Replacing Tractor Parking Valve

Star Dreamer · August 16, 2017

I checked the Resource guide and didn't find anything on this so I figured I would ask here.

I need to replace my parking valve and even though it looks fairly easy, I figured I would check to see if any one has any tips.

On our Freightliner, the yellow and red handle valves are in one combination unit with a bunch of airlines going to it, so they both get to be replaced. At the same time I am going to replace teh dash piece they mount to as the Freightliner's dash has a habit of breaking from the constant use of the valves. I had replaced ours when we first bought the truck 5 years ago but it recently broke again and since I have to take most of it apart to change the valves I may as well replace it again. I may look to reinforce the areas that break this time too.

Of course this all was discovered in a recent pre-trip test. Better to have it happen at home rather than on the road.

I had not drove the truck for a few weeks and finally decided it was time to change out my drivers license from MN to SC. In MN you can drive on your regular car license as long as it is an RV and our HDT had been registered as a Motorhome. In SC, you have to have a class F license to have a combination of RV greater than 26000#s with the trailer hooked up. (Class E license if for RV greater than 26000# but do not pull a trailer.) Since MN did not have a separate license, SC requires us to take a written and driving test. I had scheduled the test for this past Monday. Over the weekend, I decided to do my pre-trip inspection ahead of time so I would be all ready to pull out Monday morning for the test. The driving test at the license branch will require one too. First part of the brake test went well, held the brake for one minute and air pressure held. Second part of the test doing the fanning of the brakes, the alarm went off as required, but the valve did not pop out. (Touching it made it pop out, but you cannot do that in the test). I tried a few times and still the same but I never ran it all the way down to zero air. I figured I would try again in the morning before I took the test. Fired the truck up on Monday, air pressure good and headed out but as soon as I step on the brakes, air was hissing from the dash valve. Basically it would fail on the first part of the test now. drove around the block and parked the truck and trailer back in the driveway and called to reschedule my test which now will not be until August 28th. Gives me time to fix the brakes!

I have the new parts already (Freightliner had both the valve and the dash piece in stock locally), so has any one change out their valves and have any tips they care to share?

Dave

beyerjf · August 16, 2017

Your instrument panel is the same as mine. I am on my 3rd set of valves. In order to get to them easily you need to take all 8 panels covering all of the wiring, dash, everything. On our wonderfully designed trucks that means starting at the right side of the instrument panel, and in this order:

1.remove "air bag " cover held in place with 4 hidden spring loaded clips

2. remove the fuse cover

3. remove the passenger side knee panel

4. remove the valence panel around the radio and Heater AC controls(exposes other fasteners

5. remove the 10"x2" corner cover panel, one screw at bottom, spring clip at top

6. remove all screws holding the top cover in place. Remove all screws holding the front passenger side cover panel

7. You should be able to lift off the top cover and the front passenger side cover exposing everything.

Because Freightliner went out of their way to hide fasteners and use hidden clips, which in turn break the plastic panels, they are referred to as "throw away trucks" . Removing and Replacing the valves are straight forward, although because they didn't give you even 1/4" more air line than needed, it requires small hands and lots of patience. Take a look at the other air connections in the neighborhood. If you see oil trails that means they are leaking also. Good time to see if the various air operated linkages for the heating system are not leaking, they fail frequently.

I rebuilt my entire instrument panel with about $1500 worth of parts about 5 years ago. The entire assembly starts to break because the AM/FM radios are installed improperly by the dealers, they just slide them in the DIN mount and don't install a bracket to hold the back of the radio, which bounces up and down and breaks everything. After i solved that problem, 5 years and 400,000 miles later, no breakage.

Star Dreamer · August 16, 2017

Thanks Jeff

Star Dreamer · August 19, 2017

On 8/15/2017 at 10:12 PM, beyerjf said:

Your instrument panel is the same as mine. I am on my 3rd set of valves. In order to get to them easily you need to take all 8 panels covering all of the wiring, dash, everything. On our wonderfully designed trucks that means starting at the right side of the instrument panel, and in this order:

1.remove "air bag " cover held in place with 4 hidden spring loaded clips

2. remove the fuse cover

3. remove the passenger side knee panel

4. remove the valence panel around the radio and Heater AC controls(exposes other fasteners

5. remove the 10"x2" corner cover panel, one screw at bottom, spring clip at top

6. remove all screws holding the top cover in place. Remove all screws holding the front passenger side cover panel

7. You should be able to lift off the top cover and the front passenger side cover exposing everything.

Because Freightliner went out of their way to hide fasteners and use hidden clips, which in turn break the plastic panels, they are referred to as "throw away trucks" . Removing and Replacing the valves are straight forward, although because they didn't give you even 1/4" more air line than needed, it requires small hands and lots of patience. Take a look at the other air connections in the neighborhood. If you see oil trails that means they are leaking also. Good time to see if the various air operated linkages for the heating system are not leaking, they fail frequently.

I rebuilt my entire instrument panel with about $1500 worth of parts about 5 years ago. The entire assembly starts to break because the AM/FM radios are installed improperly by the dealers, they just slide them in the DIN mount and don't install a bracket to hold the back of the radio, which bounces up and down and breaks everything. After i solved that problem, 5 years and 400,000 miles later, no breakage.

Jeff,

The info on replacing the valve helped, I had a couple of stubborn hoses but managed to get the valve the replaced. The dash part holding the valve was still good but the mounting tabs on the passenger side dash cover near the valves were broken, so I may see if I can exchange the parts.

The repair fixed the valves popping out but not the air leak when hitting the brakes, looks that is a a brake light switch down by a manifold below the valves and hopefully not the manifold.No one nearby has the switch so it may have to wait till Monday.

Dave

beyerjf · August 20, 2017

I just replaced my brake light switch. You are right, it slips into the manifold with one of those "chinese handcuff" type of push on connectors that is part of the manifold. I do not want to change my manifold, but I fear it is in my future. Those push on connectors are great for the manufacturer in assembly but eventually fail with enough vibration.