2.7l Engine Noise

[niall]

Hi
I am new to the 6 cylinder air cooled engine seen.

When my 911 is fired up the engine sounds quite rough with a knocking sound which gets quiter once the engine is warmed up.

Is this normal as I have heard that these old air cooled engines can sound very rough when cold?

Thanks
Niall

[Grady Clay]

Niall,

Welcome to the Forum.

I would find someone local with a practiced Porsche ear to give a listen. That can range from “no problem” to “don’t start it again”.

What year and model?

Any other symptoms?

Best,
Grady

[niall]

Hi

Its a 1975 2.7.

Its just had the cams and tappets replaced before I bought it.

It had very low oil level when i got it, could this have caused the problem maybe?

I am not experienced with porsche engines, but it sounds similar to a big end or small end conrod bearing has worn out, is this likely?

Thanks
Niall

[bigchillcar]

sure it isn't a 'tapping' sound, indicative of the need for a valve adjustment?
ryan

[schamp]

When you say the oil level was low, what did you do? You have to check the oil with the engine running and up to temp, and on level ground. If you overfill you get several problems.

[bigchillcar]

more specifically, as schamp has indicated, level ground, running and car at 'operating temperature' - 182 degrees technically-speaking, 180 practically-speaking. the reason of course is owing to the large volume of oil, as temp increases, volume increases, so when cold it's going to read low. if you have an 'oel' gauge (engine oil level), remember that it's only accurate at this precise engine temperature..
ryan

[schamp]

I am afraid he saw his guage showing the oil level as low and started adding until it moved. Niall, it will work best if the guage shows the level toward the low side than the high. The oil will make it to the intake some gets burned and some gets just all over everything including under the car. Don't feel bad. Every first time porsche owner does it, at least once. I hope that is all it is. Good luck.

[niall]

Oh Oh, due to lack of experience I suspect I have made an expensive mistake.

I drove the car for a while not knowing its optimum running temperature should have been 180, it was running at 230 for most of the trip due to fact that oil level was low I think.

Next day, I then filled the oil tank to maximum level but engine was running cold, and that knocking sound was noticable, I left it warm up and it got quieter. I then turned it off and I have not started it since.

Could the oil top up when cold have caused the knocking or is it more than likely mechanical damage.

I dont think its tappet noise because it sound like more of a deeper knock than a tapping noise.

Thanks for your advice
Niall

[bigchillcar]

overfilling shouldn't make a mechanical racket..it would just burp it back up the blow by tube, making an oily mess. 180 is considered normal operating temperature, but it's in the middle of a range. i wouldn't worry about seeing 230. my car has seen nearly 280 for brief moments in summer..at that point i was looking for a place to pull off and let it 'cool off'. for me, i start watching it very closely if it begins to creep above 240, but i've let it sustain temps like 250 on the highway wih no ill effects on my car. but keep in mind, my car has NO AUX OIL COOLER. this means 220 is more normal for mine..cars with the cooler in the summer may be able to maintain 180-190 temps. i'm going to suspect that yours doesn't have the aux cooler either.

get your car up to 180, let it continue idling and check your dipstick..then report what you find here.
ryan

[niall]

Its just got the standard oil cooler by the engine.

My first planned project was to fit another oil cooler up front.

I will fire it up when I get back home, let it heat up to 180 and check how it sounds then. If the knocking sound is then gone, would you think the engine is ok?

Niall

[moneymanager]

On my car the heat exchangers rattle a bit till things heat up. It's a fairly alarming noise until you find out what it is. You can test this by starting the car cold and poking a screwdriver or something similar into a heat exchanger where an exhaust pipe passes thru it. If the sound changes, you've found your problem. Do this on both sides of course.

[bigchillcar]

be sure and check the dipstick, too..let's see what your actual oil level is now. i wouldn't want to hear knocking. might crawl under and check to see if any exhaust components have worked themselves loose..i'd much prefer that to engine internals! also, many will take a long screwdriver and put it on different areas of the engine and listen with their ear against the handle to hear inside..just take care not to let it get close to the fan belt..which reminds me, check belt tension, too.
ryan

[bigchillcar]

moneymanager and i were just sharing the same wavelength..er, bandwidth..
ryan

[niall]

I will check all those, its possible something has come loose after the cams and tappets were changed before I bought it, its done about 1000 miles since that job.

[Grady Clay]

Niall,

OK, STOP right now.

There is too much chance of it being a big-end connecting
rod bearing. In may not be that but if it is, continued driving
can totally destroy the engine.

Now for some serious diagnosis.

At this point you (or a competent mechanic) should examine
the engine sump plate. Drain the oil via the drain plugs in
the oil tank and the sump plate into a clean container.
Remember the engine can have 12 quarts or possibly more
if over full. It might be valuable info to eventually strain the
oil (warmed) through a coffee filter. Do NOT drain the crank
case by just loosening the sump plate. The reason is that
you want to inspect the area of the sump screen next to the
crank case. If you drain oil from there you may loose any
evidence of what is happening (or not).

Here in the States there is available a big can opener to cut
open the oil filter. It would be beneficial if you could find a
workshop with one. If so, take your oil filter paper element
and stretch it out. You need to be looking at the bottom of
the folds.

At either the sump screen (red arrows) or in the filter element
you are looking for copper/brass/gold colour flakes or almost
dust. You should also inspect the sump plate for this also.
The bearing material isn’t magnetic so it won’t accumulate
on the drain plug magnets. Have a digital camera with a
macro lens and post some clear and detailed images here.
With good and clear images we can help with the diagnosis
from across the Atlantic.

"
"
© Dr. Ing. h.c. F. Porsche A.G.

If it isn’t a bearing, we can go to diagnostic step two.

Best,
Grady

[niall]

Thanks for the advice much appreciated, I will drain down and check on the weekend.

[bigchillcar]

niall,
okay, i defer my advice to start and warmup the car on the basis of grady's concerns. google grady and you'll see there isn't a more knowledgable person on this very extensive bbs. please take his advice on this..he obviously smells something..
ryan

[Grady Clay]

Ryan (Pelican bigchillcar,

When you Google me, you have to add the search word ‘Porsche’ otherwise you get my dad, Grady Clay, Jr. (91), the journalist, editor and author of note. You also get my Grandfather Grady Clay, Sr. the Ophthalmologist-surgeon who brought back from WWI significant advances in eye surgery to Emory University teaching. Also there is Henry Grady, Civil War General. You also get Muhammad Ali’s mom Odessa Lee Grady Clay. I met Cassius when he was boxing Golden Gloves. His great … great grandfather was a slave “owned” by my great … great uncle Cassius Marcellus Clay, Senator from Kentucky in the 1850s: A sad part of our history. I suppose in our lame old age we should reconnect. I wonder if he would like a 911? I’ll ask.

Best,
Grady

[bigchillcar]

'float like a butterfly, sting like a bee..in my new 911, you'll never catch me..!'

[niall]

I'm back eventually with news which is not so bad but I suspect not so good either.

I drained down the oil and found the following waiting above the oil screen where indicated on Grady's diagram.
1.Lots of chewed up plastic granules (broken up chain guides)
2.Fours end pieces run off/run on, broken chain guides (must have come from 2no guides.
3.Two very small/hard metal pieces, looks like gear teeth (tooth width less than 1/4inch, tooth height about 1/8inch, there is a wear pattern so I'm pretty sure they are gear teeth, but i did'nt think there were gears that small within the engine.

Any ideas guys?