Hi guys

I've really been breaking my head over this issue. Whenever I drive my car uphills, there is a strange rattling/scratching sound coming from the engine bay.

Video here:
Focus on the end part of the video especially where noise is much clearer.

Bought the car second hand 5 years ago with +-120000km on the clock. Car currently has 173 012km on the clock.
This rattle only started popping up midway through 2023.

I have since tried the following:
- Oil changed to car spec (5W-40 Castrol Magnatec) & oil filter replaced
- Installed BMC air filter (One that fits inside air box, not cone)
- Did coolant flush on system, and replaced with Castrol Radicool SF Premix (The pink stuff)
- Replaced EGR valve (TOPRAN aftermarket)
- Replaced Fuel Filter (GUD)
- Replaced Spark plugs (BOSCH Platinums)
- Decarbed engine (Compression Stabilizer)
- Replaced Battery
- Replaced Thermostat (TOPRAN Aftermarket)

Any guidance will be highly appreciated, as I have taken the car in multiple times but did not help.

 

not sure what all those changes would have to do with a rattle/scratching sound. If you suspect the noise is pinging (pinking) - I'd expect a CEL for a misfire code since you didn't mention any fault codes or a CEL I'd assume you have a mechanical problem. As going uphill puts a load on the engine, which can stress axles, wheel bearings, motor mounts etc. I'd probably start by looking for signs of rubbing on the exhaust or heat shields and checking the motor mounts (to do this enlist a buddy and look for excessive motion of the engine when doing a "power brake" (safely - stand to the side and point the car away from the garage door!)

 

Just another update on this.
No engine codes showing up at all, and I noticed that clouds of white smoke comes from the exhaust whenever I pull away from a stop when the engine is in operating temp and the rattle occurs (Not even hard acceleration).
I did a live data view on both the oxygen sensors before and after the cat, and the second sensor's voltage fluctuates quite drastically (which is apparently not good and a sign of a bad cat)



Also, just a disclaimer - I am not an expert when it comes to mechanical parts of car engines and merely started getting interested about a year or 2 ago. Hence I decided to post all changes I made to the car recently, even if it potentially does not have anything to do with the scratching sound

Engine mounts and heat shields have been checked numerous times also, unfortunately

Taking the car in again tomorrow to a Volvo workshop. Fingers crossed they find the issue.

 

Alrighty, had the workshop check out all of my concerns on the car and they came back with the following:

- Engine rattle is due to worn flaps in intake manifold (I've read a few posts about this before)
- Engine does have a ping though, and suggested first step is to clean the 1st O2 sensor after manifold replacement/fix mentioned above.
- Black soot from exhaust on startup - Pipe between breather box and intake manifold is broken.

There was also a DTC stored on the accelerator pedal and 1st step was to tie cable tie around pedal.

Currently waiting on quotes for replacement parts but also gonna do some research into the issues to understand it more.

 

Did a swirl flap delete on the intake manifold today, but unfortunately did not make any difference to the rattling noise

Also, the pipe between the breather box and intake manifold seems fine without any issues.

 

After swirl flap delete, rattle issue still persists: