BoostLover99

Context:
- Car is 100% stock, '06 MR, except for clutch (ACT HDSS), brake pads (Ferodo DS2500), and tires (Bridgestone RE-01R).
- Clutch, pads, tires have been on since 22K miles w/o any issues.
- Car had 60K mile service performed @ 59.8K miles.

- Service included: timing belt (Mitsu OEM used to replace), serpentine belt (Gates), balance shaft belt (Mitsu OEM), water pump (Mitsu OEM), upper & lower radiator hoses (Mitsu OEM), new coolant, transfer case fluid (Mitsu OEM), tranny fluid (Mitsu OEM), rear diff fluid (Mitsu OEM), oil & filter change (Mobil 1 10 W 30, Mitsu OEM), engine air filter (Fram).

Problem:
1) *Significant* increase in cabin volume during normal driving @ all RPMs; droning present at steady 70 mph cruising.
2) Irritating rattle from engine compartment above 3K RPMs; increases in volume linearly with RPM > 3K.

Troubleshooting Steps Already Taken:
a) Checked to see that timing belt was in time.
b) Checked to see that balance shaft and balance shaft belt was in time.
c) Briefly ran car *without* serpentine belt and belt covers; rattling still present.
d) Checked exhaust system for leaks; no leaks found.
e) Searched EvoM; read previous threads that indicated the rattling was related to a timing shaft out of time.

Questions:
i) What have you done to solve the rattle?
ii) What have you done to solve the drone?

The rattle is a much bigger issue than the increased noise; it is really detracting from my enjoyment of the car.

Thanks a million in advance!

batty200

iTrader: (3)

The balance shaft mark can be on and still wrong. You prob have the balnce shaft out of time by a whole rotation. The directions to time the balance shaft are in the manual.

FutureNoob

Easy fix in my book.. Take it back and tell them to fix my ****.

fre

iTrader: (4)

As was stated by batty200, rattling in the 3K range is defefinitely a balance shaft issue. Get the engine to TDC and remove the bolt on the front of the block behind the turbo. Stick a screwdriver in there and if you can't get it in very far then it is off 180 degrees. Note the balance shaft will look like it is lined up, but it isn't. Simply spin the oil pump/balance shaft until it lines up again and try the screwdriver again.

Of course you can just take it back and explain that to them, I am sure they won't get offended that the customer knows more than they do hah.

WHTEVO

iTrader: (18)

Like the others have said, it sounds like you have a balance shaft out of phase. I wouldn't even mess with it. Take it back to the shop you paid to do it and tell them to fix it.

Aaron

BoostLover99

Thank you all for the responses!

RE taking it back and having them fix it, what is the correct procedure to ensure that the balance shaft is in the right phase if the timing mark is unreliable? The screwdriver thing is useful but I'm sure I'm going to need to thoroughly explain this to them (and perhaps even show them myself) so I want to be crystal clear.

I don't have a service manual.

On a pure curiosity level, why doesn't the entire engine vibrate substantially at high RPM if the balance shaft is out of time?

Thank you!

BoostLover99

Nevermind - I found a thread w/ pics. Thanks everyone!

https://www.evolutionm.net/forums/ev...-belt-how.html

fre

iTrader: (4)

Not sure why it isn't as bad at higher rpms, that is just the way it works like between 3k and 4500 is where all the vibration is. Probably a harmonic frequency that only happens at certain rpms. Same thing happened to me, except my balancer shaft belt stripped all the teeth off. Got lucky it didn't get into the timing belt.

BoostLover99

Yeah, I looked online for an animation to better understand the harmonic imbalance of an inline 4 and haven't found anything.

I'll update this thread with results in a week or so when I can get back to the shop and check to make sure the front balance shaft is in time. I should have RTFM but I expected the shop to do that.

BoostLover99

Just following up and closing this thread; the suggestions posted here were 100% correct - both the increased exhaust/engine noise in addition to the 3KRPM rattling was caused by the front balance shaft being out of time.

I printed out the instructions and made my shop use the screwdriver trick; we got the shaft in time and the car is ridiculously good now.

I've noticed the following benefits:

1) Almost zero vibration at idle.
2) Very smooth while increasing/decreasing revs.
3) Substantially reduced noise.
4) Revs "hang" better after shifts.
5) Heel toe downshifting multiple gears is a pleasure.

I can't thank everyone enough for providing the education to both my shop and me; I wouldn't have had the confidence to go back to them a 3rd time without you!

Thanks!