ALARM GP 1236449 - Caterpillar

All 3500 Series EnginesAll 3500 Series Engines have two oil sequence valves. One is located in the left front face of the cylinder block beneath the front drive housing. The other is located on the right rear face of the cylinder block beneath the flywheel housing. During engine start-up the oil sequence valves block the flow of oil to the piston cooling jets until the lubrication system oil pressure is more than 138 kPa (20 psi).
If the spring for the oil sequence valve plunger is not installed correctly, it can stick on the edge (step) of the cylinder block counterbore (see Illustration 1). This can cause the oil sequence valves to remain in the closed position. If the valves remain closed, oil flow to the piston cooling jets is blocked and can result in piston seizure.
Illustration 1. Oil sequence valve installation.Use the procedure in the Service Manual to install the oil sequence valves in the cylinder block. In addition, add the following steps.
1. Be sure the spring is in the bottom of the hole and not on the step of the counterbore.2. Push the plunger in and out to be sure it moves freely.3. Install the cover and press on the center of the cover while tightening the bolts.When a 3500 Series Engine is tested on a dynomometer, check oil sequence valve operation by measuring the oil pressure to the piston cooling jets. This oil pressure can be measured at the drilled oil galleries in the sides of the cylinder block. These galleries are covered by two 8N8056 Covers (see Illustration 2). Modify two 8N8056 Covers (purchased separately) as shown in Illustration 3. Remove the two engine covers and install the modified covers and pressure gauges to check oil sequence valve operation. After the test, install the original covers on the engine.
Do not leave the modified covers installed on the engine after testing is completed.
Illustration 2. Location of 8N8056 Cylinder Block Cover.
Illustration 3. Modified 8N8056 Cover.