Maintenance Tips for the Mature CC Motorcoach Part 2 of 3

Here is part 2 of a 3-part article authored by one Brian Keys--great guy, smart guy, and a funny guy...anyway here is part two of a wonderful technical article on taking care of your Country Coach.

Maintenance Tips for the Mature CC Motorcoach - Part 2 of 3 
 by Brian Keys, Country Coach Electrical Engineer

In Part 1 of this article which was published in the spring issue of Destinations, we began a discussion on the maintenance requirements of aging coaches with information on filters and sealants. In this article, we shall continue the discussion with a look at the remaining maintenance requirements of your coach's chassis. Before we begin however, let's take a few moments to discuss some safety concerns that you should always be aware of should you prefer to tinker on your own coach.

SAFETY FIRST

- Always ensure that your engine cannot be cranked either by you or, more importantly, another party when you are working in the engine compartment area.

- Don't wear any loose clothing when working around moving components, such as the engine, while it is running.

- Never crawl beneath the coach unless it has first been raised off the ground using ramps or other approved lifting apparatus, and is supported on jack stands where applicable. The air system in your coach can lower at any time, and there are easier and less painful ways to achieve the slender look!

- Always wear safety glasses when working beneath the coach. This list of 'dos and don'ts' is not conclusive of course since there are approximately a bazillion ways to pinch your fingers or get dirt in your eyes. The purpose of this article is to raise awareness of the various maintenance requirements for your coach, and to equip you with some knowledge that you can take along to your next service appointment to ensure nothing is overlooked. With that, let's dispense with the salad and get to the meat and potatoes!

DRIVE-TRAIN

What on earth is the drive-train you say? Simply put, the drive-train is an all inclusive term for the mechanical components that take the power from your engine/transmission, and apply it to the road to get you moving, including the rear axle, and its umbilical cord to the transmission - the driveline (or propeller shaft for the Europeans out there). Another term you may be familiar with is 'power-train'. This is identical to drive-train, only the term also accommodates the engine and transmission.

1. Axles.

Your coach has at least two, and those with a Tag axle have three. The first item we need to discuss here is wheel bearings and their adjustment. A mildly loose wheel bearing adjustment is probably not the end of the world, but you can expect a higher bearing wear rate and other problems that may arise from lateral movement of the hub including ABS sensors that repeatedly go out of adjustment causing a warning light on the dash, erratic speedometer reading on coaches built with a Gillig chassis, and perhaps a groaning sound as you apply the brakes. Wheel bearings that are very loose will be fairly obvious due to oil contamination of the brake linings from leaking rear hub seals. But what about wheel bearings that are a little on the tight side? This is much less common, fortunately, since tight wheel bearings are at risk of overheating and possible seizure. Early warning signs are oil contamination of the brake linings caused by overheated rear oil seals and elevated wheel temperatures after you have traveled a significant distance. In the latter case, it is generally a good idea to monitor your wheel temperatures after any hubs have been removed from your coach for axle or brake servicing etc. This is best done after having traveled a distance of fifty miles or more on level terrain. Decelerate using the Jake or exhaust brake as much as possible before gently applying the brakes to minimize the heating effect that your brakes will add to the wheels. Then, with the coach stopped, immediately check the temperature of all the wheels. An Infra-Red temperature gun is ideal for this, but you should be able to detect any significant differences in wheel temperatures by simply placing your hand on the wheel. Wheel temperatures should be similar on both sides of the same axle but be careful, that wheel may be quite hot! The correct procedures for wheel bearing adjustment for coaches with Meritor or Dana axles can be found on the appropriate company website. For Meritor, the web address is www.arvinmeritor.com and for Dana axles this information is located at www.roadranger.com  

Still on the subject of axles, let's take some time to discuss seals; not the sea animal variety, but the oil seals that are responsible for keeping your wheel bearings lubricated, and your brakes dry. Each axle hub has two seals, an outer seal on the hub cover or axle shaft, and an inner seal that runs on the spindle.

A leaking outer seal should be immediately obvious by unsightly oil streaking on your nice shiny wheels, and is not an immediate cause for concern provided you frequently check your hub oil levels until you can have the problem addressed. Leaking outer seals are frequently caused by overfilling of the oil hub, or a plugged vent hole in the rubber plug that resides in the center of your hub cover sight glass. Leaking inner seals, on the other hand, should be addressed immediately due to the risk of oil contamination on the brake linings. As mentioned above, inner seals generally fail due to out of adjustment wheel bearings, and this seal should always be replaced with a new one when your hub is removed.

Your chassis manual provides valuable information on lubrication types and service intervals, and further information can be found at the web addresses below including newer synthetic lubricants that may be available as a replacement for your existing oil.

 

2. Driveline.

The driveline is the shaft that connects your transmission and drive axle. This shaft is subjected to extreme torsion forces when you stomp your foot on the gas pedal, climb steep grades, or worse still, encounter wheel spin followed by good traction which may occur on roads with icy patches, or when traversing from soft sand or gravel onto pavement. Country Coach fortunately uses very strong drivelines on the DynoMax chassis so problems such as twisted or broken drivelines are unheard of. That said, we still have to respect the critical role that this component plays in ‘motorvating' your coach. Your driveline must be well maintained and frequently inspected. When looking over your driveline, take a close look at the universal joints on each end, watching out for cracked ‘cross pieces' (the piece that looks like a ‘+' with a bearing on each end), and failed bearings. Use a pry-bar to exert force between the cross piece and the ‘U' shaped yokes it is mounted in to determine if there is any free play that may indicate ‘trunnion' bearings in need of replacement. Also check the bolts that secure the trunnion bearings into the yoke to ensure they are tight. There are many different names for this driveline joint such as ‘universal joint', or ‘spicer joint', but the terminology above is widely accepted and recognized. For lubrication, the cross pieces on each end of the shaft are provided with a grease nipple, and fresh grease should be pumped in until it visibly purges from all four bearings on each cross piece. Once again, please refer to your chassis service manual for specific service intervals.

One maintenance item that is often overlooked when it comes to drivelines is the slip-joint. This is where the two pieces of your driveline come together, and its purpose is to allow the driveline to lengthen or shorten as necessary to accommodate suspension travel. The slip joint should never bind and must therefore also be lubricated when greasing the universal joints on either end of the driveline. The slip joint should be lubricated at its shortest travel which means the coach should generally be at ride height. Pump six to eight shots of grease into the grease nipple on the side of the slip joint (approx 1oz or 28grams). If you find that the grease is purging from a small weep hole at the end of the driveline, just plug this hole with your finger and continue pumping the required amount of grease into the slip joint. Any grease that purges from the aforementioned weep hole, or from the slip joint dust seal should be wiped off before it finds its way onto your driveway or shop floor. Those of you who neglected to ensure that the driveline was at its shortest travel for this operation will be rewarded with some blobs of grease on the ground as your coach returns to ride height.

While in the area of the driveline, take a look at the oil seals where the driveline meets the transmission and drive axle differential housing. Some light oil staining in this area is not uncommon and is not a cause for concern, but significant oil leaks that are evident by a thick coating of wet oil should be rectified as soon as possible.

Engine/Transmission

Now that we have covered the components that use power and torque to get your coach moving, lets backtrack a little to where it all began… the engine and transmission. In the first of this series of articles, we discussed the filters for both the engine and transmission, and we shall avoid the subject of lubricant types and service intervals because we all have our personal preferences on the former, and the latter. Recommended service information is readily available in your chassis manual. So what is left to discuss? Well, lots actually. Lets begin…

1. Belts.

We are all hopefully up to speed on the importance of regular checks on your engines belts including tension, evidence of wear/cracking, frayed edges, and evidence of perforations on multi-rib belts from driving perhaps a little too fast on loose gravel surfaces. But what about the belt pulleys? With the engine running at idle, do your V-belts run smoothly, or are they oscillating between the pulleys like a heavily struck guitar string? If the latter is true, then try replacing the belt first, ensuring the correct tension is attained. If the problem still exists, then one or more of the belt pulleys on your engine is likely in need of replacement due to uneven wear. This guilty culprit is usually fairly obvious upon close inspection with the belt removed. Multi-rib belts are less prone to oscillation and uneven pulley wear, but keep an eye on the automatic belt tensioner as the engine is running. Is it bouncing frantically on the belt, or is it relatively stationary as the tensioner pulley spins? If the former is true, then with the engine stopped and disabled, release the tension from the automatic tensioner and remove the multi-rib belt. Check the pulley on the tensioner and all idler pulleys for worn bearings or eccentricity and replace as necessary. Belts that have frayed edges may indicate an alignment problem with the pulleys.

2. Throttle System.

Just what exactly is the throttle system you might ask? Those of you with an electronically controlled engine may be left wondering because your coach doesn't really have one, with the possible exception of the throttle pedal itself. However, those coaches that pre-date the insurgence of electronic controls will require some means of linking the throttle pedal at the front of the coach to the fuel injector pump on the engine. This is done by air on earlier models, and an ETS (Electronic Throttle System) on later models. To discern which type of control was used on your coach, simply explore the area between the carpet and the underside of your throttle pedal. If you see a bulky pneumatic valve in this area with air lines sneaking beneath the carpet, then you have the earlier air throttle. If, however, you see a roller connected to an electrical sensor with its associated wiring, then you will have the later ETS system assuming your engine is not electronically controlled by way of an engine computer. If you have a CAT C9, C10, C12, C13, C15, or Cummins ISC/ISL then the remainder of this section does not apply to you. Does your engine respond immediately and smoothly as you press your foot on the throttle pedal, or does it ignore your request for more power at first before delivering it in an embarrassing surge as you push the throttle pedal down a little further? This problem may be a result of a worn air actuator on the engine, or an indication of a throttle linkage that is in desperate need of lubrication. The air actuator is a small pneumatic device that bolts onto your engine and connects to the fuel pump via a linkage of some sort. A worn actuator will allow air to blow by the seal as you initially press your foot on the throttle, before taking hold with a vengeance as more throttle is applied. A replacement actuator is the preferred solution as opposed to a rebuild kit if one is indeed available. A sticking throttle linkage on the other hand is easily rectified with a liberal application of a light lubricant such as WD40. Heavy lubricants are to be avoided as they will cause dirt to adhere to the linkage. Pay particular attention to the throttle shaft as it enters the fuel pump.

How about a different scenario? As you press your foot on the throttle pedal, does your engine build power in a normal fashion before suddenly releasing back to an idle? This is obviously not an ideal situation, particularly when you are trying to merge with traffic on an on-ramp. This is a symptom of a slipping clutch on the later ETS system and, as before, the culprit is most likely a binding throttle linkage caused by insufficient lubrication. No conversation on the earlier throttle systems is complete without a brief discussion on springs, specifically the throttle return springs that are responsible for returning your engine to an idle once you have lifted your foot of the gas pedal. These springs endure frequent extend/contract cycling as you vary the position of the throttle pedal during driving, and are therefore prone to eventually break. If you haven't done so already, I strongly advise you to replace them (generally two side by side) at your earliest convenience, and every year thereafter regardless of the mileage. These springs are easily located at the throttle linkage on your engine, and should be replaced in pairs. Take care that you use the correct spring however, as an increased pull tension may result in symptoms similar to a sticking throttle linkage.

3. Exhaust Brake.

The Exhaust Brake has been covered several times in recent Destinations articles, but let me go through the drill once again here to ensure this article is complete. If you have been tinkering on your coach as you make your way through this article, then you probably don't want to add burns to your growing collection of nicks, cuts, and bruises. For that reason, please ensure that the engine - in particular the turbo and exhaust brake assembly - has cooled sufficiently before you begin working on it.

Once you have gained access to the exhaust brake, look for any signs of soot on either side of the exhaust brake as it mounts to the turbo and exhaust system. If present, this can generally be rectified by applying more tension to the band clamps as you gently tap them around their outer circumference with a hammer. In some cases, a new band clamp may be required. With the auxiliary air system pressurized, the next step is to ensure your hands are clear of the exhaust brake, and that the exhaust brake switch is in the ‘on' position. Watch the exhaust brake closely while your accomplice cycles the ignition switch off and on without cranking the engine.

Does it move freely through its complete stroke and release rapidly every time? If yes, then apply some high temperature silicone based lubricant to all moving parts and call it good. This specialized lubricant can be purchased from us as part# 500070, or from PACBRAKE as part# 18037. PACBRAKE can be contacted at 800-663-0096 or info@pacbrake.com If you find that the exhaust brake binds in both directions then try the aforementioned lubricant first. If this doesn't solve the problem, then disconnect the pneumatic cylinder from the exhaust brake butterfly flapper and move the flapper itself. If the flapper moves freely then your pneumatic cylinder likely needs to be replaced.

If the cylinder extends rapidly, but is slow to return, first check the small valve at the base of the cylinder for a mud dauber or other insect nest that may have blocked the exhaust port. Next, try to extend the cylinder by hand. If it extends easily, then the cylinder's internal return spring is either weak or broken, which will necessitate a replacement of the complete cylinder.

Another scenario you might witness as the ignition cycles is a pronounced air leak and an immobile exhaust brake. This is usually caused by a failed, or partially missing ‘rapid exhaust valve'. This valve, which is located at the base of the pneumatic cylinder, only exists on older exhaust brake systems, such as those used on the Gillig chassis. Newer exhaust brake systems use a two way pneumatic valve located beneath the bed deck to control the exhaust brake cylinder. This valve can easily be retrofitted into earlier coaches and eliminates the need for an often difficult to find rapid exhaust valve. Did I mention that you should keep your hands clear of the exhaust brake at all times when the ignition is turned on or off? Your fingers will appreciate this warning…

4. Engine Kill Circuit.

The engine kill circuit is technically part of your coach's electrical system and should therefore be relegated to the third and final article of this series that will publish in the next issue of Destinations. I want to raise the topic briefly in this article, however, for those who have difficulty starting their coach after having spent some time tinkering in the engine bay area. You see, lurking somewhat menacingly behind, or perhaps adjacent to the emergency stop switch (or engine kill switch) located in the upper right corner of your engine compartment is a small black relay of the single pole, double throw variety (SPDT). This relay is generally well behaved until your coach has quite a few miles or years beneath its belt, at which time it can become temperamental. All is well until you perhaps nudge it with your elbow, close the bed deck a little too hard, or shoot it with a stubborn throttle return spring and now suddenly, you find your coach refuses to start… Well that's not quite true actually. Your coach may start just fine, and continue to run as long as you crank the engine over, but once you let go of the key it immediately dies! Current models have not used this relay for several years now, so if you have one, it is probably time to replace yours. It may never become a problem. However, the relay is inexpensive and it does play a critical role in keeping your engine running, or more importantly, stopping quickly when you don't want it to run. The relay is readily available in various brands from most automotive stores, and is commonly sold as part of an installation kit for fog lamps or similar. It must have five pins (most do), and the center pin must be marked ‘87a', not ‘87' which would indicate an incorrect single pole, single throw (SPST) relay.

Suspension

To bring this article to a close, let's move our attention to the components that connect our driveline to the coach, and keep our teeth from falling out on bumpy highways; otherwise known as the suspension. As with the driveline, your suspension will appreciate a little grease now and then to keep it from binding and to prevent excessive wear and tear. Just about any suspension component that

moves will have a grease nipple associated with it, and specific information on grease type, service schedule and grease nipple locations can again be found in your chassis manual. When greasing rod ends with a rubber boot, stop injecting grease when the boot begins to swell to avoid damage to the boot itself. In other areas such as the ‘king pin', and suspension bushings, apply grease until it begins to purge somewhere in close vicinity to the grease nipple, and wipe off the excess grease before it finds its way onto your driveway, or brakes. Replace any grease nipples that refuse to accept grease.

If you feel your suspension is perhaps a little on the noisy side, particularly when entering driveways or driving on rough roads, then a re-torque may be in order. This simply involves tightening all the suspension bolts, bits and bobs back to factory specifications, and your chassis manual should provide the necessary service schedule for your specific coach.

Alignment is important for good handling and even tire wear and should be checked periodically, especially after making significant changes in how you load your coach, or if your suspension has been worked on. Uneven tire wear is an immediate justification for having your alignment checked by a qualified alignment technician.

Last but not least are the lug nuts themselves. These should be checked periodically to ensure they are tight. On the rear duals, this will require loosening the outer lug nuts one at a time to check that the inner nut is secure before retightening the outer nut and moving on to the next one. Lug nuts generally don't come loose if they have been tightened correctly the first time, and it is here that the following advice is valuable for both your coach and tow vehicle…use a torque wrench. How many times have you seen lug nuts tightened without a torque wrench? More often than not probably, but this practice applies uneven pressure to the brake drum or disc that is sandwiched between your wheel, and the hub. You probably won't notice this as much on the coach as you will on the tow car where a pulsing brake pedal is a sure sign of a warped disc, but the advice still holds true in both cases.

In the final article of this series to be included in the Autumn 2004 issue, we will take a look at some electrical gremlins that may arise and how to avoid them. Until then, drive safe wherever your journey takes you and have fun along the way.

...TO BE CONTINUED....