Hydroboost rebuild question

[Rideicon]

Followed the instructions posted here on replacing seals on the hydroboost assembly. My question is this, is my accumulator check valve supposed to have a ball bearing in it? The *generic* schematics included show one, and everything I see online shows a ball bearing. Cautionary videos online say to make sure you put that ball bearing back or severe damage will be caused. But I am about 87% sure I did not have a ball bearing inside my valve when I took it apart.

 

can anyone give me any insight. 

 

 Edit, working on 99 Cummins.

 

Edited August 11, 2016 by Rideicon

[Me78569]

There are a number of members that have done this so I am sure someone has the answer.

[Haggar]

Ride,

 

I looked through all my pictures of my rebuilds.  No loose check ball.

In this cross section, notice that the accumulator charging check valve, is behind a plug (appears to be o-ring sealed, but can't tell if there are threads)  If you were doing a standard reseal, I don't think you took it apart far enough to have done anything with it.  

I added a picture where I circled it.  I did not remove it during rebuild.

 

Hope that helps!  Welcome to the forum!

 

Hag

[Rideicon]

Yes, that's the part. It slides out pretty easily and I did remove it... But I don't know if there was a ball in there. There is no spring tension or anything so it couldn't have shot far.

 

[Haggar]

Sorry,  I didn't go in that far.  Just from a manufacturing aspect, I would think is a "cartridge" like most hydraulic valves are.  Not like a loose ball in a trans valve body or in a carburetor.  I am going on a limb here, but the schematic is showing it more like a cartridge than a ball trapped in a path too.  So if you didn't see one fall out, it was probably all part of the item you pulled out.

 

I can tell you, I don't think it would be a catastrophic failure if it were missing (unless it fell somewhere else inside the unit).  You would not have any accumulation though, and so your boosted brake force would vary with engine speed, and in case of engine off or (not our system) a power steering belt failure, you would have no reserve boost for applying brakes. 

 

Now if you were rebuilding it because it was something wrong in the accumulation system, you may have found the problem!

 

Here found another exploded view....  It shows a complete cartridge, no loose ball.   see item 10.

GL  HTH

 

Hag

[Rideicon]

Perfect, all the generic schematics I found online show a ball, and one video on YouTube the guy claims to have misplaced the ball on a rebuild, 85 Chevy, and the unit went full host and broke and bent some shafts on startup... But I will take your advice and throw this in as is. I think only my piston seal was bad I had a bad leak out of my weep hole. 

 

[Rideicon]

Re-installed and the pedal went to the floor on startup. Guess it had a ball bearing.

[Haggar]

Ride,

Sorry,  what a total pain in the behind! 

I still don't see how the missing ball could cause that issue.  you can see that the ball moves out of the way when there is pressure from the pump.  When the pump is stopped (engine off) the ball should roll and plug the orifice, so that the pressure cannot return to the pump backwards. 

 

A self apply after a rebuild can come easily from two places.  the first is not fully seating the brake rod into the spool valve.  this will make the hydroboost think you are stroking the brake.   Did you leave the rod connected to the brake pedal, or did you remove this with the unit?  The other thing I have heard is that the lever can go back on backwards.  (I am looking for the thread where the guy was trouble shooting his rebuild, and found he put something in backwards.  I think his would self apply also.) (I looked through my pictures... I can't see what can go in backwards or upside down, but I know there was something.)

 

On the GM hydros, I have pictures of measuring the back of the hydro to the center of the actuator rod.  after you do the rebuild the location has to be nearly the same or "it won't work."  I never new what the "it won't work" symptoms are, because after assembly it was back inthe location within a 1/16".  (apparently GM was bad about having a bunch of different rod lengths. So when swapping from vehicles and such you had to control that, or adjust it so it would work.)

 

I hope you find it!

 

Hag