Cross Post - Another "what's this noise" thread
 

** Please see post 7 after this, I've updated with new testing results***

I started this in the engine rebuild forum because I'm afraid that's where it's leading. It was suggested I cross-post here to get the attention of some of the masters. For reference, not in my initial post:

1975 911 with a 78 (iirc) 3.0. Oil level is good (in the middle of the stick after warm), oil pressure is 30 on the gauge, warm temps never get above 200-220.

I purchased it a couple of years ago, had been sitting a while, failed restoration. I got it running and have driven it 1-3 times/week since until the last month or so. Totally unknown engine history. I've probably put 7-8k miles on it, have changed the oil 3 times, last about 6 months ago and at that time tried to adjust the valves and discovered I couldn't get the right valve cover off due to hitting the aftermarket header that's on the car.

Ok, videos:

Initial Start - Cold:
<iframe width="640" height="480" src="https://www.youtube.com/embed/36kPfznsTIU?rel=0" frameborder="0" allowfullscreen></iframe>

Taken when warm:
<iframe width="640" height="480" src="https://www.youtube.com/embed/epPHfxll98E?rel=0" frameborder="0" allowfullscreen></iframe>


It seems my new "knock" comes on strong after a few seconds, it's steady with RPM, seems to be coming from the middle of the motor. There is a "tick" that I have undoubtedly identified to the middle right (5?!) cylinder with the long screwdriver method. All others are relatively quiet. I can't identify the exact location of my knock with the screwdriver.

Pictures:

This is the "diaper" under my car, haven't driven it in 3 weeks at all, as you can see it's not leaking but a drop here and there. She has never in my time consumed any oil to speak of:
http://forums.pelicanparts.com/uploa...1344098542.jpg

Right Bank - shows my clearance issue w/ the header:
http://forums.pelicanparts.com/uploa...1344098683.jpg

Right side showing cam cover:
http://forums.pelicanparts.com/uploa...1344098718.jpg

Bottom of the engine:
http://forums.pelicanparts.com/uploa...1344098773.jpg

Left Bank - this side clears the header
http://forums.pelicanparts.com/uploa...1344098833.jpg

Left Cam:
http://forums.pelicanparts.com/uploa...1344098888.jpg

Valve clearance issue to much gap.

The right-side ‘tick’ is probably valve related. Take the covers off and check the valve clearance, inspect for rocker arm shaft sliding out and inspect for broken valve spring.

The center ‘knock’ is worrisome.
Drain the oil through the sump plate drain plug into a clean container and then carefully remove the sump plate. (Don’t drain the oil by loosening the sump plate.)
Inspect the sump plate for ‘gold color’ debris (flakes).
You want to inspect the small area between the sump screen and the crankcase opening, particularly where the screen is attached to the flat housing.

Drain the oil filter and cut apart (there is a special ‘can-opener’ tool for this job at most shops.
Spread the paper element out linearly.
Using laquer thinner, clean the filter element by washing through the filter, leaving the debris in place.
Again, inspect for debris.
Please post images of anything you find.

Best,
Grady

Thank you, I ordered a leakdown tester this morning, had planned to try and do a leakdown & compression test before I drained the oil, I'm assuming it's time to drop this engine for several reasons and wanted data to report before I started opening things up.

Is this too much of a risk at this point? I've only driven the car twice since I started hearing this new knock.

Travis

To me, that sounds valve related, but not sure what a main bearing knock would sound like in a flat-6. It doesnt sound like a rod bearing because those double knock.

Checking valve lash should tell you pretty quick if it's bearing or valvetrain related IMO.

Yeah the center knock sounds like a wrist pin. You should get turbo valve covers for the bottom.

Updating
 

I humbly [re]summon the 3-liter whisperers...... apologies for the delay, I've had weeks of pummeling work and started my ~40 y/o a$$ self back to college. Please prepare for an onslaught of data, I really really appreciate your feedback.

So I spent most of today doing a full boat of tests suggested above here are the results:

First.....What engine do I have? 6383878 - I've triple checked it, looking in Zimmerman's book the 2nd digit makes no sense but otherwise seems the '78 3.0 I thought it was.

Spark Plugs:

http://forums.pelicanparts.com/uploa...1345946954.jpg

All black in color, I am fairly sure I've been running it rich, not any wetness when I pulled them out

Leakdown Test:

Ran my compressor at 110psi, adjusted the left dial to 100psi, each cylinder showed ~98-99% and never moved. Every single cylinder held 2% loss or less, left each one ~5 minutes.

This is good news right? Is it possible I botched the test? I did at one point play with it off the car and was able to see it drop and swing up and down as I capped the pressure off with my finger so?!

Compression Test:

Cyl 1: 150 psi
Cyl 2: 148 psi
Cyl 3: 150 psi
Cyl 4: 98 psi
Cyl 5: 125 psi
Cyl 6: 145 psi

Remember my issue earlier with not being able to adjust the lower valves on the right side. Hoping that is the source of my odd compression #'s on that bank?!

Oil Drain/investigation:

- First off, whoever suggested straining it through the old white t-shirt, not cool dude! - (maybe I prefer too thick t-shirts )

http://forums.pelicanparts.com/uploa...1345947638.jpg

Drain plug, screen and plate-

http://forums.pelicanparts.com/uploa...1345947680.jpg

http://forums.pelicanparts.com/uploa...1345947711.jpg

http://forums.pelicanparts.com/uploa...1345947734.jpg

as you can see, clean

Ok, here's the fun part:

http://forums.pelicanparts.com/uploa...1345947823.jpg

http://forums.pelicanparts.com/uploa...1345947844.jpg

http://forums.pelicanparts.com/uploa...1345947862.jpg

http://forums.pelicanparts.com/uploa...1345947889.jpg

So what the hell is that half a ring that dropped out? On the good side I could find no real shards otherwise, no flakes of metal, what's on my fingers I believe to be carbon? I found 1 goldish flake in the t-shirt. The oil that came out of the sump was the same, found no more pieces, see below the plug, had sludge but no flakes.

http://forums.pelicanparts.com/uploa...1345948066.jpg

So there's the investigation, I open it up to the world.

Sometime in the next couple of weeks the engine is coming down so I can address whatever is going on including the valve adjusting problem. What am I looking at here?

Thank you, Travis

Is that piece magnetic? Looks like a broken valve spring probably on # 4 cylinder.

I dunno, but I'll check tonight

99.9% sure thats a piece of broken valve spring! Although it looks hollow, so don't know for sure if valve springs are/were hollow, or if that's just a anomaly from the picture... Magnetic test will tell you the answer.

IMHO, The sludge you show pictured on the rag next to the magnetic drain plug is fine metal debris most likely from your bearings. That's a lot of bearing wear. If it builds up like that between oil changes that would be very worrisome to me and almost certainly dictate a bottom end rebuild.


Good luck and keep this thread updated as thee are several Pelicans doing similar diagnosis on sounds coming from their engines...

Must be a picture anomaly, it's definitely not hollow. Are the springs magnetic?

There was none of this on my engine plug, and the oil wasn't sparkly. IIRC I had quite a bit of this my first oil change after the engine had been sitting for several years. - still think bearing wear?


Thanks, I will keep updating as progress continues until she is back pounding the pavement. If this really is a valve spring can I hope there's a possiblity of getting out of this w/o having to open up the case?

Others have successfully changed valve springs without tearing the engine apart. Compressed air is your friend. Do a search, I've seen a few threads about it.

The piece doesn't appear to be magnetic (didn't pick up any of the nuts or bolts lying on my workbench).

Read a bunch of threads on spring replacement yesterday and those pictures certainly do look like mine. I did notice more "spiral" in the shard than I'd seen this weekend.

So could a broken spring cause the knock I have? Valve bumping the piston? All conjecture until I drop the motor and find out more?

sobamaflyer,

Please post more images of the broken part.
It appears to be round at one end and flattened at the other.
If so, this has the profile of the end coil of a valve spring (probably an inner spring judging by the diameter).

OE valve springs should stick to a magnet. I suppose some aftermarket springs (stainless, titanium) would not stick.

If this is a piece of a valve spring, this may be the ‘tic’ at your #5 cylinder.
You can inspect this in the car by removing the #5 rocker arm (intake first) and inspecting the valve springs.
There are valve spring compression tools (different for intake & exhaust) that will allow you to replace springs in the car.

It would be very unusual (almost impossible) for the broken piece to have caused any distress in the ‘bottom end’ of the engine.
The ‘center noise’ is probably a separate issue.


I’m concerned about the low cranking compression on #4 cylinder.
The ‘good news’ is it didn’t show on the cylinder leak.
That would lead me to suspect the tests.
I would repeat both tests.


Was the ‘fuzz’ on the drain plug magnet accumulation over only a few miles since the last oil change and magnet cleaning?
If so, inspect all the cam lobes and rocker rub-pads.
The material is obviously magnetic.
Cams and rockers are magnetic, babbit bearing material is not.
Check (measure, not reset) the valve clearances.
If the cam lobes & rockers had been rusty from the sitting, they (one or all) may now have high wear having breached the hardened surfaces.


Get yourself an automotive stethoscope from a local auto parts store.
From under the running engine, see if you can better locate the center ‘knock’.
Use the stethoscope probe on the cylinders.
Also see if there is a fore-aft difference.

If the piston were hitting the valve (due to broken inner spring), it probably would bend the valve and show as a cylinder leak.


Best,
Grady

http://forums.pelicanparts.com/uploa...1346188669.jpg

http://forums.pelicanparts.com/uploa...1346188687.jpg

- It stuck nicely to a magnet

- crap


- can I repeat those 2 tests on a cold engine?


- I last changed my oil the end of last year, maybe 2-3K miles ago


- 10-4



Best,
Grady - Thank you!

So I started my first 911 engine removal this morning.

I've read a couple dozen threads over the last few weeks on this subject and don't really want to start another so I'll question here.

Why is it that half I read says take the engine and tranny out as a unit and half the pictures I see show the tranny left in?

So far I've disconnected everything but a stubborn fuel return connection and continue soaking my left engine bracket bolt as even my impact wrench isn't wanting to budge it. (To take only the engine out). Part of me doesn't feel like disconnecting all the tranny apparatus and part of me says take it all down and use this as a cleaning/refresh under there opportunity. I've even got the 3 attachment bolts out, still need to fight with the 10mm allen.

Pull the transmission with the engine.
This is a much ‘cleaner’ R&R. Particularly going back together.
Flat-rate mechanics just pull the engine and charge for both.

Yes, that is a piece of valve spring.
Why coming out?
What did you find?
Replacing a valve spring can be done with the engine in-situ.

And yes. You can do cranking compression test and cylinder leak test on a cold engine.
The ‘fuzz’ accumulation over 2-3K mi. is not all that unusual, particularly given the sitting history.
Cut apart the oil filter.

Best,
Grady

Make sure the battery is disconnected.
I personally find it easier to remove the engine and transmission at the same time. Separating them on the ground and mating it back together is simpler when they are sitting on 2 dollies than when laying on my back under the car. Trying to reach the top bolts, or getting the release fork on the throwout bearing.
Once you get the center of gravity they, come down nicely together. Besides, you may want to change some seals on the transmission while your in there. Disconnecting the transmission linkage is easy enough. Disconnecting the wires from the starter is not much either. Maybe check the CV joints. Gives you a chance to inspect the brake lines easier also. Might as well make sure evrything is in good shape now so you don't have to drop it again later.

I've been wanting to take the engine out since I bought the car to perform a really good cleaning and replace the sound mat but I enjoy driving it too much and have too little time so I've yet to do it. I have known it means probably months of the car being down.

I had gathered 1 problem was nailed down to a valve spring and had read it could be done in the car, but your prior warnings and fears about my newer knock not sounding like it could be related has me scared to grenade what is otherwise seeming like a healthy engine.

Is your advice then to proceed a little further before dropping it? Try to get the header off the Right bank in the car so I can properly access that valve cover and address the spring issue and new valve adjustment? Am I being counter productive spending the effort to take it out at the moment?

I haven't yet gotten the stethescope you suggested and I have been going back and forth this week as to whether I needed to fill it back up with oil to do more tests, and not sure I can hear the knock during cranking or just running?

I'd love nothing more than to think I could fix this [relatively] little issue, oil it back up and return to my couple times /week of 911 stress relief.

Sorry … I have to laugh (politely).
You want to take the engine out (for several reasons).
Yes, go for it, with the transmission also.
You will enjoy the process.
Just make sure you get it back together asap for your ‘911 fix’.

Replacing the valve spring is simply easier on an engine stand compared to in the car. The process and tools are the same.
Difficult is that you can’t then run the engine and tell if the “central noise” has gone away.
I’m not convinced that they could or could-not be the same.
I’m a proponent of repairing the valve spring in the car and only then, if necessary or desired, pulling the engine & trans.

In the process, get rid of the exhaust that precludes you removing the lower valve covers. There are better options.

Best,
Grady