Hi guys, I know I should have post this on the Ralliart forum but I thought this problem could happen to any car so I post it here.

This just happen to me recently when ever the road is wet and strangely only when the road is wet. So something in my engine bay doesn't like it when its wet. Here is a link to a video on youtube that I post.

I am not even sure if this noise is engine knock or something else because the noise only comes out when the road is wet.

Audio Video Link :
Symptoms:

1. Dry Road - No knock

2. Wet Road and:
Accelerating - No knock
Decelerating - Knock
Hitting puddle - Instant knock
Decelerating until 0km/h - Knock
Idle - No knock
Idle in Neutral + Gas ~5000rpm - No knock

So I have this "engine knock" problem only when it is raining heavy or when I hit a puddle of water (<1 inches deep or less) especially during deceleration.

Say I am coasting around 80km/h on the highway and it was raining heavy, then I let go of the gas pedal with or without break decelerating the engine would knock so hard even if you drive beside me you will hear it. Keep in mind I have a down pipe and a catback UR muffs, the knock can be heard very clearly.

If you have similar problem in the past, any help will be very appreciated.

Current suspicion:
1. Axle
2. Oil filter not properly installed (but no oil leak)
3. Something in the engine bay that doesn't like it when its wet

 

Do you have an aftermarket intake?

Edit: just watched the video. I don't think that's knock.

 

If you have a CAI then get a Hydro shield

 

@Thomar
Mods done on the car are:

1. Mid pipe
2. UR Catback exhaust

No intake
No engine mods yet

@Kartyman550
I will double check on it, could you recommend me a good Hydro sheild?

 

You said you have the stock intake, therefore you don't have an aftermarket cold air intake and don't need a hydro shield. Unless you take it to a dealer when it rains you could maybe have someone hold the throttle down to 2500 RPM or whatever while you spray water at it from the front towards the engine. I never heard of a noise like that.

 

By the way, you should also post in the ralliart forum.

 

That sounds like heat-shield rattle to me, which is definitely sensitive to weather. The two that I'd check first are those on the turbo and cat.

 

PROBLEM & SOLUTION :


PROBLEM:

OK guys, guess what!

I took my car to this shop and it took them pretty quick to find what the problem was!

The problem was with my rear differential bushings, since they are stock bushings they are soft and made my rear diff vibrate causing the after market UR exhaust pipe that goes underneath the car hit the crankshaft. It only hits the crankshaft when you splash water on the pipe because hot metal expands. I could see some marking that the driveshaft made to the aftermarket UR exhaust pipe. The aftermarket UR exhaust pipe is slightly big.

FIX:
Changed out the differential rear bushing with a stiffer aftermarket rear differential bushing kit. Since I live in Vancouver, BC, Canada in North America. I had to pay shipping fee to ship the rear differential busshing from Whiteline. The shop also shifts the hangar for the exhaust pipe 1/4" further away from the crankshaft.


NOW:

With the aftermarket rear differential bushings from Whiteline, I feel the RA shifts much smoother.
ALSO!! You guys notice the Rear diff clunk after a hard upshift?? I don't feel it anymore, maybe sometimes but not that noticeable.

Thanks to : SpeedSyndicate, Burnaby, BC
Mechanics: Eric, Kevin,Ken
Admins: Alex, Curtis

- July 18, 2014
67k kms, running smooth

 

Huh!

Cold water 'shrank' the metal (not expanded it)...

I am glad it was a cheap/easy fix.

 

No, Hot exhaust pipe + road water = Metal pipe expansion

But

Yes, Hot metal allowed to cooldown + cold water = Shrink metal