Re: [T3] Low Compression

["Shad Laws" <shad@aircooled.net>]

Hey Lauren-

> Well I drive a '71 Squareback...and I just got it back from taking it in
to
> a shop to get it all checked out. I've only owned it for about a month.
The
> guy said for the most part it's in great shape...but the compression is
low
> in cylinder 3 (55lbs). He didn't tell me why that would be...and I'm not
> exactly sure what that means. I'm taking the car down to LA on Friday
(from
> near Sacramento), and he said I should just get it checked again when I
get
> down there, to figure out the problem and get it fixed. Any suggestions/
> warnings before I make the trek. And any possible explanations of what
he's
> talking about would be great...I'm learning about owning a VW...but I'm
> still pretty much car-engine illiterate.

If the compression is that low in the cylinder then there is a definate
problem that should be attended to pretty soon.  I certainly would not drive
that car from Sacramento to LA right now.

A compression test is this: essentially, you take out a spark plug on a
cylinder and put in a pressure guage that records the peak pressure.  Then,
you disconnect the ignition system and open up the throttles all of the way
and crank the car over.  The point of the exercise is that you want to be
able to see what kind of compression that cylinder can hold.  A stock engine
should be around 100-125 psi or so.  If you are holding significantly less
(only 55 is VERY significant), then you have a problem.  It could be as
simple as malaligned valves - if one is held open, the cylinder won't seal
and won't hold compression.  Or, you could have blown a ring, cracked a
valve, dropped a valve seat, cracked a head, etc.  At best case, right now
you just have really bad gas mileage and really low power.  At worst case,
that problem will soon cause a much more major problem...

Take care,
Shad

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