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 brake bleeding - small cap reservoir
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green96v4
V4 Fanatic

Canada
445 Posts

Posted - 11 May 2019 :  12:27:17 Show Profile Visit green96v4's Homepage Reply with Quote
Finally got the seal kit in the post from John-Saab and fitted everything back together - now I have another problem/question

I'm getting plenty of piston pressure from the BMC on the bench and we've bleed it on the bench as thoroughly as we can, but now everything's fitted to the car and I'm bleeding the brakes at the calipers and rear cylinders it looks like the brake fluid is getting sucked back up (old skool tube and jam jar) when lifting off the pedal and we're struggling to get any pedal pressure

Should we be pressure bleeding or is there a decent technique for these brakes?

or is this a symptom of a larger problem? (seal kit seemed to fit very well and as previously stated had plenty of "spurt" out on the bench

Thanks in advance

chris steeden
V4 Beginner

United Kingdom
92 Posts

Posted - 11 May 2019 :  13:16:20 Show Profile Reply with Quote
The car bleeds just like any other model of that year i.e. open bleed valve with tube attached terminating in a jar with a bit of brake fluid in the bottom, push brake pedal down, close bleed valve, lift pedal up, open valve, press pedal down etc.etc. Making sure to keep fluid reservoir topped up.
Pressure bleeding is not normally required. Did you fit the master seals facing the right way around? Easy mistake to make.I think that the seal/washer has the tapered side facing inwards or outwards not sure which way, into the cylinder.

Edited by - chris steeden on 11 May 2019 13:27:36
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green96v4
V4 Fanatic

Canada
445 Posts

Posted - 11 May 2019 :  13:24:50 Show Profile Visit green96v4's Homepage Reply with Quote
Thanks Chris - that's what we were doing last night, but couldn't get any pedal pressure

I'm pretty sure I fitted everything correctly and did a one-for-one when replacing so I wouldn't get them mixed up, but I may just double check things as you've got me second-guessing myself!

I also have a hand vacuum pump - I'm going to have a go with that today to see if there's just some air being stubborn
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chris steeden
V4 Beginner

United Kingdom
92 Posts

Posted - 11 May 2019 :  13:31:17 Show Profile Reply with Quote
If you havent got a manual for the car you can download one from here: http://www.vintagesaabmanuals.org/1960-64-95-96-and-gt.html

See the parts book which depicts the correct assembly.

All the best

Chris

Edited by - chris steeden on 11 May 2019 13:32:35
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green96v4
V4 Fanatic

Canada
445 Posts

Posted - 11 May 2019 :  18:35:37 Show Profile Visit green96v4's Homepage Reply with Quote
Ok so a bunch more bleeding and fiddling and I've narrowed the problem down to the front part of the BMC, (I can press the brake pedal and have it work on one front wheel and the opposing back wheel)

there doesn't seem to be any air left, but strangely the circuit that doesn't work "sucks" fluid back up the bleeder tube when the pedal is released.

I've pulled the BMC back off to see what's going on - images below on the seal fitment




Only thing I can see that maybe off is the springs have different compressions, and I'm wondering if I've got those the wrong way around (I have it that the heavier spring is in the middle) but they may have been mixed up


Chris - thanks for the links, I've fitted the later post '71 BMC and servo

Puzzling.....
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chris steeden
V4 Beginner

United Kingdom
92 Posts

Posted - 11 May 2019 :  20:10:22 Show Profile Reply with Quote
Hi, in your top picture the seal tapers do not appear to go the same way. Is this right as it looks like seal (position 10) faces the wrong way.

Edited by - chris steeden on 11 May 2019 20:14:58
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green96v4
V4 Fanatic

Canada
445 Posts

Posted - 12 May 2019 :  10:49:50 Show Profile Visit green96v4's Homepage Reply with Quote
Hi again

they are supposed to go in opposite directions, there's a YT how to video of a guy rebuilding an MGB BMC, (internals are the same)

https://youtu.be/jvI7cUAvV14

he also states black spring goes in first, but I can't see any plating on either of my springs to tell if one is black or not!

Therefore, I swapped my springs around and bench bled it again and wasn't getting the "sucking" I was getting before, installed it and bled everything again and I have brakes!!! (still needs another bleed as there's a bit too much pedal travel, but I have made progress!)

thanks for your insights on this - I was just about to pull the trigger on an MG BMC and cut my losses!
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James Ranaldi
V4 Guru

United Kingdom
1414 Posts

Posted - 13 May 2019 :  21:43:21 Show Profile Reply with Quote
Most interesting guys as I am just about to fit new seals etc to my 1968 V4 Brake Master Cylinder.( Lockheed).

The youtube link and the vintage Saab Manuals are very helpful.

Thanks again.

1968 V4 96 ,LHD
1984 99 GL
1992 C900i Convertible
1993 C900 LPT Convertible
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James Ranaldi
V4 Guru

United Kingdom
1414 Posts

Posted - 14 May 2019 :  17:25:14 Show Profile Reply with Quote
I have got as far as removing the Nylon Guide Bearing and it is stuck fast.

Did you have to remove this bearing green96v4 ?

If so, how did you do it ?

Cheers

1968 V4 96 ,LHD
1984 99 GL
1992 C900i Convertible
1993 C900 LPT Convertible
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chris steeden
V4 Beginner

United Kingdom
92 Posts

Posted - 14 May 2019 :  18:12:19 Show Profile Reply with Quote
Is that the one with the 'pin' through it as in position 15 in the above diagram? I'm sorry, but I do not own a V4 or master cylinder to check it out.
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James Ranaldi
V4 Guru

United Kingdom
1414 Posts

Posted - 14 May 2019 :  22:07:37 Show Profile Reply with Quote
Apologies,
My master cylinder is different.
Mine is 1968 with six bolts holding the brake fluid reservoir on.
Thanks

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green96v4
V4 Fanatic

Canada
445 Posts

Posted - 15 May 2019 :  11:06:23 Show Profile Visit green96v4's Homepage Reply with Quote
no worries, sorry I wouldn't be any help on this style of BMC
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