That metal-grinding sound may not be what it seems

by Jim KerrBackyard Mechanic . Jun 08 2018

Question: I have a Chevrolet Impala. The trunk lid began falling and would not stay elevated when open. I had new trunk struts installed about a year and a half ago. They functioned smoothly and quietly when they were first installed.

The trunk lid struts seem to still be functioning fine, but I can now hear a grinding sound inside the struts when the trunk lid is raised and lowered. I am wondering why they are making this noise now and if there is something I should do about it.


Answer: Sound can transfer easily between metal components and a grinding sound would typically appear to be metal rubbing against metal, but sounds are also deceiving. The sound could be coming from the shaft seal on the trunk lid struts as the shaft moves through the seal. Often, these seals will make a squeaking or squealing noise when they get dry, but they can make other sounds. Apply a thin film of lubricant to the shaft and open and close the trunk lid several times to get the lubricant into the seal surface. I use silicone grease to lubricate these seals — the same type as I use on door-opening seals — but any type of grease or oil will lubricate the seals, so you can see if the noise is coming from the seal.

If the noise is still there, then I would try some spray lithium or white grease lubricant on the strut pivot points (mounts). Also lubricate the trunk hinge pivot points. These moving parts don’t need lubricant often, but lubricating them every two or three years keeps your vehicle in top shape.

If there is still noise, it could be coming from inside one of the struts as the piston rubs against the inside of the housing. This is very uncommon, but possible. If this is the case, the only repair is to replace the strut, but I would wait until it stops functioning unless you really can’t stand the noise.


Question: Our Civic Si (1996) is making a huge roar that’s not engine-speed dependent, but is vehicle-speed dependent. The front wheel nuts are also very hot after driving. Could it be wheel bearings or is it something else? Is it expensive to repair?


Answer: From your description, it sounds like you have a wheel bearing problem or something that is related to wheel speed, such as the final drive bearings in the transmission. I would suspect wheel bearings though.

To try and identify where the problem is, drive at about 20 to 30 kilometres per hour in a clear area and turn corners left and right. When you turn left, it places more load on the outside (right) wheel bearing and when you turn right the load goes on the left wheel bearing. A bad bearing will get louder when the load is placed on it and usually gets quieter when the load is reduced. If the noise doesn’t change, the problem could be bearings in the transmission.

Changing a wheel bearing requires special equipment such as a press to remove and install the bearing in the wheel support hub. Many auto parts suppliers sell the bearing and support hub as an assembly, which is often a better way to go. Even though the parts are a little more expensive, the labour to install them is much easier. Expect to pay about 1½ to two hours labour costs plus about another $100 to $150 for parts. You will possibly also need to have a wheel alignment done after the hub is replaced.

As for the hot wheel nuts, this could be caused by braking the vehicle to a stop. A bad bearing could generate more heat, but usually that heat is dissipated though the hub assembly. It is normal for the wheel and wheel nuts to get hot from braking, but if one side is a lot hotter than the other, check for dragging brakes on that side. With the vehicle jacked up, the wheel should rotate easily.

If not, then the brake calliper may be binding and the mounts need cleaning and lubricating or the caliper replaced.