PacBrake problem

[Papa_Jim]

Cruising down the highway, came unexpectedly to construction, suddenly had to slow down from 60 MPH to 45MPH to enter into single lane between construction pilons and concrete abutments, so I pressed on the PAC BRAKE pedal, which helped immensely in getting us slowed down and under control.

HOWEVER, when I lifted my foot from the PACBRAKE switch, the boost would not come up, and there was no engine power. I mean, NO engine power! We ended up in 2nd gear with my foot pushing the accelerator pedal to the floor, engine temperature rising, no boost, no power, in a single lane crossing over a bridge, praying and praying like crazy, Oh Lord, just let us get across this bridge.

Once across the bridge, the construction ended and the highway immediately became 4 lane. We darted over to the shoulder to let the hundreds of vehicles pass by.

I shut off the engine and ran back to the bedroom to lift the bed to open up the engine compartment. I have a circuit with a switch set up to test the operation of the Pac Brake unit. I used that switch, and the Pac Brake was working!

I went back to the driver's seat, started the engine, engaged the transmission, and AWAY WE WENT! Everything was operating properly. We had boost, we had power, we were back on the road!

So, we finished the trip uneventfully. I simply didn't touch that PAC BRAKE switch again!

So..... what do I need to fix?

[Paul R. Haller]

I don't know about your Monico but most pac brakes use a vacuum switch that is easily stuck or there is carbon build up in the butterfly and the brake will not release. If it were me I'd pull off the linkage and see if the butterfly valve is sticking or not. If yes, you'll have to pull the pac brake out and fix the problem of either the butterfly hanging up or the shaft corroded and/or infiltrated with carbon. If the system works as it should with the linkage pin pulled then the problem is with the vacuum valve. It's a valve inside a small solonoid that gets gummy and wont slide back and forth reliably until spotlessly clean. You can take them apart and clean them carefully and they are a long piece of brass with multiple o rings on it with holes drilled through it to allow vacuum to pass to either the open or close diaphram. It just shuttles back and forth depending on what you call for.
The loss of power you experienced is a stuck closed exhaust brake. I've seen it often but it is scary for a first timer. No power at all, no boost, lots of black smoke. It's the proverbial potato in the tailpipe! Perhaps others who know how a Moneco is put together can answer better then I. I have worked on and installed many of them on Dodge Diesels and they work off vacuum in that application and occsionally get carboned up.
Good luck,
-Paul R. Haller-

[HENZEN9]

Call Pacbrake and order a bottle of their high temperature oil for your brake. Put some oil on the top of the butter fly shaft occasionaly and this "sticking" problem should not re-occur.

Allen

[JohnQ]

Had the same problem in my coach coming down a terrible grade on Ore hwy 140. Mine had to cool down for half an hour before it would function again. The solution was a new PAC Brake.

[walt2137]

Originally Posted by JohnQ

Had the same problem in my coach coming down a terrible grade on Ore hwy 140. Mine had to cool down for half an hour before it would function again. The solution was a new PAC Brake.

I agree and get the New PRXB, Its not hard to change.

[HENZEN9]

The Pacebrake is simply a butter fly such as you would find on a carburetor. The bushings that the shaft is in and the shaft will rust or get carbon deposits preventing them from working. Pacbrake sells a special high temperature oil for their brake, for a reason. They need to be oiled occasionally.

The brake is powered by air presure and controlled by a electric selonoid. You can install a switch in the electrical line to the selonoid so you can activate the Pacbrake (if you have air pressure). If is stuck you can use a pliers to forcfully turn the butterfly until it is loose enough to work.

After is is freed and working again, an application of Pacbrake oil occasionly will keep it working. Or you can spend $600 plus to install new one.

Allen

[JohnQ]

Yep, after the trip where it stuck, I ordered, received, and applied the PAC Brake lub. Went a couple of months and the darn thing stuck on me again, this time in busy traffic, and on the way to get the coach serviced That day we order the newer style PAC Brake. Love the better low speed braking, and the way it "Comes On", no more slamming on.

[Papa_Jim]

My dilemna was, as I stated, that when I checked the operation of the Pac Brake, it was not seized! I have a test circuit with switch set up in the engine compartment, and when I flipped that switch on and off AT TIME OF FAILURE, the Pac Brake was working freely!

I believe my problem somehow is electrical, because once I shut the engine off, waited a few minutes, and restarted the engine, then the Pac Brake was released and I was able to continue on our trip.

I

[Dr4Film]

Originally Posted by walt2137

I agree and get the New PRXB, Its not hard to change.

Walt,

Did you change out your old OEM Pac-Brake for the new upgraded PRXB model yourself or did you have someone do the labor?

I have purchased the new PRXB and been trying to find someone to install it for me at a reasonable cost. So far I have gotten estimates from 3-6 hours of labor at over $100 an hour.

Dr4Film ----- Richard.

[Denali]

Originally Posted by Dr4Film

Walt,

Did you change out your old OEM Pac-Brake for the new upgraded PRXB model yourself or did you have someone do the labor?

I have purchased the new PRXB and been trying to find someone to install it for me at a reasonable cost. So far I have gotten estimates from 3-6 hours of labor at over $100 an hour.

Dr4Film ----- Richard.

I took our coach to the nearest truck repair shop, and they installed the new Pacbrake for an hour's labor. You might try those kinds of shops.