TECH Tips

The following technical tips provide repair information about specific conditions on a variety of vehicles. If you have a tough or unusual service repair, the TSS Technical Assistance Hot Line can help. Call 1-800-825-5886, prompt #2, to speak with a technical expert with the latest OEM information.

Clutch Bleeding Problems

Ford Ranger with non-self adjusting clutch sets

The non-self adjusting clutch sets may exhibit a problem of poor or no release of the clutch. The problem is caused by air trapped in the hydraulic system -- specifically the master cylinder.

In order to isolate and correct the condition, first eliminate the possibility of any worn or damaged components in the release system. With the clutch installed and the transmission in the vehicle, check to make sure there is no leakage from the master cylinder and around the fittings of the Concentric Slave Cylinder (CSC). Then, in order to determine if air is trapped in the master cylinder, disconnect the line going into the CSC and push down on the clutch pedal. The pedal should be stiff. Theoretically, if the master cylinder portion of the system is completely full of hydraulic fluid and has no trapped air, the pedal will not move at all (or very little - less than 1/2"). The reason this simple test works is due to the nature of the connector between the master and slave cylinder. When it is not connected to the slave cylinder the valve in the line stays closed and will not allow any hydraulic fluid to escape. 

During operation in the vehicle, the connections of the master cylinder are pointing down and the piston rests at the high end and is pushed down for the release stroke. This creates an air trap at the piston end away from the connector lines where fluid comes in and goes out. 

The illustration (Fig. 11) of the system as installed in the vehicle: 

A.) Location of trapped air

B.) Location of retaining clip

C.) Notice angle of master cylinder

D.) Bleeder valve

E.) Line connector

F.) Internal slave

Fig. 11

When the master cylinder is removed from the vehicle (Fig. 12) and manipulated so the lines are pointing up and the piston end points down (with the reservoir cap removed), the piston can be compressed into the slave cylinder and air bubbles will be seen escaping from the top of the reservoir if air is present. Once all the air is purged out of the master cylinder, it can be reinstalled on the vehicle. Before connecting the hard line to the CSC, push the pedal by hand to confirm it is solid.

Fig. 12

An alternative that can be tried before bench bleeding the master cylinder as described above is to raise the front of the vehicle to reduce the downward angle of the master cylinder and make it as level as possible and then bleed the system by repeating the following several times as needed:

Depress the clutch pedal fully

Loosen the bleeder screw on the CSC to allow air (and some fluid) to escape

Retighten bleeder screw

Release pedal

Power Steering Performance Concerns

2003-2006 Cadillac Escalade, Escalade ESV, Escalade EXT; 2003-2006 Chevrolet Avalanche, Suburban, Tahoe; 2003-2007 Chevrolet Silverado Classic; 2007-2008 Chevrolet Silverado, Suburban (2500 Series only); 2003-2006 GMC Yukon, Yukon Denali, Yukon XL; 2003-2007 GMC Sierra Classic; 2007-2008 GMC Sierra, Yukon XL (2500 Series only)

A lack of steering assist may occur when stopped or during parking maneuvers. This condition may go away or greatly improve once the vehicle begins to move or is above parking lot speeds. It may be aggravated by worn tires, low tire air pressure, low power steering pump pressures, and tires larger than stock size.

In all cases, it is recommended to use the proper tire size and that the maximum tire pressure is set according to the manufacturer's specification, especially for the front tires.

To repair this condition, perform the power steering system test found in the appropriate Service Information. Make any necessary repairs based on system diagnosis.

If diagnostics do not lead to any repair, this concern is a normal operating characteristic.

If the vehicle is equipped with a 670 gear box, it may be replaced with a 680 gear box. To determine if the vehicle is equipped with a 670 gear box, inspect the mounting bolts that attach the stub shaft housing. A 670 gear box will have only three mounting bolts. If replacing a 670 gear box with a 680 gear box, it will be necessary to replace the:

Power steering gear (GM part number 88965542)

Union fitting (GM part number 26025709)

Both inlet O-ring seals (GM part number 26001594)