Any Thoughts On Where Noise Is Coming From

[steamship]

Cheers all. I shall investigate all suggestions and see if I can uncover anything.

[steamship]

Originally Posted by MikkiJayne

The manifold pods might actually be a clue - if one of them has a split diaphragm it could be making a noise as its leaking. Possibly it could be a leak in part of the SAI valve system which reduces the vacuum such that only one pod can activate. Possibly something around the throttle body boot / oil separator.

I would first try disconnecting the vac pod solenoid valve, just to rule those out. It will throw a code but thats easily cleared. If that doesn't affect it, have a good look around the back of the engine with a torch looking for split hoses.

Just an update on this. Disconnected both vacuum pod solenoid valves and took it for a short run as well as doing a few errands, but noise was still apparent. I also checked both diaphragms on them and no apparent splits or holes.

I had a look at the pipe coming from the SAI pump and that is fine. I'll check all the vacuum pipes tomorrow when the engine is cold, although I had replaced the majority of these a couple of years ago.

There are two of the vacuum pipes that I'm not sure where they go. Each goes from the front of the engine to either wing, seems to connect to a stiffer plastic pipe and then disappears up towards the bulkhead. Any idea where these head off to?

I'll also get it up on ramps and check that heat shields and anything else lurking around is firmly secured.

[MikkiJayne]

Originally Posted by steamship

There are two of the vacuum pipes that I'm not sure where they go. Each goes from the front of the engine to either wing, seems to connect to a stiffer plastic pipe and then disappears up towards the bulkhead. Any idea where these head off to?

They go to vacuum reservoirs in both front wings. If you disconnect the hose at the junction after the engine has been running there should be a brief hiss as the vacuum is released.

[steamship]

Originally Posted by MikkiJayne

They go to vacuum reservoirs in both front wings. If you disconnect the hose at the junction after the engine has been running there should be a brief hiss as the vacuum is released.

Cheers MJ. Just got my version of ETKA up to date and checked it out. I might do what you suggest, as that will test their integrity, as well as me checking the rest of the vacuum lines.

[steamship]

Well, today I replaced every single piece of vacuum pipe under the bonnet. Did it one piece at a time in case I forgot where the bits went. There was only one piece that was showing its age, and that is the one at the front that goes to to top of the engine on the left side, down the side and then across to the plastic pipe leading to the vacuum reservoir in the wing. Difficult to say if it had any leaks.

Started it up and left it idle for about 10 minutes before taking for a short drive, but the noise is still there. I did check that everything was secured including the heat shields down the sides, but I forgot to check the ones underneath this evening whilst doing another little job.

I also did another little video to check the vacuum pods and noticed that one of them seems a bit hesitant to move. I doubt it has anything to do with the noise I hear, but it looks like I may be attempting this job at some stage:

40V Intake manifold fix for stuck or sluggish flap pivots

[Goran]

Just a random thought, could the gas pedal actuator itself be making the noise? its a little barrel shaped object connected to the gas pedal. Does the noise seem to be coming from inside the cabin?

[steamship]

Originally Posted by Goran

Just a random thought, could the gas pedal actuator itself be making the noise? its a little barrel shaped object connected to the gas pedal. Does the noise seem to be coming from inside the cabin?

I think I see what you're getting at. If you mean do I get the noise only when I press the accelerator and the noise then stops, then no. As long as there is a load on the engine, then the noise is there. The video may be a bit misleading as I was trying to show when I get the noise, but as it was short bursts, it could look like that.

Think of if you're driving along the motorway at 70mph. You will hear the noise constantly. You then notice up ahead that traffic is getting busier so you ease off the pedal to slow a little. Just doing that is enough to stop the noise, until you put your foot on the pedal again.

As to where the noise is coming from, I'm tempted to say that it comes from the transmission tunnel, but as we all know by now, cars seem to move sound around so it sounds like it's coming from somewhere else.

I had thought about putting the GoPro on the outside, but then you pick up wind noise or tyre noise. I'm not even sure if it can be heard outside.

[Goran]

I was thinking of the accelerator electronic mechanism, as long as its not at rest it could make a noise? I dont know exactly how it works but it can move the gas pedal on its own when in cruise control, check it out its freaky . When you press the gas its constantly under some sort of tension. I assume it must be electrical since it has no vacuum hoses going to it possibly its some sort of solenoid to move the pedal electromagnetically?
However that should mean it would make a noise even when car is stopped in neutral and revved.
Maybe there is nothing in there to make a noise anyway.

[HPsauce]

The pedal only moves (very slightly IIRC) with the PF cruise control, Sean has an FL model where it's all integrated into the engine management, no separate module.

[Goran]

Ah, ok, maybe I got confused with my old car, a Volvo, that pedal definitely moved when pressing the + / - button on the cruise control. Its a long time since I used cruise control on a D2, it doesn't work on my current car it only worked on my previous S8 and that was 4 years ago.