I wanted to jack all four off ground & run in gear so I can isolate wheel bearing noise. Anyone ever do this? Where is best placement of jacks? On pinch weld seam where factory jack points are?

Yep. Put the jack stands under the factory lift points.

You don't actually need to run the engine when you search for wheel bearing noise. Once it's up in the air, out of gear, and the handbrake is off (or not in park). Turn the wheel by hand, with your other hand on the strut below the spring. You can usually feel the roughness of a faulty wheel bearing.

 

This is a generic test, but it would help if you mention year and model of the car. Good luck isolating the noisy bearing.

I had to work hard to figure which front wheel bearing was bad a while back.

To me, running it on jackstands is sketchy.

 

If I resorted to doing that,

a) I would have someone in the car ready to smack on the brakes at the slightest sign of trouble

maybe do it with the wheels off (bonus- you can retract the caliper pistons and move the calipers so there's no brake noise)

 

On mine, I put both fronts up, put it in neutral, wheels on, spun the wheel with my hand and used a mechanics stethoscope* going to the strut spring.

 

 

* as in, 1/2-inch metal rod held against the spring, thumb over the end, thumb jambed in my ear tight enough to block all sound/air.

If there's a Harbor Freight nearby, you can get a stethoscope for $2.99 or so

To me, running it on jackstands is sketchy.

 

If I resorted to doing that,

a) I would have someone in the car ready to smack on the brakes at the slightest sign of trouble

maybe do it with the wheels off (bonus- you can retract the caliper pistons and move the calipers so there's no brake noise)

 

I think it's sketchy too.. but I absolutely wouldn't do it with the wheels off!

 

If you have the wheels pulled and the car falls off the jack stands, then the ENTIRE CAR becomes a crushing hazard!

You use a big floor jack to lift it an end at a time from the front crossmember and the rear diff, and put jack stands under the 4 lift points on the rocker panels.

 

Running it in the air is dangerous enough, don't have it sitting on a hydraulic jack or worse a scissor jack.

I think it's sketchy too.. but I absolutely wouldn't do it with the wheels off!

 

If you have the wheels pulled and the car falls off the jack stands, then the ENTIRE CAR becomes a crushing hazard!

 

Good lord, I hope no one would go under it in either case...

 

It would be much less likely to come off the jack stands with the wheels off, I think.

 

 

Dave

I would think on jackstands it would be pretty stable. I would accelerate and brake slowly. Like no flooring it or slamming on the brakes, those large counter torques would the most likely things to jostle it. I mean Ferris Bueller did it with just a bumper jack, and that took quite a few kicks to knock it off.

Good lord, I hope no one would go under it in either case...

 

You wouldn't have to be under it to get hurt.... because a car on jackstands isn't going to fall straight down, it is going to fall sideways when the jackstands tip (side, front, back, any direction is possible).

 

So you can pretty much look at the extended height of your jackstands, and figure that the car could come at least that far toward you if it comes down. If you're close enough to be handling parts of the car, you're within range. :-\

I recommend against placing the jack stands on the pinch weld, as if the car has any amount of rust, it will distort or cave in.

 

If you decide to run the car on the stands, have someone in the car. It may be hard to hear any noises over the engine and driveline running.

 

I like the suggestions of feeling/listening through the spring with the wheels off and the brake calipers swung out of the way (which can be done without having to bleed or move the piston, as long as you don't hit the pedal while the caliper is off.

I jacked up rear only & hand spun wheels, with my stethoscope against each rear spring, & I dont think it is a wheel bearing. I think something is rubbing metal to metal somewhere, and transmitting sound.

Maybe loose heatshield of exhaust touching the driveline components?