[bmw] Compression readings

[Stas Lotyczewski <slotyczewski@xxxxxxxxxxxxxxxxxxxxxx>]

Listers,

Since my eldest son was going to be looking over a 1989
325ix he was interested in buying, and had previously heard 
some ominous ticking coming from the engine, I thought 
I'd get him a compression gauge to help him decide whether 
the car was going to be a good investment.  We bought a 
cheap one (about $25), and practiced using it with my 
daughter's 1984 318i, which is home from college at the 
moment.  After warming up the car a little, the four cylinders 
ranged from 165 to 172 psi.  Squirting a little oil into each 
cylinder raised the reading by about 5 psi.  Slightly worn 
rings, not surprising.  As I understand it, the compression 
reading for each cylinder should be around 150 psi, so these 
numbers seem rather high, particularly for an engine with 
147,000 miles.  

As far as I can tell, the gauge seems reasonably accurate -- 
I rigged up some spare parts and tested it on a 100 psi bicycle 
tire and a 32 psi car tire, as measured by various tire pressure 
gauges, and the readings were apparently within one or two psi.  
I haven't yet tracked down another compression gauge, perhaps of 
higher quality, to re-test the car.

I'd be interested in people's thoughts about how to explain the 
compression readings.  Should we worry?  

(BTW, the 325ix's readings were around 100 psi per cylinder, both 
dry and wet.  Looks like some valve problems.  No sale.)

Thanks in advance for any replies.

Stas Lotyczewski
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