Odd Engine Noise/Resonance

[mtnbikaah]

1993 Accord EX Wagon, 5spd, 138k, STOCK STOCK STOCK.

I have been experiencing noise/resonance coming from the engine bay starting about 3 weeks ago. No excess noise coming from the exhaust. The resonance occurs in time with engine speed. It is mostly quiet at idle and gets louder as the rpms rise. There is also a pronounced "buzz" as the engine's rpms come down.

Oil level, fine and clean.
Exhaust manifold gasket and engine pipe gaskets replaced, didn't fix it.

Noise/resonance occurs when the engine is warm or cold. And also with the clutch in or out.

The bracket that holds the engine pipe to the block is fine. I inspected it when I changed the manifold gaskets.

Motor mounts appear to be fine. There is no excess rocking in the engine. I can grab the engine and it only moves slightly in any direction. I compared it to my sedan last night. Same movement. There is NO shaking under heavy acceleration.

The mid-pipe (with the resonator) was also replaced.

The noise sounds like it is coming from the block.




**EDIT: Car was cold in the video. Resonance continues when the car is warm.**

if you watch it on youtube select 720p to get higher quality audio.

This really has me stumped.

[Fleetw00d]

Sure you don't have an exhaust leak in the flex pipe or at the converter? When's the last time you adjusted your valves; they seem more noisy than any of mine?

[mtnbikaah]

Valves have not been adjusted since i've owned the car (since March). The do need an adjustment.

I am almost positive there isn't an exhaust leak. (replaced the mid-pipe a week ago, when it was all put back together there wasn't a leak. Took the exhaust manifold off replaced the gaskets, re-assembled, no "lisping".)

I should also note that the video was shot with a cold car.

[Losiracer2]

kinda sounds like there's a strain on something. But it seems to go away at idle.

I'd maybe check the belt tensioners possibly? One of the bearings could be bad? T belt or balance belt could be rubbing on the inside of the timing cover?

Or...going with the resonance only at certain RPMs, check you intake system since it looks stock from the vid. I know that that has a bunch of resonators built into it....maybe one came unhooked somehow or is cracked allowing excess air in? I found a cracked breather tube inlet on the daily I fixed up...though it didn't cause that loud of a sound, still plastic breaks over 20 yrs.

Have you noticed a drop in mileage since this noise started happening?

[mtnbikaah]

I am almost positive we changed the timing belt tensioner and the balance shaft tensioner when we did the timing belt back in March.

I guess one of those could have gone bad.

I will take a look at the intake system this evening.

I plan on crawling under the car this evening with the engine running to see if I can pinpoint anything. Perhaps I can shoot another video from under the car.

No drop in fuel economy since the noise started.

[mtnbikaah]

Checked the intake system. It's fine.

I removed all of the accessories on the driver's side, power steering pump, alternator, and A/C compressor. Found that two bolts were loose on the A/C compressor bracket. Tightened them up, bolted down the compressor and started the engine. Still resonates.

(in this process I have also learned that one of the bearings, in either the compressor or the a/c clutch is starting to go bad. I bought a shorter belt to bypass the a/c compressor. The A/C wasn't working anyway, compressor wasn't kicking on. Funds are too short right now to replace the compressor.)

The resonance is definitely coming from the driver's side of the engine, down low.

I'm hoping it's not a bearing in the balance shaft belt tensioner or timing belt tensioner. (they were both replaced back in March.)

Could the balance shafts belts be off a tooth? Would that cause a resonance, or more of a shaking? (there isn't any significant shaking.)

it might be time to start taking timing belt covers off to do some more investigating.

[dj_ender]

Maybe a loose heat shield? There 2 around the cat, and one under the shifting mechanism.

[mtnbikaah]

the heat shields are fine. I crawled under the checked them out today with the car the running...

[dj_ender]

Maybe even open up the timing cover, another member had a similar issue recently, ended up being his balance shaft belt getting eaten to bits.

[Losiracer2]

yeah i have a bad feeling that one of the belts, either timing or balance shaft, is rubbing on something. So you might have to take those covers off

[mtnbikaah]

Next step is going to be re-tensioning the timing belt. If that doesn't fix the problem, then I will take off the timing belt covers.

On the plus side, the noise/resonance isn't getting any worse.

[i-07]

yeah man? wut tb kit did you use?

[mtnbikaah]

Honda timing belt, and water pump

Aftermarket balance shaft belt, and tensioners.

[i-07]

Honda timing belt, and water pump

Aftermarket balance shaft belt, and tensioners.

my ebay one works fine but i do need a valve ajust cus i sound like a deisel

[dj_ender]

Next step is going to be re-tensioning the timing belt. If that doesn't fix the problem, then I will take off the timing belt covers.

On the plus side, the noise/resonance isn't getting any worse.

Lol, uh, if your gonna redo the tensioner the timing cover will already be off. Just saying...