[T3] Engine Rattling.... Update...

Jim Adney jadney at vwtype3.org
Fri May 25 20:04:08 PDT 2012


On 25 May 2012 at 15:17, J. Jonik wrote:

> Re/  71 sqbk FI Std shift....with a seemingly worsening rattle in engine area.
> 
> A  good diagnosis and explanation came in over the phone from a mechanic who's worked on the old bombs for decades. He knew just the sound I described...tinny, like a rattle-snake, when changing  gears and at idle...not when driving steadily.
> 
> Yes...(as explained here not too long ago) it's about too much play in the crank shaft, as seen by moving the fan pulley in and out.   It's largely about old age of the engine....as the bearing dowel holes in the case have gotten a bit elongated and are not holding the bearings, and the crank, snugly any more.  How four dowel holes can wear out is a mystery.
>   He figures the case is shot.   But, to be picky, a few more questions...

I don't think excess end play will cause the thin metal rattling you 
describe. You may have 2 problems, or someone may have jumped to 
conclusions.

First, verify that there actually is excess end play. The end play is 
set by the #1 main bearing and has little to do with the dowels. It's 
more about how well the case is gripping the bearing. If the bearing 
has come loose, then that bearing can move around a bit on it's dowel 
and that will damage the case and can eventually destroy the engine.

Measure the end play. If it's more than .010" (1/4 mm) then you may 
have a loose main bearing. If you do, the case can usually be saved 
if the play is less than .040" (1 mm.)   

Normal play is on the order of .005". If that's what you measure, 
then you have a much less serious problem.

> * Exactly what thin-sounding metal parts are rattling together?

My bet is still on either the heat shield over the muffler, or loose 
screws that hold the front fan housing half to the case. It could 
also be a fan that's breaking up.

> *  Any chance it's not the case, but the bearing shells? Or do both
> dowel holes get out-of-shape at once? 

There are actually 5 dowels and 5 dowel holes, but only one is 
important here: the one in the #1 main bearing.

> *  No leaks from oil seal...yet....but will that be drastic (can't drive home) or gradual?

That's sort of a sign that you don't actually have excess end play.

> *  Engine does not have as many miles on it as some others.  This one
> had only 60 thou, or less, when I got it...and I may have put that
> much again on it  AFTER new pistons and cylinders.  What is normal
> life span vis a vis mileage?  Or does this have anything to do with
> careless assembly ten years ago, or bad driving practices? 

If it's excess end play, it COULD be careless assembly, but it could 
also just be bad luck. There's not always someone to blame.

> *  Would it have helped if case nuts (top and bottom, front and back)
> were checked and re-torqued (if needed) every so often?  (Don't know
> yet if they aren't as tight as should be.) 

There are only 2 nuts that might affect this, and they are on the 2 
front (of the 6) main bearing studs. Those are 17 or 19 mm nuts that 
I'm not sure you can reach with the engine assembled and in the car.

Checking the others is never a bad idea, but the real strength of the 
assembly is in the 6 large studs and nuts. If they get loose, things 
go bad. If you wanted to work at this, you could remove everything on 
the right side of the engine, including the cooling tin, and then you 
could reach and at least inspect each of those nuts. I've done this, 
and it's a big job.


-- 
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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