Jump to content
Mopar1973Man.Com LLC

  • Welcome To Mopar1973Man.Com LLC

    We are a privately owned support forum for the Dodge Ram Cummins Diesels. All information is free to read for everyone. To interact or ask questions you must have a subscription plan to enable all other features beyond reading. Please go over to the Subscription Page and pick out a plan that fits you best. At any time you wish to cancel the subscription please go back over to the Subscription Page and hit the Cancel button and your subscription will be stopped. All subscriptions are auto-renewing. 

Hydroboost Leaks

cummins2k
 Share

Recommended Posts

cummins2k

cummins2k

Posted
Posted

I have seen the question asked a million times on other forums. It usually comes down to someone claiming to be an awesome mechanic stating that hydroboost brake boosters aren't rebuild-able/resealable or that they are so complicated if you took them apart you would never get them back together. :banghead:

Well even though my hydroboost has been doing a great job keeping my undercarriage lubricated the constant top offs with power steering fluid and air in the system got pretty annoying. I decided that I would take a peek inside of it and possibly reseal it. I didn't plan to rebuild the unit as there are a couple specialized tools you either have to purchase or improvise.

First off when my power steering system wasn't low and had set for a bit to allow the air to work itself out the brakes worked fine. Once the booster saw air it was hard to push them and they had a tendency to jerk. So in other words my booster was functioning. Just leaking fluid and drawing air.

I started off by finding a kit. I purchased a MBM #50 kit that cost me $25 through piratejack brakes.

Posted Image

Next I flushed the system, not that it needed it because it went through powersteering fluid constantly.

Removing the brake booster is frustrating because of course it requires you to remove 4 nuts and the pedal rod from under the dash. The pedal rod is held on by a washer and clip. The 3 out of the 4 nuts were quickly removed using a 3/8 air ratchet, swivel, extensions, and a 15mm deep socket. The last one was removed using a ratchet, short extension, and a deep 15mm socket.

Of course there are 2 15mm holding the master cylinder to the booster. Two pipe fittings 16mm (power steering), and a hose that is held on by a clamp (also power steering).

Afterwards I had to remove two plastic line holders from the brake lines to allow them to move a bit. Then I merely slid the master cylinder off it's studs and moved it to the side being careful not to bend the brake lines. I found this gave me the benefit of not having to bleed the brakes and bench bleed the master.

At this point carefully manipulated the booster out of the truck.

Posted Image

Once on the floor I placed it on a rubbermaid container lid to catch any fluid that spilled out once opened. I removed 2 15mm nuts that held on the adapter plate that bolts to the master cylinder. At this point a star retainer, spring, rod, and plastic washer will come out. The star retainer will come off by itself but the spring, rod, and plastic washer assembly should remain as one piece.

Posted Image

Next I removed the 5 3/8" bolts that held the casings together. It took very little persuasion to separate the case halves. It is important to note at this point I remembered I had forgot to apply the brakes 10 times with the engine off to de-pressurize the booster. Not such a big deal cause I had no intentions of removing the gas canister on the booster anyway. Once the halves began to come apart the spool valve fell out. Not a big deal as it can only go back in one way. Oddly enough I found the check valve was missing and in the back of the casing. I noticed matching marks on the check valve and housing right behind the fork on the pedal rod. I am still not sure what happened here, cause the booster seemed to work. All parts were accounted for so I moved on to resealing it.

Posted Image

I removed the original figure eight seal that sits between the two housings. Comparing the new and the old as well as looking at marks on the housing it would seem this was my problem seal. The old seal was considerably thinner, probably due to shrinking. The new seal can be pushed into place with fingers.

Posted ImagePosted Image

Next I used some small hooks that I had to fish the piston seal out of the piston bore without damaging the bore. Pay attention to the orientation of the piston seal when removing it. Once again the new seal can be installed simply by fishing it in there and working it in with your fingers.

Posted Image

Posted Image

I now reinstalled the check valve and the spool valve. I connected the pedal rod to the spool valve and reinserted the piston into it's bore.

Just as before press the housings back together, this shouldn't take anymore than hand force. Reinstall the 5 3/8" bolts and snug them down. Back on the other side of things reinsert the spring, rod, and washer assembly. Place the star retainer back on the rod making sure to have the curved points toward the inside.

Reinstall the master cylinder adapter over this, it will retain the spring assembly. Tighten the 15mm nuts.

After that it is pretty much reverse of removal. Place the booster back in the truck. Tighten the 4 15mm nuts under the dash that retain it to the firewall. Reinstall the pedal rod, washer, and clip. Back under the hood reconnect the power steering lines, and master cylinder.

Top off the system with power steering fluid and work the wheel back and forth, lock to lock while pressing the brake pedal. It will feel funny at first but it will tighten up as the fluid gets to it. You may hear strange noises due to the air in the system but don't worry the air will work it's way out after sitting for a bit.

I have yet to notice a leak. Took her on a trip around the neighborhood for a bit after degreasing everything and haven't noticed anything new. My brakes even feel stronger. Hopefully this helps someone not spend $200 over a simple leak. :spend:

  • Like 2
Link to comment
Share on other sites
  • 3 weeks later...
  • 6 months later...
bsmith

bsmith

Posted
Posted

I resealed my hydoboost according to this write up, but I can't seem to get all the air out of the lines.I turned it lock to lock mutiple times while pumping the brakes. Took it for a ride down the road. Still no luck.Any help is muchly appreicated.ThanksBrianTo add, it sounds like its low on fluid humming sound. I've added fluid but it ends up over flowing once it gets warm.

Link to comment
Share on other sites
bsmith

bsmith

Posted
Posted

How long has it sat Brian? If you're not introducing new air through a leak it can still take a couple shales for the cavitated fluid to settle out an finish working the air out.

I did the job last week, didn't start the truck till yesterday. Messed with it yesterday and today trying to get the air out.

I turned the wheel side to side while pumping the brakes, with the truck on and off. It sometimes feel normal but goes back to feeling like no power steering at all. I've added fluid cause it sounds low, but it overflows after turning it side to side mutiple times.

I'm almost to the point of pulling it off to make sure I did the job right. Should my pedal feel really stiff?

Thanks for the reply!

--- Update to the previous post...

Ok I messed with it some more today without luck. It does sound better, it isnhumming and foaming out the top.

It is still too hard to steer to drive. Feels like it doesn't have power steering at all.

Also I pumped the brakes so hard I mus hae cracked a line or something cause I had to bleed the brakes.

I'm pretty close to pulling it back off and re installing it.

Link to comment
Share on other sites
  • 1 year later...
  • 1 month later...
 Share
Go to topic listing
×
×
  • Create New...