2.0 Liter w/light knocking

[spiffy]

Hi all, getting ready to take the 78 over to Tacoma for two weeks and I was changing out the ATF and cleaning the underbelly. Fired it up and went for a run to warm up the tranny fluid, I just went around the block to get a ballpark level and pulled into the garage. While I was checking the trans fluid I decided to rev up the engine a little (it was luke-warm at best) when I heard a little knocking right off idle and it would return (ya can't hear much when the engine starts reving higher) when I would let off the throttle. It is very subtle but there. I do know that the bottom end of this engine has about 80k on and the top end (including rods/bearings) was rebuilt about 20k ago.

Need the low down on some testing I can do to determine what I might have going on. I know the candidates are rod knock/piston slap/main bearings going south (yes I know about the shortage). I know some forms of knocking are load sensitive and would like ideas on testing methods to hone in.

Crazy that we were just talking about this in Maupin.

[hambone]

Could it be a slight exhaust leak?

I've heard type4s knock when cold only to go away after warmup... and then run for years.

[spiffy]

Could it be a slight exhaust leak?

I've heard type4s knock when cold only to go away after warmup... and then run for years.

I wish, it is a very "internal" sound if that makes any sense and very subtle at this point.

[hambone]

When/how often do you drive it any more? Maybe it just needs to be "broken in" after sitting for a spell?
Take it for a good decent drive and try again. You could be spoilt on yer new rocketship engine...
If it's still there, you could be looking at loose rod bearing tolerance.

[spiffy]

When/how often do you drive it any more? Maybe it just needs to be "broken in" after sitting for a spell?
Take it for a good decent drive and try again. You could be spoilt on yer new rocketship engine...
If it's still there, you could be looking at loose rod bearing tolerance.

It gets driven a fair amount (at least 6x/month) and I almost always let it get up to operating temp. Maybe I'll take it for a spin tonight and give a listen when I come back to the stable.

[tristessa]

Could it be a slight pinging..?

[Amskeptic]

The well-known 2.0 piston slap. See if it is gone with a fully warmed-up engine, then rest easy.
Colin

[Hippie]

Busted engine sounds

http://www.ratwell.com/mirror/Muir/Muir.html

[Westy78]

The well-known 2.0 piston slap. See if it is gone with a fully warmed-up engine, then rest easy.
Colin

Mine even has a little of that for the first minute or so on a cold engine. Barely audible unless I'm parked next to something where there's a little echo back to my ear. Isn't it a characteristic of the boxer engine? I've heard even the Subaru's do it.

[spiffy]

The well-known 2.0 piston slap. See if it is gone with a fully warmed-up engine, then rest easy.
Colin

Mine even has a little of that for the first minute or so on a cold engine. Barely audible unless I'm parked next to something where there's a little echo back to my ear. Isn't it a characteristic of the boxer engine? I've heard even the Subaru's do it.

Nice long run tonight and no more clitter-clatter, sounds as good as ever. Momentary freak out, thanks for the sanity check.

We are a bueno at this station.

[hambone]

No no it's quite allright to be COMEPLETLY PARANOID

[spiffy]

No no it's quite allright to be COMEPLETLY PARANOID

I think yer right, almost a requirement. Good for the senses.

[Amskeptic]

The well-known 2.0 piston slap. See if it is gone with a fully warmed-up engine, then rest easy.
Colin

Mine even has a little of that for the first minute or so on a cold engine. Barely audible unless I'm parked next to something where there's a little echo back to my ear. Isn't it a characteristic of the boxer engine? I've heard even the Subaru's do it.

It is characteristic of the larger displacement air-cooled engines that have to have greater piston-to-cylinder wall clearances to cover the expansion of the aluminum pistons. VW managed to keep things quiet for the most part up to 93mm bore with the cam ground piston skirts. The TSB for the 2.0 engines was all about curing piston seizures, the notched rods for piston oil cooling, the deletion of the head sealing rings, and the new piston cylinder clearances that were opened up. Apparently, aluminum expands "exponentially" while cast iron expands "linearly" as you increase bores.
Colin

[hambone]

It's a scary sound, like a rod knock. But then it goes away...
Weird stuff.

[sgkent]

Pull the spark plug wires one at a time and see if that changes the noise. If it is a rod it may quiet it.

Piston slap does not sound like a rod bearing. It is quieter and is more like someone tapping on your door with a key instead of a hammer.

Key on door - piston slap
knuckle on door - rod
hammer on door - (more a thud) main bearing.
carbon on cylinders - marbles inside and bad cases soft hammer on door.

Carbon, rod or main knock don't go away with heat - piston slap does. So does valve noise sometimes. I did have an intake valve stick one time in cold weather and it made one hell of a racket.