C5 master cylinder on C3 question.

69427

69427

The Artist formerly known as Turbo84
Joined
Mar 30, 2008
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Clinging to my guns and religion in KCMO.
Just picked up a C5 master cylinder for my (power brake equipped) '69. Looks like it's going to be a straightforward swap (Thanks again, TT). The old cast iron unit looks to be about 7-8 pounds, while this m/c barely moves the scale needle (about a pound). Up front and up high weight reduction. Excellent.
Before I recommend this lightweight m/c to my buddy for his '72 non-power brake system, is there anything significant to consider?

thanks,
Mike
 
Yes, the adapter lines can be a little spendy....and it's a 1" master, perfect for manual brakes.
 
Just for kicks, is it possible to adapt the other direction? I was curious if I can get a couple metric lines to attach to the m/c, but then cut the lower ends and re-flare them for the older double flare type to attach to the junction block. IIRC, you mentioned that two different adapters were needed up top, so I assume that there are normally two different size lines on the C5 m/c. Am I understanding that correctly?
 
The problem is, the metric line and the imperial are sized differently so you either have the flare nuts too loose or you have to drill them out. The flex lines are so much easier, any competent hydraulic shop should be able to make you some. The top is a metric bubble flare, the tools to do those are spendy. Both lines are 3/16. The flare nuts are M12x1 & M12x1.5 it's just the thread pitch that differs.
 
Twin_Turbo said:
The problem is, the metric line and the imperial are sized differently so you either have the flare nuts too loose or you have to drill them out. The flex lines are so much easier, any competent hydraulic shop should be able to make you some. The top is a metric bubble flare, the tools to do those are spendy. Both lines are 3/16. The flare nuts are M12x1 & M12x1.5 it's just the thread pitch that differs.
Click to expand...

I wonder what the point of the different thread pitch was. Oh well, just for amusement I might pick up a couple hard lines this week and play around a bit. If nothing else, it'll get the curiosity out of my system.
Thanks again for the help. Chances are I'll have additional questions as things progress.

Mike
 
So you can't mix up the front and rear circuit, that's why :) Remember, with the ABS unit there's a bunch of lines there.
 
Twin_Turbo said:
The problem is, the metric line and the imperial are sized differently so you either have the flare nuts too loose or you have to drill them out. The flex lines are so much easier, any competent hydraulic shop should be able to make you some. The top is a metric bubble flare, the tools to do those are spendy. Both lines are 3/16. The flare nuts are M12x1 & it's just the thread pitch that differs.
Click to expand...

So I need

M12x1 to 3/16

M12x1.5 to 3/16

Hopefully this place can make them

http://www.goodyearrubberproducts.com/
 
TT: Refresh my memory.

TT,

Stopped at a few parts stores while running errands, and everybody and their dog has adapters (metric bubble to double flair) and hard lines for the M12-1.0 port, but nobody has anything for the M12-1.5 port. I haven't even seen (in catalogs) any adapters that go from that port to an AN fitting, either. What did you end up doing on your setup? I was hoping to run all hard lines, but I hate to have to resort to getting a chunk of line off a late model GM car in a junkyard.

Just curious.
Thanks.
 
I know, they are next to impossible to get. I had some custom flex lines made by goodridge. They were 100 euros for 2.
 
you're telling me this thing mates up perfectly to our vacuum booster? I tried removing my suburban m/c and putting it on and there's no way. I've even bought other truck m/c off ebay and there is still no way.

i'm a skeptic on this one.
 
My only progress so far has been to slide the m/c onto a used booster I got off of a wrecked '72. It fit on there fine. My unknowns at this point is the (push)rod adjustment, and possibly just getting a couple lengths of tubing off of a wrecked latemodel vehicle (the m/c looks just like the unit on my '05 Silverado, which surprised and amused me) so I can reuse the threaded fittings.
 
turtlevette said:
you're telling me this thing mates up perfectly to our vacuum booster? I tried removing my suburban m/c and putting it on and there's no way. I've even bought other truck m/c off ebay and there is still no way.

i'm a skeptic on this one.
Click to expand...

Trucks use a much larger MC, mine does too....

NO WAY?????....WAY!!!!!!!!!!! all hooked up, even suing the level switch

5485d7024d608a.jpg
 
Twin_Turbo said:
.... all hooked up, even suing the level switch

5485d7024d608a.jpg
Click to expand...

TT: I've got the original m/c off, and fitting the C5 unit. I'll have to shorten and tap the booster pushrod (which I assume you had to do). My question: Does the pushrod just slide out after the vacuum seal (near the m/c) is pried out? It looks like the seal should come out reasonably easy without destroying it. Is that correct?
OBTW, man it looks like it will be close between the reservoir cap and the underside of the hood.
 
Maybe I'm missing some parts but my pushrod will just pull out of the bore with the seal on it.
 
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