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Old 01-21-2021, 08:06 PM   #1
Scooby Newbie
Member#: 365071
Join Date: Aug 2013
Default FA20DIT 2016 whomping noise at 900-1000rpm

I'm trying to understand which part of the engine does this nasty whomping at 900 to 100rpm.

Long story short. Got a new WRX in September 2016 (MY17). When the odometer was at around 20k (12500 miles) km I noticed a whopping noise above idle rpm which was disappearing once oil temp was hitting 30C (86F). After about 6-7 months and another 5k km (3k miles) the noise became permanent and can be heard at any engine temp.

I visited the dealership numerous times but they don't know what it is. We fired up a few other WRXs with different mileages ranging from 0 to 40k km. The new vehicle didn't have it. 7k km unit had it but it was really hard to hear. 40km unit had the noise but was less noisy than mine (I'm at 43k km now). All cars we checked were MY17.

Dealerships, I visited, have two versions: high-pressure fuel pump or CVT pump. I don't think it's CVT pump. You can easily hear that beast while driving the first few minutes when it's cold outside (I'm from Canada ). It sounds like a hydraulic power steering pump on older vehicles under the load.
I'm not sure about the fuel pressure pump working noise, but it's an electrical pump and its noise shouldn't be linked to engine rpm but to engine load.

I know at least one person with the same complaint. He also can't find the source of whooping.

Any ideas what it can be?
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Old 01-23-2021, 09:28 PM   #2
Scooby Newbie
Member#: 494147
Join Date: Nov 2018
Location: Nashville, TN
2017 WRX


If I’m understanding your description correctly mine does it as well… I am at 81,000 miles on my 2017 and haven’t had any issues. Do you have any modifications?
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Old 01-23-2021, 10:42 PM   #3
Scooby Newbie
Member#: 365071
Join Date: Aug 2013

I removed the serpentine belt today and started the engine without it. No noise.

Then I took a stethoscope and listened to 3 possible sources: tensioner, pulley and AC compressor. The tensioner is the noisiest guy on this list. I'm still not 100% sure as it was the very first time in my life I used a stethoscope but at least I know it's not the engine and it will be an easy and not expensive fix.

I bet all WRXs have this noise. All we checked at the dealership had it. However, for the manual car it's not a big deal as you almost don't drive in that rpm range.
CVT is a different story. When the engine is still cold and you stop at traffic lights your idle at Drive will be around 1000. Same rpm if to drive very slowly at 10-12mph which happens to me every morning.
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