AutoPark parking brake system on a 1992 Pace Arrow with very small leak

Auto Park parking brake on a 1992 Pace Arrow with very small leak

One of our users sent the following:

“I was advised by one of the forums to send you a email at and that you were the go-to-person to help solve my AutoPark problem.
I have a 1992 Pace Arrow with the 454 engine and I have noticed that I have a very small leak at the MaxiBrake/AutoPark unit.
It says MaxiBrake on the unit but someone informed me that its the hydraulic actuator. They helped me with my Air Bags installation and hopefully you can help with this problem.
I have tried to tighten the 6 nuts on the unit and have done 4 but can’t figure out how to get to the remaining 2 but I guess that will not help if the O ring is leaking. Any assistance will be greatly appreciated. Ed via email”


Here is our response:

Here’s what we can do:  Normally, I send out a bunch of background info first, but in your case we can start with some specific information.  I’ve just sent you a PDF file with an illustration of the actuator.  Print it out so you can study it as you work thru this explanation.

Notice in the lower illustration, the spring is compressed.  Also, take note of the nut (#3) on the shaft coming out of the actuator on the left hand side.

Explanation:  All of the GM literature says you don’t dare work on these actuators because the spring in them is very strong, and when you take them apart things may fly all over hell and injure someone.  True enough if you don’t know what you are doing.  BUT,  here is what you can do – – You can compress that spring and cage it (keep it compressed)  BEFORE you take the actuator apart.  This is done by simply turning that #3 nut to the right, up against the actuator housing, until you have the spring compressed – – by virtue of the nut pulling the shaft to the left.  I’ve just sent you a photograph of the shaft and nut – – the nut has a flange on it that will act as a washer against the actuator housing.  It would be a good idea to grease that flange nut so it will turn more easily as it pulls the shaft to the left and out of the actuator.   In the picture, we are calling that #3 nut the “jam nut.”

Before you can turn the jam nut up against the actuator, you will have to loosen it from up against the long hex adjuster nut – – you’ll need a pair of wrenches to do this.

Here is an important thing you have to consider before you start this process:  If you start working on this with the brake APPLIED,  there is gonna be a LOT of tension on the cable, and the actuator shaft – – The big spring in the actuator is pulling hard on the shaft and cable to apply the brake.  I’m sending you another illustration (you should print this one too so you can study it as you read this).  This is a simpler illustration than the  pdf one that I sent a bit ago.  If you really study and memorize this page, you’ll know all the basics about how your AutoPark works.   This is a big safety issue here:  In order to take this actuator out of the motorhome,  you need first to get the cable disconnected.  In order to disconnect the cable, you need the tension off of it BEFORE YOU TRY TO DISCONNECT IT!  The safest way to do this is to first loosen the jam nut from the adjuster nut, put some grease on the flange nut , and screw the nut to the right until it is up against the face of the actuator.  Sending some more pictures here:  This is a wrench that Sum1 made to make this job easier – – He bought a cheepo Chinese wrench, and cut a segment out of it with a 4 inch disk grinder.  Without this wrench, it is pretty hard to turn the nut in the cramped quarters – – the pictures show this pretty well.

When you get the tension off of the cable, you can disconnect the cable by unscrewing the long hex nut off of the actuator rod.  Now you can disconnect the hydraulic line going into the back of the actuator,  unbolt the whole actuator assembly and remove it from the coach.  At this point, you now have the actuator and big spring “caged” or compressed.  You can put it on your workbench and open it up – – just leave the jam nut tight against the housing and KEEP IT THAT WAY.  You’ll be able to open and inspect the whole assembly, and the spring will be compressed, but in no danger of expanding and hurting anybody.

Finally, I’m sending a mechanical drawing of the actuator.  It shows what it looks like inside.  You can’t tell much by looking at the drawing on the face of the email, but if you open it as an attachment, you can use the zoom feature to get a better look at it.

I don’t have the part numbers for the O rings, but a good auto parts place like NAPA should be able to help you with that.  Or, you could go directly to Haldex (the maker of the actuator) online and order them that way.

So study this email, and also the pictures, illustrations and drawings I sent you that are now on our web-site.  See if they make sense to you, and get back to me if you have questions.  It may take a few emails to get this all sorted out.

Questions and comments are always welcome, oldusedbear

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