This seem to be a common problem but can be avoided if cleaned regularly.
"Solution Number: 80404
Solution Summary: 737/757 Engine Overheat kit - Use kit to prevent debris from entering engine
Publication Date: Aug 8 2008
Engine has low power, poor performance or misfire due to one of the following:
Blown head gasket
Seized intake or exhaust valve
Valve guide(s) has moved
Push rod(s) has came off of rocker arm and/or are bent
Problem or Situation :
Engine has overheated due to debris build up around the cylinder head cooling fins. When this occurs, engine temperature exceeds normal operating temperature, and can cause several visible and audible failure modes; i.e. poor performance, misfire, blown head gasket, seized engine. Upon inspection of the engine and components the following may be found: bent push rods, stuck valves, valve guide(s) moved, seized or broken piston(s), etc.
Operator's are not following recommended Service Intervals in the Operator's Manual on removing engine shrouds and cleaning engine cooling fins.
NOTE: When operating in severe conditions, dusty and/or high ambient temperatures, service interval may need to be increased. Daily cleaning of the engine fan screen maybe necessary if it shows signs of debris build up.
Solution :
1. Remove engine shrouds and inspect for debris around the cylinder head(s).
2. Remove any debris from behind engine shroud and cylinder head(s).
3. Remove engine valve cover and inspect:
NOTE: Rocker arm and spring may need to be removed to determine if the valve guide(s) have moved. Refer to the picture Fig1.jpg for measurement.
•If valve guide(s) have moved, replace cylinder head assembly.
•If valve guide(s) have not moved, but push rod(s) are bent from stuck valve(s), replace damaged push rods and valves. Before inserting new valves into cylinder head, clean valve guides using a 6 mm (0.236 inch) reamer.
4. If push rods and valve guides meet specifications listed in Technical Manual proceed with removing cylinder head to inspect head gasket. If the head gasket has failed and shows signs of carbon tracking, clean cylinder head mating surfaces. Check cylinder head for warping by using a flat piece of stock to check for flatness. If cylinder head is warped, replace complete head assembly and reinstall shroud.
NOTE: Maximum head warp specification is .002”
5. If you have a machine that has a head damage described above, order and install Heavy Duty Overheat Kit TCA18947.
This repair is not covered under normal warranty.
NOTE: Kit has a perforated screen to help clean the air before it reaches the fan shroud. Fig2.jpgThe Updated shroud and PEP plate from solution 77392 will not be used with this kit.
Additional Information:
PRODUCTS AFFECTED :
737A (TC0737A030001 – )
737B (TC0737B030001 – )
757A (TC0757A030001 – )
757B (TC0757B030001 - )
757MB (TC757MB010001 – )
Installation of this kit should take 3 hours or less to install. "
