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Strange Engine Clonk. Idler? Water Pump? Tensionser? wtf? [With Video]

2K views 16 replies 5 participants last post by  timworx 
#1 ·
2002 325i 135k here.

So, I changed my engine and A/C belts about 2 weeks ago. Piece of cake.

Now, however, I'm noticing a "clonk". I didn't notice it until the temperature dropped a few days after the belt change (NY). Now it makes the clonk until it is nice and warmed up.

The Video

It didn't sound absolutely terrible from inside the cabin, but with the hood open it makes me want to get into the fetal position with my hands over my ears and rock back and forth.
That poor girl, the pain and agony I'm putting her through. Help me help her.

My initial guess is the tensioners? I would imagine a consistent sound if it were a shot idler, right? (Like a normal shot bearing of any sort). Could it be the water pump (no idea when or if it was ever serviced.)? I haven't a clue.
 
#3 ·
Unfortunately it was just me and myself so I couldn't get in there well.

But it's that very loud tapping sound that is of concern. The sound is not really consistent in pattern, and goes away once the car is warmed up. The car idle's fine, accelerates fine, etc. These don't really seem like DISA related issues, do they?
 
#5 · (Edited)
No dice on the DISA, thank you for the suggestion though.

So, like I said it was pretty loud, and here she is. The noisemaker in all her glory.

View My Video

Tinypic screws with the aspect ratio, but you can see the wobbling idler. Strangely, this goes away (at idle at least) once it's warmed up.

On a side note, I also noticed rough *driving*, at like 35+- mph. Like forward and backward roughness, not side to side. Related, or just hypersensitivity because of this current issue?
 
#7 · (Edited)
I am assuming you didn't change the "engine" just the A/C and accessory drive belts. The wobbly pulley is the tensioner. It shouldn't wobble. If its a spring one perhaps the spring is weak or suffered when you backed it off to remove the belt. I believe new ones are hydraulic. You might want to change it. I don't recall there being any "grease" in the region of the belts. Last thing you want near drive belts is grease. They don't work when greased up.
 
#8 · (Edited)
It seemed so odd for it to go away after the car is warmed up. I mean, it's not like worn out wheel bearings stop grinding after you've driven the car a few miles.

The the tensioner pulley uses a sealed bearing, so there is lubricant (i.e grease) in there, or else it would seize up after short. So, I'm wondering if it's a matter of cold effecting the already worn out idler, making it that much harder to turn (with much less viscous lubricant in the cold) before it warms up.

I'm off to order the pulley. I'm wondering if I should get the whole tensioner assembly after the abuse it has taken from that wobbling pulley.
EDIT: Looks like you have to buy the entire assembly for mechanical type. (Pelicanparts)
 
#11 ·
That could easily be just the pulley. Most likely your tensioner is fine. Replace it and be done before the thing does come flying off and you need a new belt and overheat your engine. No use in speculating. Plus if the tensioner is also shot you should be able to tell that there isn't good resistance when you try to relieve the pressure. In any case your pulley is def gone so order that up first. You might as well get the idler pulley too because that is probably also shot or will be soon.
 
#13 ·
Problem has been solved:
While the tensioner pulley does seem as though it is due for replacement soon, it was NOT the cause of this issue.

I was going to mention the "far fetched" idea earlier that there could possibly be something on the belt, causing tension to build and release every time it goes over a pulley. But I figured people would think I was crazy.

Well, that turned out to be the problem. The cause was a sh*tty Continental belt from PelicanParts.com. I looked at it after I got it off and you can see buildup on the grooves from the manufacturing process.
Went around the corned to Advance Auto for a new one and low and behold; no more horrendous sound.
 
#17 ·
Manufacturing crud, their inspector didn't look close. It's belt material, still attached to the belt itself. I started scraping it out (not easy since it's attached), but decided against wasting my time and went around the corner to Advance Auto.
 
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