Boxster Autocross Sound

[charles5448]

Hey all,

I have been auto-crossing my 1999 Boxster Base a couple of times this summer and started getting a strange noise out of the car. The noise only happens in hard cornering while auto-crossing. The tires are brand new. The noise almost reminds me of the noise that ABS makes when it is working. It feels like it is coming from the rear of the car. No loss of power and no evidence of a tire rub.

I was at a PCA autocross yesterday and it was making the noise only when cornering but drove home great. Starting to wonder if maybe it could be the front motor mount or maybe even a wheel bearing? What do you all think it could be? Would be happy to provide more information if this post seems vague but I am in the early stages of diagnosing the problem. It just feels like a rumble in the rear end of the car.

[ianacole]

Do you have TCS on the car? If you're getting into traction control you should see a flashing yellow light on the lower part of your dash.

Does it happen only when turning one direction, or regardless of the direction you're turning? Does it happen when braking hard in a straight line? Have you put it on a lift and taken a look for any rubbing marks around axles, wheel wells, motor area?

[ianacole]

Duplicate...

[charles5448]

I have the traction control button on the dash but it didn't matter if traction control was on or off. Seemed to be worse when I would turn to the left. Didn't happen when braking hard but I was going to get it up in the air tonight and give everything a good once over.

[blue62]

CV joint>
Center motor mount.
Transmission mount. but they usually leak when going bad.
Yes they are fluid filled.

[ianacole]

If it's worse one direction than the other I'd put my money on a CV joint, as blue62 mentioned.

[charles5448]

Do you guys know a good way to test the motor mount or the CV axle to maybe narrow it down?

[blue62]

Originally Posted by charles5448

Do you guys know a good way to test the motor mount or the CV axle to maybe narrow it down?

CV boot = jack the car up check the condition of the boots first. look for grease escaping at boots or either end of axle. grab axle twist back and forth feel for clunking or anything that doesn't feel right. Grab wheel twist left and right feel for clunking or anything that doesn't feel right.


Take car to a area where you can go in a tight circle. Circle left, circle right, vary your speed. If it clunks and it varies with the speed probably CV joints.


Motor mount= if your in tune with your car and have a standard trans.
As you let the clutch out in first from a dead stop you can sort of feel the engine roll forward. At least I could with mine. I could sort of feel a softness in how the drive train was transferring torque to the ground on first gear start out.
Sometimes you can feel it in the shift handle or a little thump or nudge at your back when you shift gears.


You can't see it visually unless you remove it. (damn right). But one thing is near certain with the front motor mount. if you car is a 1999 and the motor mount has never been replaced. It is about a 100 % certainty that it is shot. The rubber center on mine was totally gone at 47000 miles.

But if your hearing a sort of stuttering or pulsing sound when cornering like ABS brakes make, then my guess is CV joint.

[charles5448]

Great information! Going to mess with it more tomorrow. Have the front engine cover off so that will give me good access to see if the motor is jumping around. It all still feels smooth but that was just revving the motor standing still. Didn't see any evidence of anything rubbing or making contact. Just feel like a weird pulse or vibration in hard corners or when I hit a bump in a corner.

[blue62]

keep us posted I always like to know outcomes.

[Geof3]

100% what Blue62 regarding your motor mount. Even though the MM is unlikely the cause of your noise, it is pretty much certain it is shot. Mine is an 02 and like Blue mentioned, my center mount just fell out when I removed the cradle. It is most likely a CV, maybe a wheel bearing. A dead motor mount could contribute to some funky loading on hard cornering.

[charles5448]

Originally Posted by blue62

keep us posted I always like to know outcomes.

Will do, might be a while though. I am going to be away in Germany for a little bit. Maybe someone in Stuttgart will have some answers!

[charles5448]

Drove it around tonight with the front engine cover off and letting the car lug in gear and then stabbing the gas the motor moved quite a bit. Almost sounded like it was bottoming out in the motor mount. Hopefully this is the culprit. Are there any decent upgrades from the factory style? I am pretty rough on the car during an auto-cross and wanted to find something a little more permanent.

[blue62]

Originally Posted by charles5448

Drove it around tonight with the front engine cover off and letting the car lug in gear and then stabbing the gas the motor moved quite a bit. Almost sounded like it was bottoming out in the motor mount. Hopefully this is the culprit. Are there any decent upgrades from the factory style? I am pretty rough on the car during an auto-cross and wanted to find something a little more permanent.

Sounds like the motor mount is shot.
Not to difficult to replace.
I had to drop my engine an inch or two to remove one or two of my bolts.
I also disconnected a coolant hose or two just to make things easier.
If you need guidance you have the forum.

Yes there are upgraded motor mounts available but I have read that they create a harshness in normal everyday driving.
And they are more costly

Something to keep in mind: (These are just my thoughts).
Anything made with a rubber component= the rubber in the part is most likely made in China. Most rubber products made in china don't seem to last. So if you go for an upgraded motor mount and the rubber component of the mount is made in China you have possibly gained a harshness to you ride but no gain in the useful life of the part. At a premium price.

Question: does your issue only arise during hard cornering in autocross conditions???? Or: does it arise during everyday normal driving (cornering) conditions as well?????

[charles5448]

Originally Posted by blue62

Sounds like the motor mount is shot.
Not to difficult to replace.
I had to drop my engine an inch or two to remove one or two of my bolts.
I also disconnected a coolant hose or two just to make things easier.
If you need guidance you have the forum.

Yes there are upgraded motor mounts available but I have read that they create a harshness in normal everyday driving.
And they are more costly

Something to keep in mind: (These are just my thoughts).
Anything made with a rubber component= the rubber in the part is most likely made in China. Most rubber products made in china don't seem to last. So if you go for an upgraded motor mount and the rubber component of the mount is made in China you have possibly gained a harshness to you ride but no gain in the useful life of the part. At a premium price.

Question: does your issue only arise during hard cornering in autocross conditions???? Or: does it arise during everyday normal driving (cornering) conditions as well?????

Only happens under hard cornering during an Autocross. Haven't been able to drive hard enough on the street. There was one section of the track a couple of weeks ago that was bumpy and after hitting it in the middle of a turn it started to make the noise/feeling. Now everytime I corner hard during the Autocross I get the same noise/feeling.

At first I was convinced the tires needed more air. Tried this and there was no change. My boxster has a TC button so I thought maybe that was the culprit but after doing a run with it off, nothing changed.

Jacked the car up today and gave the CV axles a good once over and didn't see or feel anything outside of the ordinary. Gave the wheels a good shake and didn't feel any slack and didn't hear while rotating the hub.

So it only makes the noise under hard cornering during the autocross. Sound and feeling is speed dependent (gets louder and harder with speed). It also doesn't seem to matter if I am turing left or right. No signs of anything rubbing underneath and the car drives GREAT when being street driven. I can shift freely through all the gears and the shifter doesn't have any slack or play in it.

Really at a loss for what it could be. Leaning toward motor mounts after seeing it in action today but thinking there might also be something else at play here.

[blue62]

I always like to go with the simple things first and work my way up from there.
I would check the torque on the torx bolts holding the axles to the drive plates at the transmission end.

I would replace the motor mount then see what happens at an autocross.
keep us posted.

[BYprodriver]

Originally Posted by charles5448

Only happens under hard cornering during an Autocross. Haven't been able to drive hard enough on the street. There was one section of the track a couple of weeks ago that was bumpy and after hitting it in the middle of a turn it started to make the noise/feeling. Now everytime I corner hard during the Autocross I get the same noise/feeling.

At first I was convinced the tires needed more air. Tried this and there was no change. My boxster has a TC button so I thought maybe that was the culprit but after doing a run with it off, nothing changed.

Jacked the car up today and gave the CV axles a good once over and didn't see or feel anything outside of the ordinary. Gave the wheels a good shake and didn't feel any slack and didn't hear while rotating the hub.

So it only makes the noise under hard cornering during the autocross. Sound and feeling is speed dependent (gets louder and harder with speed). It also doesn't seem to matter if I am turing left or right. No signs of anything rubbing underneath and the car drives GREAT when being street driven. I can shift freely through all the gears and the shifter doesn't have any slack or play in it.

Really at a loss for what it could be. Leaning toward motor mounts after seeing it in action today but thinking there might also be something else at play here.

I have a motor mount with a harder than stock bushing I was going to install for racing when mine wore out. I have stopped racing so it is for sale $170 shipped to East coast.

[morgal48]

Mine started clunking going over those red and white striped thingys at corner apexes. Motor mount and both xmission mounts failed. Ended that day at the track, but drove home 100 mi. with no noises. Consider replacing all three now.

[charles5448]

Any chance you all think it could be the Automatic Brake Differential? The car has the traction control and automatic brake differential option code (222,224). Does anyone happen to know how these old traction control systems work?