-
Air Leak or Pandora’s Box ??
-
We used to use CR seals almost exclusively until about the late 80’s and then started using more National and SKF. We saw less failures after the switch. I think that CR made some changes back then that was the cause of our problems. I have no idea about how they are doing for longevity today.
-
You guys don’t miss a thing. By plastic mallet I meant to say that the force generated by a few taps on the1X6 (S4S,KD, no crown, for your purest’s) sent the seal into it’s proper position. We did not use any form of sealant or cement.
I had the opposite side changed a couple of years back at a local truck repair facility after a leak was discovered during a routine LOF; that was about a 45 minute job for them from start to finish. I saw impact wrenches, sledge hammers et al, in use. When we did the job we were much slower, we cleaned everything in solvent, inspected and packed the bearings, used a calibrated torque wrench (we are required to have them recalibrated once each year). I bead blasted the dust cover, after a solvent soak and primed with zinc chromate and then repainted it with Imron, 4 coats with 2000 sand paper treatment between coat’s…..just kidding, we used a rattle can after a solvent wipe!
What I am saying is that with a modicum of mechanical knowledge, a few tools, a maintenance manual and access to a parts manual, these things are not difficult to repair. The parts are big and unfortunately they also tend to be heavy, as is the bus; safety should be your highest priority when doing these kinds of repairs. Also I do feel that these coaches are essentially bullet proof. I have a couple of 80 KVA power carts for larger jets, both have Detroits, one a 6-71 the other a Series 60 (I know these are engines not buses but I think you get my drift!). I think we change the oil on occasion, they both run quite nicely on Jet-A (fuel) and the engine times are in excess of 6000 hours, to my knowledge they have never been apart. I think it is easy to get in our collective heads that these are Ferrari’s, there not! At the same time they are not “dirt haulers” either so we essentially have to walk a fine line, with safety and safety of operation being the highest priority, course that 70″ TV doesn’t hurt anything either!
-
I think John is full of it. As an aviation guy I think he is trying to blend in with us shade tree mechanics but as soon as he used the term “rattle can” he was spoofing us. He used his aviation mechanic guidelines which (simply stated) require what he is working on to be as original or better. He has undoubtedly had the metal parts refinished, magna fluxed, yellow tagged, and the entire process logged.
All tools used were certified. Before he returned the coach to service he had a second set of mechanics sign off on it.
-
You forgot the safety wires…..unless they no longer use those…
-
The safety wires are the only thing holding planes together.
Actually as every plane owner on this forum will realize the only thing holding planes together, and up in the air is……..
Wait for it……………
MONEY!
-
Wait, I need to get my feet up in the air, it’s really getting deep here..
-
Safety wire? I’ll bet money that Jon has a full safety wire kit, couple of pairs of twist pliers in assorted sizes, 4-6 spools of SS wire in different gauges and a small spool of copper wire that is used on emergency exits and switches to be used only if necessary, provided that they are equipped with switch guards. Yes, for a few hundred dollars you too can make the cockpit of your bus look like the space shuttle, Colored circuit breaker collars add a nice finishing touch!
Ever been under the bonnet of a Dino? Put’s a whole new blush on the term safety wired! Got to be on your toes because the Italians use an interesting mix of rh and lh threads which, if done improperly, can make the entire procedure pointless, after all safety wire is designed to hold the component on and, in torque!
For field operations I prefer dye penetrant to detect cracks and imperfections. spray it on, wait awhile then spray the developer and any crack or defect will be manifested under a black light within 15 minutes. Look carefully at any threaded portions because cracks (IMHOP) tend to manifest there first! We had a magna-flux unit but it dimmed the lights in the neighborhood when we used it and that was with three phase power; obviously, it was far from portable.
A true purest would replace all of the hardware on these buses with AN, aircraft grade hardware. May want to dig deep in your jeans for the coin to pay for it but, all bolts, nuts, etc. can be purchased, pre-drilled for safety wire. There all treated with anti-corrosives and each nut, bolt, washer has been inspected to assure q.c. Step it up a notch and use stainless aircraft grade.
As for the inspectors, that was my job on this project. I even used my handy-dandy yellow stamp that states, “Inspected by 13”, after putting a small drop of torque seal (again I use yellow) on each nut, after checking for proper assembly and installation. I then completed the log book and endorsed, with my certificate number, an authorization for “return to service”.and presented myself with a hefty bill!
Now I head for the LID, the roof which I covered with Temp Coat a couple of years back. I am starting to have that sinking feeling that Temp Coat may be as the name implies!
-
John,
My garden can use some of that stuff you are spreading. Any chance you could ship some east?
I do have 3 gauges of stainess wire and 3 wire twist tools.
-
John,
got my lean and raise height fixed at prevost. Couple or 3 vavles and some leaking fitting. Got up under bus and they were showing me what they done. Those boys are good folk. Strange, they showed me Airbags and said they were original but didn’t need replaced for cracks this time and wouldn’t replace until they started leaking or went out. Asked if I kept/srayed any rubber protectant on them. No. only owned the bus 2 years. Well we will see. I can just see one blowing out at 75 miles an hour.
-
Glen shows how different people have different opinions on what constitutes an acceptable maintenance schedule.
Prevost has stated their position on air bag replacement is to wait until they leak. If I could be assured their failure would always be in the form of a slow leak I might subscribe to that schedule. But if one blows out or develops a leak the compressor cannot keep up with I am stuck with a bus sitting on the bottom of its suspension travel. Not safe to drive, and not easily raised to replace the bad air bag. So I have my self imposed 10 year plan.
Prevost on the other hand states clearly in their maintenance manual that brake chambers must be replaced every year or 100,000 miles, whichever comes first. I had one brake chamber leak at around 10 years of age, so I arbitrarily chose 5 years as my schedule.
What is important is each owner have a plan and records to be able to keep track of what’s due and what has been done.
-
I remember a few years back, we were sitting around shooting the breeze at TGO in Titusville while having a little mini rally and WHAMMMM. Tuga’s Newell blew an airbag justing sitting there. He had hard enough time getting it replaced even though there was a repair shop right at the campground, but it he would have been on the road, things would have gone from bad to worse.
I’m a fan of the 10 year deal myself, but when I did mine, they were 97 originals and cracking on the outside, but like new on the inside. I’ll be changing out all of mine this summer when it’s warm. Jon agreed to come help, can’t beat that deal.
-
My job will be to drink Truk’s beer before it gets warm. I love watching him work.
-
As a follow up, after nearly three weeks the bus has no leans and brake pressure is a bit over 80 psi…this without the engine running for the entire tiem. I think we can call this operation a sucess! You too can do it!!
-
Folks the bus “after the Prevost shop trip” is leaning this morning every so slightly but going south. Already called and will get it up north next week or 2. It’s about a 4 hour or better drive. I need to build some ramps that I can drive up on and get it a little higher in the air for creeper work. Think I will build some stands like the ones on this post at the same time. Nothing like doing it yourself.
Thanks
-
Glen,
Eliminating the leans is not something done in one visit anywhere. Depending on which suspension is giving you the grief, there are two or three valves to consider, two or three air bags, multiple fittings and no one way to insure whatever repairs were made actually resolved the issue.
For anyone to spend a day with a coach and proclaim it leak free, especially if part of the day involved changing out parts, is risky and probably misleading. There are multiple methods for leak detection and with most repairs the only one I have ever seen used by “professionals” is soapy water, and I stated somewhere else there is no way soapy water will show all leaks, ESPECIALLY AIR BAG LEAKS.
Since the leans are caused by air leaks I know of only two sure fire ways to find or eliminate those leaks The first is to use a device such as Hector’s Texas Bubbler defined in the articles section. It doesn’t have to be the only way employed because using that device is very detailed and time consuming. But it will find every leak. You just need patience. You can use quicker methods to find or rule out leaks using soapy water, a stethoscope, and ultrasonic leak detector or even your ears, but if you have used all of those methods and the coach still leans you will either have to use the Texas Bubbler or the alternative.
The alternative is to quit chasing leaks and just use new parts. Before anyone considers me crazy for saying that, take a hard look at the number of hours mechanics spend to find leaks. I can almost bet at $100 per hour or so, plus the cost of diesel fuel for return trips, you would almost be money ahead to just replace the Norgren valves and the air bags.
That is one of my reasons for my 10 year plan regarding valves and air bags. Twice I have sorted out coaches with the leans and twice the number of hours spent chasing air leaks if figured at $100 per hour I would have been better off to just replace all the parts so that is what I do. Lots of good parts are thrown out, but except for an occasional fitting leak (rare) the leans are not part of my ownership experience.
Just keep in mind if you intend to get beneath your coach, especially if you are working on the suspension make absolutely certain the chassis is well supported.
Log in to reply.