Strange noise

rollandburn · rollandburn's Garage

Hi everyone, I'm looking for any first ideas about a noise i noticed coming home from work today. It sounded kind of clackety like really loose valves but only presented itself when I would, for example, be cruising along at 1800rpm in 4th on a flat slow road.... and then give a little gas. I know the sound of being in too high a gear and trying to give it too much gas (lugging the engine) ..... this isn't the same, although it does sound like a severe version of it. I'm just talking about giving it a little bit of gas, not pass-a-car flooring it (obviously at that rpm). It's hard to tell if it occurs higher in the rpm ranges because of the noise of the engine but i didn't hear it.

Any ideas or reccommendations to help my preliminary diagnosis are appreciated.

ossiblue · 04-08-2009, 04:10 PM

Could be loose chain due to weak/failing tensioners. What kind of tensioners do you have, and how old are they?

jcpyor · jcpyor's Garage

Broken head stud. Know that noise well!

DRACO A5OG · DRACO A5OG's Garage

Your clutch will normally make a chatter noise at low RPMs.

Can you make a sound clip from you cell or PDA?

theiceman · 04-08-2009, 05:39 PM

my first inkling would be to say tensioner failure. But to check for a broken head stud takes about 15 minutes. Take the rocker covers off and prey a stud doesn't fall out. chain tensioner WAY easier to fix.

rollandburn · rollandburn's Garage

Thanks for the feedback. I'm not much of a mechanic, starting points really help. Oddly enough many of the comments ring a bell.

ossiblue/theiceman - i've noticed a couple of times when giving a quick shot of a lot of gas during a quick downshift at high rpm sometimes there is a fast rattle, my pal says it could be the chains. What kind of tensioners and how old?.... you know, i have no idea. The car has 70,000 miles and I've had it for 2 yrs. Completely stock, euro car, not even a cat bypass. I had the engine out and did the valves last year and didn't notice anything odd. Experienced drivers have had it out and said 'it's pretty average all the way around'. I assumed the PO was a lazy owner but not entirely neglectful. The engine always has been 'noisy' in my opinion, too noisy. Clickity clackety....more so than the other two 911's in the neighbourhood.

DRACO A50G - until today I've only ever been aware of one problem with the car, the clutch has never been right. It's got strong engagement but it's 'lumpy'. Porsche mechanic says it may be broken 'fingers' on the pressure plate but it works fine, just not smooth. I could try to take an audio clip with the cell phone but it car has to be under load, stationary throttle revving doesn't seem to produce it. If I get anything worthwhile I'll post a link.

On that note, thanks again for the ideas and I'll be sure to post back any findings!

theiceman · 04-09-2009, 01:27 PM

i would be very interested in your findings . I have a few additional comments but others with more experience can comment .
Yours is an 85 so it will probably have a 915 gearbox, there for it is not the G50 gear rattle that can sometimes be associated with G-50s. That said it could still be noisy all round. Some years had rubber centred clutches, although maybe just SCs. This was "perceived" to be a weak point so some owners upgraded to spring centred clutches. The spring centred clutches on some cars transmitted a lot more gear noise to the cabin and driver. This could be the case here.

Also if you have an 85 you should have dhydraulic tensioners ( look in the engine bay and if you see two small oil lines going down the very back to the cain box covers ( one each side ) you have the hydralic tensoners. Although not often they do fail.
I would NOT be giving it shots of gas to make it happen , only bad things can come of this , especially if your tensioner totally fails .
Checking for the head studs is another low cost option. If one is broken it is engine tear down time soon. Although I have heard of guys leaving it htis way if you start blowing between cylinder and head that is BAD news.

Some of the basisc checks you can do yourself , some of the more advanced ones leave to a copetant mech .
Good luck and please post back.