987.2: Trouble again!
- Thread starter marc_tt
- Start date
AndrewT
Member
Could it be wind noise, the engibe cooling fan, or even the ventilation system? If your old ears are anything like my old ears it’s not always immediately obvious whether noises are coming from the front or rear of the car, in fact when there are younger ears in my car they usually hear noises which I can’t!
I hope you find it whatever it is.
I hope you find it whatever it is.
Is it only me with this Boxster?
Recent cold start smoke has dissapeared but, another issue has taken its place of course.
At the very end of our Euro tour when the plug tops failed in Austria the car was driving well but a background hummm had started.
I chose to ignore it.
We are now pondering that humm, not louder, and is the subject of this post, may need some help.
All tyres are good, correct pressures and the car straight as can be. Very nearly 80k miles, last 45k with me.
From about 30 mph to aroundd 50 mph there is a drive train humm.
it varies with road speed and is independent of the engine speed or gear.
It is there no matter what the road surface.
There are NO vibrations at all just this hum that is louder than the engine cruising.
Appears to be at the rear.
There are no cv joint tick tick ticking and no play of wheel bearings at all.
There is no noise putting the power on or off, so seems nothing is loose.
Never ever done this before, on my third set of rear Bridgestones and fronts are replaced twice.
All have great tread depth.
So...any ideas or experiences please?
Recent cold start smoke has dissapeared but, another issue has taken its place of course.
At the very end of our Euro tour when the plug tops failed in Austria the car was driving well but a background hummm had started.
I chose to ignore it.
We are now pondering that humm, not louder, and is the subject of this post, may need some help.
All tyres are good, correct pressures and the car straight as can be. Very nearly 80k miles, last 45k with me.
From about 30 mph to aroundd 50 mph there is a drive train humm.
it varies with road speed and is independent of the engine speed or gear.
It is there no matter what the road surface.
There are NO vibrations at all just this hum that is louder than the engine cruising.
Appears to be at the rear.
There are no cv joint tick tick ticking and no play of wheel bearings at all.
There is no noise putting the power on or off, so seems nothing is loose.
Never ever done this before, on my third set of rear Bridgestones and fronts are replaced twice.
All have great tread depth.
So...any ideas or experiences please?
AndrewCS
Active member
When the plug tops failed in Austria the car was driving well but a background hum had started. Were any covers / heatshields removed - disturbed at this time ? From about 30 mph to around 50 mph there is a drive train hum It varies with road speed and is independent of the engine speed or gear
There is no noise putting the power on or off, so seems nothing is loose
Not drivetrain if independent of ^ these ?
There are NO vibrations at all just this hum that is louder than the engine cruising
As AndrewT mentioned, something affected by airflow - windspeed ?
Air duct - shroud - trim ... loose - foreign body present ? You may have to remove the engine covers to inspect ...
There is no noise putting the power on or off, so seems nothing is loose
Not drivetrain if independent of ^ these ?
There are NO vibrations at all just this hum that is louder than the engine cruising
As AndrewT mentioned, something affected by airflow - windspeed ?
Air duct - shroud - trim ... loose - foreign body present ? You may have to remove the engine covers to inspect ...
Thank you all.
The 6 plug tops were changed after the Eurotrip by Zuffenhaus during a slightly premature 80 k service. However, would be good to check.
I changed the air filter after the service. However, the start of this hum was in Austria, before any plug tops etc, so suspecting the wheel bearings.
Going to carry on with the car to see if it gets worse which may then give a clearer pointer to the culprit.
Will probably return the car to Zuffenhaus for an inspection of the cvs and bearings and check if anything else is amiss.
Odd that there are no vibrations etc from anywhere, runs a dream above 60 mph, but road noise could deafen the hum.
The 6 plug tops were changed after the Eurotrip by Zuffenhaus during a slightly premature 80 k service. However, would be good to check.
I changed the air filter after the service. However, the start of this hum was in Austria, before any plug tops etc, so suspecting the wheel bearings.
Going to carry on with the car to see if it gets worse which may then give a clearer pointer to the culprit.
Will probably return the car to Zuffenhaus for an inspection of the cvs and bearings and check if anything else is amiss.
Odd that there are no vibrations etc from anywhere, runs a dream above 60 mph, but road noise could deafen the hum.
Wheel bearings or tyres would be the usual suspects Graham, although the latter often is accompanied by heterodyning. If the noise disappears on bends I’d be inclined to think that a dodgy wheel bearing is the cause.
Another source could be a moaning final drive, although you’d expect to get that on lighter throttle tip-in tip-out.
All very difficult to diagnose without some indication of the frequency of the noise … discrete or broadband?
Jeff
Another source could be a moaning final drive, although you’d expect to get that on lighter throttle tip-in tip-out.
All very difficult to diagnose without some indication of the frequency of the noise … discrete or broadband?
Jeff
Just a thought a few years ago a friend had a C4S and it had a hum whine what ever you want to call it, tyres bearing looked to be in good health.
Anyway getting to the point he changed the rear tyres even though looked ok
Whine hum gone.
Try to borrow a set of rear wheels from someone give it a try.
Good luck.
Anyway getting to the point he changed the rear tyres even though looked ok
Whine hum gone.
Try to borrow a set of rear wheels from someone give it a try.
Good luck.
Thank you as ever!
I have a good friend with a 996 C4s so will ask.
Im leaning towards the tyres.
absolutly zero play on the wheel bearing when gripping the rear wheels by hand in the old school way. Handbrake off!
swerving the car leftright at 40 with humm noticeable, smooth road, engine in 5th, sound does not change a single note.
slow tight corners i.e. Car park, and no cv joint ticking, no noises at all.
I had the rear wheels off after the Euro trip but could see nothing on the outside Walls or tread face.
Cold this morning in Scotland, pressures are 32 psi rear, 28 front, but doubt those would cause issues.
I have a good friend with a 996 C4s so will ask.
Im leaning towards the tyres.
absolutly zero play on the wheel bearing when gripping the rear wheels by hand in the old school way. Handbrake off!
swerving the car leftright at 40 with humm noticeable, smooth road, engine in 5th, sound does not change a single note.
slow tight corners i.e. Car park, and no cv joint ticking, no noises at all.
I had the rear wheels off after the Euro trip but could see nothing on the outside Walls or tread face.
Cold this morning in Scotland, pressures are 32 psi rear, 28 front, but doubt those would cause issues.
Some time ago I had the same experience as Cliff’s friend on my ancient Mk5 Golf GTi Graham. Although it had plenty of tread, one of the rear tyres was time-expired so I replaced both rears and the problem disappeared.
Just a thought but if you can get a nitrogen fill that may have a positive effect on your problem as it will have an effect on the tyre cavity mode of vibration. Much cheaper than a new tyre
]
Jeff
Just a thought but if you can get a nitrogen fill that may have a positive effect on your problem as it will have an effect on the tyre cavity mode of vibration. Much cheaper than a new tyre![
]Jeff
Love the techie suggestion, easy to get done locally, well with the try.
Tyres are about 1/2 worn, but no older than 2 years.
I had thought of changing them side for side so rotation is reversed.
Tyres are about 1/2 worn, but no older than 2 years.
I had thought of changing them side for side so rotation is reversed.
Bit more on this.
A/C not on or used but tried it today to test, no difference.
throttle on off, hard or gentle, nothing changes
round bends at 50 or any speed, nothing changes.
no vibrations felt at all, none.
have had this car for just over 6 years, this is new.
will jack the car up this weekend.
hand rotate each rear wheel to check the wheel bearings for play and noise.
check the drive shaft cvs for anything and that the shaft floats axially.
check any covers are not open or loose, but this humm sounds more mechanical that whistle.
change wheels over side for side, road test.
if no change, book the car into Zuffenhaus for check over.
if no change, sell it.
It is hard to justify this car when it keeps giving me grief.
A/C not on or used but tried it today to test, no difference.
throttle on off, hard or gentle, nothing changes
round bends at 50 or any speed, nothing changes.
no vibrations felt at all, none.
have had this car for just over 6 years, this is new.
will jack the car up this weekend.
hand rotate each rear wheel to check the wheel bearings for play and noise.
check the drive shaft cvs for anything and that the shaft floats axially.
check any covers are not open or loose, but this humm sounds more mechanical that whistle.
change wheels over side for side, road test.
if no change, book the car into Zuffenhaus for check over.
if no change, sell it.
It is hard to justify this car when it keeps giving me grief.
Day after getting back from the Scottish trip, time to see if anything obviously wrong at the back of this car. To be checked Tyre shape/damage/wear Wheel bearing noise/feel etc Drive shaft play inc the ease to plunge in the CV's. Boot damage etc Any loose wheel arch covers etc, loose pipes or otherwise (check brake wear too) Reverse the wheel positions. Go for a 50/60 mph drive and see if the humm has gone or changed. Results in order from above One tyre not as round as the other using a wax crayon marker against the tyre face when rotating wheels. Ovality about 1mm or less. (correct pressures, 34 psi) No tread wear, tread about 2mm from raised wear rib, nothing uneven, no inner thread wear, both looked good. Absolutely zero bearing wear/movement/ silence/play, both solid as granite. No play, just usual slack when in gear, play from gearbox. Shaft plunges beautifully on both sides, smooth as can be, all gaiters sound. Nothing loose in the arches, suspension etc, all solid. Wheels WERE on the opposite side to the positions when new. My mistake early in the summer. Now wheels on correct sides. Test drive. Noise might have gone, so difficult to be convinced, but different in a good way to the long runs in the car over the last few days in Scotland. Will use the car this week and take the wife too, she has the hearing of an owl. All worth doing even if not 100% conclusive
That sounds like a very comprehensive check Graham, and it sounds as though you inadvertently swapping around the rear wheels could be the cause. Probably best to give the tyres a little while to resettle before making a final judgment, and replacing them could be the only long-term solution if the improvement is marginal; although as I suggested, try a nitrogen fill to see if that helps.
Jeff
Jeff
Agree!
Good bit is the tough bits are really good, the bearings and the drive shafts.
tyres are a consumable, so I will probably driver the until they are worn, and replace.
Looked at selling the car.
very hard to find an alternative at the same price....
got a small belch of smoke on start up to test drive the car..typical!
Good bit is the tough bits are really good, the bearings and the drive shafts.
tyres are a consumable, so I will probably driver the until they are worn, and replace.
Looked at selling the car.
very hard to find an alternative at the same price....
got a small belch of smoke on start up to test drive the car..typical!
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