997 GT3 Death Rattle on Start up
Discussion
chanjam said:
thanks. is this the same as a piston slap?
Whereas piston slap is where the pistons knock the bores through wear. If it's anything like the 996GT3 noise, if you had piston slap that sounded like that, your pistons would be escaping the constrains of the block.If you look at the OP gauge, the death rattle stops as the oil pressure shoots up.
Bert
Apologies if I am off the mark but the specialist I use tells me that it is common in many Porsche models to get a bit of a 'rattle'. He told me that is is not all that unusual for it to persist even when warm and is noticeable when the car is out of gear. His explanation sounded very similar to what fergus describes.
I think I'm correct in saying that the rattle you get on startup is very specific and there only on startup after a time of not using the car. If you have that rattle at other times, you are in deep poo.
There may well be other rattles you can here. Just listen to the noise the 6GT3RS diff makes for example. Talk about box of spanners - hot or cold.
Bert
There may well be other rattles you can here. Just listen to the noise the 6GT3RS diff makes for example. Talk about box of spanners - hot or cold.
Bert
LuckyP said:
Death rattle!! What a good way of describing it!! Yes, comon to the Gen 2 also. Death rattle and smoke, what more dramatic way to start your early Sunday morning hoon!!??
Yes, and a lot of smoke as well! The 3.6s smoked a bit, but my Gen2 smokes quite a lot. It's always gone after a few seconds, and oil consumption has not been measurable in 4,500 spirited miles, so I am not remotely perturbed, but it does make onlookers stare.Combined with the start up rattle and the noise from the single mass flywheel, and the car cannot be accused of pandering to the boulevard cruisers
. In fact, I love the fact that in the handbook is has a section on compromises to comfort made in the interest of performance. Cheers
There are a number of noises, some of which sound similar to an untrained ear.
The cam followers pressuring up is a common noise. This occurs when the cam follower or bucket is compressed and the gap between the cam and follower is too big. As the follower expands he gap decreases and the noise goes away.
Another common noise is chatter from the clutch release bearing. A solid flywheel amplifies this problem. It will be a constant chatter at idle, reducing as the revs increase and the engine smoothes out. The way to identify this one is to put your foot on the clutch. The noise will go away as the release bearing is loaded up and stopped from rattling around.
Another possible noise is a timing chain rattle. This is caused by the under tensioned chain hitting the inner wall of the timing chain housing. It may require a new tensioner. A broken tensioner ramp will also cause timing chain noise. Finally with timing chains it could have come half off the tensioner ramp. A number of engines have suffered broken timing chains 50 or so hours after a mechanically driven over rev (ie too low a gear is selected by mistake). This causes the chain to jump off the ramp and eventually it fails.
In truth there are any number of things that could make noise and sometimes even the best trained ears can be left scratching their heads. Things like piston slap and big end shell noise are altogether more sinister and actually quite rare in a 911 engine. That's not to say they don't exist, but in this instance I'd say far more likely the cam followers (also called hydraulic lifters, cam buckets or hydraulic tappets), pressuring up. If at all in doubt a good marque specialist should be you first port of call.
Keep smiling and fingers crossed you all manage to avoid piston slap this weekend when you're gracing the dance floor of the over 30's night at the Wolverhampton welders and pipe fitters social club.
Henry
The cam followers pressuring up is a common noise. This occurs when the cam follower or bucket is compressed and the gap between the cam and follower is too big. As the follower expands he gap decreases and the noise goes away.
Another common noise is chatter from the clutch release bearing. A solid flywheel amplifies this problem. It will be a constant chatter at idle, reducing as the revs increase and the engine smoothes out. The way to identify this one is to put your foot on the clutch. The noise will go away as the release bearing is loaded up and stopped from rattling around.
Another possible noise is a timing chain rattle. This is caused by the under tensioned chain hitting the inner wall of the timing chain housing. It may require a new tensioner. A broken tensioner ramp will also cause timing chain noise. Finally with timing chains it could have come half off the tensioner ramp. A number of engines have suffered broken timing chains 50 or so hours after a mechanically driven over rev (ie too low a gear is selected by mistake). This causes the chain to jump off the ramp and eventually it fails.
In truth there are any number of things that could make noise and sometimes even the best trained ears can be left scratching their heads. Things like piston slap and big end shell noise are altogether more sinister and actually quite rare in a 911 engine. That's not to say they don't exist, but in this instance I'd say far more likely the cam followers (also called hydraulic lifters, cam buckets or hydraulic tappets), pressuring up. If at all in doubt a good marque specialist should be you first port of call.
Keep smiling and fingers crossed you all manage to avoid piston slap this weekend when you're gracing the dance floor of the over 30's night at the Wolverhampton welders and pipe fitters social club.
Henry
Henry-F said:
Another common noise is chatter from the clutch release bearing. A solid flywheel amplifies this problem. It will be a constant chatter at idle, reducing as the revs increase and the engine smoothes out. The way to identify this one is to put your foot on the clutch. The noise will go away as the release bearing is loaded up and stopped from rattling around.
Henry
I have never come across this fault before, how does the bearing rattle around when its fixed to the pressure plate and held by the release bearing fork arm..? When you load a faulty release bearing up it gets louder if the bearing is at fault.Henry
The chatter you can hear is more than likely the gearbox gears chattering against one another and when the clutch pedal is depressed the input shaft stops turning thus the noise goes.
Thats just my take on things... as for the original question if its a "death rattle" then get it looked at by another specialist and get a 2nd opinion as if it is as bad as it sounds you may have some problems. If it rattles as soon as the key is turned and goes away within 10 seconds it could be a crank rumble until the oil pressure builds up and fills the main bearings, seen this alot on 1999 GT3 cars and they were around 40000 miles.
Mike
It seems that many GT3s have a rattle at startup. Some say this is normal whilst some may ask why?
Apart from crank bearing failure or failure of a hydraulic tappit (which is unlikely but could be serious) I wonder if the engine's origin may point to a likely cause?
The crank and bottom end is derived from the 964R air cooled engine.
The cylinder barrels are a hybrid water cooled liner system with forged pistons. I think we can discount barrel/piston problems as they dont rely on oil pressure and take much more than a few seconds to warm up
The heads are another hybrid using the variocam system designed in the 996 engine.
Do 964s commonly have a rattle problem? Is there a camchain tension flaw?
Do 996s have a rattle problem (other than IMS and liner cracks)
Have Porsche revised any of the main components since the engine was designed?
I ask these questions rhetorically because mine rattles for about 5 seconds as well
Apart from crank bearing failure or failure of a hydraulic tappit (which is unlikely but could be serious) I wonder if the engine's origin may point to a likely cause?
The crank and bottom end is derived from the 964R air cooled engine.
The cylinder barrels are a hybrid water cooled liner system with forged pistons. I think we can discount barrel/piston problems as they dont rely on oil pressure and take much more than a few seconds to warm up
The heads are another hybrid using the variocam system designed in the 996 engine.
Do 964s commonly have a rattle problem? Is there a camchain tension flaw?
Do 996s have a rattle problem (other than IMS and liner cracks)
Have Porsche revised any of the main components since the engine was designed?
I ask these questions rhetorically because mine rattles for about 5 seconds as well
sorry for late replies. I'm still digesting all of them!Looking up the Rennlist site there are quite a few posts that describe it perfectly along with the random puff of oil smoke that is sometimes there sometimes not. Basically the way it's been described is like a GRAAAAAAACK, or wheel nut gun that's spinning after reaching maximum torque, or grinding gears into reverse without fully depressing clutch. It's pretty random when it occurs liek the puff of smoke though the two aren't linked. The favourite theory as to why they do it is due to pressure in the oil system decreasing - specifically the chain tensioners and valve train - I don't know enough about it - all I know is it sounds horrible when it happens and it lasts between 0.5secs and 2 secs when it does. A whole bunch of people including the GT3 "expert" at Porsche Redding says it's normal across all the GT3 range from 996mki through to 997mkii but I wonder if it is easily cureable if not all cars suffer from it. For example my C2S never smoked on startup and I wonder if it is just a random issue about the orientation of the rings in the cylinder from manufacture and where exactly in the stroke that the engine happens to stop. The random nature of how the awful sound happens (although far more likely if the car has sat for a while and far less likely (zero) when the car has been used that day makes me think that there must be a random issue taking place on switch off where the oil pressure either dissipates or is maintained.
BertBert said:
chanjam said:
thanks. is this the same as a piston slap?
Whereas piston slap is where the pistons knock the bores through wear. If it's anything like the 996GT3 noise, if you had piston slap that sounded like that, your pistons would be escaping the constrains of the block.If you look at the OP gauge, the death rattle stops as the oil pressure shoots up.
Bert
BertBert said:
I think I'm correct in saying that the rattle you get on startup is very specific and there only on startup after a time of not using the car. If you have that rattle at other times, you are in deep poo.
There may well be other rattles you can here. Just listen to the noise the 6GT3RS diff makes for example. Talk about box of spanners - hot or cold.
Bert
Yes you are right - its is only on startup and does not last long. To be honest, almost everything rattles on the GT3 when you're moving (compared to the carerra that is :-))There may well be other rattles you can here. Just listen to the noise the 6GT3RS diff makes for example. Talk about box of spanners - hot or cold.
Bert
chanjam said:
sorry for late replies. I'm still digesting all of them!Looking up the Rennlist site there are quite a few posts that describe it perfectly along with the random puff of oil smoke that is sometimes there sometimes not. Basically the way it's been described is like a GRAAAAAAACK, or wheel nut gun that's spinning after reaching maximum torque, or grinding gears into reverse without fully depressing clutch. It's pretty random when it occurs liek the puff of smoke though the two aren't linked. The favourite theory as to why they do it is due to pressure in the oil system decreasing - specifically the chain tensioners and valve train - I don't know enough about it - all I know is it sounds horrible when it happens and it lasts between 0.5secs and 2 secs when it does. A whole bunch of people including the GT3 "expert" at Porsche Redding says it's normal across all the GT3 range from 996mki through to 997mkii but I wonder if it is easily cureable if not all cars suffer from it. For example my C2S never smoked on startup and I wonder if it is just a random issue about the orientation of the rings in the cylinder from manufacture and where exactly in the stroke that the engine happens to stop. The random nature of how the awful sound happens (although far more likely if the car has sat for a while and far less likely (zero) when the car has been used that day makes me think that there must be a random issue taking place on switch off where the oil pressure either dissipates or is maintained.
It's normal - forget it. Reading this thread with just give you nightmares. chanjam said:
sorry for late replies. I'm still digesting all of them!Looking up the Rennlist site there are quite a few posts that describe it perfectly along with the random puff of oil smoke that is sometimes there sometimes not. Basically the way it's been described is like a GRAAAAAAACK, or wheel nut gun that's spinning after reaching maximum torque, or grinding gears into reverse without fully depressing clutch. It's pretty random when it occurs liek the puff of smoke though the two aren't linked. The favourite theory as to why they do it is due to pressure in the oil system decreasing - specifically the chain tensioners and valve train - I don't know enough about it - all I know is it sounds horrible when it happens and it lasts between 0.5secs and 2 secs when it does. A whole bunch of people including the GT3 "expert" at Porsche Redding says it's normal across all the GT3 range from 996mki through to 997mkii but I wonder if it is easily cureable if not all cars suffer from it. For example my C2S never smoked on startup and I wonder if it is just a random issue about the orientation of the rings in the cylinder from manufacture and where exactly in the stroke that the engine happens to stop. The random nature of how the awful sound happens (although far more likely if the car has sat for a while and far less likely (zero) when the car has been used that day makes me think that there must be a random issue taking place on switch off where the oil pressure either dissipates or is maintained.
my car does this, randomly too. Sometimes the next day after a drive, sometimes not drive for 1 month and doesnt do it. Never had smoke, but a friends 997GT3 does smoke sometimes. Pure random stuff.mine did it at 69k miles and still does at 90k. Have had chain tensioners replaced but still does it. Think its a GT3 thing
Gassing Station | Porsche General | Top of Page | What's New | My Stuff