PAN-OIL 2P7828 - Caterpillar

Engine: G3520B (S/N: TPC100-UP; GLF100-UP)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
The turbochargers surge on some G3520B petroleum engines. This condition occurs mainly in cold ambient conditions below 10° C (50° F). A symptom of turbocharger surge is sudden fluctuations in the manifold air pressure which causes fluctuations in speed. This generally occurs when the engine is being loaded. Also, this generally occurs between 50 percent and 100 percent engine load. Noise from the turbocharger may be present while the turbochargers surge.The turbocharger surge is caused by an increase in the pressure across the turbochargers. An increase in turbocharger boost enables the engine to maintain higher manifold pressures at lower throttle positions. A reduction in the throttle position for a given manifold air pressure reduces the air flow through the compressor side of the turbocharger. When the air flow through the compressor decreases enough, the turbocharger compressor will surge. When the turbocharger surge occurs the air flow through the compressor can reverse. This will result in a sudden drop in manifold air pressure. Also, the speed will become unstable.Solution
When the problem is encountered, the compressor bypass must be adjusted in order to reduce the boost pressure. Perform the procedure in the coldest ambient temperature in the engine's operating range. Use the following procedure to adjust the bypass valve for the turbocharger.
Stop the engine.
Turn the engine control switch to the STOP position.Note: The Electronic Control Module (ECM) and the actuator for the compressor bypass must be powered. This will keep the bypass actuator in position.
Illustration 1 g01735314
(1) Sleeve (2) Coupler (3) Set screw (4) Nut
Mark the location of sleeve (1) on the coupler (2) .
Loosen the set screws (3) on the coupler (2) .Note: The flats on the nut of the valve (4) are 60 degrees from each other. Use the sleeve (1), the nut of the valve (4) and the coupler (2) as a reference.
Illustration 2 g01735402
Flow arrow
Rotate the shaft of the valve in the direction of the flow arrow. Adjust the valve so that there is approximately 15 degrees between the reference mark on the coupler (2) and the sleeve (1). This will slightly open the valve of the compressor. A small adjustment of the valve will have a large effect on the differential pressure of the throttle. If the valve is adjusted too much the throttle will go to the 100 percent position before the engine reaches rated load. This is due to the loss of boost pressure.
Tighten the set screws (3) to 15 1 N m (11 0.7 lb ft).
Restart the engine and attempt to load the engine.
Repeat the procedure increasing the angle of the bypass valve, if the engine surges with a load.
The engine must stabiliz