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General Information and Engine Specifications

If you need to identify which engine you have, refer to the dataplate. The model will be on the column that is the furthest left. For older engines in this series, the dataplate will be on the right, rear side of the engine. For the newer engines, it was moved to the left bank of the front gear cover. This will tell the type and size of the engine.

Coolant type: Maximum chloride 40 ppm / sulfur 100 ppm.

Lubricating oil type: SAE 15W-40, low ash.

KTA38 cooling capacity: 32.7 gallons.

KTA50 marine cooling capacity: 52 gallons.

KTA50 with heat exchanger, cooling capacity: 60 gallons.

Maximum tank-top coolant temperature: 203-205 degrees F.

Maximum oil pressure: 70 psi.

Minimum oil pressure at idle: 20 psi.

Maximum oil temperature: 250 degrees F.

K38 oil capacity, sub base sump: 23 to 30 gallons.

K38 oil capacity, double deep front (or rear) and center sump: 37 to 44 gallons.

K50 oil capacity, sub base sump: 45 to 65 gallons.

K50 oil capacity, deep center sump: 46 to 54 gallons.

K50 oil capacity, front and front center sump: 45 to 65 gallons.

Exhaust valve: 0.027 inch.

Intake valve: 0.014 inch.

Firing order (engines built before Sept. 1986): 1R, 1L, 3R, 3L, 7R, 7L, 5R, 5L, 8R, 8L, 6R, 6L, 2R, 2L, 4R, 4L

Firing order (engines built before Sept. 1986): 1R, 1L, 3R, 3L, 2R, 2L, 5R, 4L, 8R, 8L, 6R, 6L, 7R, 7L, 4R, 5L


Troubleshooting and general guides

If you need help diagnosing problems, this can be a guide to figure out which Cummins KTA38 parts or KTA50 parts need to be replaced.

Problems with alternator

If you suspect that you are having problems, check the following areas. These are sources of possible problems with the performance of your overall engine.
• Check the alternator belt and the alternator drive pulley (to make sure it is not loose on the water pump drive shaft.) If either are loose, it can cause the alternator to not charge.
• If you are experiencing repeated problems, the alternator may not be the right size for the engine, and should be replaced with a proper unit.

Installing a new alternator
If you want to install a new alternator on your Cummins KTA38 or Cummins KTA50, use the following as a general guide:
• Make sure the two sleeves are in place in the bracket. Then, install the flat washers and capscrews, and tighten to a torque force of 66 ft•lb.
• Attach the alternator brace to the front gear cover using the capscrews. Make sure the four plain washers and the two lock washers are in place. The plain washers act as spacers and must be correctly installed.
• Place the lock washers between the alternator brace and the capscrew and tighten to 65 ft•lb.
• Locate the slot in the brace, which is a slightly curved line at the bottom of the brace. Install the belt and adjust the tension.
• In the bottom bracket, install the vibration isolators, followed by the plain washer and nut. Make sure that the isolators are not overtightened. When it is compressed, it must be about 13 mm tall.
• Put a vibration isolator in-between the main guard and top bracket The belt guard can then be installed, and the capscrews tightened to 35 ft•lb.
• When installing a new alternator the pulley mounting nut must be tightened to a torque of 75 ft•lb.


Problems with coolant, or engine overheating

If your Cummins KTA38 or KTA50 engine is experiencing problems with coolant temperature, use the following as a guide.

Troubleshooting gradual overheating:
• First, check to make sure the coolant level and cooling system does not have any collapsed tubes. Then check the fan to make sure it is not showing signs of damage. Check the cooling system pressure cap for any signs of leaking and replace with a pressure cap that is rated for higher pressure.
• Check to make sure the oil levels are not too high or low, and that the vent lines aren’t damaged. Check the fuel level as well, since too much fuel can lead to overheating.
• Check the radiator core to make sure it is not damaged. Check the heat exchanger to make sure it functions correctly.
• Replace the water pump.
Troubleshooting sudden overheating.
• Check the drive belt for the fan drive and make sure the fan is working properly.
• Check the coolant level and for any signs of leaking.
• If it is a marine engine, check the sea water strainer to make sure it is not plugged.
• Check the heat exchanger and radiator fins to make sure they are not damaged.
• Make sure it is not a problem with the thermostat or gauge.
• Check the water pump and replace.

Water pump replacement:
• Prepare by disconnecting the battery, draining the cooling system and removing the coolant bypass tube.
• Remove the radiator hose from the inlet.
• Locate the two capscrews on the support bracket and the heavy washer, and the four capscrews that hold the housing to the water pump. Remove them and pull the support bracket housing from the pump, discarding the o-ring.
• This next part involves parts that weigh over 50 lbs, so be sure to get help or properly prepare. Take the four capscrews and four capscrews out. The pump and coupling can be removed, along with the plate. Discard the o-ring seal and the gasket.
• Remove the two tubes that lead to the aftercooler and the jacket water bypass.
• Remove the hose clams from low temp aftercooler outlet. Then remove the pipe. Locate the jacket water bypass pipe and remove the hose clamps and the pipe itself, discarding the gaskets.
• Remove the four capscrews and the jacket water radiator inlet connection. The support bracket can then be removed followed by the pump itself. Remove and discard any gaskets, making sure to clean any gasket material off of the surface.
• Signs that the pump must be replaced includes worn, damaged or cracked shaft or splines.
• Once you have the new pump, install the support bracket. Then install a new gasket and the connection. Tighten capscrews to a value of 30 ft•lb.
• Install the draincock and tighten to 133 in-lb.
• Using vegetable oil, lubricate the new o-ring and install it in the groove of the adapter plate.
• Put the adapter plate on the body (thinner side must be the side closest to the pump body.) Lubricate the bearings with clean engine oil and install the spline coupling.
• Install the adapter plate on the pump and the spline coupling on the shaft of the water pump.
• Put a new gasket on the pilot (where the drive meets the pump.)
• Rotate the pump so the splines on the water pump drive shaft and the spline coupling match. Tighten the screws enough to hold them together, but not all the way.
• Put a gasket between the cylinder block and the adapter plate, rotating the housing so the pump outlet and adapter plate are as close as possible.
• Tighten pump-to-pump drive capscrews to 44 ft•lb. Tighten the capscrews on the cylinder block connection to 30 ft•lb.
• Install the larger o-ring in the housing and lubricate with vegetable oil. Reattach the housing and tighten the four capscrews to 30 ft•lb. Tighten the bracket to hand hole cover to a value of 44 ft•lb.
• Reattach the bypass connections with new gaskets. Tighten capscrews to 33 ft•lb and the hose clamps to 50 in-lb.
• Replace the coolant filter and the radiator hose to the water pump inlet. Connect the water lines.

Changing the cylinder liner

The Cummins KTA38 and Cummins KTA50 are known to be reliable engines, but like any engine, they will require an overhaul and new cylinder liners with extended use. This section outlines changing the cylinder liner, along with signs that they need to be repaired. Always trust a Diesel mechanic for any major repairs.
Signs that your cylinder liners should be replaced:
• The liners have cracks.
• The outside diameter has corrosion or pits that are larger than 1.6 mm in length.
• The inside has scores or deep scratches. If it can be felt with a fingernail then it should be replaced.
• The inside has a mirror like finish.

Installing a new liner
• Install a liner puller into the block, and withdraw the liner. Mark the cylinder it came out of.
• Remove the crevice seal and the two d-rings.
• Use vegetable oil to lubricate the packing ring bores of the block.
• Put any shims into place if needed.
• Using the installation tool, move the new liner into place. Make sure that you do not tighten to over 35 ft•lb.