Guys - I bought a Delco 18M1027 master cylinder to use in my disc/drum (mounted on the frame) setup. I'm using a 5# check valve on the front discs and a 10# valve on the rear drums, with a proportioning valve between the check valve and the rear hose. Both reservoirs are the same size on this M/C however one of the fittings for the brake line is larger. What's up with that? Does it tell me which is the front and which to use for the rear? Instructions only address bench bleeding. Thanks!
First of all you never use a check valve on disc brakes...only the drums...the larger line goes to the front brake but you always bleed the furtherest brake from the master...that would be the right rear. You should also bleed the master first. Sent from my iPad using Tapatalk
He might mean a residual valve, if that's what was meant then YES you do need a 2 lb res valve IF your master is lower then your calipers. BTW, larger tube nut might not indicate front or rear. Also you have a drum/drum master if the reservoirs are the same size, the disc set up has a larger reservoir. I used that master on my '64 Chevy panel truck 4 wheels drum, the front port is for the front brakes. Make sure the master has no res valves behind the tube seat before you add more. Not sure if this holds water, but I found it on google.
No. The different size is to keep the line worker from messing up the lines, by forcing them to the wrong ports. Generally, but not always, the port farthest from the firewall, in the original application, is the front. As has been mentioned, make sure that this master cylinder does not have built-in residual valves. If the flare seats are part of the master cylinder body, it does not. If the flare seats are brass, it probably does. In the online pictures, they look like brass. If it does have brass flare seats, gently insert an unfolded paper clip, and very gently insert it in the hole in the flare seat. If you feel something squishy, that is a residual valve.
Keep in mind, this is a 4-wheel drum master cylinder, and should have 10lb residual valves on both the front and rear, unless they are already in there.
School day for me. Thanks. Please Sir....... As a matter of interest, and I've heard many times about the need to remove unwanted valves, but what exactly does that entail? Chris
screw a screw into the brass seat, and pry out the seat, then remove the valve and replace the seat, preferably with a new seat. It might be easier to find a disc brake mc to replace the drum/drum mc.
http://www.ecihotrodbrakes.com/brake_facts.html Lots of good facts at the ECI site. Including the fact that having a residual pressure valve in the master as well as one in the line doesn't make them twice the pressure. Go ahead and put one in the line. And, ECI sells very nice brass residual pressure valves. Much better than the aluminum ones sold by many other places.
I am unsure as to why you would want to try to use this for a disc/drum application. You might be in for a nasty surprise when your front pads wear down. The reason why a dis/drum master cylinder has a larger reservoir for the front, is to have enough fluid available to run through all of the friction material, without running the reservoir dry on fluid. As the pads wear, the piston moves out to compensate, and the effective chamber in the caliper gets larger. The fluid to fill that has to come from somewhere, and that place probably should NOT be this master cylinder.
I wonder how many hot rods, or old cars in general, get driven enough to run low on brake fluid from pad wear, before it gets checked? Sent from my Trimline
No, it's a serious question. I know I check fluid way more often than I wear out a set of brake pads.
A seldom discussed issue is brake fluid...when using brake fluid in a vehicle with disc brakes the fluid needs to be a high temp fluid but that fluid is designed to absorb water to protect the internal workings of the high temp brake system...so that means if you live in an area with high humidity the fluid needs to be kept in capped containers and preferably smaller containers, plus flushing the system and installing freshly opened fluid is advised. Just some food for thought because a lot of people have issues and don’t know the cause. Sent from my iPad using Tapatalk
is there a modern brake master cylinder, i.e. with a plastic non opaque reservoir, with dual circuit, a low level fluid warning float, compatible with a servo/booster, that fits the gm foot-print, i.e. 7'' dual can booster that is compatible with drum - drum, more importantly ideal for 40 ford wheel cylinders OR IF a brake master is specific to disc/drum, 'might' it be plauseable that it 'MAY' caome equipped with internal residual valves at 10 and 2 rather than 10 and 10 does a 40 ford wheel cylinder want a bore or 15/16 or 1'' or 24mm - 25mm
Uhh...disc and drum brake systems use the same brake fluid, dot 3 is fine for almost everything... and it’s hygroscopic so technically once the container is open it should be discarded if it’s not used right away, brake fluid should be changed once it hits 3% moisture content. Sent from my iPhone using H.A.M.B.
Dot 3 and dot 4 are able to be mixed but dot 4 has a higher boiling point so it is not recommended that you mix 3 with 4. But you can run 4 in a system designed to use dot 3 if you do need a higher boiling point. (not much higher) Both will absorb water and the water lowers the boiling point and causes corrosion. Dot 5 fluid is silicon based and has a higher boiling point and will not absorb moisture like glycol based 3 and 4. Dot 5 is not compatible with some old style seals like brake light switches that are activated by fluid pressure. Harley sells a brake light switch that is compatible with dot 5. Dot 5 is also a bitch to bleed, air bubbles can sometimes take hours to settle out. They recommend you pour slowly so you don't cause bubbles when just filling the master cylinder. I agree with 57 Fargo, change fluid when it hits 3% water, there are test strips you can use to take a sample and see the moisture content.
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