Motorhome repair - REBUILDING A PAC BRAKE (exhaust brake)

Last weekend we were at our fellow Safari-owning friends, Mel and Paula's house.  They have a Safari similar to ours.  The guys were yakking and conferring and configuring all weekend on items on our rigs.  Seems Mel's pac brake (exhaust brake) on their Safari has stopped working properly.  And it turns out that ours was NOT working at all either!!!!

We didn't notice the pac brake was not working, as we have not had much occasion to use it, as it's mostly utilized in mountainous driving conditions.  When we hit the button to engage the pac brake, the engine shifts wayyy down too to assist it.  We thought that WAS the pac brake working.  Guess not!   Who knows how long this has been non-functioning?  Perhaps over the last 6 years since we owned the rig, it was already rusted or frozen into place before we even bought it????

The guys examined Mel's and decided their Humphrey Valve had gone bad.  They yanked his valve out and robbed ours off our motorhome to see if they could get his to work.  VOILA!  It worked!   That was easy.  So Mel's pac brake functions as it should now.

But the bad news, on our rig, it was not the Humphrey Valve that was a problem on ours, it was the interior butterfly would not turn and close inside the exhaust pipe.  It was rusted (frozen) shut tight! It gets heated so hot from the exhaust that over time it has swelled up and stuck.  Fortunately, it was stuck in the OPEN position and not the CLOSED position.  Whew!

Now we needed some serious pounding with a hammer.... on the lever that controls the butterfly inside the pac brake cylindrical tube.  Many whacks later, it still didn't knock it loose!

We left our valve in Mel's motorhome, seeing as his was correctly functioning now.  He ordered a rebuild kit for the other valve to be shipped to our house (along with an extra new valve for him to keep on hand, seeing as he only has a used one in his for now)

Steve would have torn ours down last week and got on it right away for a repair, but we needed the rig to get to the wedding up north over the weekend... so he waited till Sunday evening to work on ours, once we were home, safe and sound.

Our diesel motorhome has the engine in the back, underneath our king sized bed.  We lift up the heavy bed together.  He props up the bed mattress and deck with a heavy pole and can crawl right into the engine compartment to work on it!

This is the Humphrey Valve that needed the little inside rubber diaphram and the rubber O-ring changed out.  That was the easy part.

But now for the other part.... 

He tried and tried hammering on the lever for the butterfly to loosen it up... no go.  

Now  he figured he needs to remove the entire pac brake to work on it out on the work bench.  So he needed to loosen the two flange clamps and get that entire pac brake outta the engine area so he could work on knocking the butterfly inside loose.

Sound easy huh?   Well.. of course it's NOT.... once the two clamps were loosened, the entire pac brake housing was rusted in tight!!!!   He had to use a chisel and a big hammer.... after many whacks (Steve estimates about 20)  it finally came loose!!!!!!

Next hurdle, the butterfly inside the pipe was of course stuck in the open position, which the two fins of the butterfly intruded into the exhaust pipe and turbo unit on each side of the pac brake that he was trying to remove.  It was a very difficult job to try to flex back the exhaust tube (which doesn't flex much) to give enough clearance to slide out the pac brake with the stuck butterfly valve.  Arggghhhhhhh

Whew!  There... it is OUT!!!!

See how that center piece (the butterfly) is stuck in the open position?    We stuffed a rag in the opening for the turbo and taped off the end of the air line to the Humphrey valve too.

Yup, this is what is "broke"

A pac brake is not a cheap item to replace...  it runs in the $700-1,000 range.   That is why we are going to try to loosen the stuck butterfly ourselves. The piston part is not the problem.   The piston part functions correctly, and it the part that gets lubed with special pac brake lube.   But the rusted up butterfly lever IS the problem and that takes such high heat when the engine is running, that lube does not work on it.

Steve hammered on it out on the bench,

then in the vise, 

then with a bigger hammer... 

nada..  

it was NOT going to move! 

So he took it to work, and on his lunch break he used a rosebud torch tip with high heat map gas torch...   and lots of flame and heat to finally break it loose!  And it worked!!!!!!!!!!!!!!!!

He will re-install it probably later tonight with me holding the flashlight, tools, and snapping pics.  Wheweeeeeeeee  

(added later)

Yes, he put the pac brake back in, and it went in very easily now that the butterfly could be shifted to the closed position.  Dropped it right into place, hooked it all up, clamped down the clamps and then added Pac Brake Lube to the 5 points of lubrication indicated on the bottle.   There.. .done!

We then took it for a test drive and it worked perfectly!   Steve even had me drive for a bit and let him look with the bed lifted up, so he could see it actually working.  What a reward for a job well done! 

Good going, Steveio, you just saved us $1,000 or more having it replaced-------