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  #1  
Old 10-20-2012, 05:39 AM
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compression issue om617

hi guys,

several guys told me that after the (last year) overhaul my compression numbers
(25-25.5-26-25.5-26.5 bar) can be explained that overhaul is not done
properly.

basically they say that after proper one it should be at least 28 bar across the cyls.

book says 24-30 bar.

any true in those statements?

thanks

ChO

.

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  #2  
Old 10-20-2012, 06:34 AM
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Was the compression test done hot or cold?

What was done at the overhaul?
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  #3  
Old 10-20-2012, 08:53 AM
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cold

.

stone cold

"everything but the chain"...as they told me...new cyl.sleeves,valves,guides
all gaskets,head hydro tested,new piston rings...etc...

to be sure I will change a chain and tensioner also one of these days... but
I'm still confused about those compression numbers..

cheers

ChO


.
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  #4  
Old 10-20-2012, 09:21 AM
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Hmmmmmmmmmmm, 25 Bar is about 360 psi. I think that is good cylinder pressure.
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Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership
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  #5  
Old 10-20-2012, 09:56 AM
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A cold compression test will give lower values. The 24–30 bar from the FSM is for warm compression tests (@ 80ºC temperature). I've read about 10 bar difference between warm and cold compression test.
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  #6  
Old 10-20-2012, 10:28 AM
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Why are you doing a compression test ?

Hard starting?
Rough running?
Oil consumption?
Exhaust smoke?
Too much time on your hands?
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Greg
2012 S350 BlueTEC 4Matic
2007 ML 320 CDI
2007 Leisure Travel Serenity
2006 Sprinter 432k
2005 E320 CDI
1998 SLK230 (teal)
1998 SLK230 (silver)
1996 E300D 99k, 30k on WVO
Previous:
1983 240D, on WVO
1982 300D, on WVO
1983 300CD, on WVO
1986 300SDL 237k, 25k on WVO (Deerslayer)
1991 350SDL 249k, 56k on WVO - Retired to a car spa in Phoenix
1983 380 SEC w/603 diesel, 8k on WVO
1996 E300D 351k, 177k on WVO
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  #7  
Old 10-20-2012, 11:41 AM
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Everyone seems to have an idea what is considered and Overhauled Engine.

If you were to buy an Overhauled Engine from let us say Metric Motors you would expect new Pistons, Sleeves, Bearings and so on and a rebuilt cylinder Head with new Valve guides.
Point; if any thing less the Metric Motors was done don't expect the same results.

Also you can't expect the Cold Compression reading to compare to the Hot one in the Manual.
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  #8  
Old 10-20-2012, 11:45 AM
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My 617.950 with 1,244,000 only put out 240 psi and was hard to start cold. That was why we rebuilt the engine. After Dad & I rebuilt it in 2005, the pressures were over 400 psi, but I don't really worry over the numbers. It will still start instantly (after a single, full glow cycle) in Big Bear, California (6000+ ft/asl) on a 28°F morning...Robert
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Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership
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  #9  
Old 10-20-2012, 12:31 PM
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TX

.

thanks guys

I will consider my bar/psi numbers as good ones from now on


cheers,
ChO



.
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  #10  
Old 10-20-2012, 12:54 PM
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How many miles since the valve lash was checked? Although I would expect it to be only a few cylinders down if they were tight enough.

During you rebuild did you do the valves? If the lower end had serious wear I might suspect a valve job might have been nice at the same time. Unless there was some indication it had been done already.
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  #11  
Old 10-20-2012, 01:11 PM
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There are many different variables in a compression test - such as

1) Is the gauge accurate
2) Is the starter turning the crank fast enough
3) Is the battery man enough for the whole job - does it start to get weak towards the end of the test?
4) How warm is the oil / how old is the oil
5) Type of oil - we all know synthetic makes it turn faster!!!!

I'm sure there are more...

...how about altitude effects? Apparently not everyone lives at sea level!

The best thing you can expect from a compression test is that all the measurements for the cylinders register the same value (more or less).
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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



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  #12  
Old 10-20-2012, 01:14 PM
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new valves

.

valves in/out are both new ... at least they told me so...

.
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next wish/project: w114 coupe OM603 powered
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  #13  
Old 10-20-2012, 01:31 PM
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cho cho is offline
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Quote:
Originally Posted by Army View Post

...how about altitude effects? Apparently not everyone lives at sea level!

The best thing you can expect from a compression test is that all the measurements for the cylinders register the same value (more or less).
interesting statement

at 7% uphill I can not go over 60 mph .. on flatland I have no issues with power
or speed... I did 95 mph steady for hours on highway recently...

yeap,all filters new,banjo's cleaned,Alda maxed...etc

.... so my car has a wrong altitude with me now?


ChO

.
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w126 500SEC gen II euro, powered by OM617 turbo stolen from 84 300SD 2.88 diff,EGR blinded
next wish/project: w114 coupe OM603 powered
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  #14  
Old 10-20-2012, 01:48 PM
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...like a shield of steel
 
Join Date: Sep 2009
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Quote:
Originally Posted by cho View Post
...

.... so my car has a wrong altitude with me now?
...
She's alive!
__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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  #15  
Old 10-20-2012, 01:55 PM
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cho cho is offline
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Join Date: Dec 2011
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.

...Christine I say ......

.

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next wish/project: w114 coupe OM603 powered
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