let's play Name That Engine Sound

[InfinitR]

All excited about new tires coming and adjusting shifter...then I hear this seemingly metallic rhythmic sound from under running engine and my wallet and I are scared 🙉 💸 . I don't really have a reference point as I am just familiarizing myself with the car.

Mostly hear at idle...don't have anyone else around at the moment to listen.

Local shop suggested to change the oil and inspect first to see if I can visually see anything, which I am planning to do today.

But thought I should ask here to see if anyone can help.

1977 2.7

Apologies in advance, phone audio kind if cuts in and out a bit.

Thank you.

Links:

Engine Sound

Engine Rev

[ccallana]

Check your fan pulley.... I had a similar sound an the crankshaft pulley was loose... pain to get to if you have to tighten it, but easy fix. Catastrophic if it gets worse though

[ant7]

Possible cam chain tensioner not holding pressure ??? but to be honest, its not very obvious as to where its coming from, Also check distributor shaft for play, and correct operation of the weight advance assembly.
Hope this helps.
Ant.

[Dpmulvan]

Get a stethoscope or some chassis ears.

[Joesmallwood]

Originally Posted by Dpmulvan

Get a stethoscope or some chassis ears.

^^this. Need to know where or what region it is coming from.

[InfinitR]

Thanks all. Changed the oil first to check. Oil looked clean to me. I also do not see anything contacting on fan or pully. Seeing about getting my hands on stethoscope.

[InfinitR]

Put a scope on it and checked all around.

Seems to be coming from here...

That's an air line?

I also probed exhaust on each side, sump, chain covers, valve covers, smog pump, fan, distributor. I tried to record the sounds but didn't pick up, may try that again. But definitely heard it when touching that pipe.

[InfinitR]

I think this is the part I am looking at (found in another post, part 91111304301).

Is anyone familiar with the inner-workings? I'm wondering if something is loose and broken inside of it, or if I am hearing something resonating through it from elsewhere. The sound did seem pretty localized though still poking around.



/edit

Suspect. I had a chance to trace it. There's a gap here but it's thin. Don't really see a scar on the pipe. Going to take another look in the morning.

[ant7]

The pipe work pictured is from an additional air pump, run from the fan pulley, it injects air into the exhaust outlets on the heads to reduce the emissions.
Does your car still have the pump fitted ? show us a picture of your engine bay from the top, if the pump is still on the engine, then its possible the issue is with that, and the noise you hear is traveling down the pipe.
Ant.

[InfinitR]

Interesting, that is the most recent part I had replaced...

[ant7]

Try running the engine without the air pump belt fitted, let us know.
Ant.

Originally Posted by InfinitR

Interesting, that is the most recent part I had replaced...

[pmax]

I would get rid of those things and that exhaust unless your state requires them or the car is a "preservation" specimen whatever that means to you.

[InfinitR]

thx will see about that.

..and, California.

[pmax]

Yeah ... figures, welcome.

That just carries air from the pump to each cylinder's exhaust.

Not surprised if it has sprung a leak after that many years of corrosion. Don't think it matters much when some of that air escapes.

[InfinitR]

Regarding running engine with the belt off the air pump, just want to verify that is okay without plugging the holes where the airline connects? it's fine to just leave everything else connected and disconnect the pully belt?

And after, as far as reestablishing the tension on the belt, should I just use the current position of bracket as reference or is there another way to determine the belt tension?

Also, as far as removing the parts, I'm all for simplifying, lightening, etc...just obviously concerns with smogging, though these days I'm not sure how tight people are on visual inspections as i've passed without thermal reactors.

Will have to give it a go with more sunlight..it's the rattle that concerns more than anything else.

[ant7]

I would guess that most folk who could have removed the air pump system, would have already done so, as its only needed for tight emission laws in certain states etc. Here in the UK they are not necessary, However; before removing it, do your homework, and find out for sure whether you still need it in your area.
All the pump related parts and pipework can be removed quite easily in its entirety, From memory [others hopefully will confirm] You will need to plug the holes where you remove the injector nozzles from the cylinder head exhaust etc.
I think You can get the plugs from our host here.
Anyway, just remove the belt for a short time, and run the car just to see if the noise is still there or not, and let us know.
DO NOT REMOVE THE ALTERNATOR BELT!
Hope this helps.
Ant.

Originally Posted by InfinitR

Regarding running engine with the belt off the air pump, just want to verify that is okay without plugging the holes where the airline connects? it's fine to just leave everything else connected and disconnect the pully belt?

And after, as far as reestablishing the tension on the belt, should I just use the current position of bracket as reference or is there another way to determine the belt tension?

Also, as far as removing the parts, I'm all for simplifying, lightening, etc...just obviously concerns with smogging, though these days I'm not sure how tight people are on visual inspections as i've passed without thermal reactors.

Will have to give it a go with more sunlight..it's the rattle that concerns more than anything else.

[InfinitR]

was away for a bit but tested w removed air pump belt.

I think it did sound better... but honestly was a bit hard to tell as I still hear mechanical and exhaust sounds that I am unfamiliar with. It did seem to 'rattle' less...so thinking/hoping something just loose it that spider tube.

Still, took it by the local shop today to get second opinion from local air-cooled mechanic and will go from there before deciding,

[Schulisco]

Pull the valve covers and check all headstuds if one is broken. Ditto the valve rockers.
Measure the amount of injected fuel for every single cylinder. If one gets too less fuel the exhaust valve will overheat and getting too long which also may cause such a clattering/hammering noise.
Does the sound disappear when you press the clutch?
Hear with a engine stethoscope for collapsed chain tensioners.
Check engine timing and for weak ignition cables.

Otoh - if you're new to aircooled engines - due to the absenxlce of watercooling and a double walled engine case and the coolimg fins being free im airstream and swinging by themself too and due to the absence of hydros and a incorporating a static valve train propelled with chains this all is part of the uniwue sound experience an aorxooled Porsche engines produces...

[InfinitR]

thanks for all that info. I'm new on these motors so I'll have to read that back a few times and do some more research on what you are saying.

Talked to the shop looking at it as well. It's a sound 'they havent heard before' (great lol) however they seem to be in agreement that the sound changes when the air pump belt is connected versus when not. They want to do some things to try to shoot any debris out...at quite an expense...they are also theorizing that it's a problem with the check valve.

So I think I am going to take it back home and attempt to remove the spider tube and plug it up to see what I hear at that point. Hopefully I can accomplish this.

It's not something the shop wants to do anyways as they comply with the smog situation in CA..and I'm not trying to be bad to the environment but I'm sure you guys understand my dilemma.

Of course, I do need to smog again, but step one here is to diagnose.

[InfinitR]

It took a bit to get back to car but I was able to remove the tube and air injectors.

Once I did, I found this bolt inside the tube. It only could have passed into the tube through the check valve side. I guess it's the best case scenario, but I'm not sure exactly how it got there. However, the last work at shop was replacing air pump, and I'm not sure if they disconnected the check valve at the time. But logically can't think of another time this would have occured.

Plugged the injector ports for now and it's seems good again.

So it's a weird one, still wondering what this bolt is. The head is smaller than one on pump bracket but when I get back to it again I will remove and check threads.

Thank you for help.