hydroboost

[gab46]

I have a hydroboost on my 79 jeep/ w a v8 and 35 in tires. With the engine running, I have a good intital hit with the brakes. Then the pedal drops about an inch or two, and it appears to go into manual braking, not much power assist. I have an early model corvette master cylinder, and stock power steering pump.

[777stickman]

Originally Posted by gab46

I have a hydroboost on my 79 jeep/ w a v8 and 35 in tires. With the engine running, I have a good intital hit with the brakes. Then the pedal drops about an inch or two, and it appears to go into manual braking, not much power assist. I have an early model corvette master cylinder, and stock power steering pump.

Hi gab and welcome to the forum. You're probably gonna get moved from this one 'cause of your '79 Jeep. But?? So before that happens here's my . I have 3 concerns. 1st, "stock power steering pump" may not be putting out the pressure required for the hydroboost. 2nd, plumbing should be from the pump to the hydroboost to the steering box and return to the pump (that's how my '98 Sub is plumbed). 3rd, master cylinder??? Sorry but there's a 4th, a good job of bleeding including a bench bleed of the master cylinder.

Another thing to check is what does the steering do when the brakes go away?.........Steve

[ChevyWonTon]

It sounds like the brake assist for the hydroboost is not matched to the system demands. Since I think you're saying both the hydroboost and the power steering pump are both original equipment (plumbed together on the same circuit), I'm leaning towards that mating of the Corvette M/C.

M/Cs and Brake Boosters are carefully matched in pressure and fluid displacement characteristics with all the rest of the brake system (calipers and drum wheel cylinders), by the amount of brake pushrod travel and M/C size and the internal porting of the M/C. Unless you have some good authority or knowledge telling you to mate that Corvette M/C with that hydroboost based on the rest of the brake system, I'm not so sure I'd make that pairing. The hydraulic properties of the Corvette M/C may not be compatible with the hydroboost and/or wheel brakes.

If the hydroboost came off of another completely different vehicle, then you've got quite a hodgepodge of brake parts. I also like stickman's idea of checking the steering at that instant, but your gonna want to do that in a parking lot!!!

Please provide more insight into how you came up with the combination...