The Weekly H-Boost/Chevy disk Discussion!

[BG's 68 Bronco]

Alright I know do a search, but I read so much I can't think anymore. I've done both the chevy disk and h-boost. I'm having issues with very limited pedal pressure for the front brakes... meaning I have maybe 20% braking force coming from my front brakes. Rear brakes are working get... I can lock them up in a second with h-boost.

Anyway, I've bench bled the MC as per instructions and I know it isn't causing the problem because the MC did exactly what the instructions specified. I've bled the lines.. no air. Ground the knuckle down can't see it binding anywhere, as it has 1/4" or more clearance everywhere. I even watched the functioning of the calipers while a helper pushed the brake pedal down and no ballooning of brake lines either. Everything is working, but only at 20% on the front. There is nothing wrong with linkages etc under the dash good pedal travel and fluid motion but the pressure doesn't build up when stepping on the brakes until you hit the rear brakes. I have a corvette MC paired up w/ K5 blazer calipers.


One thing I have noticed is the stock brake lines, which connect to the MC are the same dia. and when you look at most other brake systems the brake line for the front is usually a larger dia. Could this be my problem, or have some of you with the same set up used the stock lines with no issues?

Thanks boys and girls

 

[SaddleUp]

I'm still using the stock brake lines as far as I know. I know the diameter is the same on both. Do you have the lines hooked up backwards. The front brakes attach to the reservior closest to the firewall which is reverse of the way it would seem like it would be. The symptoms you describe are what happens when they are reversed.

 

[Nobody]

Your lines are reversed. On most chevy masters, the front brakes go to the front reservoir, and the rear brakes to the rear reservoir. Ford masters are generally opposite.

 

[BG's 68 Bronco]

Reservoir closest to the firewall is hooked up to the front brake line.

 

[SaddleUp]

Your lines are reversed. On most chevy masters, the front brakes go to the front reservoir, and the rear brakes to the rear reservoir. Ford masters are generally opposite.

I haven't owned a lot of Chevies but in all of them that I have (half a dozen or so) the front brakes were still the one closest to the firewall.

 

[BG's 68 Bronco]

I haven't owned a lot of Chevies but in all of them that I have (half a dozen or so) the front brakes were still the one closest to the firewall.

I think your right SaddleUp. I'm going to PM Mad, as he uses the corvette MC's he should be able to clarify.

 

[Sac '68 sport]

Is the Corvett a 4 wheel disk master?
You have drums in back right?

 

[BG's 68 Bronco]

Disk/drum master cylinder. I have rear drums.

I'm hoping Nobody was correct in that I need to flip the lines at the MC. I flipped them at lunch, but I still need to bleed now, so I won't know forsure if that will solve my issue, or if someone can tell me which reservior feeds the front and the rear.

thanks!

 

[eb66to77]

Disk/drum master cylinder. I have rear drums.

I'm hoping Nobody was correct in that I need to flip the lines at the MC. I flipped them at lunch, but I still need to bleed now, so I won't know forsure if that will solve my issue, or if someone can tell me which reservior feeds the front and the rear.

thanks!

If you have a disk/drum master cylinder then the reservior near the mounting surface is gonna be for the front brakes, it is also larger than the front reservior furthest from the mounting surface that feeds the rear brakes. Small res. rear brakes.

 

[BG's 68 Bronco]

both reservoirs look the same size... if anything the res closest to the radiator looks the biggest!

 

[76Broncofromhell]

If it's the Corvette M/C the one closest to the firewall is the front brakes. It sounds like a proportioning valve problem here. I would check which lines go where down on the valve. Brakes aren't very complicated, so my guess is something has gone awry down in the metering portion of the valve like the pressure bypass piston for the front brakes is frozen.

Personally I despise the stock-style valve. I like the adjustable ones with their own separate check valve for the rear drums.

 

[BG's 68 Bronco]

I only have the H-block, which from what I've read doesn't affect the system?? Is that correct?

 

[toddz69]

I only have the H-block, which from what I've read doesn't affect the system?? Is that correct?

Correct - that shouldn't affect it. I'll second the recommendation in an earlier post - sounds like you need an adjustable p-valve in the rear line.

Todd Z.

 

[SaddleUp]

Disk/drum master cylinder. I have rear drums.

I'm hoping Nobody was correct in that I need to flip the lines at the MC. I flipped them at lunch, but I still need to bleed now, so I won't know forsure if that will solve my issue, or if someone can tell me which reservior feeds the front and the rear.

thanks!

See my first post above. The front brakes always go to the reservior closest to the firewall. It doesn't matter if it is drum/drum, disk/drum, or disk/disk and it doesn't matter if it's Chevy, Ford, or Dodge. I left it as is above simply because I have been out of the auto repair business for 10 years or so and haven't followed the latest technology on most vehicles. I.E. There may be some newer exotic cars that are set up differently and as soon as I tell you there are none then someone is going to pop in to say that such and such exotic vehicle is different. For the purpose of this discussion though all of them will have the reservior for the front brakes next to the firewall.

 

[Kansas Corey]

BG - I had the same problem with my Hydroboost for a while. I have tried hooking up a proportioning valve that I got with the Hydroboost (1990 Chevy Astro) but have been having troubles trying to bleed the brake lines. Basically, I don't know if it has solved the problem or not yet. Let us know what happens when you get the system bled with the lines reversed.

Anyone have nice and easy suggestions for bleeding brakes by yourself?

 

[72Sport]

See my first post above. The front brakes always go to the reservior closest to the firewall. It doesn't matter if it is drum/drum, disk/drum, or disk/disk and it doesn't matter if it's Chevy, Ford, or Dodge.

According to my 74 Chevy exotic light truck manual: "The cylinder has two separate reservoirs and outlets in a common body casting. On all C-K10, G10 power and P10 Manual vehicles, the front reservoir controls the front brake system and the rear reservoir controls the rear system. On all other series vehicles, the front reservoir controls the rear brake system and the rear reservoir controls the front system."

I guess this means that even GM couldn't make up there mind.

I looked in my 73 Chevy car manual and Chevy cars are both ways also. Bendix master cylinders are the same as Ford and Delco Moraine are reversed.

If his late model Corvette Master cylinder is for 4 wheel discs what difference does it make which way it is hooked up?

 

[Nobody]

See my first post above. The front brakes always go to the reservior closest to the firewall. It doesn't matter if it is drum/drum, disk/drum, or disk/disk and it doesn't matter if it's Chevy, Ford, or Dodge.

I hate to call you on this, but it is absolutely wrong. Most of the Chevy's are opposite of ford, including the popular corvette master. This is why everyone is always having a problem with rear wheel lockup.

This is a good website for looking up master cylinder bore sizes. They also include pics of many of the parts. http://www.discountautoparts.com/

Just to pick at random, here is a '78 blazer 4x4, and a 76 camaro. Note the smaller reservoir is to the rear.

76 camaro

 

[BG's 68 Bronco]

My master doesn't look like the above posted... it's the pot belly style and both reservoirs look to be very close to the same size. I might try another M/C I have (1997 GM 3/4 ton) I definitely know which is the front and rear reservoirs on that one.

 

[Wes harden]

See my first post above. The front brakes always go to the reservior closest to the firewall. It doesn't matter if it is drum/drum, disk/drum, or disk/disk and it doesn't matter if it's Chevy, Ford, or Dodge. I left it as is above simply because I have been out of the auto repair business for 10 years or so and haven't followed the latest technology on most vehicles. I.E. There may be some newer exotic cars that are set up differently and as soon as I tell you there are none then someone is going to pop in to say that such and such exotic vehicle is different. For the purpose of this discussion though all of them will have the reservior for the front brakes next to the firewall.

Your right Saddleup there is a new style is called split diagonal front left and right rear are conected, and vise versa. I do agree the firewall reservior is front brakes.

 

[Wes harden]

bleeding

Anyone have nice and easy suggestions for bleeding brakes by yourself?

I use a 2 liter plastic soda bottle and some windshield washer tubing. Put brake fluid in the bottle to cover the tubing,
connect the other end to the bleeder nipple with a loop higher than the bleeder nipple, no air will be drawn back into system if a snug fit at nipple. can be used solo less than 5 bucks and you get to drink the soda