Help I'm confused

[Split50]

After 2 months of driving with the car making a strange noise a local specialist diagnosed it as pulled head studs.
However driving to work today I noticed that the noise has gone and the car seems to be pulling much more strongly, if this wasn't odd enough I appear to have gained some oil! the needle has gone from its usual place at the bottom of the gauge to the top.
Anyone have any idea what could be going on?

[Joeaksa]

Do not pay much attention to the oil level gauge. Its accurate only when the motor oil is at "operating temp" and after idling for a but.

You will notice that after driving a bit and stopped for a traffic light that the level seems to come up. This is the only time its worth looking at and you need to always check your oil level with the dipstick.

Let the engine idle for a minute, again with the oil warm, and check the level with the dipstick. Be careful replacing the dipstick as many 911 owners have dropped it in the tank.

Cannot help with the "head stud" question...

Joe

[Jim Sims]

There is also a baffle in the oil tank that can break free and jam the level sender float upward. One other possible cause of an increase in oil level is emulsified water that stays in the oil and increases the level. Slow driving and/or short trips tends to cause this as the oil doesn't get hot enough to boil off the water. If the car is taken on a long drive where the engine stays hot for a long time the water will boil off resulting in a noticable drop in oil level.

Pulled, loose or broken head studs do not mend or re-tighten themselves. If the sound has truly departed, a failed stud was a misdiagnosis.

[Joeaksa]

Split (what is your name?)

Jim is correct and I assume that you are fairly new with your 911? Many people take the oil cap off of the tank and find a milky white foam there. Thinking that they have a problem they rush to the mechanic.

This is from doing too many short "in town" drives and not getting your oil up to proper temp. If this happens, treat yourself to a 20 minute roadtrip and then stop at a pub. Let the engine idle for a minute then both look at the oil cap as well as check the level with the dipstick.

Joe

[Split50]

Not that new I've had it over a year.
To be honest I'm not that bothered by the apparant increase in oil level, I haven't checked the tank level properly as its not warm enough. I just thought it was odd that it coincided with the engines miraculous self repair

So if it wasn't a pulled head stud what could it be?

Tim

[masraum]

What noise was it making? Did you have any other symptoms?

[Split50]

At first I thought it was the big ends knocking, it was kind of like an irregular knock that worsened under load but with good oil pressure and 2 months later i don't think its bearings.
Then I suspected loose baffles in the stainless Dansk muffler but it seems ok.
I changed the pre-silencer a few weeks ago as it full of holes but that did nothing to change the sound and then this morning after not using it all weekend, its fine. Very odd

Tim

[Joeaksa]

Tim,

Does it happen only under accelleration or while running?

If you can head the noise while it is idling then get a screwdriver or long piece of wooden dowel rod. Place one end on various parts of the engine and other near your ear. This will magnify the sounds.

Move it around and see if you hear the noise you are talking about in one particular area, like the muffler baffles or one side or the other of the engine.

Joe

[Split50]

Joe,

Can't do that now, its stopped doing it.
It always sounded ok when idling it was mostly during acceleration especially up hills, I wish I'd tried some tests while it was doing it!
I'm a bit suspicious now that its going to grenade the engine.
Thinking back to when it first started making a noise there was drop in oil level, a big drop, I topped it off with a whole 5 litre can (measured with the dipstick at correct temp & RPM) I wonder if that means anything?
I'll check the oil properly during lunch tommorow and report back.

Tim

[Joeaksa]

Tim,

If you are really concerned that the motor is coming apart inside, you can do a oil change and take a sample of the oil. Get it checked by one of various shops around the country who do oil samples.

They can tell you how many parts per million of whatever is in the oil. Silica shows that your air filter is not working well, copper or bronze bearings and so on. Cost is around $20 here in the states so its not that much money to confirm that all is ok or that you need to look futher inside.

If you are interested you can talk to a aircraft maintenance shop or heavy equipment operator. Both do oil samples on a regular basis and can direct you to a lab.

Joe

[Phoenix]

Did you put in a higher octane gas during your last filling?

[jdowty3]

The oil level could be a failed sender or broken\loose wire since it will peg the gauge to the top if you loose the ground connection.

I also had an intermittant knock that I thought might be a broken head stud or an exhaust leak. But it was only mild detonation caused by low octane fuel and the Texas summer heat. It only happened when the temp gauge was at the 9 oclock position, running low octane fuel and I would hop on the pedal.

[steven polaski]

Check to see if it's gas in your oil sometimes the gas can get in the oil raise the level had it happen with my cis.

[Randy Webb]

to the top ... does it stay all the way up all the time?

Maybe a wire came off, or oil level sender failed. I'm not sure (w/o looking at my broken one) but I think they 'fail high.' Also, jiggle and clean the wire contacts. See what that does. If they do fail high, and yours is all the way up, and wire jiggling or removal changes nothing then order a gasket and new sender and change it at your next oil change.

[Split50]

Thanks guys,
The needle hovers around near the top of the gauge its not pegged there.
Same gas as normal, filled up 1 week ago.
I'm going to check the oil with the dipstick later to see how much there actually is or if theres gas in it etc.
Could it really be detonation?
I might try the water decoke method later as well

Tim

[jdowty3]

Does the needle drop as the engine pulls oil from the tank when you accellerate? Maybe a dipstick got dropped in the tank and the sender is hung up on it.

[Split50]

Lunchtime testing is over.
The oil level is about 3/4" above the minimum and the cap and filler neck were covered in bright yellow foam.
I couldn't find a way to get water into the inlet manifold to clean out the carbon.
The noise is kind of back but not as bad as before, when revving the engine hard from idle there is a loud pop from the exhaust.
It has always backfired when cold starting but has a pop off valve fitted which it once blew out.
Could the mixture or timing be the problem?

Tim

[Paulporsche]

Yes, your mixture could be too lean or your timing advanced too far. Also check your points/dwell. You want 35-41 degrees.

If you needed 5L to top up you were way too low.

The bright yellow foam is from condensation. It should go away once you get the engine up to some higher temps. But I don't know if that's a good idea to try right now.

Joe's suggestion of an oil change and analysis sounds good to me. You might want to look for the other usuals like the WUR and if your distributor is advancing correctly. Make sure you have no vacuum leaks and be sure that popoff valve is secure.

[Joeaksa]

Tim,

If you are seeing the yellow foam then like Paul said, it is moisture in the oil system. Take the car out for a nice drive and keep your foot OUT of the gas pedal until you have confirmed that the fuel is ok and timing is correct. Mission here is to is to get the engine and the oil that keeps it alive to good operating condition and keep it there for 10-15 minutes.

One problem we all have with the 911 is the front mounted oil cooler. There is a thermostatic valve mounted on the right rear wheel well. It does not open until the oil temp gets warm. It then shuttles oil to the oil cooler in the right front fender. Reason for bringing this out is that until the engine is warm it does not open the valve and until the valve is open the oil in the entire hose and oil cooler system stays there...

You need to warm up the entire system and get it circulating. In the UK (and most of Europe for that matter) this time of year and until next Spring this can be difficult if you do not drive regularly at least 20 minutes every day. Try to make it a habit to do one 20 minute drive a week or couple of weeks. Your car will be happier and so will you!

JoeA

[RoninLB]

Originally posted by Joeaksa

Try to make it a habit to do one 20 minute drive a week or couple of weeks. Your car will be happier and so will you!

my engine likes about 10mi at 3-3.5k to stabilize. I avoid under 2.8-3k at cruise whenever possible.