problem in one of the rear wheels now that i am looking. One does not grab when using the E-brake so i will start there.
If i switch to the 67 MC, will i be able to mount my belly pan without chopping it? Sure would like to stick that back on.
Will report back but likely not for a few weeks as i do not see time in the near future to tackle this.
Matthew |
|
| Back to top |
|
|
|
