School Bus Mechanic Videos, pictures on repairs and maintenance on Diesel Engines and School Bus components and systems. Lots of "How To" repair information from a Certified Commercial Transport Mechanic. Comments and Questions Welcome! Statistics Unique Visitors: Total Unique Visitors: Outgoing: Total Outgoing: 0 0 29 2145

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Cat 3116 Engine-Repairing Common Engine Oil Leak 2008-02-01 22:32:00 The Cat 3116 Engine has a common oil leak that is very easy to fix. The first step is to remove the steering pump which is driven off the air compressor. The next step is to remove the rear housing from the air compressor, it's held on with 4 nuts on studs, there is a square o-ring that seals the rear housing to the main compressor body. The Compressor is a "Bendix 850 Model" which is a 2 stage [2 cylinder] unit. The Cat 3116 Engine oil pressure guage and air compressor oil feed lines run off the housing pictured here bolted to the engine block which is connected to the main oil pressure gallery. There is an o-ring seal between this housing and the engine block. This 2nd block is the air compressor rear support block that has an o-ring seal as well. This block also serves as an oil drain for the 3126 model which has a oil pump above that supplies high pressure oil to the HEUI system [Hydraulic Electronic Unit Injectors].Pictured here is the oil pressure manifold housing removed. The ...

Cummins Engine Repair-Adjusting Valves ISB 2008-01-26 10:44:00 Valve adjustment on a Cummins Engine Repair is the final step. Engine position is very important because the intake and exhaust valves must be in the closed position. Rotate the engine clockwise [looking from the front] until #6 cylinder rocker arms are both rocking. When you're on the correct stroke the exhaust valve will be moving into the closed position, then once it closes keep rotating the engine until the intake valve JUST starts to open. You are now on #1 Compression Stroke & ready to adjust 1/2 of the engine valves.Note: The crossheads pictured here on top of the valve stems [#5 & #6 Cyl] are located with the elongated contact surface towards the exhaust manifold. The Rocker arms are held down on aluminum cradles with one retaining bolt and torqued to 27 ft. lbs.Cummins 24 Valve Turbo Diesel Valve Adjustment Specs.With the Engine on #1 Compression Stroke.*Adjust #1 #2 #4 Intake Valves to .010 inch.*Adjust #1 #3 #5 Exhaust Valves to .020 inch.*Rotate Engine One Full Tu ...

Cummins Engine Repair - Installing Injectors 2008-01-20 10:57:00 Cummins Engine Repair Replace o-ring on the injector body and copper sealing washer on injector tip. Position into head with orifice pointing towards fuel connector tube opening. [click photo to enlarge] The injector hold down installs only one way to index the injector position aligning it with the fuel connector tube. The hold down retaining bolts are torqued to 89 in. lbs. Install fuel connector tubes [with new o-ring] into the head bore. The tube has a tapered tip that aligns with injector body. Torquing the fuel line retaining nut forces contact and a proper seal between the injector body and connector tube. The injector lines are what retains contact between the fuel injector and connector tube. Torque the fuel line nuts to 28 ft. lbs. using a crowfoot wrench.That's it for this post with more to come on Cummins Engine Repair. ...

Cummins Engine Repair - Torquing Cylinder Head Bolts 2008-01-19 18:38:00 Cummins Engine Repair - Torquing Head Bolts on a Cummins 24 valve turbo diesel. The torque pattern is circular starting from the middle and working both ways to each end of the cylinder head.Torque Specs Are As Follows:59 ft. lbs.77 ft. lbs.Check again at 77 ft. lbs.Finally advance each head bolt an additional 90 degreesSince each flat side of the "hexagonal" bolt head is 60 degrees [60 X 6 sides=360 degrees]One flat and 1/2 = 90 degrees.This is the most important step when replacing any engine cylinder head gasket. If the proper torque specs are not followed bolt stretch [over torqued] or coolant leaks [under torqued] will occur and you'll have to start all over again with your Cummins Engine Repair. ...

Cummins Engine Repair - ISB Model 2008-01-13 21:41:00 Cummins Engine Repair on a 2002 Thomas Freightliner School Bus. The head gasket was leaking coolant from the right front corner. The first step is to unhook the battery and drain the coolant.The Turbocharger [pictured] can be removed as a complete assembly attached to the exhaust manifold. The fuel lines are removed from the opposite side. The Cummins 24 valve turbo diesel has 2 intake valves and 2 exhaust valves for each cylinder. The parts displayed here have been cleaned and inspected for pitting, hard surface wear and corrosion [head bolts]. Head bolts are measured for length, with a special guage provided by Cummins [usually comes with the head gasket kit]. The cylinder head itself weighs approxiamately 80 lbs. [3 Mechanics removed the head off the block manually and it's a clumsy operation!]Here I'm using the hydraulic hoist to install the head, the only problem we encountered was the reach was not long enough on the hoist boom so I removed the front wheel to enable rolling th ...

Haldex Brakes-Self Adjusting Slack Adjusters 2008-01-05 11:53:00 Haldex Brakes self adjusting slack adjusters are installed at the factory on all Thomas Buses equipped with air brake systems. This allows much better control over brake adjustment especially for a large school bus fleet operation. At the same time there are operating and maintenance procedures that must be followed to get the best performance out of Haldex Self Adjusting Slack Adjusters. Here Are Some Important Maintenance Steps To Follow:Visual and operational checks must be made at every scheduled PM checkCheck adjusters and anchor brackets for visual damageAutomatic Adjusters should not be operated as manual adjusters Standard chasis grease may be used to lubricate Haldex Slack adjustersLubricate the Standard 409-10 model every 50,000 miles or 3 mthsLubricate Reduced Maintenance 409-10 once a yearNo-Lube 429-10 adjusters are sealed and do not require lubricationDO NOT use Moly-disulfide grease as this will effect the operation of the slack adjusterReplace the slack adjuster if the ...

Thomas Buses HDX Electrical Panel 2008-01-03 01:43:00 Thomas Buses have changed through the years and one model with a different electrical layout is the HDX. This 2004 has everything in a totally different layout compared to the Saf-T-Liner. The Body Electrical [lights and accessories] Schematic is nicely displayed on the side door panel below the driver's side window.[Click On Each Photo To Enlarge] The circuit board shown here has been unfastened and tipped downward so you can see the many connectors that hook up with relays and battery supply junctions. There are 3 circuit boards in total with specific spots for each connector.The circuit board is upright once again [located in the side panel] Here you can see the main battery power supply on the left with the many fuses and relays required to run lights, heater motors, solenoids etc.The LED lights above indicate which relays are active, YELLOWindicates the relay coil has been activated while the GREEN LED indicates the circuit is connected to the load.Thomas Buses have evolved from ...

DC Generators Fundamentals 2008-01-01 14:29:00 Looking at DC Generators Fundamentals you can easily relate to Hybrid Automobiles which are powered by a fuel driven engine to create DC current that charges the batteries that drive the electric motors that drive the wheels.Diesel locomotives are, for example, an example of a hybrid drive train, as the diesel engine does not cause the wheels to spin, but instead generates electricity that turns electric motors that then cause the wheels to spin.There are two kinds of hybrid drive trains:* Serial hybrid: The thing which turns the wheel is an electric motor, and the gasoline engine is used purely to generate electricity. * Parallel hybrid: Both the electric motor and gasoline engine can cause the wheels to turn.These "new" hybrid cars are all of the parallel design pattern. Not a one, so far, is of the serial design pattern even though that would be a much simpler vehicle to design and build. A simple-and-obvious-to-construct serial hybrid vehicle would be an otherwise pure electric car ...

Charging System Test - Heavy Duty 12 Volt System 2007-12-20 00:51:00 A charging system test is a very basic operation with the right tools. Pictured is a Leece Neville 160 Amp Alternator which works very hard to keep the three 900 CCA [Cold Cranking Amps] bus batteries charged. Thomas School buses have a large demand with extra lights, electric motors and the engine air intake heater. The diesel engine in this case is a Cummins ISC Electronically controlled unit. You're probably wondering what the heck is that device hooked up to the batteries? That's my tool of choice, a 'SUN' VAT 33 [Volt Amp Tester]. This model has been around for decades and still very reliable, our shop does have a digital tester but I like this one for doing a quick check on the charging system. The reason I'm testing the charging system is because of an unusually low voltmeter & ammeter reading.The main leads are hooked up to the positive and negative battery terminals while the amps pickup is clamped around the positive cable to read alternator ouput back into the batte ...

Cat 3116 Engine Installation-Thomas Buses 2007-12-20 00:29:00 This is a Cat 3116 Engine installation into a Thomas Pusher. This process is much easier with the transmission installed [MD 3000 series]The transmission jack supports the trans. and the hydraulic crane hooks on nicely to the front engine lifting eye. With some assistance we rolled the whole assembly into the backend with ease. You'll notice the rear subframe and bumper have been removed. This is one great advantage of owning a Thomas pusher although we don't want to be doing this particular operation too often... ...

Thomas Buses-HDX Electrical System Repair 2007-12-15 13:14:00 The electrical system on Thomas Buses vary depending on the model, pictured is an HDX model built in 2004. We are going to change a module that controls the main power to the body and chassis electrical systems. A hoist is handy but not totally required, I had to enlist a grinder with a cut-off wheel to remove the existing bolts. This unit is called a dual power switch that is mounted on the frame on the passenger side across from the transmission. Since it is exposed to the elements the terminals are exposed so corrosion can develop. Consequently their is a possibility of an intermittent power problem to the lights or engine/trans controls when turning on the ignition. As you can see the middle terminal is connected directly to the main batteries. The chassis and body battery supply terminals are located on each side while the ignition feed connector is plugged in on the top left corner.When the ignition is energized a signal is sent to this module and power is directed to both syste ...

Need Mechanic Information? 2007-12-12 01:09:00 Mechanic information is easy to come by if you have a regular certified mechanic to go to with your questions. Finding a mechanic you can trust is essential, once you find one hang on tight because you will gain loads of mechanic information and save oodles of cash at the same time! What Makes an Honest/Qualified Mechanic Word of mouth & referrals from happy customers is a good startA Certificate of Qualification is a MUST HAVE!Cleanliness Willing to share knowledgePositive AttitudeAlways has the old parts available Has been trained on the latest technologyQuality workmanship Stands behind every jobAdvises customer before going ahead with extra repairsIf you've had a bad experience with a repair shop and they did not try to fix their mistake or your original problem then it's time to go hunting for a new Repair Shop/Mechanic. The smaller private shops are usually more personal and have a small staff so jobs don't get lost in translation. One way to start is by asking around ...

School Bus Racing 2007-12-07 00:47:00 School Bus Racing from Michigan, it hurts to watch this video since I've spent so much of my time fixing school buses! But it's rather ironic to see the recklessness on the track compared to the stringent rules and regulations school bus drivers have to follow. ...

Diesel Coolant-What Color Should You Use? 2007-11-29 00:35:00 Diesel Coolant has changed over the years and the most apparent difference is the various diesel coolant colors available on the market, there's green, red, purple, blue, orange etc. So what do all these colors signify?In my part of the country the authority on coolant is a company called Recochem who manufacturers coolant, this is what they have to say.Both packaged and bulk heavy duty diesel engine coolants will be transitioned from green to purple by June 1, 2007. The change of color will not affect the performance of the coolant. Green and purple coolants can be mixed and will perform to specs.Four Types Of Diesel Coolant Are Described below:Green coolant [Ethylene Glycol] needs to be pre-charged with DCA4 & tested regularily with proper test strips provided by Fleetguard.Purple & Pink [Ethylene Glycol] coolant is a conventional heavy duty fluid that is already precharged to specs. no treatment is required.Blue colored coolant is a Propylene Glycol that is the equivalent ...

Found a Used school bus For Sale ? What to Look For... 2007-11-26 09:26:00 Finding a used school bus for sale online is not as easy as driving down to the local auction house and kicking the tires of a potential school bus that has caught your eye. There is however a huge market available online with thousands of school districts all over North America retiring twelve to fifteen year old buses with a lot of life left in them.The one thing most online shoppers may be thinking is how honest is the seller and how much of a hassle will they have to go through to get a great deal. With the diversity of the Internet buyers and sellers can interact with pictures, descriptions and email to make a great deal with confidence. The following are areas on a used school bus for sale that you should check out carefully.Most school districts have a strict maintenance program and every action performed on their school buses will be documented either in a log book or on a computer. This information is the bible on the school bus you're interested in. You can see what has bee ...