Hydro boost question, air in system?

[iacucv]

Hey guys, I am not familiar with the hydro boost system in general. I'm trying to learn about it, and how the power brakes and power steering work with each other.

So I recently put a new steering gearbox in and did 2 alignments and spent a ton of time bleeding the air out of my PS system. I still have what seems to be air in the steering system. All hard parts are tight and no slop, had it double checked by 2 shops. New springs, shocks, steering damper, tires. I have not gotten to the brake system yet which makes me wonder as I ponder the hydro boost system... Also spongy brake pedal after sitting.

Would air in the brake system also make my power steering system feel like it has air in it? If so my tentative plan is brake system rebuild, and was anyway. New rubber lines, wheel cylinders, shoes, calipers and pads. If not, then I believe the PS system is sucking air somewhere. Replace all PS hoses.

So can anyone tell me if the symptoms are from one side of the Hydro or another, or could be either, or could be master cylinder? I will replace all these components eventually, time and money are tight right now tho. Have to pony up for 3 sets of tires before the snow flies and pay for a wedding. Thanks for any insight guys.

 

[rustystud]

It can a long time to "purge" the air out of the brake booster/power steering system. I had to go over a week before all the air came out of my system once. The best thing to do is jack-up the front axle and with the engine running turn the steering wheel full left and full right about a hundred times ! Do it slowly so you don't froth up the fluid.

 

[iacucv]

Thanks for the response rusty stud. I have already had it on jack stands twice turning the wheel lock to lock.... A lot. I can't seem to lose the spongy dead spot in the middle and the soft brakes. I think there is something more going on here, but my inexperience with hydro boost systems might mean I'm just wrong. Would air in the brake system effect the PS like air in the PS system effects the braking system?

ETA - I've also put about 1,000mi on the truck since replacing the steering box, between that and the driveway air purges I would think the air is out?

 

[rustystud]

Thanks for the response rusty stud. I have already had it on jack stands twice turning the wheel lock to lock.... A lot. I can't seem to lose the spongy dead spot in the middle and the soft brakes. I think there is something more going on here, but my inexperience with hydro boost systems might mean I'm just wrong. Would air in the brake system effect the PS like air in the PS system effects the braking system?

ETA - I've also put about 1,000mi on the truck since replacing the steering box, between that and the driveway air purges I would think the air is out?

Since the power steering fluid drives the brake booster, when there is air in the system it effects both the steering and braking. For some reason this GM system makes it extremely difficult to purge out the air. Like I said before, I drove my truck for a week after replacing my brake booster and it still had air in it. At this point just drive it as much as you can. It should get better. Now if after several weeks there still is a spongy feeling in the brakes or steering, then it is time to take it into a shop. They usually are better equipped to find leaks where it is sucking in air.