The air throttle pedal on my GM 4108 started making a noise today, a slight 'farting' sound when the pedal is released. I imagine that the cause is a dry seal or o-ring inside.
Anyone have information on the process? This is the OEM air throttle, and the book talks about rebuilding the assembly if it doesn't operate smoothly but contains no instructions on doing so that I can find.
The air throttle pedal on my GM 4108 started making a noise today, a slight 'farting' sound when the pedal is released. I imagine that the cause is a dry seal or o-ring inside. Not a major issue as the pedal still works okay, but I'm sure that it's not going to get better on its own, only worse, especially if the o-rings are getting dry.
The pedal itself seems like a bugger to pull off, with the two air lines being inward of the brake treadle and its maze of air lines below the floor. You have to be a contortionist to even put a hand on the air line fittings, let alone turn one.
Any advice or suggestions would be welcome.
Remove the panel between the headlamps. Behind it is a handhold, approx 4x6 held with 4 Phillip's screws. You can access those fittings through it. OR, you can remove spare, lay on your back in the hole and remove the large ceiling panel, about 8 or 10 small cap screws. I found this panel after cleaning and rebuilding my brake components through the compartment under driver. What a bitch that was.
Oh, if you need to order a kit from Luke, make sure it is the correct one. The one I got wasn't correct. Fortunately mine was ok.
Quote from: chessie4905 on September 07, 2020, 06:28:11 PM
Oh, if you need to order a kit from Luke, make sure it is the correct one. The one I got wasn't correct. Fortunately mine was ok.
How do I know which one is the correct one? There are numbers on a tag on the valve assembly. Anything else I need to know?
How difficult is the rebuild once I get the kit? Anything that I should watch for that might shoot out of the thing as I open it up? Any secret sauce necessary?
From the parts book, it looks pretty simple, but I've never opened one of these before.
I am lazier than sin, and hate taking things apart when there's something else to try first.
If you think it may be dry... feed it a careful dose of air tool oil and see what happens?
You were all fired up to dig into it anyway, so nothing ventured, nothing lost?
Happy coaching!
Buswarrior
Quote from: chessie4905 on September 07, 2020, 06:26:35 PM
Remove the panel between the headlamps. Behind it is a handhold, approx 4x6 held with 4 Phillip's screws. You can access those fittings through it. OR, you can remove spare, lay on your back in the hole and remove the large ceiling panel, about 8 or 10 small cap screws....
I found the access panel(s) from the front that you mentioned. Should make it easier to get the air lines removed, for sure.
Quote from: buswarrior on September 07, 2020, 06:44:58 PM
...If you think it may be dry... feed it a careful dose of air tool oil and see what happens?...
Buswarrior
Air tool oil? Is this the best option? Is there anything that is close to Parker O-lube which will flow? (That stuff is more like thin grease). Is mineral oil compatible with the o-rings and seals? Just afraid to put something in there which would make things worse.
Ditto what buswarrior said - lubricant.
I wouldn't think you could go wrong with introducing some air tool oil upstream... IMO
I wouldn't try oil with that diaphragm. But diya. You will need to disconnect the two lines AND remove elbows on end of extension nipples, unless they thread out easy. Pretty tight to get them loose. They are different diameters, so can't be mixed up. Better to leave nipples on. You will need to remove bolts that attach unit through floor.
Your air tools have seals, etc in them, so one would hope it will be friendly to automotive air valves.
I hope everyone is lubricating their air tools?
Happy coaching!
Buswarrior
Do mine occasionally. That air throttle doesnt see oil easily from the air routing. Mine was totally dry. Maybe the diaphragm is made out of air bag material.😊
The sleeve becomes pitted from moister over time and they need to be replaced,oil I don't know the repair kits come with a special grease for assembly,the bolts will break is why a kit comes with all new bolts.I get my kits from the manufacture Brake Service in Portland Or
I talked to Luke this morning, and he didn't think it would help to put lubricant in upstream. He had the correct rebuild kit in the shelf and is sending it out today.
The screws that come in the kit - I assume those are the ones that hold the two halves of the outer shell together. Will I need any special technique to get them out if they are prone to breaking? Don't want to make this more difficult than necessary.
Does look like the kits come with a bit of lubricant, but I've also ordered some pneumatic tool oil to have on hand for future use. Found one by Super Lube, a company I've generally found to have good products.
They either come with or you fabricate a ring from cardboard to assist in getting the bellows to fold over itself. Similar to how the air bags do on newer coaches. Those little screws should remove easily on yours since it is in such good condition.
Bellows??
Searching online, this looks like the parts that come in the kit: https://www.accupart.com/wil417103-kit-major-wm90dx-type-valve-modulating/
Looks similar to what the GM parts book shows.
Quote from: richard5933 on September 08, 2020, 12:42:01 PM
Bellows??
Searching online, this looks like the parts that come in the kit: https://www.accupart.com/wil417103-kit-major-wm90dx-type-valve-modulating/
Looks similar to what the GM parts book shows.
I
I don't know which throttle you have but I know what Chessie is talking about I call it a loader that comes in the kit,a different kit than shown
Any suggestions on which thread sealant to use when reinstalling the brass elbows on this thing? Lots of choices from Loctite and Permatex - not sure which is ideal for this application, or if not ideal which is correct.
The one you show looks right for pedal end the one I was talking about is the engine end actuator. Sorry for the confusion. Been two years since I did them.
Rebuild kit came in today. Rain stopped for a while, so I was able to get the pedal assembly pulled and on the bench. The kit had apparently sat on a shelf for a while, but everything in the kit looked good and correct, including the rubber o-rings and such. The only thing that looked odd to me was the brown grease they supplied - where they had pre-applied some to a part it was looking chunky. So, I substituted some Parker O-Lube I had in the shop. Hope that was an okay substitution.
Pulling the pedal was not too bad once I got the access port opened. Still basically working blind, but it went without problems. Going back in will be more difficult, as I'll have to reinstall the elbow fittings and then try and line up the copper lines and their compression fittings. I've got some nylon air lines I can use to replace the last bit of each one if lining up the copper proves too difficult.
The rain came back just as I was about to reinstall and test. Drats. Hopefully Sunday will have better weather. In the meantime, I hooked up the pedal assembly to the shop's air supply to do a little bench testing. Looks like everything works, and good news in that the free play in the pedal is gone. The photo below will show that it was a good thing I decided to rebuild the pedal assembly, as the crud in there was only going to continue to make problems for me.
When I rebuilt all of my air system, I replaced almost of the lines under there with dot nylon. Much easier to connect, especially the brake valve.
Quote from: chessie4905 on September 11, 2020, 07:27:24 PM
When I rebuilt all of my air system, I replaced almost of the lines under there with dot nylon. Much easier to connect, especially the brake valve.
Still might do that, but only on the air throttle. No real need to touch the brake valve right now - it's not in my way and there are no leaks.
The feed line for the air throttle connects to the air regulator in the tool compartment and terminates at the air throttle, also in the tool compartment. It's easy to reach on both ends and will be easy to replace with nylon if needed.
The output line is a 1/4"OD line going from the air throttle back towards the bulkhead. There is a union coupling about 12" rearward of the air throttle, so if I find it difficult to reconnect the copper line I can replace the piece from the air throttle to the union. Not as easy to get to at the feed line, but doable.
First attempt will be to reuse what's there. If that takes too much work I'll switch to nylon. I have enough left from the wiper valve replacement to do the change if needed.
I went to nylon on the brake valve lines because there was no way to get those big copper lines reconnected without cross threading. Remember, I was working through the under driver's compartment. I didn't discover the access panel in spare tire compartment till after I was done.
I got the pedal reinstalled today. Went pretty well. The 1/4"OD output line reconnected with minimal struggle. The nipple for the 3/8"OD supply line ended up about 30 degrees off where it was before, so there was no way to get the copper back on. I installed nylon to replace it and carried on.
Not sure I like the nylon so much though. I checked on the lines I installed last year on the wipers and found them to have developed a few minor leaks. Took a turn or two on each to snug them up. I don't like that they settle in so much.
Maybe you didn't tighten enough in the first place.
Road tested the pedal today and everything seems fine. Pedal felt pretty much as it did before, only with less free play and no more farting noise when letting up on the pedal. I'm calling this one completed.
Quote from: chessie4905 on September 13, 2020, 04:33:18 AM
Maybe you didn't tighten enough in the first place.
Just how tight is 'tight enough' with the nylon air lines? Always afraid I'm going to over tighten the fittings, even with the metal insert inside the tube.
Probably a spec somewhere. Did you use dot style ferrules or the smooth sided barrel shaped? I do mine by feel from personal experience.
Quote from: chessie4905 on September 13, 2020, 04:00:05 PM
Probably a spec somewhere. Did you use dot style ferrules or the smooth sided barrel shaped? I do mine by feel from personal experience.
DOT for everything. I'll have to dig a little and see what specs are out there. Wonder if they even make a torque wrench for stuff like that though.