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  #1  
Old 03-19-2009, 07:15 PM
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300te Compression test?

1989 300te...losing oil..maybe smoky exhaust (hard to tell - still cold out).
In the old days (1960's) we did compression tests on our cars. Kinda fun, informative...usually scared us with the #'s.
What is the procedure for doing one on the 300te? Specifically!
This is what we 'used to' do:
1. remove all plugs
2. screw tester in #1 plug hole
3. crank 4-5x, write down #, repeat.
4. do this for all cylinders.
To test for rings, we would squirt some oil into the plug hole and repeat test...if # is different, possible ring problem
---Is this the method? Do I crank 3-5x? What are 'normal' #'s? How do I 'really' check for ring problems? How much oil do I inject into the top of the cylinder?
Thanks.
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  #2  
Old 03-19-2009, 07:19 PM
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Yes, thats the right way to do it, but disconnect the Spark lead at the coil.
We have done a couple of these and you should expect about 180psi.
My son's 300TE was losing oil but the compression is fine, turned out to be the valve stem seals... very common problem.
How many miles?
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1984 Mercedes 190D 2.2 209k miles
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  #3  
Old 03-19-2009, 07:47 PM
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A compression test is not an oil use test. The causes of oil burning, bad oil control rings and worn valve stem seals, do not affect compression.
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Old 03-19-2009, 08:21 PM
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Quote:
Originally Posted by Chas H View Post
A compression test is not an oil use test. The causes of oil burning, bad oil control rings and worn valve stem seals, do not affect compression.
But, won't the compression test indicate if there is piston ring leakage? My head was rebuilt about 50,000 miles ago.
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Old 03-19-2009, 09:09 PM
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Quote:
Originally Posted by Eliot View Post
But, won't the compression test indicate if there is piston ring leakage? My head was rebuilt about 50,000 miles ago.
A compression test tests the compression rings and valve sealing, not the oil control rings.
Low compression results in a poorly running engine. Your problem is oil consumption, if I read your first post correctly.
What work was done to the head when it was rebuilt?
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