2.0T Thunk noise on decel at exactly 24km/h every time I stop

[andybrrr]

Hey guys

I've had a 2018 GT-Line RWD for a couple of months now, and I recently fitted a BOV valve to the vehicle. During messing with spring tension I have noticed I have this thunk coming from the footwell area at exactly 24 km/h, every time I stop.

I assume it is a solenoid activating/deactivating in the ABS unit or something, but now I've noticed it, it is driving me mad!

Considering going to see the dealer about it as it still has some warranties on it, but I kind of what to point them in the right direction as I feel like I might get fobbed off.

Thanks in advance!

 

[MerlintheMad]

Welcome. Your weird "thunk" only happens when you stop or just when you are slowing down and reach "exactly 24 km/h"? If you coast through that speed without braking, I'm assuming that you don't feel any "thunk". What happens if you coast below "exactly 24 km/h" then apply the brakes?

 

[andybrrr]

Just when I slow down, I don't have to stop or anything. Just go below 24kmh while braking. I'll try coasting and see what happens. Its very strange.. I'm a mechanic myself but I'm hesitant to touch anything because of warranties etc.

I'll try experiment a bit with coasting and report back my findings.

The noise occurs at 24kmh regardless of whether I stop or not

 

[andybrrr]

OK so I did a bit of experimenting on the way home from work (as much as I could in Auckland traffic) and when I coast, it seems to do the same thing but at a slightly lower speed more like 20kmh~, and if I apply the brake between 24-20 kmh it does it on application. I'm fairly certain it's in the ABS unit or something, I can feel the thunk through the footwell/pedal box

 

[AusStinger]

I'm thinking transmission.

 

[MerlintheMad]

The coasting would rule out ABS. Something is kept whirling by centrifugal force until it reaches that speed, then drops into "place" with a "thunk". Check your wheels for something that you might have picked up. In any case, get the car in the air and do the minute inspection thing.