Resealed Hydroboost and Brake Pedal Locked

[Dkoch124]

   I recently noticed that I had power steering fluid leaking from the weep hole on the bottom of the hydro booster of my 01 Dodge 2500. So I ordered the seal kit containing the inner seal and figure 8 seal.

   The install went as follows:

   Pumped the brake 3 times, unbolted the master cylinder from the hydro booster, unbolted the brake booster, removed the 3 power steering lines, and then removed the hydro booster and brake booster in one piece. I then separated them and replaced the seals while making certain that the inner seal actually went around the piston and didn't tear. I bolted the 2 housings back together then put the spring, rod, and washer back in before bolting the master cylinder adapter back on. After checking to ensure that the rods functioned and pushed back out properly I reinstalled it in the truck. I bolted the master cylinder back to it and reconnected the power steering lines.

   I filled the power steering reservoir, then cranked the truck, turned the wheels left to full lock, then full lock to the right, then back to center, killed it, and then pumped the brakes 5 times. This was repeated 3 times.

   After that I checked the reservoir and the fluid didn't even touch the stick so I filled it again and began the full lock, brake pumping procedure again and it was at this point my brake pedal went to floor as soon as I cranked the truck and it wouldn't return. I couldn't even pull the pedal up. It does release when the truck is off.

  I looked through a couple of forums and found that others had had similar problems and it was suggested to them to bleed the brakes. I half attempted to bleed the brake lines starting with the left rear working counter clockwise around to the left front. The left rear squirted fluid and ran down to a light stream, the right rear squirted a little and it too ran down to a light stream. Both front just dribbled.

   Could it be that when the reservoir went dry that the lines filled with air at the top going into the hydro booster? 

 

   Any help would be greatly appreciated!

 

   I should also mention that I noticed that the power steering lines got pretty hot.

[Haggar]

D,

Something went really wonky in the hydroboost.  (it should not self apply.) 

 

Somehow you are getting pressure past the primary valve and into the boost cavity without actuation.

 

I have seen this during reassembly by getting the ratio leaver installed incorrectly, but usually the pedal to the floor happens almost immediately.  I wonder if yours didn't do it immediately because there was insufficient fluid in the system until you bled it a bit?

 

Take it back apart and look for dirt, trash or anything not allowing the primary valve spool to seat properly. 

 

Did you disconnect the rod from the brake pedal? or how did you take that part out.  (this is very important)

 

 

 

 

HTH

 

Hag

[Dkoch124]

   I disconnected the brake pedal when I unbolted the booster from the firewall. The brake fluid reservoir and the power steering reservoir were both topped off prior to cranking. I assume you mean that there may have not been enough fluid in the lines before disassembly?

   I just finished working the air out of the power steering lines by working the wheels left and right to full lock and checking the fluid level every 3 times with the motor off. At first it pushed fluid out of the cap so I added more and repeated that process until there were no more bubbles coming out on the dip stick.

   After that I cranked the truck and the pedal still went to the floor. It did return when I turned it off. Note that I never touched the brakes working on it today.

   I'm really trying to avoid taking it all apart and starting over if at all possible but I'm beginning think I'm going to have to.

[Haggar]

Did you leave the rod attached to the booster and only take it loose from the pedal?   The length of the actuation rod is extremely important, and any change in that could cause the issue you are having.  (that was why I asked how you removed it.)

 

I know you don't want to take it apart.  But it usually seems the problem with self actuation after repair is the primary valve spool is in the wrong position at rest.  Power steering fluid from the pump is allowed into the boost section without having to move the pedal.

 

I don't know exactly what the problem is.  I have never experienced it.  A few people have.  A couple solved it by disassembling and correcting something. (of course they never list what it was, and may not have known what they fixed.)

 

I swear I remember that there was a part in the linkage from the primary valve to the power piston that could be assembled backwards.  I have no pictures of this in my records, so my memory could be muddled.   And I think the way you did the work, you did not take that assembly apart. 

 

Did yours come apart like this?  (the primary valve stayed stuck in the main body?)

 

You have to make certain the ratio lever connected properly into the groove on the primary valve.

 

 

Note:  I have done a bit more researching.....  Its a fairly rare problem but happens.  Some say it can be dirt in the check valve etc. 

I hope you can find it.  I am thinking it is something simple during reassembly.  

 

GL  HTH

 

Hag

[Dkoch124]

   Yes, that's the way it came apart. From what I could tell the rod can't be removed from the booster, but yes I only took it loose from the pedal.

 

   I took it back out last night and could feel the pedal rod sticking when I function tested it. Then I disassembled it the same as before and cleaned every bit of it with a toothbrush. It had what appeared to be varnish on the lever, spring, top of piston, and all over the secondary valve end. I wiped out anything that was loosened. I even removed the primary valve to make sure it was clean and to check the condition of the spring.

 

   Unlike last time the check valve did not come out. I hit the side of the housing numerous times with a wrench and it still wouldn't fall out. Could this be part of the problem or would it be pushed free once it has pressure?

  

   After that I reassembled it making sure that the accuator seated in the lever, functioned properly, and then I reinstalled it in the truck.

   

   I did notice a tear in the seal between the master cylinder and the hydro boost so I'm going to try to find one today before bolting the master cylinder back on. I wasn't able to find a part number or anything for it though.

[NIsaacs]

I just did mine, here are a few pictures, not much instruction tho.

 

https://www.turbodieselregister.com/threads/weekend-maintenance-on-the-01.259915/#post-2558205