| Author |
Message |
Larry Bennet (Eurof3) (152.163.100.133)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, October 15, 2004 - 1:13 am: | |
Can someone tell me what it takes to fix, clean, lub or replace my pressure release valve on my MCI 96A3.
When my air gets to the 140+ psi zone it pops off as normal and the valve seals up fine. But as the air goes down the valve seems to open and release quick little bursts of air until I get low air lights.
Just a little touch of a finger make the valve snap closed. I have sprayed WD40 on the outside and up in from the bottom to clean it up and lub it. Still wants to be a stinker or sticker.
Does this pop off valve come off for cleaning somehow ? Thanks for any advise in advance !
Getting tired of crawing under the front bumper.
But very thankful for 29 nights on board sense June and this was the only problem of the summer.
Larry, A Bus Nut in Michigan |
Bus Jock (4.41.169.129)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, October 15, 2004 - 9:57 am: | |
Larry,
Sounds like the Pop off is working correctly. It is there to prevent exploding your tanks with over pressure. When it pops is should take the pressure way down. Pop off valve ( safety valve) tripping is a serious matter. It means that your compressor govenor is not unloading your compressor ar 120 PSI as it should (starts at 90, off at 120# A new regulator is about $25-30 at any truck parts store, sometimes at NAPA. Easy to replace.
Please don't drive until you have the compressor properly fixed. Those tanks can be a real BOMB!
Jock |
BrianMCI96A3 (69.34.169.50)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, October 15, 2004 - 10:30 am: | |
Yes, I am totally in agreement with Jock, you most likely have a problem with the governor...
Thank your lucky stars that your relief valve was working.
I'd replace the governor and build air in the system, this time the AIR DRYER should blow a short burst of air at 120 psi
If your air dryer hasn't operated for a long while it may have a bunch of crud in it
I'd let the air build and cycle the dryer a few times
If you still find the pressure relief valve leaking, I'd replace it with a new one, they are not that expensive and as Jock mentioned those tanks can be like bombs, the safety valve prevents them from going off.
Brian |
Buswarrior (Buswarrior)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, October 15, 2004 - 11:13 pm: | |
Hello all.
The weakest point in our air system is the one that will let go first. Rubber or plastic lines, compression fittings slipping apart, diaphragms, rubber seals inside the various valves, the flex line off the compressor and the like.
The 150 lb setting on the safety valve is intended to protect the soft bits. The metal tanks are not going to blow apart that easily!
Is there anyone on here who could give us an idea of the pressure needed, and how a metal air tank might fail under a gradually increasing pressure to bursting?
happy coaching!
buswarrior |
Niles (Unregistered Guest)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, October 16, 2004 - 1:12 am: | |
BW - I think it would depend on the type of metal the tank is composed of and the max pressure of the pump - don't most of the pumps put out max pressure at 150 psi ? steel is some what pliant , aluminum will not contract once it has been over expanded and the threads for the fittings are acutely vulnerable to failure (all these things I recall from my days of scuba diving)
Niles |
Stan (Unregistered Guest)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, October 16, 2004 - 8:33 am: | |
New tanks are likely pressure tessted to double the safety valve pressure (300 PSI test). Most of us have busses with severely rusted tanks and the bursting pressure is completely unknown. |
BrianMCI (Unregistered Guest)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, October 16, 2004 - 9:03 am: | |
Stan has his finger on the real trouble, sure our tanks are burst rated, but just how long ago was that for most of our equipment?
I don't know about you, but a system that has a relief valve that is poping off AND appears to be malfuctioning a bit, scares the daylights out of me.
Brian |
Larry Bennet (Eurof3)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, October 16, 2004 - 1:28 pm: | |
Wow thanks Jock and Brian for the information.
I am not sure if I am talking about the same item. Please understand I am not experienced in dryers or or air tank pop off valves (safety valves)yet !
I took a close look at my air gauge with my glasses on and at 120 or a little over it lets out a short burst.
What my point is, I beleive this burst to be coming from the bottom of the dryer not from an air tanks safty valve. The burst comes from the bottom of a centered 8 inch cylinder centered between the front wheels which must be the dryer. Not a safty refeif valve on an air tank.
So 2nd question can this dryer valve be replaced.
My mistake in the original question was the high air presure. And thinking the dryer was an air tank. My coach never goes over 122 or 123 befor the air pops off a burst. NOT 140+ sorry.
What I do not understand is why this seals up after the 120 burst and as the air goes down to the 90 recycle it starts to let off more air causing low air. Just a touch of a finger makes it snap back up and seal then my air climbs back to 120 and lets off. The air holds for a long time befor this dryer valve opens a little and causes low air again.
My coach is in very good condition rust and line wise and never has trouble with air. The dryer lets off about 1 or 2 times an hour depending on stops or highway driving. The dealer run it with me and it was the same air burst in all the other coaches I test drove.
I see this as an air dryer release problem not an air tank high presure problem.
What I have done is get my buddies service manual and will be doing catching up on my diesel macanic`s. Looking forward to your reply.
THANKS SO MUCH. Hope it did not post this 2 times. Larry |
Jim Ashworth (Jimnh)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, October 16, 2004 - 2:13 pm: | |
With the further details, what you describe is normal dryer action, except the valve on the bottom is probably dirty which makes it stick. Disconnect the airline and wire from the cover, remove the three 1/4" bolts and push the cover up into the can about 1/4". Remove the large snapring and then pull (wiggle) the cover out. Check for dirt and clean with an airhose. Then remove the huge nut in the center and clean the valve. Re-assemble if parts look good.
There is nothing that is going to fly apart in this asembly. There is no air under pressure to harm you if the engine is off and the governor has "popped off". Worst part of this job is getting the bus safely high enough to get under it.
One other thing to look for is the amount of oil inside the can. There will be some, mixed to a milky color if the compressor is ok. If there is black oil, the compressor needs changing. While you're under there, it would be a good idea to change the dessicant cartridge. Only $30 or so, exchange. With winter coming, it is a good time to have the air dryer in good condition.
Jim |
Larry Bennet (Eurof3)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, October 17, 2004 - 12:35 am: | |
Thanks Jim for the most excellent instructions on the valve cleaning. I was sure this was no big problem. I will be printing your instructions.
Also I will be reading about the dessicant cartridge in my copy of the service manual I now have made from my buddies copy. Again the dessicant cartridge is new to me also and I will do the right thing and take care of it.
In anticipation of being under the bus, I had pulled the bus up on some wood blocks when we parked it from Last weeks run to Holiday Inn. Yes it took a few tries to get the front end up some.
This should get me some room under it to make the repair.
What a great time at the Holiday Inn. They had 30 amp hook ups, water and a dump station for $45 a night. They wanted $180 for a room by the pool. The kids had a blast in the 100 foot long pool with hot tubs on both ends of the pool. So did dad and mom enjoy our 29th night on the coach. Seems strange pluged in at a Holiday Inn with a picknic table, out side grill and a golf course. Sad to see my bus time slowing down for winter.
Sorry to rattle on.
Again thanks for everyones input. Its nice to have BNO to get such quick answers. Thank you to BNO for being there. Hope to send some of my photos of our beautful 96A3 to BNO.
Proud owner of the MCI "Naturopath". Larry |
BrianMCI (Unregistered Guest)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, October 17, 2004 - 12:42 am: | |
Seriously, if the situation is as you say, then no, you do not have a problem with the relief valve...
And, believe it or not, a few months ago I ran into almost this exact problem on an air system.
The work order for the job mentioned a leaking air dryer...
At that time I KNEW it was not the dryer because I could see that the dryer had been replaced recently.
As it turned out this same problem had cropped up on this truck a couple of months prior and the road mechanic had simply replaced the whole dryer...to save time I suppose
Somewhere in the back of my mind I knew I had run into this same situation years before, and remembered that the problem had nothing to do with the dryer, and everything to do with the governor.
I have to believe you have the same problem, replace the governor and you'll be good to go.
Having said that, I do suggest you service your air dryer, and the purge valve on the bottom of it as it probably has been a long time since that has been done.
For that matter, I suggest anyone who has no idea when the last time their dryer was serviced do so, because a lot of ills in the brake system are avoided by a properly working air dryer.
The do last a long time, but fresh dessicant will only make the dryer function at it's peak.
Brian |
Larry Bennet (Eurof3)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, October 17, 2004 - 1:50 am: | |
Hay Brian
Can you tell me where to locate the governor and a little about its replacement. Again I am not sure of the location on the coach or what it looks like.
Where might I order one or get a replacement.
With our coach as with any coach owner. My biggest worry is air, then I hope for no tire problems....
Again can`t thank you all enough for the concern, powerfull pointers and advise.
Larry |
TWO DOGS (Unregistered Guest)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, October 17, 2004 - 9:17 am: | |
gov. is located on the air compressor...8v71 ,it is left rear of engine...has two bolts that hold it on..it's about the size of a pack of cigarettes,with a rocket ship looking thing comeing out of it... |
BrianMCI (Unregistered Guest)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, October 17, 2004 - 11:13 am: | |
Just like Two Dogs says Larry... Can't hardly miss it... Maybe 15 minutes to change if it's in a REALLY REALLY tight spot.
Brian |
Jim Stacy (Unregistered Guest)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, October 17, 2004 - 8:57 pm: | |
Changed one 60 days ago. New style was VERY tiny, $12 new (not reman), and didn't have an exhaust port, but it worked fine.
Jim Stacy |
Larry Bennet (Eurof3)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, October 18, 2004 - 8:50 pm: | |
Thanks all for the pointers.
The Dryer valve was dissasembled and cleaned. I am Happy to say I am back to normal operation and sealing up holding air psi as normal.
The Governor inspected and looks like a new or replaced item. I am Not changing the governor. But am now aware of what could happen to it.
I got my binder for my service manual copy. Or I should say my wonderful wife got it for me...Man its chucked full infomation on everything ! What a referance yes yes yes.
Again thanks Jim Ashworth for Instructions.
Larry |
Jim Ashworth (Jimnh)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, October 18, 2004 - 9:16 pm: | |
You're welcome, glad it helped.
Jim
PS Where do the new smiley faces live? I needed one for this post. |