Knocking could be power-steering pulley

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This article was published 17/04/2009 (6046 days ago), so information in it may no longer be current.

QUESTION: I recently had a blown power-steering hose and pump replaced in my 2000 GMC Sierra 2wd 4.3L. I picked up the truck from the shop and as the week progressed, I noticed a very loud ticking or slapping sound coming from the engine compartment when the truck is stone cold. Once the engine is warm, it seems to be happy and the noise goes away.

Starting the truck again does not repeat the sound, but leaving it overnight does bring it back. I have not noticed any changes in gauges, power, etc. On visual inspection, I cannot see any wobbly pulleys or anything in the way of a fan blade. Could something have not been installed right at the shop, or am I just noticing something sounding like a bad valve/lifter co-incidentally?

Ryan

ANSWER: While the noise could be a coincidence and coming from an unrelated area, there are a couple of power-steering items that should be checked that could cause the noise. The first item to check is the position of the power-steering pressure hose. If this hose, especially the metal lines at the ends of the hose, are touching the frame, body or engine, they could cause a knocking sound. This problem can be more noticeable when the engine is cold because the power-steering fluid has not warmed up yet and takes more pressure to pump. Repositioning the hose will quickly solve this type of problem.

The other power-steering-related problem is a little more difficult to see. It is possible the pulley on the power steering pump is not in alignment with the other pulleys on the engine. This causes the multi-ribbed serpentine belt to try to climb out of position and as it does this, the spring-loaded belt tensioner rapidly snaps back and forth causing the knock. Once the belt has been run for a short while, the rubber warms up and the problem is not as noticeable, but continuing to operate with this problem will cause belt and tensioner failure later on.

It can be difficult to "see" the pulley alignment on these multi-ribbed pulleys, but GM does make a laser alignment tool that some shops have to help identify a problem. The pulley is pressed on to the power-steering pump shaft and can be moved in and out, so repositioning it isn’t a big task if you have the special pulley removal tools. Because the pump has just been changed, I suspect the problem is with belt alignment. You may be able to see it visually or watch the tensioner to see if it jumps.

 

QUESTION: Could you shed any light odropn this problem? I have a 2005 Buick Allure with 3.8-L engine. It has leaked oil internally on six cylinders since new and has been driven 25,000 kilometres. All intake and exhaust valve seals were replaced — then it leaked internally again. I was on low oil after 800 km. They took the engine out of the car and have rebuilt it. Now the leak has slowed to where I am on low oil at 3,000 km. Is this OK?

— Walter

ANSWER: According to GM, oil consumption will vary greatly based on driving style, vehicle load, engine speed and engine design. However, they do reference an accepted rate of oil consumption of .946 litres (1 U.S. quart) in 3,200 km. This applies to normally driven vehicles that are using the correct oil and maintained properly with under 58,000 km on them. It would appear your rebuilt engine is very close to that accepted level of oil consumption.

As you have no external oil leaks, the oil has to be used internally. If it is being used in around-town driving, excessive clearance in the valve guides or valve seals are the likely problem. If the oil is used on the highway, bad piston rings are a more likely cause.

There are many variables when measuring oil consumption. These include the angle the vehicle is sitting at, how long the engine has been stopped to allow oil to drain back to the oil pan, and if the dipstick is being pushed in all the way. It is also possible to have an incorrect dipstick in the engine that will indicate excessive oil consumption. If the dipstick is too short, then the oil level is set too high and this causes more oil to be used.

Jim Kerr is an experienced automotive mechanic, and instructor of automotive technology.

kerr.jim@sasktel.net