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Discussion Starter · #1 ·
Help!!! I have a Danchuk style master cylinder/booster assembly in bits and appear to be missing some kind of seal between the master cylinder and booster, see pic, I know there are a few tri chevy projects on the go out there, just hoping someone may have one laying around and be able to post a pic of what im missing, any help much appreciated:tup:

 

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I'm most probably wrong,but i don't think there is anything between the two,just bolts up together.
I'll know for sure after the weekend as i've got to take mine apart :sniff:
 

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I'm most probably wrong,but i don't think there is anything between the two,just bolts up together.
I'll know for sure after the weekend as i've got to take mine apart :sniff:
Your right !
Nope nothing missing between master & booster, just bolt them together :tup: Don't forget to bench bleed the master first :cool:
 

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I'd rather be blown
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Discussion Starter · #5 ·
Have seen this question come up before as it looks like something should be there.
My thoughts too Steve, as the booster operates under vacuum I would have thought an air tight seal would be needed

Originally Posted by Neil G
I'm most probably wrong,but i don't think there is anything between the two,just bolts up together.
I'll know for sure after the weekend as i've got to take mine apart
Your right !
Nope nothing missing between master & booster, just bolt them together Don't forget to bench bleed the master first

Thanks Bob/Neil:tup:
 

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I'd rather be blown
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Discussion Starter · #6 ·
Another question whilst on the subject, should the pushrod from the booster be adjusted to just make contact with the cylinder piston when bolted together or should there be some pre-load:?:, I only ask as I didnt dismantle this myself.
Cheers
Vince
 

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vince, im sure my one doesnt have a seal, its a sealed unit, re pushrod, you need to have a small amount of clearance, if not you can suffer from the brakes gradually locking up, as you drive down the road and use your brakes the fluid warms up and expands and if the pistons are not fully back the fluid cant get back into the reservoir, so it pushes the caliper pistons and wheel cylinders out instead, untill you grind to a halt:D

kev
 

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I'd rather be blown
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Discussion Starter · #8 ·
vince, im sure my one doesnt have a seal, its a sealed unit, re pushrod, you need to have a small amount of clearance, if not you can suffer from the brakes gradually locking up, as you drive down the road and use your brakes the fluid warms up and expands and if the pistons are not fully back the fluid cant get back into the reservoir, so it pushes the caliper pistons and wheel cylinders out instead, untill you grind to a halt:D

kev
Cheers Kev, when I try to bolt the two together the piston compress's about 1/4 inch which is another reason why I thought maybe a rubber seal or spacer was missing
 

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Cheers Kev, when I try to bolt the two together the piston compress's about 1/4 inch which is another reason why I thought maybe a rubber seal or spacer was missing
Vince, nothing between the two on my dual booster set up.
As Kev's said, there shouldn't be ANY pre-load on the m/c, you need to back off the adjustment on the booster. Leave it and your brakes will drag or if you're unlucky, lock up altogether. If you pm me your email address I can send you a classic performance products .pdf guide to brake installation which makes this very clear. It mentions a tool to help adjust the clearance, I just used a lump of bluetack on the rod to eyeball and adjust the gap required.
Al
 

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Discussion Starter · #10 ·
Vince, nothing between the two on my dual booster set up.
As Kev's said, there shouldn't be ANY pre-load on the m/c, you need to back off the adjustment on the booster. Leave it and your brakes will drag or if you're unlucky, lock up altogether. If you pm me your email address I can send you a classic performance products .pdf guide to brake installation which makes this very clear. It mentions a tool to help adjust the clearance, I just used a lump of bluetack on the rod to eyeball and adjust the gap required.
Al
Thanks Al, that pdf may be usefull, pm'ed my mail address:tup:
 

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Thanks Al, that pdf may be usefull, pm'ed my mail address:tup:
I have fitted a couple these & there is a certain amount of pressure between the rod & piston, this allows the rod to centralise in the piston cup (0.2 bar pressure, i think was said)
Because when sitting idle without vacum, leak down etc: there's a chance of the rod dropping out of the cup, when after awhile when the booster starts wearing in, and the rod becomes sloppy.

Hope all this makes sense :tup:
 

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Hi Bob, let me know your latest email and I'll send you that .pdf file which I was going by. It's from CPP who I guess know their onions.
Hi Al

I didn't think you were talking to me :sniff: after that feasco with the sender unit, which i feel so guilty about after you helped me out :tup: please do send me that, would be much appreciated.

Thanks Bob
 

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I'd rather be blown
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Discussion Starter · #15 ·
I posted this question on trifives.com, click HERE to see thread

interesting link to "how stuff works" but I still don't understand how the booster can maintain vacuum or partial vacuum when air can get in around the mating face of the m/c to the booster, sorry if this is getting boring:sleep:
 

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No worries Bob, if you're at wheels day I'll rearrange your plug leads while your not looking:D I've got 3 email addresses for you, let me know the right one.
Cheers
Al
LOL Al

Yeah I am a man of many emails:cool: but the one I use most of the time is [email protected]

Cheers me old mate :tup:
 

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I didn't really look at the servo in your pic but assumed your original question referred to the step in the master cylinder. So does the hole for the vacuum inlet connect through to that exposed area...ie can you get something right around there?
 

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Discussion Starter · #19 · (Edited)
I didn't really look at the servo in your pic but assumed your original question referred to the step in the master cylinder. So does the hole for the vacuum inlet connect through to that exposed area...ie can you get something right around there?
yes mate, its all open, the only thing in the way is the spring, that servo pic you posted is almost identical to mine and if you look closely at your pic there is something there, a cap or seal or whatever.....

ALs57 mailed me a pic of his, looks like I have someting missing after all....:cry:

 

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Sorry Vince, when you asked the initial question I assumed you were asking about a seal to go on that step on the master cylinder. I should have paid more attention to the servo.
Sounds like somebody has been playing with it.
 
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