cjoenck

I know this will be a tough one to describe as it involves sound. I have a stock C2 Targa '90 Tip on 17" wheels lowered slightly, stock engine mounts, and later style 4-pod calipers in the rear. All calipers were rebuild by GoldLine Brakes about 2,000 miles ago. Rear axles and rear bearings are less that 3,000 miles old.
I do get a distinct grinding noise that is speed depended. Barely there below 10 mph and then getting progressively louder. First thought was rubbing break pads due restricted brake lines. The flexible lines were replaced 7 years ago but is it possible the final hard lines to the caliper clog and restrict hydraulic fluid flow? One of them looks like it has been torqued and then bent back. Bleeding the lines only gets me a trickle of fluid under pressure using the Motive Bleeder, especially the rear right, furthest away from the reservoir.

What am I missing? Thanks.

Rocket Rob

Have you tried lifting the car and spinning each of the wheels by hand to try to isolate which wheel is making the noise? You will also be able to feel if one wheel takes more effort to spin than the others.

cjoenck

I have the car on a lift right now. Tried spinning the wheels by hand and I am getting a little rubbing / mechanical noise when spinning the rear wheels. None are binding though.

This is probably a stupid question but do the pads retract completely, ie don't touch the calipers when not engaged or do they just ever so lightly rub and make a slight noise?

Has anyone run the engine in first gear and listen or is this a big no no while the car is on a lift?
Problem is, I can't spin the wheels fast enough by hand to positively reproduce the sound.

Rocket Rob

The pads do not retract. They are always touching the disks.

Can you run the engine while on a lift? Yes, of course. Just be careful of those around the car. You don't want anyone or a pet to bump or touch a spinning wheel.

Rtz

Might be a defective wheel bearing, but you’d probably hear grinding noise soon after installation.

cjoenck

Both bearings are about 3,000 miles old. Did anyone ever see the new bearings fail fast? I believe they used OEM but not sure.

cjoenck

Spent some more time under the car this morning. The rear wheels are turning freely with just ever so slight resistance. The front wheels only turn about twice before coming to a stop. So not really binding but also not turning freely.

Is that normal? I have had this car so long - almost 10 years - that I can't remember what it felt like when I first drove it.

Happy 4th everyone.

Rocket Rob

The front wheels have more drag than the rear? That seems odd since the rear has the drag of the CV axles and transmission.

cjoenck

Yes, that surprised me too. I had another thought I need validation on - is it possible that a worn / defective upper shock mount could transmit more road / roll noise to the tub and inside the car. I would imagine that Porsche tried to decouple the roll noise transmitted through the shock assembly from the car.

What would worn upper shock mounts sound like?

Rocket Rob

When I refreshed my shocks and springs, I checked the strut mounts and one side felt grumbly so I replaced both sides. I don't think you would hear it inside the car. Does the grinding noise happen as you turn or does it happen when the steering is stationary?

I'm wondering if your front wheel bearings are the fault.

cjoenck

It's independant of steering input, only speed dependent. The sound is barely there below 10 mph and the steadily builds as speed increases.
When I replaced my bearings I only replaced the rear so you might be be on to something. Although it's not the typical bad bearing sound that sounds more like a chopper following you.

Goughary

If you happened to have *** bearings installed- there is a high likelihood of failure as many are shipped either without grease or with very little. We found this out the hard way.

Pull the axles out and spin the hubs. You will know right away if the bearings are dead.

cjoenck

I found one old front and one of the "new" rear bearings to be questionable. Which manufacturer should I go with for replacement. I think I will do all four to be done with it.

Goughary

I would use Porsche oem, or skf.

There is nothing wrong w the *** bearings, except for the grease issue. So if one pulls the seals and adds grease, they are as good as the others. But to avoid that i now use skf.