Wiper motor air leak

richard5933 · October 03, 2018, 04:16:26 PM

It rained during our recent two-week trip to the east coast. A lot.

Prior to the trip, the air gauge would hold 90+ psi overnight. It would take a couple of days for the tanks to fully empty out. Air bags hold air for weeks (or longer, I guess, but we haven't stayed still longer than a few weeks.)

During the trip we used the wipers. A lot. I kind of grew accustomed to the quirky speed adjustments. I even got pretty good at getting them parked the first time I tried.

One bad note though - during the trip I noticed that the air gauge was going down faster. By morning we'd be down to 60 psi. Or maybe even down to 30 psi.

The last time this happened I found a fitting on the driver's wiper system that needed to be snugged up. Today I went out to check and see if there was another fitting that needed a little wrench action. What I found instead was that the passenger wiper motor was leaking out a small amount of air.

I aired up the bus to 120 psi. Of course, now more air was leaking out. Then I ran the passenger wiper a few cycles and parked it again. This time I didn't hear any air leaking.

Is it normal for the park position of these things to start leaking air? Is it difficult to re-seal the motor? Is it even worth the effort?

Or, is the leak not in the motor at all but in the hand control (switch)? I looked in the manual and see that there is a parking plunger in the hand control which has an o-ring. Possibly this is where the leak is?

Any advice from those who have rebuilt and/or repaired these things would be appreciated.

Not wanting to replace with electric right now. I know that option is out there, but I don't think the situation is anywhere near to the point I need to go down that route right now. The wipers work well, other than this issue. Eventually I may have to go electric, but if this air leak can be solved with an o-ring that's my preferred route.

chessie4905 · October 03, 2018, 05:21:06 PM

Forget electric unless you cobble up something. Nobody offers any conversions for GMC's at any price. I replaced my wiper controls. Luke had them and not that costly. I also got kits and rebuilt the motors. After 35 years, o-rings and seals shrink and crack. The manual shows you how to rebuild them. Be careful of getting the indexing marks correct on reassembly. You need a spanner wrench to get the big nut off the main wiper shaft. They are reversible if you switch the valve body. Its the 4or5 inch tubular shaped piece attached to the main unit. Inside the valvebody is a shaft with o- rings. Later models utilized nylon or plastic and tend to crack around the threaded air line ports. Be careful with them. Older ones were diecast and more robust.
Even though your coach is in such great shape with low miles, you are seeing that some things are gonna need maintained.
Btw, have you ever changed your differential oil?

richard5933 · October 03, 2018, 05:54:36 PM

Thanks for the info. Maybe I will start with the wiper controls. Seems like the path of least resistance, and for now I am leaning towards the leaking at park being the fault of the control.

Luke/Bill replaced the differential seal last summer before I bought the bus. I'm assuming that the oil was changed at that time. I'll have to check the paperwork to confirm. Is this a known problem area?

chessie4905 · October 03, 2018, 06:05:03 PM

As rare as the 4 1/8 rears are, I'd take good care of it.

richard5933 · October 03, 2018, 07:01:47 PM

Quote from: chessie4905 on October 03, 2018, 06:05:03 PM
As rare as the 4 1/8 rears are, I'd take good care of it.

I just pulled the invoice from what Luke & Bill did last summer. Apparently the pinion drive bearing seal was replaced, but I don't see any differential fluid on the invoice. From what I can tell this seal can be replaced without draining the differential, so there's no telling when the differential oil was last changed. I'm assuming that the original owner did some maintenance on the bus, as he owned a charter bus company and kept the bus there, but there's no was to know for certain.

When the bus was in his shop last week Bill did check the differential oil level, which was okay.

Other than knowing the oil level in the differential is okay, I know nothing about the age or quality of the oil. I'll have to add this to my list for the spring maintenance, probably along with repacking the wheel bearings at all four corners. We're not going to put that many miles on between now and then, so I'm guessing things will be okay for now. Book calls for 140 wt multi-purpose gear lubricant, which I assume is still the fluid of choice.

richard5933 · October 11, 2018, 04:06:41 PM

So, I got the new wiper control valves from US Coach today. The valves currently in the bus have one end port (air in), and two side ports (output and park).

The new valves have all three ports on the end of the valve. Apparently the end port valves are the replacement for the old valves and the side port valves are NLA.

The bus is plumbed with copper tubing with flare fittings. I'm going to assume that it will be very difficult to reconfigure the existing copper tubing to change over to the end ports without danger of crimping the tubing or otherwise causing problems.

I know that there are new-fangled ways to run air lines using a nylon/plastic tubing which is much easier to work with and much easier to bend around obstacles. Can someone point me to information about this? I'm going to need to connect it to the feed from the wiper air filter outlet and possibly to a few existing flare fittings, so I hope that there are ways to accomplish this without reinventing the wheel.

Thanks.

chessie4905 · October 11, 2018, 04:32:17 PM

I changed mine over to dot nylon tubing and fittings. I got my tubing and fittings from McMaster Carr. Tubing is 1/4" and you reuse fittings. You can reuse nuts, just get new dot ferrules and reinforcement inserts from them also. Made it much easier to plumb in my pulse wiper control also, which works nicely btw. Just finished it today.

richard5933 · October 11, 2018, 04:35:47 PM

Quote from: chessie4905 on October 11, 2018, 04:32:17 PM
...you reuse fittings...

Flared fittings as well? Or are the fittings that look like flared fittings actually compression fittings?

Also looks like there are two sizes of tubing currently in place, but it's hard to tell for certain since some is covered with a braided wrap/cover. Are these tubing measurements OD or ID? Then I can check with calipers to see if it's all 1/4 or if there is some 3/8 mixed in.

luvrbus · October 11, 2018, 04:57:03 PM

The nuts on air line are longer to handle vibration they can be flared or compression those are not nuts you by from your local Ace Hardware.They are B/W (Bendix Westinghouse) nuts,flares,compression and the threads are different

richard5933 · October 11, 2018, 05:14:44 PM

Are these fittings a NAPA item or am I going to be ordering everything from the internet? Milwaukee has quite a wide range of supply houses, but I've never shopped for things like this. Something the truck parts counters would have?

Feeling a bit overwhelmed for some reason on this, mainly because I have no idea of how much or what kind of tubing I'll need or how many and what type of fittings I'll need. Probably won't know until I get the thing taken apart. It's been a rule I've followed for a while to not take things apart until I've secured all (or nearly all) of what will be needed to put it back together. Sounds like that might not be the case on this project.

chessie4905 · October 11, 2018, 05:36:14 PM

https://www.mcmaster.com/air-brake-lines.

1/4 inch od. The connections are all compression fittings. You use New 1/4" ferrules and inserts in end of tubing to keep it from collapsing when you tighten the nut. Reuse the old nuts as they are dot. and threads are different from lowes or ace hdwe, etc. Just buy a 10 foot roll of dot 1/4 tubing, compatible dot 1/4 inch ferrules and inserts for 1/4 dot tubing. The Parker stores carry fittings and nuts,etc. Our local one didn't carry any tubing. I've also purchased the tubing from Ebay. Just make sure you are buying dot nylon tubing. The next size larger tubing is 3/8" which may attach to the air filter. If you have any 3 /8" in your system, just buy tubing, ferrules, and inserts for that size also.

richard5933 · October 11, 2018, 06:31:51 PM

Quote from: chessie4905 on October 11, 2018, 05:36:14 PM
https://www.mcmaster.com/air-brake-lines.

1/4 inch od. The connections are all compression fittings. You use New 1/4" ferrules and inserts in end of tubing to keep it from collapsing when you tighten the nut. Reuse the old nuts as they are dot. and threads are different from lowes or ace hdwe, etc. Just buy a 10 foot roll of dot 1/4 tubing, compatible dot 1/4 inch ferrules and inserts for 1/4 dot tubing. The Parker stores carry fittings and nuts,etc. Our local one didn't carry any tubing. I've also purchased the tubing from Ebay. Just make sure you are buying dot nylon tubing. The next size larger tubing is 3/8" which may attach to the air filter. If you have any 3 /8" in your system, just buy tubing, ferrules, and inserts for that size also.

Thank you - that does clear it up. All I need to have on hand is the tubing, ferrules, and inserts. I'll lay in a supply and try and get it done before the temps get any colder. (Seems like winter is in a hurry to get here this year.)

I'm going to take from this conversation that I was correct in assuming that it was pointless to try and reuse the old copper. That being said, I plan to replace from the air filter up to the valves and then to the wiper motors.

luvrbus · October 11, 2018, 06:56:52 PM

Everyone does different but I don't uses the plastic DOT lines close to a dash ,I have seen the stuff melt when a wire shorted out and you have to make long sweeps or it kinks ,mice love it,one thing it is cheap and easy to work

richard5933 · October 11, 2018, 07:12:32 PM

If the connections are all compression fittings, the I could just bend new copper to do this as well, correct? I've always had much better luck bending new using a bending spring than trying to re-work old lines.

If I decide to go with copper for all or some of the lines, is there a particular variety of copper that is used in these air lines? Something tells me that I can't just use the stuff sold at Home Depot if it's going into the air system.

luvrbus · October 11, 2018, 07:27:41 PM

NAPA sells the DOT copper so does the Truck Supply parts houses