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Discussion Starter · #1 ·
my passat is a 2000 v6 manual transmission.

i was driving today and all of a sudden i started to hear a grinding/cranking sound come from the engine bay. it's really loud when the car is idle and tends to get a little better once i'm driving but it still has the sound.

it sounds like something is clanking or grinding. any ideas where i should start my search to try to figure out what the problem is?
 

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What part of the engine is the noise coming from? Might be bearings in one of the pulleys going. When my ribbed belt tensioner roller started to go, it had a metallic grinding/clanking sound that was more noticeable at idle than when engine rpm was increased. If you take a piece of PVC tubing or the like and use as a stethoscope, you can generally put one end to your ear and the other to where you think the sound is coming from (being carefully of the fan blade and moving belt) and the sound will get louder when you find the equipment making the noise.
 

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Depending on when (and if) the waterpump was replaced, it could be sending you a warning message.
IIRC they can go at 60k miles - nm+ had one go at abouit 60k, the replacement went bad about 30k after that.
The V6 is a strong, forgiving motor but the waterpump seems to be an Achilles heal.
 

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Discussion Starter · #4 ·
i just had my water pump, timing belt, and serpentine belt replaced about 3 months ago at around 76K, my car is now at 78K.

i'll go check to see where the sound is coming from and report back
 

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Discussion Starter · #8 ·
so i went to my shop today. it turns out that the bolt for the timing belt tensioner broke. i ordered the timing belt/water pump kit/set/package from ECS Tuning. the shop doesn't know if the broke because of faulty parts or if it was incorrectly installed.

i'm pretty sure this is going to be an expensive fix. do you guys know how much the ballpark figure may be to fix the engine? any ideas/tips as to how i should handle this problem?

thanks in advance.
 

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The tensioner bolts are reused from the old tensioner. If they are overtightened they could snap but that usually happens while tightening. A bad tension roller may stress the tensioner but usually will tear up the belt.

You might need a metallurgist or forensic engineer to inspect the bolt to determine the cause of the failure. Pete1 was a forensic engineer, send him a pm for advice.

As for cost, since the car was running, I would think at least $3500 for a rebuild or engine change. Dealer would charge about $7K. Hopefully the shop will cover the repairs.
 

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Discussion Starter · #10 ·
i think that the tensioner included a new bolt. when the shop reordered the part, it included a new bolt for the tensioner.

thanks for the advice to PM pete1
 

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My guess would be that if the part was defective, all you will get is a new part since most parts warranties exclude consequential damages. You have a better chance recovering damages if the shop screwed up and you can prove it. Also, usually if the shop supplies the parts, they will pick up the labor to replace a defective part. In your case since you supplied the parts, they may not. Good luck.
 

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i think that the tensioner included a new bolt. when the shop reordered the part, it included a new bolt for the tensioner.

thanks for the advice to PM pete1
Hey, I got your PM. I'm not sure how much I can help, however.

What is the status of your engine? Did you lose timing (from the loose belt) and damage the valves? :nervous:

Can you post pictures of the failed parts? Close-ups of any fracture/failure surfaces would be really nice. Same goes for the threaded ports on the block (very hard to photograph this, however).

With the aluminum block in these engines, the typical fastener failure is due to over-torquing the bolts until they strip the threads out of the block. Because of the "soft" aluminum block, it is almost impossible to break the bolts by over-torquing: the threads tear out first.

Describe the shape of the bolt fracture surface... is it at the interface with the head, or is it farther up the shaft? If on the shaft, is it on the non-threaded or the threaded part? Is it a spiral/cone shape (kind-of like the surface of a spiral pasta noodle), or is it flat, with a stretched-out bit at one edge.

Does the fracture surface have "tree rings", or does it appear to be fairly-uniformly weathered?

Can you easily re-thread a nut on the used bolt (use very light hand effort only -- you don't want to disturb anything)? How about threading a new bolt into the block (again, be very careful and use very light hand effort only)?

I'm trying to get a feel for what type of forces caused the break... torsion, flexure, shear, or a combination, and also determine if there was a small crack that slowly grew its way across the bolt.

Hope this helps...
 

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Discussion Starter · #13 ·
The engine stopped running completely. I would turn the key and it would make the starting noise but i think the entire engine block is stuck.

i spoke with the shop and they said that they torqued it according to manufacturer specifications.

i looked at the bolt yesterday and it was towards the middle of the shaft, on the threaded part. it point of fracture was flat. the shop was able to get the part of the bolt out by using a wrench but they had to drill into the rest of the bolt to get the second half out. i can go to the shop later today to take a look at the bolt and report back more later.
 

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i think that the tensioner included a new bolt. when the shop reordered the part, it included a new bolt for the tensioner.

thanks for the advice to PM pete1
Sounds like the tension roller bolt broke. That bolt is included with the tension roller. It is a larger bolt? The tensioner (aka tension damper) is held in by small 10mm head bolts.
 

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i looked at the bolt yesterday and it was towards the middle of the shaft, on the threaded part. it point of fracture was flat. the shop was able to get the part of the bolt out by using a wrench but they had to drill into the rest of the bolt to get the second half out.
That seems like a tensile failure of the bolt. How far "in" was the failure surface? (one thread turn? five?) A "clean snap" two or three turns in is consistent with an over-torqued bolt.

Perhaps there was grease on the threads, so there was too much twisting before the torque spec was reached (the relationship between tightening torque & bolt shaft tension depends on the amount of friction between the surfaces).

BTW, to correct something I posted above... PZ pointed out that the block, or at least the bolt anchor holes may be steel, not aluminum. I'm certain the heads are aluminum, but the block may be steel... I have to check. If the block is steel, that makes it more likely that the bolt could have failed due to over-tightening.
 

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Could they have over tourqued the tensioner causing the tensioner roller bolt to fail from to much lateral stress??
Yes, they could have. The shape of the failure surface should be a bit different, however, depending on whether it was a shear or tensile failure in the bolt. (Pictures would be worth a thousand words here).

The belt is initially tensioned by rotating a cam on the face of the tensoner, in order to push the tensioner firmly onto the belt. After that, as the belt stretches (and belt tension relaxes) the one-way valved "plunger" on the tensioner maintains a minimum preset tension.
 

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Could they have over tourqued the tensioner causing the tensioner roller bolt to fail from to much lateral stress??
I doubt it. Even if the belt were overtensioned, the plunger is not one way. It will slowly compress within a few minutes to maintain the desired tension.
 
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