Low end sound when cold and at high RPM under load

[Why_Anything]

Very specific info here, 1996 Volkswagen Jetta with a 2.0 8v and 131K miles. When the car is cold a distinct piston slap or knock can be heard. Not super loud but it is there. It clears up 90% when warm. When hitting high RPM's in neutral still OK but under load the sound comes back in sequence with the RPM's. I just picked up this car and now im going over everything and this sound like it could be the death blow of a bad deal. I have dealer records since this car was new, everything was done by the book. WFT

Im going to seafoam the crank case and then change the oil with Shell Rotella T6 see if this does anything. But feel dumb and secretly think this is all in vain and i got duped and the bottom end of this motor is POS. I have never seen a VW 2.0 8v get bad like this at low millage and with the deal service history it just seems nuts.

I have a 1996 GL with 170K miles and its sounds NOTHING like this.

Does anyone have any insight?

 

[ThirdeYe]

I can't really speak on behalf of VWs as I've never owned one, but FWIW my '95 Acura has had piston slap since I've owned it, and it's still going strong at over 200k. It mostly goes away when warmed up, much like the GM 3.1 that I maintain. I have all of the service records from my car since it was new, and it's been very well maintained. Oil changes were always on time.

 

[Why_Anything]

Just did the oil change, yes at midnight and its 39f not too bad. Anyway, as soon as i started the car the oil light flashed for 3 times then went off and the motor was insane noisy. Then it mellowed out and is less pronounced over all.

I used a stethoscope and listened at the top of the motor and around the oil pan and bottom end as best i could. It seems the sound is cumming from the top of the block but i cant say its in the head. But i would think if it was a knock it would be coming from the bottom end right?

 

[Why_Anything]

http://www.youtube.com/watch?v=jr3qekx-Bzw

 

[Why_Anything]

compression test revealed normal results, new question, how long can a motor last with piston slap?

 

[SteveSRT8]

Originally Posted By: Why_Anything
compression test revealed normal results, new question, how long can a motor last with piston slap?


Piston slap can be quite different from engine to engine, but it normally goes away quickly after a cold start as the piston warms.

You may have a wrist pin issue. That's certainly not a lot of miles on that motor unless it was abused. A knocking noise at half engine speed may be a cam bearing.

Pretty hard to do diagnosis over the Internet!

 

[Why_Anything]

The noise goes away when the motor warms up, its there but just a tiny bit. 90% less. Almost normal sounds.

 

[Why_Anything]

I have been told by a VW pro this is piston slap. Now i wounder how long the motor will last. When its cold out, in the 20F's this thing is LOUD like a diesel truck.

 

[babyivan]

I wouldnt worry about it really, if it goes away (mostly) when warm.
I would imagine you can go a LONG time with the noise.

My mother had a Subaru Forester with a CONSTANT noise at idle since it was new (dealer told her it's nothing to worry about) and that thing went over 200k with no problems (other than the noise).

If you have no recourse with the dealer, then you will have to accept it for what it is.
Don't rev her when she's cold, be gentle.

 

[ARB1977]

Our 97 Jetta 2.slow sounded like diesel. No matter what oil I used the noise was still there.

 

[Merkava_4]

The piston slap is caused by excessive space between the cylinder wall and the
piston skirt. The cure is to fill the space up with thicker oil, plain and simple.

 

[SteveSRT8]

You were ok till you specified a cure.

Absolutely not true, know what an oil control ring does?

 

[babyivan]

Using a thicker oil is something You should never do, especially considering winter is about here.

Thicker oil would also put unnecessary strain on the oil pump, IMO.

I believe it's best to stick to manufacturer's spec fluids and viscosity. The car is engineered to work at its best using spec'd fluid.

Same goes for spark plugs and wires, I only use OEM.

 

[Cardenio327]

Another free test you can do is disable each cylinder one at a time while revving the engine, listening for the noise to get worse or go away. This will tell you which cylinder is doing it.

 

[Why_Anything]

I think its cly #2 but compression testing was all spot on across the line. The other night when it was 20f the car sounded like a tuck then after a 20 mile drive it sounded like a VW 2.0 N/A normal. Let it sit for an hr and then it was back, so i know its piston slap and im going to try to forget about it.