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#1
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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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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 |
#2
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Was the compression test done hot or cold?
What was done at the overhaul? |
#3
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cold
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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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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 |
#4
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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 |
#5
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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
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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 |
#7
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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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84 300D, 82 Volvo 244Gl Diesel |
#8
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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 |
#9
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TX
.
thanks guys I will consider my bar/psi numbers as good ones from now on cheers, ChO .
__________________
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 |
#10
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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. |
#11
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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 Don't leave that there - I'll take it to bits! |
#12
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new valves
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valves in/out are both new ... at least they told me so... .
__________________
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 |
#13
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Quote:
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 |
#14
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She's alive!
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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 Don't leave that there - I'll take it to bits! |
#15
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.
...Christine I say ...... .
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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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