Hydratech Hydraboost and brake bleeding problem

[Hydratech®]

Here is a section of the installation instructions that you need to correct in your installation:

NOTE: This system is designed to connect to the brake pedal in the uppermost of the two pedal rod connection points usually found on most pedals. This connection point is approximately one inch higher on the brake pedal than the power brake pedal rod connection point. This upper hole is commonly referred to as the manual brake setting hole. If this hole does not exist on your brake pedal, you will have to remove the brake pedal and drill a new 3/8 hole in the brake pedal. In some cases, this mounting point is occupied by a bolt and a sheet metal tab. Rod angle between the brake assist unit and the brake pedal should be as straight as possible. Brake pedal rod angles exceeding more than 3 degrees off center may eventually fatigue the brake pedal rod causing failure of the linkages, and excessive wear to the assist unit due to side loading the input piston.

If you have the brake pedal rod connected to the lower power brake spec hole, this can side load the brake pedal rod badly enough to bend it if you have really stomped down on the brake pedal. Please examine the threaded brake pedal rod carefully to see if you have possibly bent it any. You should be able to get a clear view of it when you are swapping the connection point from the lower hole to the upper hole, and will be able to see if you bent it when spinning the rod deeper or shallower into the horseshoe clevis to adjust your brake pedal height. If it is bent, it most definitely needs to be sent back in to us to be replaced to prevent a possible future failure.

Next, we have observed that the spacer bullet that inserts into the deep MC pushrod hole on the MCPV-1 to be about .090" - .115"~ too long most every time we have worked with one (and have passed this info along to CPP). You mention that you have .050" clearance between the tip of our MC pushrod and the spacer bullet inserted into the MC. Did you machine down the spacer bullet any? I have baffled many any engineer that felt they had measured appropriately and completely by asking them how they factored in the radius of the round tip of our MC pushrod installed in the brake unit against the coned seat in the MC piston... Long story short, a flat MC pushrod against a flat MC piston seat could be measured in a simple fashion, but interfacing a coned seat against a round rod will toss most all quick measurements out the window as inaccurate. To cut though all the tech, unless you buzzed the pointed tip of the CPP supplied spacer bullet some, I believe you are up against a MC piston preload condition that is not allowing your pistons to fully release against the snap ring in the backside of the MC. How to nail it? Loosen the MC mounting bolts up about 2 full turns - if brake fluid starts dripping out of the ports on the MC just like it did on the bench = you have identified where your problem is and can now correct it and move on.

We have an article called Brake Bleeding 101 on our website that you should read:

http://www.hydratechbraking.com/Hydratech/tech.html

Oh yes - one more thing: Uncap the brass low pressure return nipple on the brake assist unit during bleeding (since you don't have the PS system plumbed yet), as this can hold some (mild) pressure inside of the brake unit. This is a very minor point of little consequence only worth minor passing mention. You would also do well to place a towel under the brake unit, as it may expel some PS fluid out of this nipple when uncapped / unconnected (as these units are all live dyno tested and therefore full of fluid). Please also be very cautious about dirt and dust...

Let us know what you find -

[BBC69Camaro]

My main problem was indeed mounting on the lower brake pedal hole.

Having tried so many things and read so many posts. I kind of lost track. Sometimes things stare you in the face and you don't see them.

My brake pedal switch was adjusted all the way out which made it difficult to mount on the upper hole. But once I adjusted the switch all the way out, I was able to mount it on the upper hole just fine.

Now I get full pedal travel and a steady stream of fluid out both the primary and secondaries (with M/S mounted and lines running from the output back to the reservoir). Still got to bled the rear brakes but should be be able to now that I can actually push fluid out the master cylinder.

So to recap:

1. Read the instructions again
2. Hydroboost mounted to upper hole on brake pedal
3. Adjust brake pedal light switch all the way out until you get things mounted then adjust as needed.

Thanks for all the replies and help!

[BBC69Camaro]

Thanks for the response Paul and correcting my install.

Originally Posted by Hydratech

Next, we have observed that the spacer bullet that inserts into the deep MC pushrod hole on the MCPV-1 to be about .090" - .115"~ too long most every time we have worked with one (and have passed this info along to CPP). You mention that you have .050" clearance between the tip of our MC pushrod and the spacer bullet inserted into the MC. Did you machine down the spacer bullet any?

That is odd. Because I did machine .090" off the bullet after I measured with my install on the lower brake pedal hole (looked too logn). That gave me my .050" clearance.

Now when using the upper brake hole, it looks like that the bullet would be fine in length. I should have left the bullet alone as that would have now given me the correct clearance. As I am now about .090 too short.

Thinking of buying a new bullet to correct this.

Originally Posted by Hydratech

I have baffled many any engineer that felt they had measured appropriately and completely by asking them how they factored in the radius of the round tip of our MC pushrod installed in the brake unit against the coned seat in the MC piston... Long story short, a flat MC pushrod against a flat MC piston seat could be measured in a simple fashion, but interfacing a coned seat against a round rod will toss most all quick measurements out the window as inaccurate. To cut though all the tech, unless you buzzed the pointed tip of the CPP supplied spacer bullet some, I believe you are up against a MC piston preload condition that is not allowing your pistons to fully release against the snap ring in the backside of the MC. How to nail it? Loosen the MC mounting bolts up about 2 full turns - if brake fluid starts dripping out of the ports on the MC just like it did on the bench = you have identified where your problem is and can now correct it and move on.

As far as measuring goes I measured from the tip of the Hydroboost rod and the valley of the bullet. I see your point and I'm probably off a bit. Do have a good way to measure this distance accurately? How long should it be? I think the one I got as 1.500" long from tip to back edge (Total length, not including coned seat)

I don't think I am under a preload as I can now feel some freeplay on the pedal before it starts to compress the M/S. Also it is very easy to mount the M/S I don't have to compress the M/S to mount it (if that makes sense).

[BBC69Camaro]

Ends up the solution on measuring the current clearance with the adapter bullet installed as to put some modeling clay at the end and install the M/C and then remove and mic the clay. Ends after milling .090" off the bullet I have about .060" clearance. On the high side but within .030-.060".

Thanks all for your help (including Paul from Hydratech).