Is this engine sound normal?

[strother]

Originally posted by 450knotOffice ... In fact, just about every manual tranny I've driven with sounds like that at low revs and high load. My 1998 F-150 pickup with a manual tranny sounded like that all the time. ... Yeah, I guess I'm being a little sensitive. I think you're right on with the F-150 comparison; I originally said it reminded me of a bus accelerating. (An F-150 is not exactly a bus...) I've recently driven a Jetta and a New Beetle with manual transmissions, and they don't make the sound. Nonetheless, I think you've convinced me it isn't the engine. I WILL ask a Porsche wrench next time I take the car in.

[tshih]

You know that 1st gear in an SC is good for 40 mph so when your speed drops below 30 mph you should learn to double clutch and down shift back to 1st. Doing it properly is fun and doesn't hurt your gearbox one bit!!

[MysticLlama]

Mine makes the same sort of sound.

It really bothered me for a while, and still sorta does, but I was really worked it was pinging, and then I drove a 74 with a friend.... got that thing on the freeway and hit the gas, and wow, so THAT's what pinging sounds like. (needless to say, he didn't buy that one)

My problem is that I have to go up a hill to get to my house, and it's in a residential neighborhood. I have no cat and a Bursch muffler, so bombing up it in 1st or going 3500+ rpms in 2nd to keep the noise away is kinda out of the question unless I want someone to call the cops, it's just kinda rude anyway...

I do think it's tranny related though, can't hear it with the window down at all, and it goes away when you let up, and as long as you give it just barely enough gas to slowly accelerate when the hill gets a little shallower it goes away.

So hopefully I'm right and it's nothing serious, I recently had a full service/valve adjustment/plugs/distributor clean up/etc. as well.

[Craig 930 RS]

My first thought was the trans. Any mods done in there?

Ought to hear mine with the LSD and WEVO system - marbles in a muffled can ;-)

[strother]

Originally posted by Craig911
My first thought was the trans. Any mods done in there?

Ought to hear mine with the LSD and WEVO system - marbles in a muffled can ;-)

No mods... In fact, just had the 915 rebuilt -- all new synchros, some new dog teeth and new sliders too. It made this noise both before and after. (It was making other -- shall we say -- "disturbing" noises before the rebuild.)

[strother]

Originally posted by MysticLlama
Mine makes the same sort of sound.

It really bothered me for a while, and still sorta does, but I was really worked it was pinging, and then I drove a 74 with a friend.... got that thing on the freeway and hit the gas, and wow, so THAT's what pinging sounds like. (needless to say, he didn't buy that one)

My problem is that I have to go up a hill to get to my house, and it's in a residential neighborhood. I have no cat and a Bursch muffler, so bombing up it in 1st or going 3500+ rpms in 2nd to keep the noise away is kinda out of the question unless I want someone to call the cops, it's just kinda rude anyway...

I do think it's tranny related though, can't hear it with the window down at all, and it goes away when you let up, and as long as you give it just barely enough gas to slowly accelerate when the hill gets a little shallower it goes away.

So hopefully I'm right and it's nothing serious, I recently had a full service/valve adjustment/plugs/distributor clean up/etc. as well.

Sounds like we are in the same boat. I wish the sound wasn't there, because otherwise, the engine's sound is like zen to me. Truly a sound to behold. (Can one behold a sound??)

[911mot]

It could be clutch chatter if it only does it on the move.
Can you make the noise when stationary by bringing up the idle? If so I would check the chain tensioners

[strother]

Originally posted by 911mot
It could be clutch chatter if it only does it on the move.
Can you make the noise when stationary by bringing up the idle? If so I would check the chain tensioners

Do you mean when the clutch is disengaged? No weird sounds there. I like the word "chatter" to describe the sound though... That's what it sounds like.

[911mot]

If it's clutch chatter you will only hear it with the clutch engaged (foot off) .

Found this if its any help :
Dust build up causes chatter and slipping due to the slip/grab action of the dust. The 6 to 9 springs around the disc hub may range from loose to tight. Not to worry, the looseness/tightness does not affect the operation of the disc. They're there to asborb shock and help eliminate engine pulsations (lumpy cams). By far the most critical element of the disc in eliminating chatter is the "marcel". This is the term given to the crimped plate, or wafer, between the 2 clutch linings. The purpose of the marcel is to prevent clutch chatter by giving the clutch disc some "give" during clutch engagement. The marcel also helps prevent the lining from sticking to the flywheel and/or pressure plate (due to the spring effect of the marcel) when the clutch is being disengaged. The marcel thickness (the distance the linings are held apart by the marcel when the disc is not under compression) will vary depending on the type of use the disc is designed and built for. Basically the thicker the marcel, the smoother the clutch will engage and the spongier it feels to your foot. The absence of marcel makes the clutch grab, but makes for a much more postive lockup (less slippage and ability to handle more horsepower). As the marcel thickness increases, it will require more clutch lever travel to engage/disengage the clutch. A pure drag/race car clutch marcel will be from 0.000" to 0.010" since engagement is quick and abrupt and chatter is not a problem. Truck clutches use marcels in this area also. A street/strip clutch will generally have marcels from 0.015" to 0.025". Pure street clutches will use marcels in excess of 0.025". A super soft clutch uses marcel in the neighborhood of 0.030" to 0.040".

[kqw]

Just by chance.....

Check the shield under the cat. to make sure the shield has not broken away from it's bolts. This will cause a sound at low RPM that simulates chain rattling.

[mattxbart]

My G50 makes the same noise you describe under the same types of conditions. It is like a growling-chatter sounding thing that isn't very noticeable. My mechanic said it is completely normal and I haven't really worried about it since.

[Craig 930 RS]

MYSTICLLAMA - You have a PM - !

Craig

[agfours]

Originally Posted by strother

I've probably asked enough basic questions to brand me for life, but I've got another one. Before I start, I'll tell you that I've spent the past 1.5 hours reading archived posts that turn up when I search "load" and "noise"...

My engine makes a rattling noise briefly when I accelerate hard under load -- usually from about 2000-3000 rpms or so in 2nd gear when driving around the neighborhood. It isn't horribly loud, but it is an additional sound on top of the engine noise. The noise only lasts a second or so until the rpms pick up in the gear I've selected. This is going to make it sound worse than it really sounds, but it reminds me of the sound a bus makes on accelration.

Is the sound normal? After reading the archived posts, I'm paranoid about broken head studs, and worried about timing and mixture. You should know that I just had the engine tuned up, including valve adjusment. It was doing this before and after the tune up.

Hi All,

I'm pulling an old post forward to get some clarifying thoughts....the original post outlines the issue sounds very similar to one I'm having, but want to clarify the scenario a bit.

Part 1:

I'm getting this same gravel-like 'dieseling' sound from the power train. It has a mid-timbre sound, has a substantial presence over the normal cruising engine sound, but is not loud. I can't hear the sound when the convertible top is up, but it is very prevalent when the top is down.

The sound happens between 2500 - 3500 RPM's and is there under load, but is present under light throttle as well as heavy throttle. The timbre is a little more 'tinny' under light throttle than under heavy throttle. and goes away when you take your foot off the throttle. The time I hear the sound most is when I'm under light throttle at around 3k RPMs cruising. The sound is not there when sitting still in neutral, either at idle or revving the motor.

Part 2:

Now, not sure if this is related or not, but I hear a separate and different noise when I'm idling that is coming from the area around the heat shield under the cat -

Here's the weird part on part 2: when that sound eminates, i've noticed that the Oil pressure guage needle lifts bearly (1/8") and freezes (instead of bouncing about as usual) while the sound is eminating. This sound is intermittent, lasts about 3 seconds each time, and re-occurs about every 20 - 30 seconds on average when idleing.



These sounds sound quite different from one another and they are in different situtations, but these sounds have also been both suggested as being connectected to one another in this thread. (cat baffles deteriorating, or heat sheild coming loose.) I'm just not so sure, as the Part 1 sound gives a more substantial presence (more than just a loose piece of tin like in Part 2)....


The sound is quite disconcerting, and I want to make sure it is nothing critical like the chain tensioner. I know it is hard to diagnose a sound through words, but I'm looking to see if anyone can shed any light/experience that would help distill this further to help determine if this is a chain tensioner, cat going bad, head sheild coming loose, or normal tranny noise.

Thanks!!!

[shuzboomer]

I had the same sound plaguing my peace for months after I bought my 81sc. I took her to two Porsche techs who told me that they could not hear anything wrong with the car. It wasn't until I put a trusty and crusty Porsche club member into the passenger seat and drove him around for 5 min. that the mystery of the strange noise was exposed.

The guy looked at me and said, "there is nothing wrong with the car, the problem is how you drive it. It's a Porsche stop treating it like a Toyota. " then he demonstrated what the power curve of the 911sc is all about.

In short, if you look at your manual, you will see that the car gets its power between 4-5k rpm. That means if you are driving under 40 mph, you want to be in 2nd gear (and loving life). Don't be afraid to take your car past 4k RPM, its designed to do that.

Do I speak the truth? Someone with more experience, please chime in.

[MysticLlama]

This is digging up the past a bit, 7 years now since I posted on it.

Mine ended up getting worse, so I took it to John Walker.

He listened to it for about 30 seconds and told me to shut it off.

Popped the engine lid, took the distibutor cap off, and there was noticeable play/wiggle in the shaft the rotor rides on. Was causing the timing to jump around.

Worth a try, it's free and <5 minutes.

[shuzboomer]

What was the fix?

[MysticLlama]

In my case was a new distributor, there wasn't a rebuilt readily available and it was my only driver at the time.

I think they can be sent out to be rebuilt if they aren't too bad.

It is something relatively easy to check, and at least rule out.

[Reuben911]

I have the same engine rattle that sounds like a musical cymbol in a drum set.

Happens when the engine is warm (60km run) in second gear and only around a bend in the road.

New Clutch, new engine and tranny mounts, new chain, new tensioners, new alternator, new head bolts and new every thing and still get that sound.

The other thing that pisses me is the damn whistling sound, louder when the engine is warm

[Superman]

Cymbal. Brake backing tin contacting something? These are thin metal disks which cover the brake disk from the back side.

[Reuben911]

Originally Posted by Reuben911

I have the same engine rattle that sounds like a musical cymbol in a drum set.

Happens when the engine is warm (60km run) in second gear and only around a bend in the road.

New Clutch, new engine and tranny mounts, new chain, new tensioners, new alternator, new head bolts and new every thing and still get that sound.

The other thing that pisses me is the damn whistling sound, louder when the engine is warm

Thanks will check that out