CYLINDER GP-HYDRAULIC 2767646 - Caterpillar

Introduction
The problem that is identified below does not have a known permanent solution. Until a permanent solution is known, use the solution that is identified below.Problem
A severe engine vibration can occur on certain 305 CR Mini Hydraulic Excavators. The severity of the vibration can vary from one machine to another but in some instances the vibration can be severe. The cause of the problem is still under investigation but it is thought that the problem relates to the rack instability.Solution
Remove existing 253-9180 Oil Filler Cover and replace it with a 253-5566 Cover As . Use the procedure that is described below. This fix will result in the loss of the normal fill point for the engine oil. However, engine oil can be topped up through an alternative location on top of the engine. This alternative location is more difficult to access but provides a temporary solution.
Table 1
Required Parts    
Qty     Pt. No.     Description    
1     253-5566     Cover As    
1     199-2332     Gasket    
Illustration 1 g01260855
(A) 24 mm (0.945 inch)
Inspect the 253-5566 Cover As . Dimension (A) from the plate to the tip of the spring should be 24 mm (0.945 inch).
Park the machine on level ground.
Remove any other modifications that have previously been installed on the machine in an attempt to fix this problem.
Set up a photo tach or other transducer suitable for measuring engine speed.
Start the engine. Ensure that the left console is raised in order to disable the hydraulics. Move the engine speed control to the high idle position.
Measure the high idle speed and record the high idle speed. The high idle speed should be approximately 2600 rpm.
Stop the engine and remove the 253-9180 Oil Filler Cover (4 bolts).
Illustration 2 g01254751
Cover and spring orientation
Loosen the adjustment screw in the new 253-5566 Cover As until the screw does not touch the spring. Orient the spring as shown in Illustration 2. Install the cover assembly and a new gasket.
Start the engine. Ensure that the left console is raised in order to disable the hydraulics and move the engine speed control to the high idle position.
Illustration 3 g01241056
Measure the high idle speed again. Turn adjustment screw (1) on the 253-5566 Cover As until the high idle speed is 50 rpm higher than the setting that was established in Step 6 above. Refer to Illustration 3. This action forces the spring on the cover assembly against the rack and preloads the rack. This should stabilize the rack and eliminate the vibration. Lock the adjustment screw with the locknut when high idle is established.
Illustration 4 g01241072
You must use fill point (2) on top of the engine to top off the engine oil while this temporary fix is on the machine.Please report the result of this modification to the product analyst that is listed below:Neil Grewcock
grewcock_neil
Alternative ContactsShaun Cooling (Senior Service Engineer)
cooling_shaun_a
Peter Bray (Service Engineer)
bray_peter_w
Tim Gunter (Service Engineer)
gunter_timothy_o