Have had for some months, an engine noise when the engine is not fully warmed up. It almost sounds like a very light rod bearing rattle. Increases when free reving or acceleration but never really very prominent from inside the car and almost inaudible when fully warmed up.

Under the hood It is just barely noticeable when free reving the motor. Not even as loud as valvetrain, just a sightly lower pitch noise... not deep like a main.. If anything the noise is near the front of the engine in the timing gear area.

Engine has 150k, more or less... but sat for 18 years.

I am considering pulling the motor and inspecting the lower end and Plastiguaging it. I havea strandard set of rod bearings just in case for a temp repair.

Or is it possible the timing gears are noise source. I have read they can be due to the fiber cam gear.

Unfortunately my B20 is not nearly complete. Since my jetta tranny took a dump I have been relying on my 122 for daily trans. Better safe than sorry!

Your thoughts?

In the 240's you can get a noise like this from "piston slap", particularly on higher mileage cars. I don't recall hearing of this problem in the B18's or B20's, but the symptoms sure sound the same--a knocking sound in a cold engine that goes away as the engine warms and the tolerances get tighter.

I bought one of those auto stethescopes a couple of years bachk and they really do work well. if you don't have access to that you can hear quite a bit by pressing a big screwdriver to your ear, and to various spots on the engine.
or you can make something up from tubing etc if you want to get creative.

the auto stethescope has a rod at the end which connects to a tin plate , which helps amplify the sounds. it is surprising how much you can hear going on in there.

I have had a timing gear come loose , and it made a racket! you can change it without taking the pan off. and you can get the pan off if you jack up the engine,with the motor mounts off but you have to finesse the oilpump out first.

also if you think it might be from the valvetrain you could try adding a .010 or so shim under the valvesprings. valve float can make a clacking noise. I had this problem and it took a while to find. just don't put too much or you could make the coils bind.

Phil

It is pretty hard to tell if the timing gear is coming loose but you
might be able to see some play by wrenching the cam nut lightly back
and forth.
A rattling wrist pin makes more noise revving freely than under load.
And of course there is the ubiquitous valve noise....
Also if it is coming from the back, sometimes parts start working loose
in the clutch.

I may just snatch it out this weekeend and put it on the rotiserie and give it the once over.

I figure I can pop the timing cover and pan and check for bearing or gear problems and back in by money. With luck, Murphy will be out campaigning.

My understanding is, rods and mains are pretty robust in B-18s and 20s and don't usually cause a lot of trouble, right?

Thanks guys.

P.S.
George.... Send more schematics when you get a chance.

The rotisserie will not be much help because you can do the timing gear
without it and the pan will not drop until you remove the front crossmember
which includes the entire front suspension so you gotta hold the engine up
while you do that (motor mounts are ON the crossmember).

Unless your engine is severely abused your lower end should be OK.

More diagrams coming - may be a bit.

Hey George!

Engine really runs well and I always drain the oil (two days ago most recently) through a magnetized strainer and get no iron (poor mans oil analysis). Very low oil consumption... less than half a qt. in 2000 mi.

Zero sludge build up everything I have seen.

No problem on the schematic .. take your time. I'm error checking the first one and making illustrations of connectors. I figure a good first one and the rest become edited versions. How's the first one look?

Thanks

Mike

The one you sent me had some fine brown print that was hard to read
but otherwise looked pretty good. I'm eager to see the final.

I would pull the timing gear cover and have a look in there for two possible failures:

1) Timing gear starting to separate from its hub.

2) Cam retainer plate wearing and allowing excessive cam endplay.