[shadams]

Were there any DTC's set? There are quite a few reasons the engine could overheat other then a failed cooling fan clutch. I wonder if the fan is always on because the engine is alwys running hot? This is from the engine overheats diag:

This condition may be caused by any of the following possibilities:

• Installation of an aftermarket grille.

• A plugged charge air cooler.

• Fan clutch not operating properly.

• Drive belt slip.

• An overfilled transmission.

• Turbocharger not operating properly.

• A plugged air filter.

Do you know if they verified any of these other things? I have only had one other Duramax with those types of problems but he was really working that thing much harder then you state you are.

As far as the steering goes, it sounds like they have thrown a bunch of parts at it instead of telling you that it may be normal. Now of cousre, without feeling it, I really cant say that it's normal, but here is the info in the service manual about what you mention. Notice the part where it says replace the flow control valve, you said they replaced that, right?

A lack of steering assist could occur if the brakes are applied and turning the steering wheel with the vehicle stopped or during parking lot type maneuvers. This concern can be aggravated by worn tires, low tire air pressure, low power steering pump pressures, and tires larger than stock size. In some cases, where the power steering pump pressures are at the low end of the specification, replacing the power steering flow control valve with P/N 26095470 may improve the concern.

The other thing is this vehicle has hydroboost braking, which means it uses power steering fluid pressure to assist in braking instead of engine vacuum, its possible there is a problem there contributing to the lack of assist.