| Author | Message | ||
| Russell Beam (Rcbeam)
Registered Member Username: Rcbeam Post Number: 68 Registered: 11-2009 Posted From: 74.131.51.228  Rating: N/A |
Decided it was time to investigate some air leaks today, so got out the soap squirt bottle and crawled into the spare tire compartment. Found a couple of fittings that just needed tweaking but the big item was a square silver thing that had the marking of QR1 on it. My pressure regulator for the blower belt tensioner has been leaking out the weep hole for a while, but when I sprayed it down, I had a whole nest of bubble all over it. So it was leaking much worse than I thought. Also found the air control for the missing shutters leaking lots of places so I am just going to remove and cap the air line for that. Called our good busnut friend Luke and he said the silver thing was a quick release valve (guess the QR1 was a big hint for him). He is sending me rebuild kits for both the pressure regulator and the quick release valve. I also looked at the tires on the rear. I could not find the DOT date on the drives but I found it on one tag... was 3301. Had no idea the tire was this old. The drives look really good and I cannot find any cracks any place but can't find the date either. Not sure if they put it one both sides or not. I've not really had the bus on the road much since I've had it, but guess it's a good thing. I put new steers on last fall but looks like I need 6 tires for the rear now. Guess that will take care of the best part of 3 grand. My two fronts installed were just change under $1k for the pair. Received the kits from Luke Friday and proceeded to rebuild the parking brake QR1 first. PROBLEM 1: Only two parts in the kit, diaphragm and grommet (o-ring). When I read the OPERATION portion in the manual page 4-19, it says in part "...the diaphragm spring forces the outer edges of the diaphragm against the body seat." in paragraph 2. I could not find a 'diaphragm spring' in my QR1. When I reassembled and installed the valve, aired up the bus I STILL have air leaking out of the exhaust port when the parking brake is SET, but not when released. Same condition I had before I rebuilt the valve. The diaphragm was hard in the center and so it still needed to be rebuilt, but now I have no clue why it still leaks. Could I have a leaking parking brake chamber feeding back through or something wrong some place else causing the leaking out the exhaust port or am I missing a diaphragm spring? PROBLEM 2: I also rebuilt the pressure regulator for the blower belt tensioner. It leaked out the weep hole in the back of the regulator and when I sprayed it with soap bubbles, it blew bubbles from everywhere really bad. After the rebuild I have just a few very small bubbles around a couple of screws and I snugged them down good but I have LOTS of air out the weep hole... so much that I could hear it leaking all the way from the front of the bus. It is leaking much worse out the weep hole now than it did before I rebuilt it. So I shut it all down, closed up shop and came home. On the drive home I thought about the fact that I had not yet adjusted the air pressure to 21 lbs... I did install the adjusting screw the same number of turns as before, but have not checked the pressure. I was told by a bus mechanic friend of mine that the leaking out of the weep hole is due to a leaking air cylinder but when I asked Luke about it when I ordered my kits, he said he had never heard of that. So any ideas on what I should check or do next to address the two leaking rebuilt valves? I just got back in from trying to adjust the pressure on the blower belt tensioner pressure regulator. When I hooked up my guage, it ready 35 psi, so I backed out the bolt on the back... the lowest it would go is 26 psi with the bolt almost ready to fall out. When I screwed it in, the pressure went up but the leaking out the weep hole slowed down. At any rate, it won't adjust down further than 26 psi. It looks like to me the regulator is backwards. The control valve is plumbed to the outlet side of the regulator with the inlet side going to the test port and the rear most hose on the air cylinder. Maybe I just don't understand it. I'm lost. | ||
| Jack Conrad (Jackconrad)
Registered Member Username: Jackconrad Post Number: 1414 Registered: 12-2000 Posted From: 75.216.239.210  Rating: |
To track down the air coming from the exhaust port on the QR1, clamp the lines (1 at a time) going to the drive axle brake chambers. Sounds like you might have a leaking DD3 diaphram. If I recall correctly, the belt tensioner regulator is supposed to be set at 35 PSI Jack | ||
| Russell Beam (Rcbeam)
Registered Member Username: Rcbeam Post Number: 69 Registered: 11-2009 Posted From: 74.131.51.228 Rating: N/A |
Removed the regulator valve again today and opened it up to check things inside. Put it back together, and installed it the correct way this time. I put it back on like I found it originally but it looked to be backward to me, so today I reversed it. The control valve in going to the IN and not the OUT like it was. Now it works, I can adjust the pressure to 21 lbs (metal tag on back of it says 21 lbs) and best of all it doesn't leak out the weep hole anymore. Jack, I've been thinking about your idea of a brake can diaphragm leaking. Brian on the other board mentioned that that was the purpose of the QR1 was to vent pressure from the brakes, so DUH... the light came on for me. Since it is the parking QR1 I guess I have a parking diaphragm leaking. Looks like it is time to rebuild the DD3's. Is this a hard job? Can I do it with common tools? Anything I should know? Any advice? | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 2153 Registered: 10-2003 Posted From: 71.58.71.157  Rating: N/A |
They aren't that difficult to rebuild.You can obtain all the rebuild parts from Mohawk Bus parts. Not hard to repair; you need to remove both units, disassemble and inspect/ clean all parts, then order what needs replacing. At least both diaphragms and all o-rings and anything else that looks bad. Mark the units for right and left side so the drains point down when done. Also, put index marks on the main body and ring and end cap so all the hose connections are lined up properly as before. You will need a repair manual, which you should be able to down load from the Bendix site. Some have commented that occasionally the main center section is corroded so bad inside as not to be reuseable. Mine were ok. Figure on about 250 bucks for the parts for both; more or less. If this job seems more than you want to tackle, Luke sells rebuilt units for a good deal more, but saves all the work. You can't get new ones any more for last several years. Although somewhat costly to repair compared to the now more common maxi's. Once this job is done, you'll probably never need to do it again. While you are at it, you might want to consider adding an air drier down the road. | ||
| Russell Beam (Rcbeam)
Registered Member Username: Rcbeam Post Number: 70 Registered: 11-2009 Posted From: 74.131.51.228 Rating: N/A |
John: thx for the info. My bus already has an air dryer, although it probably needs work too. So far it seems everything needs work. |
