As you know I have an 86 S10 chassis under the 37 ,my problem is that I have put disc brakes on the 9" rear end and cannot get brakes.The problem is that I tried to use the S10 master cylinder which is disc drum and I need to use a disc disc master cylinder.What master cylinder should I use.I have the S10 brake pedal mechanism in the truck.
-- Edited by Homer on Thursday 6th of March 2014 05:21:04 PM
Fiero had four wheel disc and being that its the same era GM product, fitting it to your pedal assembly might be a simple matter. Whether a Fiero master will work with your rear calipers is another question that I don't have the answer to. For the people that are able to help, I'm betting they'll want to know what you are using for rear discs.
Homer..you will need more volume and more pressure..you will probably need to swap out the rear lines to 1/4 in and use a 4X4 master cyl ..you will have to check and make sure the porportioning/metering valves are removed from either the master, or any that are fame mounted in the system and install an adjustable presure valve for the rears..I suspect you need to replace the booster as well..Can't say I have done that swap but I am sure a couple other have some suggestions and we should be able to figure it out..I think Glen is using 4-wheel discs on his new ride not sure but I think he is using all wilwood stuff..maybe he will offer up some info on his set up....
ok, the master cylinder doesn't matter unless it has a proportioning valve built into it. the proportioning valve has a residual valve that keeps a preset amount of pressure on the shoes of a drum setup to keep the shoes tight against the drum. you don't need this for disc. a slight residual valve is needed if the master cylinder is lower than the calipers. the s 10 master is fine, simply find a disc/disc proportioning valve. as for not getting brakes at the rear, some systems have a safety device that prevents rapid fluid loss when theres no pressure in the system, so pressure bleeding with the pedal sometimes wont work, I had to slowly bleed the rear brakes on my rat to get fluid to them as they kept shutting off thus blocking the fluid. I used a wildwood valve on the rear to compensate for the weight bias and tire size difference, im running a jag rear so its disc factory.
I really think the problem lies in the residual valve and also if you installed calipers with integrated parking brake. If you are using a dual master cylinder, the residual valve is usually a rubber cup inserted in the port on the M/C where the brake lines attach. If you did not remove this cup (by taking a drywall screw and using it like an easy out), the pads will retract out too far from the rotor and you will not get adequate contact. It is also necessary to set up your parking brake before attempting to bleed the calipers. When I did my 4 wheel disk, I initially install a proportioning valve but in the end removed it and I got the best braking. It's a matter or vehicle weight and weight distribution.
fatstax
I have fluid to all the calipers, even left the bleed screws open one at a time and let the fluid come out by gravity one wheel at a time.
wuga
I set the parking brakes before I bled the lines and they work great. I looked for a residual valve at the brake line connections and all that is there is steel even looked up inside and no rubber parts,but in the cylinder there was a rubber check valve that I removed from the rear container.
The more I look at it the more I think it is the cylinder that is causing me the problem,that is why I am looking at a disc brake master.I have checked the internet and have found where they have used a 75 Corvette master with a 1 1/8th bore for more fluid like Fatchuck said
Do not use a residual pressure valve with 4 wheel Disc brake systems. The residual pressure will cause the calipers to drag. the piston rings on the piston will roll it back with-out any residual pressure valve. I am sure that the s-10 had proportioning/residual valves either in the rear line port at the master or a metering valve block just after the master and between the rear line for the drum brakes so if you had drum brakes there has to be one someplace you need to find it and remove it and try to bleed again...not sure how big your reservoir on that master is but you will need to move 4 pistons that will take a fair amount of fluid
Here is a picture of a 1982-1988 S10 combination valve/proportioning valve. Look for this somewhere in the brake lines between the master and the brakes themselves. It could be mounted to the inside of the frame somewhere not too far from the front of the truck. If you are just looking at "the ends" of the lines, you could easily miss this if it is mounted out of sight, inside the frame rail.
This combination valve WILL be there somewhere (installed by the factory) unless you have already removed it, as it is an important part of the factory installed front disc, rear drum package. If your chassis was originally equipped with disc/drum, this combination valve will not be usable (as it is) with four wheel discs. I say "as it is" because it may be possible to disable the valve inside, for use with four wheel disc, I really don't know.
Edit: I searched the internet and it looks like the proportioning valve is mounted on a bracket the attaches between the master and the booster. It should be in plain sight unless some years mounted them under the truck. Find something that looks like the picture and you've found the combination valve/proportioning valve.
-- Edited by Santos L Halper on Friday 7th of March 2014 11:46:54 AM
fatstax I have fluid to all the calipers, even left the bleed screws open one at a time and let the fluid come out by gravity one wheel at a time.
wuga I set the parking brakes before I bled the lines and they work great. I looked for a residual valve at the brake line connections and all that is there is steel even looked up inside and no rubber parts,but in the cylinder there was a rubber check valve that I removed from the rear container.
The more I look at it the more I think it is the cylinder that is causing me the problem,that is why I am looking at a disc brake master.I have checked the internet and have found where they have used a 75 Corvette master with a 1 1/8th bore for more fluid like Fatchuck said
a larger diameter bore cylinder will make your brakes harder, most cars and light trucks dont need a large bore cylinder. if you have fluid at the calipers but still no rear brakes, the valve in the proportioning valve may be sticking closed. you can also remove the residual valve from the proportioning valve to make it work with disc on the back. a master cylinder is just that though, it makes no difference what you use from a drum or disc system unless its a master with a built in check valve which yours may have had.
Another thing, based on what fatstax said, the M/C should have no bearing but as Santos mentioned, for engineering sake and I'm sure for production cost, factory one piece residual/proportioning valves are meant for only their original purpose. If you haven't already, you will have to install new 2 lb residual valves and a proportioning valve. But, before you spend any more money, because the M/C is above the brakes, I would set it up without any valves and see how it behaves. I went through all these same head aches when I converted the Cutlass.
My guess is your proportioning valve has gone over center and is blocking flow to the rear discs, you can try quickly tapping the brake pedal to see if it will reset, others once tripped will need to be replaced.
Ok guys I have already removed the insides of the proportioning valve and plugged the centre of it so that it is only a tee connection now.This was done before I even started to bleed the brakes because I knew I had to remove it, for the rear discs.Yes I am getting fluid to all the calipers as I said I have even tried the gravity bleed to all the wheels and I get fluid to every one. I am thinking that may be the fluid is bypassing in the master cylinder.This is why I would like to try another master for 4 wheel brakes and see what happens. Thats why I am looking at a Corvette master in the 70 area, But would like to know if some one has used that master.
take the master cylinder piston out, i had a split seal in one i had and i had no brakes on the rear now that i think about it. if you have fluid but cant build pressure thats likely why.
Can't help you as I have no experience with Corvette masters.
If your rear brakes are aftermarket, shouldn't the manufacturer be able to guide to towards a compatible master?
(I say "if" because I still don't know which or who's rear brakes you are using).
If your rear brakes are aftermarket, shouldn't the manufacturer be able to guide to towards a compatible master? (I say "if" because I still don't know which or who's rear brakes you are using).
If go back and read his very first post he told us what rear brakes he is using..It's a 9"...That would make it FORD..
-- Edited by fatchuk on Friday 7th of March 2014 06:52:57 PM
Could be a volume issue. Put big c-clamp on one of the rear calipers. Clamp it tight so the piston is held retracted. See if the other side will then build pressure.
Do your rear calipers have integral parking brake?
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The 87 s 10 had a 1 and 5/16 bore to the front and 15/16 to the back. If you plug the master buy itself it should pump up hard even if you just join the 2 outlets. that would prove out your master. If thats ok remove the plug in the proportioning valve and feed all 4 wheels for a test it will give you an 1 and 5/32 bore feeding front and back . Unless your master is totally shot bleed by will pump hard and then drift down as you hold the pedal.
years back I put a iroc disc brake rear about a 1990 unit in my son,s 50 ford pkp. and converted to intermediate chev. discs on ford front axle , used a mid 70,s corvette m.c. . done a gravity bleed , everything seems o.k. , used larger brake lines to get the volume up , no valves , dent
Homer wrote in his first post: my problem is that I have put disc brakes on the 9" rear end and cannot get brakes.
Santos wrote: If your rear brakes are aftermarket, I say "if" because I still don't know which or who's rear brakes you are using.
fatchuk wrote: if you go back and read his Very first post he told us what rear brakes he is using, it's a 9", that would make it Ford.
Santos replied: The original poster states "I have put disc brakes on the Ford 9" rear end". This does not tell us whether he is using factory Ford components or an aftermarket rear disc brake kit designed for installation on a Ford 9". It's much easier to suggest a solution to a problem or to completely understand the problem if you know for sure what components are being used, assuming he installed Ford components (based on his first post) is nothing more than an assumption.
I think you will find 75 corvette also came with a 1 1/4 master.dont forget the rod length when changing to different than stock master or else you will not get full stroke.I agree with people on volume.that is a given
