Preventive maintenance is very important to keep up on. It will help prevent costly down time and most importantly help prevent injuries deaths. PM should be performed on all vehicles or equipment. A PM program should be set up so that your vehicle or equipment is check on a regular basis. Things that should be in your PM program are (but limited to), checking or changing fluids, greasing, changing filters, inspecting for damage or worn parts, making sure things are saucier, look for leaks, ext.
The information to I provide for PM is for a 2011 Thomas Built SAF-T-Liner HDX school bus. It runs with a Cummins ISB 6.7L 260HP engine, 2010 Allison 3000PTS transmission (4th gen controls with prognostics) and a Ege Endustri drive axle. The brake system uses Bendix and Haldex components. The front axle and suspension is DaimlerChrysler or Axle Alliance. It has both their names on it. At the back the bus has a Holland rear suspension. And Spicer wants a piece of the bus, the drive shaft and the steering shaft. So as you can see Thomas use a lot of other companies parts.
Part of the PM for this bus is changing out or checking the engine oil, transmission oil, and coolant. There is also a lot of greasing going on to.
Engine Oil and FilterEngine oil is what keeps the whole engine lube and other components; like the air compressor and the turbo charger. If there is not enough oil in the system you will have metal to metal contact of moving parts. Temperatures will raise and part will seize and brake. Metal shavings will be made and will destroy bearings. Things get worse and go downhill fast. If you don’t change your oil at proper service intervals the life of your engine will shorten. Over time the oil brakes down and it also collects a lot of contaminates. Yes there is a filter but it doesn’t get everything. There is a chance for your filter to get clogged up. Then the oil is just bypasses the filter through the bypass valve and the oil is not filtered at all. So the moral of the store is change the oil and filter at recommended service intervals. To check the engine oil level, first park the bus on level ground. Second, turn off engine and let stand for a few minutes. This will allow the oil to return to the sump. Third, pull out dipstick and whip it off. Then stick it back into the dipstick tube. Pull out the dipstick one last time and check oil level. Add or drain oil as needed.
Engine oil we use is: 76 Guardol QLT 15W-40
Filter: Baldwin – B7177
Engine Oil Capacity
pan only: 15qt
total system: 17.6qtoil filter: 1qt
Engine Oil Dipstick
low to high: 2qt
low Idle (min allowed): 10psi
at rated speed (min allowed): 30psi
oil regulating valve opening pressure range: 65-75psi
Engine Oil Temperature
maximum: 280 F
oil: 6,000 miles
filter: every oil change
The transmission oil stays cleaning than the engine oil because the soot from burning diesel contaminated oil and other factors. So you do have longer service intervals for the tranny oil and filters. None the less it is important to PMs for the tranny. If the oil is to low or to high then you will performance problems, like the tranny not shifting right. It could over heat with not enough oil. Filters can get clogged as well, making the oil to bypass without being filtered. Dirty oil will not properly lube the moving parts in the tranny. Checking the oil level in the tranny is similar to checking the engine oil level. The difference is you leave the engine running and you put the tranny in neutral (this may very between trannies). Then check the level of the oil. On the dipstick there will be cold and hot level markings. So if the oil is cool (61-120 F), use the cold level markings. If the oil is up to operating temp (160-200 F), use the hot level markings.
Transmission Oil we use: Phillips 66/Conoco/76 - Super ATF
Filter: Allison – 2954778
Oil Capacity (4in sump)
initial fill: 29qt
oil: 25,000 miles
filter: 25,000 miles
Cooling system is really important for cooling down the engine and other components. If the cooling system is not maintained properly, things will over heat. The engine, air intake, EGR, engine oil, tranny oil, and sometimes the turbo and the air compressor, all relies on the cooling system. The coolant needs to be kept at the proper levels. To low you get over heating and too much you will have coolant squirting out. Coolant can freeze, so it should be tested to that it won’t freeze in the climate that you are in. The PH should be check as well. The coolant can start eating away the insides of your engine. You should check for oil in the coolant to make sure there is no internal leaks. You should check all the hose to make sure they aren’t cracking, leaking, or rubbing against anything.
Coolant we use: Chevron Del Extended Life 50/50 Coolant – B
about 19 gallonsService Intervals
Coolant: 750,000 miles
around -34 F
There are a lot of moving parts under the bus. There is steering, brake, suspension, and u-joints. Without this grease you would have part wearing out really fast. Some part would be squeaking and don’t want that. It is not that hard to grease up all the points and it doesn’t take that much time. Keep in mind when you grease that you don’t need to pump a lot of grease, just enough to where you can see or hear the new grease coming out. Make sure that grease is going in, if not replace the zerk. Also clean off the zerk before greasing.Grease use: Phillips 66/Conoco/76 – Multiplex Red #2
Unlike the Freightliner on the lift at school witch had 43 zerks, the Thomas bus has 19 zerks.
This picture here is one of the trickier zerks to find on the Freightliner. It is up on the side of the transmission. There is on other one on the other side.
A tricky zerk to find on the Thomas bus is the one on the steenig shaft. When you pull in the wheel are pointed straight forword. At that point the zerk is on the other side and you can't see it. You have to trun the steering wheel to get to it.
Here is the inspection sheets that is follow for when a bus comes in its PM servcie interval.