Do you mean the sound at 1:38-1:40. I hear it earlier in the video mostly when letting off the throttle? If that's the sound, does it happen at idle without revving the engine up and down and/or if you hold the motor at a steady rpm like 2500?
edit: I think part of the reason I'm not hearing what you are is because you are changing the rpms and camera position throughout that video, so without knowing what I'm listening for, it's hard to distinguish between the noise you are hearing and changes just based on rpm and camera position. That said, I do hear a bit of clatter mostly when you let off the gas, like the sounds at 1:38-1:40. If that's the sound at issue, it's hard to say if that's actually coming from the valves, or maybe an exhaust leak or something loose....
What oil are you running and is the noise still there after a 10 mile drive?
Re: Diagnosing valve train noise
Posted: Wed May 14, 2025 9:07 am
by zooklm1
Does it go away after running for a while? I would look at exhaust system gaskets or a slight crack in a manifold. I say that because I had a slight crack on a Volvo turbo manifold that made a similar sound when cold but closed up when hot.
Re: Diagnosing valve train noise
Posted: Wed May 14, 2025 9:59 am
by dr bob
Diagnosing noises like this --
Grab a mechanic's stethoscope, the old-skool version with tubing and a probe. Use it to isolate the sound source by carefully touching it to suspected source locations. For airflow noises, like leaks at cracked or leaking exhaust, disconnect the headset from the diaphragm and use a hose section directly to listen locally for sources.
Casual Thoughts --
Valvetrain noises in these heads are interesting, mostly because you have hydraulic lifters that have no external mechanical clearance. Noises from those happen when they are collapsed, and also when there's excessive wear on the cam lobes. There's a lot of guidance on replacing lifters especially with used. Or even mixing up the lifters on a specific cam when the head is apart. The friction faces 'wear in' to each other. Worn lifters/followers tend to dish. So lots to look at. There's plenty of amateur opinions on what the best solutions are. There are plenty of aftermarket lifters targeted at the VW market that fit the 944/928 applications, if you need to replace. I'm not at all a fan of putting used lifters into a different engine, especially if good new are readily available.
Re: Diagnosing valve train noise
Posted: Wed May 14, 2025 11:19 am
by Jacquiles
Tom wrote: Wed May 14, 2025 7:10 am
Do you mean the sound at 1:38-1:40. I hear it earlier in the video mostly when letting off the throttle? If that's the sound, does it happen at idle without revving the engine up and down and/or if you hold the motor at a steady rpm like 2500?
edit: I think part of the reason I'm not hearing what you are is because you are changing the rpms and camera position throughout that video, so without knowing what I'm listening for, it's hard to distinguish between the noise you are hearing and changes just based on rpm and camera position. That said, I do hear a bit of clatter mostly when you let off the gas, like the sounds at 1:38-1:40. If that's the sound at issue, it's hard to say if that's actually coming from the valves, or maybe an exhaust leak or something loose....
What oil are you running and is the noise still there after a 10 mile drive?
Hmm not sure, I think we may be hearing two separate events. You’re right though, moving the camera position and not holding a steady rpm is not ideal. I will get a better video tonight.
Right now I have Valvoline 20W-50 in the motor.
The sound remains regardless of oil temperature.
Re: Diagnosing valve train noise
Posted: Wed May 14, 2025 11:28 am
by Jacquiles
dr bob wrote: Wed May 14, 2025 9:59 am
Diagnosing noises like this --
Grab a mechanic's stethoscope, the old-skool version with tubing and a probe. Use it to isolate the sound source by carefully touching it to suspected source locations. For airflow noises, like leaks at cracked or leaking exhaust, disconnect the headset from the diaphragm and use a hose section directly to listen locally for sources.
Casual Thoughts --
Valvetrain noises in these heads are interesting, mostly because you have hydraulic lifters that have no external mechanical clearance. Noises from those happen when they are collapsed, and also when there's excessive wear on the cam lobes. There's a lot of guidance on replacing lifters especially with used. Or even mixing up the lifters on a specific cam when the head is apart. The friction faces 'wear in' to each other. Worn lifters/followers tend to dish. So lots to look at. There's plenty of amateur opinions on what the best solutions are. There are plenty of aftermarket lifters targeted at the VW market that fit the 944/928 applications, if you need to replace. I'm not at all a fan of putting used lifters into a different engine, especially if good new are readily available.
Thank you for the reply. I’ll invest in a good stethoscope, the one I was using is kinda messed up and occasionally pops and blows my eardrums out lol.
The lifters I swapped into my motor actually came out of a 928. I believe they are the same lifters. But I also now have like 14 lifters sitting around. I only swapped two of them.
If it ends up being a lifter issue, I’ll be sure to check out new lifters
Re: Diagnosing valve train noise
Posted: Wed May 14, 2025 11:29 am
by Jacquiles
zooklm1 wrote: Wed May 14, 2025 9:07 am
Does it go away after running for a while? I would look at exhaust system gaskets or a slight crack in a manifold. I say that because I had a slight crack on a Volvo turbo manifold that made a similar sound when cold but closed up when hot.
It does not go away when it’s hot, but I did recently get a leak tester kit that would allow me to blow smoke through the exhaust and see if it’s leaking.
Re: Diagnosing valve train noise
Posted: Wed May 14, 2025 12:22 pm
by zooklm1
If you think it is tappet noise, try some Liqui Moly Hydraulic Lifter Additive when you change the oil and see if it is reduced. I have used it in the past and it does help.
Re: Diagnosing valve train noise
Posted: Wed May 14, 2025 4:47 pm
by Jacquiles
Here is a better video than my previous one. The best way I can think to describe it is a pulsing knocking sound. I appreciate yall watching my videos and being patient with me.
If you still can’t really tell, then no worries, I’ll just have to dig into it myself and see if I can find anything. I mainly want to make sure I’m not ignoring something that would normally be a “yeah that’s definitely a sticking lifter” type of issue.
Re: Diagnosing valve train noise
Posted: Wed May 14, 2025 6:06 pm
by Tom
My first reaction is that it sounds like any other 944 motor, but if I turn the volume all the way up I hear it, and now I can't stop hearing it. That's not the classic 944 lifter ticking or clattering sound, although hard to rule anything out. I think the pulsing is coming from the engine surging just a bit as you hold the throttle still. I'd do as dr bob suggests, and get out the mechanics stethoscope and probe around -- I wouldn't limit the search to the lifters -- belt slap, broken valve springs, exhaust leak, rod knock, a/c compressor, etc. Now that I hear it, I think you are right to track it down.
Re: Diagnosing valve train noise
Posted: Wed May 14, 2025 7:06 pm
by zooklm1
Is it the triple rap you are referring too as the unusual noise? I am still thinking it is exhaust related. The headers on these cars can warp/distort over time. How many miles are on your ride and where has it generally been driven?
That's not the classic 944 lifter ticking or clattering sound, although hard to rule anything out. I think the pulsing is coming from the engine surging just a bit as you hold the throttle still. I'd do as dr bob suggests, and get out the mechanics stethoscope and probe around -- I wouldn't limit the search to the lifters -- belt slap, broken valve springs, exhaust leak, rod knock, a/c compressor, etc. Now that I hear it, I think you are right to track it down.