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Dash Air Valve Issue (Parking Brake)


RandyA

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2004 Volvo with Meritor/Wabco Valve (page 21)

 

I noticed a major air leak when I stopped the Volvo. As it turned out the leak is from a yellow line that comes from under the dash and "opens" inside a sheath under the driver floorboard. From what I can determine, I believe it is suppose to be open as an exhaust???? from the dash valve. The air line schematic I have for my truck from Volvo does NOT show this line. The only yellow line shown is on the governor. This is not the same line. Am I correct on my supposition about the yellow line in question?

 

When the parking valve (yellow knob) is pulled out to park position air constantly flows out of the end of the yellow line until the tank is empty. When the valve is in all is OK - no air leaks out.

 

I believe the vehicle is safe to drive as no air is lost as long as the valve is out of the park position. But, if I engage the parking brake I will lose my air. Of course, if the air is gone the spring brakes will hold the truck in position.

 

Right now I am parking in-gear with chocks under the rear wheels to save air bleed down. Obviously I can't leave the cab of the truck with the engine running - I must shut down, put it in low gear and chock the wheels to keep it from rolling.

 

I am considering a temporary stop-gap measure of putting a restriction on the end of the yellow line (3/8" down to 1/8") to make air loss slower when the brake is on. This would at least allow me to leave the truck with the engine running and parking brakes on for a short period.

 

OK - what I am thinking is that the valve has a worn or blown O ring or seal inside. Don't know if it is rebuildable yet or not or if I even would want to try.

 

Getting to the valve looks like a dash disassembly.

 

This is a repair/replacement I want to do myself. Buy the part and avoid Volvo hourly rate.

 

Any tips, warnings, thoughts from someone that has done this would be appreciated. Also, any source of part other than Volvo. I would venture a good guess that this same valve is used on other brands of trucks? Is this a job doable in a campground with standard tools or should I wait until I get back to my shop in April? No experience on this one - time to learn something else <_<.

 

 

 

 

 

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Randy, I have no knowledge or experience with this valve. From your description, I'm assuming that the compressor can out pace the leak ? Oherwise you would not be able to get the spring brakes to release unless you have to hold the valve in to build pressure ?? I will be following this post with great interest and wish you the best on this issue. Charlie

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Charlie, I believe you're correct, he would have to manually hold in the yellow button for a bit.

 

Randy, I've not changed that valve on a Volvo, but on my Mack it was pretty easy, just took some fiddle'n to get all the lines and fittings pointed in the right directions. It's a common replacement item, like air governors.

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<==== Mine is doing the same but it is the red knob instead. I believe that they discharge outside the truck cab just in case anything, oil, water, dirt that may get into the air system (bad compressor rings) or the noise (released air) is mitigated. (Just an idea on my part though).

 

I had a Doge Diesel that used a vacuum pump (for the dash vents, heater controls) on the power steering shaft that the seals went bad. Can you say Rotella leaking out of the dash controls and on pairs of dress pants. Wife (and I) were not to happy with that!!!!

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No need to shut it off in gear. When you pull the red knob it releases the air that was holding the spring brake off, applying the spring brake. They don't apply only when you have no air. They apply when there is no air, such as pulling the yellow knob.

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http://epi.hbsna.com/products/product.asp?msi=0&sid=9300A9C013C54840A48D8FE8942EDE24&pf_id=KN20619&dept_id=40

 

Replaced mine awhile back. Hardest part was getting the roll pins out of the knobs. Ended up cutting them off.

New valve is an easy replacement but a little tight getting the air lines off/on.

New knobs easier to install with spring pins.

Didn't even consider rebuilding as the kit was not much cheaper and getting it all back together with no leaks is always a crap shoot.

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Randy;

 

Haven't replaced one in the Volvo, but did change the one in the Mack Dump I drive part time. Appears to be similar except that two valves are used instead of a combination. See page 22 The yellow line you refer to should be the exhaust dump. The constant air flow is indictative of a blown internal seal / o-ring in the valve.

 

They are not real expensive, I think I paid about $40 for the valve at Total Truck Parts. On the volvo the driver's right side kick panel would need to come off, not sure about anything else.

 

Not a complicated job, just really cramped.

 

And yes, I have learned to count valves in the last year....

 

PM me if you have a question I can help with.

 

Paul

 

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Randy;

 

Haven't replaced one in the Volvo, but did change the one in the Mack Dump I drive part time. Appears to be similar except that two valves are used instead of a combination. See page 22 The yellow line you refer to should be the exhaust dump. The constant air flow is indictative of a blown internal seal / o-ring in the valve.

 

They are not real expensive, I think I paid about $40 for the valve at Total Truck Parts. On the volvo the driver's right side kick panel would need to come off, not sure about anything else.

 

Not a complicated job, just really cramped.

 

And yes, I have learned to count valves in the last year....

 

PM me if you have a question I can help with.

 

Paul

 

On the Gen II the valve is vertical and upper part of dash needs disassembly. Still cramped though.

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Thanks to all for all the comments and help so far. I'm learning. Could not get price or availability on a replacement valve today (Sunday). Maybe will be able to get that tomorrow. I found the Meritor/Wabco manual that shows steps to replace valve. It says the instrument panel has to come out. That will be new to me. I tried restricting the dump line to see if it slowed air leakage. Capped the line and drilled a 1/16" hole in the cap. Did not get the results I hoped for.

 

Ronbo wrote this:

 

No need to shut it off in gear. When you pull the red knob it releases the air that was holding the spring brake off, applying the spring brake. They don't apply only when you have no air. They apply when there is no air, such as pulling the yellow knob.

 

Not sure I understand??? I never use the red valve because it makes no difference on my truck. Are you saying that pulling the red knob will set the spring brakes? I've got to check this tomorrow morning.

 

No Volvo dealer in Ft. Myers but there is a Peterbuilt shop a few miles down the road. I need to check them out as a possible parts source - also NAPA. It would be nice to get one on the spot local but I may need to use Fed-X or UPS from Tampa. I now want to get this done before we leave this location March 1. Yes Carl, I will make pics of the mistakes I will probably make. Paul - could you PM me a phone number? You know, just in case. Ray, saw the knobs off? OK - so what then? New knobs or knock the roll pins out once the knobs are off and out of the truck?

 

Man, this is a great group. I always appreciate the help given here!

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I don't know about Volvo but I did change mine on the Freightshaker though. The only problems was room to get your hands behind the dang thing to remove and install air lines. Some lines connections straight some where like 45 degree and some 90 degree. You had to get each in the same orientation as they came off the old one or they just won't fit and cannot tighten them properly. I know you will take a picture of the line orientation before taking them off so you will have no problem. Oh the Freightshaker knobs screw on no roll pins so really easy for me with knobs. :)

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Replaced mine awhile back. Hardest part was getting the roll pins out of the knobs. Ended up cutting them off.

 

On my 06 the knobs unscrew. Figured that out after I tried to knock the pin out.

 

Randy

Going from memory my truck is not here. You need to remove the fuse box cover (screws accessed through drink holder) then the two panels underneath so you can remove the horizontal strip (wood grain on mine) hiding the screws. The strip must be removed starting from the right or you will break off the hook holding the left side. I can't remember if you have to loosen the instrument cluster or not but if you do the strip hiding the screws on the left side of the wheel is removed starting at the left and working to the right. There is also some trim above the cluster that just pulls down and out if needed. Once you have the trim figured out it will be less than 2 minutes till you are fighting with the air lines. All torx screws except phillips on the air valve if you have to reuse the bracket.

 

Nigel

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I was able to squeeze the roll pins out using a large pair of slip joint pliers (Channel-locs). I found a screw in my junk box that was the right diameter, slightly smaller than the pin diameter, and less than an inch long, and butted it against the top of the pin, with the lower jaw of the pliers against the knob body just offset from the pin. Kind of like a portable arbor press. It might work better to also find a small socket with an ID to clear the pin, to use as a spacer between the knob body and the pliers lower jaw, to give the roll pin a place to push out before it hits the jaw.

It was a very large pair of Channel-locs, so I had great leverage. If you try this, do take precautions to avoid the serrated pliers jaws damaging the plastic knob, or scratching up the dash escutcheon/faceplate (DAMHIK).

Pete

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Nigel you gave away the Volvo secret about the thin trim pieces. I found out the hard way but was fortunate enough to find the broken tab and JB Weld still holding.

The roll pins on mine would not budge. Tried all those tricks. Cutting off is no big deal as the new valve comes with new knobs and they pop on using a spring loaded pin in the shaft.

Try class8trucks. they have the valve.

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Once more, many thanks for all the help.

I called Colonial Volvo (my home shop) and was quoted $469.80 for the part, Then called NEXTRAN in Tampa and Dave (parts) said he had 8 on the shelf that matched my VIN. My cost would be $282.94. I had hoped the cost would be a little less but time is not on my side to look and wait if I do the replacement before we leave Ft Myers for out 400 mile jaunt to the panhandle. I don't know why the difference in price since they are both Volvo centers. Anyway, I asked Dave to send me one UPS. Should be here in a couple of days. Then, the fun will begin! I have plenty of film in my Brownie, Carl - I'll be sure to make pics ^_^ .

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Randy & all concerned,

 

Since it seems like Randy has been able to solve his parking air brake problem of losing air during parking brake application so, perhaps my inverse problem of losing air during parking release might be of some interest to keep in the back of our memory banks for futurte ref. While my tasking does not dwell on Randy's specific problem the loss of system of air capacity is nearly identical.

 

A few weeks ago I picked up a old Freightshaker basic RV hauler that had seen much better days, as a project. Like most projects, this truck had plenty of "defered maint issues" to say the least, so I had a long list of tasks to keep me busy.

 

Prior to tearing into the "project" I talked my bride into takiing a "spin around the block" in the 8-ton-turkey........it was a short "spin".

 

I started up the truck and built 120 psi of air and kicked the tires and loaded the bride into the shotgun seat. I jumped into the drivers seat and released the park brake and selected 3rd and eased out the clutch and we started out of the driveway about .....10 feet.... and then I felt the parking starting to reset while in the backgroung I heard air exhausting. Since we had yet to enter the street I recycled the yellow knob and noted that the system was starting to build up pressure from it's fall of 50 psi. Once I had about 100 psi I released to brake again, but again, I was losing pressure fast.

 

Since the parking would not release, and the truck was now blocking the entire driveway, I needed to backup the truck to it's normal parking spot to unblock the driveway so.......... it's simple.....just select low-reverse and creep back against the spring brake.........wrong, the front tandem did not have enough traction to overpower the back drive axle.

 

At this point I had a couple of options to relocate back to the parking spot, so I selected the hillbilly option of switching the tandem interlock on and then GENTLY backing into the parking position against the spring brake. As they say "childern do not try tis at home" but since I had done this a couple times in a past life it seemd ok this time for a move of about 10 feet.

 

Once "we" were parked my bride smiled and said "well you seem correct that the view and ride is somewhat better than the ole pickup truck but I might need a longer trip to cement my opinion", I smiled back and said "I'll get back to you soon regarding our next "trip".

 

After the bride left the truck I got out and noted the air was exhausting out of the main drive axles control mounted above the power divider. Something in the back of my mind lit a dim red light but I said oh well just take a look at the std airbrake fault charts and then replace the valve. I glossed over the fault charts and then replaced the valve.....but..... in the back of my mind that dim red light said "you know this will not fix your problem dummy".

 

Sure enough I started the engine and obtained 120 psi and as soon as I released te parking the brake to air started exhausting out of the NEW valve.

My dim red light started getting a little brighter.... but not me.......

 

A couple local truck docs said just start plugging the air can lines one at a time until you find the problem so what the heck I plugged... one at a time.... all four of the service can lines and then that only left the two spring brake can lines but even with all of the lines plugged air still exhausted out of the contol valve.

 

Like a big dummy I sat there looking at the valve and I had only line left and it was the balance line from the service brake valve to the parking brake valve........ all of a sudden I was BLINDED BY THE HUGE RED LIGHT!!

 

All of a sudden the problem was obvious.........so.... I disconected the balance and sure enough air streamed out of the line.... THE WRONG DIRECTION!!

 

In my childhood I started to recall that the balance line is actually labled as a "counterbalance line" where if the springbrake is deployed and you also deploy the service brake at the same time the airpressure from the service ports streams TO the spring brake valve thereby relieving equal pressure from the spring deployment to keep from double-powering and overstressing the brake system.

 

What failed (besides my distant past memory) was that the check valve in the spring brake valve had failed and whenever I selected to OFF parking brake position the air pressure simply traveled the WRONG way out to the service brake valve exhaust port and to lack of pressure would not allow the parking spring diphram to compress the spring brake ( a fail-safe-mode).

 

Whew..... simple replacement of the parking brake exhaust valve and then my minds red light dimmed again.

 

IF you ever encouinter uncommanded exhaust flow out of your service brake exhaust port you might want to have someone apply the service brake and hold increasing pressure and see if the spring brake diphram moves into the release position while viewing the movement through the vent ports in the spring can and the exhaust flow tapers off as service brake pressure increases. Once the service brake pressure is equal to the spring pressure no exhaust flows out of the service exhaust port.

 

Hope this does not confuse too much.

 

Happy travels,

Mike , Carol & Dolly, the-paint-horse

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Wow....everytime I think I've learned a little sumpthin, a post like the one from DollyTrolly above shows up to reinforce my complete lack of compentency. Ah well, more cold & snow for tomorrow, so I'll just curl up with a good post and read that about 27 times.

 

Seriously, thanks for the insight, and welcome.

 

Paul & Paula

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