Suspension Creak

[jack14r]

Close,18,040 Lbs. but I knew that.I had Liberty add 2,8D batteries for a total of 6,and I have added a freezer,etc.all of this is in the front two bay areas.

[Jeff Bayley]

I'm getting the bus serviced as I write this over a pit in MN. Found a place here that owns a Tour Bus company (all Prevosts, mostly my vintage) and the mechanics are all Prevost trained / certified. That means they learned how to bill for an hours work while standing around the water cooler for half that time. 101 first thing they must teach at Prevost training.

I don't have a bundle to spend right now and am only wanting to address the anything critical. I'm posting this here because one of the issues is with a leak in the air system making the bus lean but it's not bad and an initial search didn't find the leak so I'll probably let that ride until it get's worse and subsequently easier to find. But I was looking for Jon's post on full replacement of the air components in the suspension system. Can't find it. Maybe Jon or someone else remembers that thread for me to re-read it. They are putting a new cartridge in the air dryer for the main air system on the coach. I just found out that was supposed to be serviced (duh). I've had the coach 50,000 miles and 5 years and never changed it and who knows when it was changed before I got it. Is a cartridge change usually adequate or do you need the whole "Kit" as Prevost calls it. Mechanic here seem to think the cartridge change is adequate.

I had the undercarriage lubed at Oreen's shop a few months ago but I might as well have them relube it again since the guy was on a crawler and now I'm on a lift and first guy could have missed some fittings. Checked the brakes at Oreen's also. Since I'm 7 years into bus ownership and continually finding out "I didn't know about that maintainence item", can anyone suggest other obvious PM stuff they should check while under the belly of the beast ?

[Jon Wehrenberg]

Unless a bus company has buses with level-low systems (which I doubt) fixing the leans can produce a bill somewhat akin to the California debt.

In simplest of terms the components likely to be the cause of the leans (not in any particular order) would be the air bags, the five port Norgren valve for that location (front, LH rear, RH rear) or in the case of the rears the three port valve between the drive and tag axle air bags.

Obviously fittings can leak either at the air line or where they thread into the components, but if they haven't leaked previously they are not high on the list of things I would suspect.

I think replacing the air dryer only was the correct thing to do, and I hope he also drained the air tanks, starting with the front working rearward to both drain moisture, but to also verify the protection valves are working.

BTW, moisture in the air system will mess up the Norgrens if they collect moisture and corrode. Failure to service the bus and air system regularly is much more expensive than servicing it per the Prevost maintenance schedule that can be accessed through the Prevost web site.

[Jeff Bayley]

Jon- First, thank you for your reply.

Yes, they drained the tanks and said there was not a lot of water in them. After changing the cartridge, they purged the system several times by bleeding the air off by way of multiple pressing of the brake and letting it recharge. They said this was somehow a process after changing the cartridge to insure it was (primed ?,) or so to speak. I feel like I'm in competent hands, at least more so than a Prevost service center frankly but of course doing the job yourself is the best way but I'm outside my knowledge base here so have to divert to them. My understanding (from them) is that changing the cartridge will do little to clean up any moisture in the system and do repair. That if that moisture got past the filter it's there to stay. Is that right ?

[Jon Wehrenberg]

If it got past the cartridge is is going to be in the tanks and in the system, but unlikely to be in the form of water in the system. Any reaching the tanks should have been removed by bleeding the tanks down to zero in turn. If any pressure remained in the tanks it would allow water to remain.

I think what they did with respect to the braking system is push air that has passed through the new dryer cartridge into the brake system and likely purged any moisture laden air. That's a guess.

But unless they did this also, they failed to exercise the entire suspension system which uses auxiliary air. By raising and dropping the coach a few times the aux system air was also purged. If you want to get it all blow the horn, sit on the driver's seat, exercise the door lock, etc.

Your air system is always exhausting air so normal operation of a system with a new cartridge and tanks which have been drained will have dry air throughout. Even as you drive the airbags are inflating and deflating in response to the bus normal movements.

[Jeff Bayley]

Thank you again for the reply. There seemed to a lean (the last few days only). Maybe it was just an intermittent problem. It's gone for now. Might see it again. I'll work the air system some more as suggested. My air loss overnight seems to be a bit less.