Power Steering Pump Noise - keywords assist diesel duty flow fluid growl hose kink medium

This PI was superseded to update Recommendation/Instructions. Please discard PIT4339.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Some 2007 medium duty conventional models with 7.8L Isuzu Diesel Engines RPO LG4 may have power steering pump noise due to a kinked fluid supply hose at the connection to the pipe on the right hand (passenger) side of the engine. The kinked hose can cause a restriction in fluid flow to the power steering pump resulting in pump operating noise and reduced power assist.

Remove the engine cover inside the cab and inspect for a kinked hose as shown in the photo below.

Note: Sometimes it may be necessary to loosen and slide the flexible heat shield sleeve down to confirm that the rubber hose is kinked. If the rubber supply hose is kinked, follow the instructions below to reposition the pipe and eliminate the kinked hose condition.

1. Drain power steering fluid per Document ID #1868159 and disconnect rubber supply hose from pipe.
2. Carefully bend the pipe so the end that connects to the hose points straight down (it is recommended to remove the pipe, place in a vise and use a tubing bender).
3. Reposition the rubber supply hose so it will come straight up to the metal pipe ( it may be necessary to shorten the rubber hose about an inch to meet the new pipe end location).
4. Connect supply hose to pipe and inspect to make sure the hose does not contact other components.
5. Fill the power steering reservoir with fluid per Document ID #682234.
6. Bleed the power steering system per Document ID #1696753.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.