Engine/transaxle mounts??
 

Need some help diagnosing a bad noise. 06 FEH 212,000 miles

After having a front half-shaft fail & replacing both front half shafts a new noise appeared with about 500 miles on the new half shafts.

It is a thumping in synchronism with wheel rotation (ie 1 times rotation rate).

It comes in after 5-15 miles of warmup/run. it doesn't appear if the car is on jack stands with engine running and wheels engaged.

It goes away when turning or on hard acceleration, light load & coasting.

Went in and replaced the drivers side wheel bearing thinking it was somehow in or around the wheel knuckle. No evidence of contact around the knuckle nor was there any apparent bearing damage when I inspected the bearing races. (Note the wheel bearings were replaced 25k ago so this was another step but did not really expect to find damage)

A friend thought it might be either a bad ball joint or an engine mount.

Ideas?

Re: Engine/transaxle mounts??
 

If it is one to one with the wheel rotation, it will either be a hub bearing or one of the CV joints in the half shafts you just replaced. I would suspect the half shafts if you bought rebuilt ones.

Re: Engine/transaxle mounts??
 

Then the exact same symptom has occurred with three half shafts. In researching things if it were the plunge joint (inner) there would be a 3X rotation noise. If it were the outer radial joint it would likely be a 6X rotation noise. That's not what I am seeing.

I've now replaced the hub bearing with no change in symptoms.

I'm strting to look at engine mounts.

Re: Engine/transaxle mounts??
 

On the gas version, one is liquid filled and I've read of them failing but owners have reported seeing the liquid.

Re: Engine/transaxle mounts??
 

If you have 4WD, a bad PTU could be a cause. Bosch has a NVH analyzer tool that should help identify the problem also.

Re: Engine/transaxle mounts??
 

Vibration analyzer for a DIY'er is a bit pricey! Had a full fledged vibration analyzing program at the Ford plant that I worked at and Ford just let it fade away. I guess that it didn't look good on paper. I had a phone interview from Fluke Corp. during their NVH product development and the guy couldn't believe what I told him.

Re: Engine/transaxle mounts??
 

Agree no need to buy a multi thousand dollar NVH tool for one job. Some larger shops/dealerships have the tool. IMO it would be worth it to find the cause of a problem before throwing parts at it.

Re: Engine/transaxle mounts??
 

I'm going to replace the engine/transaxle mounts one at a time. Starting with the bottom ones. They should be here midweek. Found out on home work that the middle rear engine mount has been redesigned so maybe there's a fault in that one.

Thought about the PTU, but it would seem that any noise from it would be a multiple of the wheel rotation rate instead of 1 to 1 with wheel rotation rate of else a continuous grinding type noise.

Re: Engine/transaxle mounts??
 

process of elimination before throwing parts at it. Remove the drive shaft from the pto tp the rear diff. Sounds to me like your rear carrier/center support bearing is going out.

Re: Engine/transaxle mounts??
 

Roger your point about throwing parts ($$) at this, well taken.

Re: the carrier bearing. The noise is specifically and directly in sync with wheel rotation at one times rotation. If it were the carrier bearing it would be at 2.73 (I think this is the rear axle ratio) times wheel rotation. It is as if there's something going on in the brake caliper or it mounting.

Along the way since replacing the brake pads the first time, I've had an interference problem with the caliper and the inside of the drivers wheel (OEM). I can find evidence of dragging inside the wheel from the caliper but what I see doesn't seem to correlate with the knocking sound I get.

Any ideas?

PS I will go look at the carrier bearing.