I recently purchased a 1983 300 TD with 220,000 miles on it. The compression across all cylinders is from 200 to 220psi. Is this reasonable or am I looking at a future rebuild. The car runs well now.Comments please.Dave

The key is in the last part of your post, not the measured compression. The car runs well, so enjoy it. These compression numbers do not indicate an engine in new condition, but why would you take it apart if it's running well.

How much oil does it consume?

Have a great day,

The usual benchmark compression that you hope for in these cars is a minimum of 300 psi. Not that 300 is a magic number, but, for example, you might see adds for these cars which would say "compression in all cylinders above 300", as a very meaningfull selling point. In my own car, I recently posted readings of 290, 315, 320, 315, and 260...a little low in a couple of cylinders, but by no means bad...and the car runs real well.

With your car, I would suggest that you adjust valve clearances on all cylinders a little on the wide side (on the wide end of the specified range, maybe a tiny little wider) then run car for a couple thousand miles, then re-adjust clearances as needed, within specified range, then check compression. You might find that compression is low due to tight valves, and that it comes up to more respectable levels after a couple valve adjustments. Then just keep adjusting valve clearances every 15,000 miles...kind of a "valve maintenance program". As long as car runs well, just keep driving it.


Another suggestion, but I'm on shaky ground in this area due to my lack of real knowledge, is to run synthetic oil for a few thousand miles...this may help remove sludge etc. and free up any stuck piston rings. (anyone else with input on this???)

By doing the above, you maximize potential compression in your car, possibly resulting in more favorable compression readings, a little better performance and fuel economy, better cold starts, etc.

Another factor, as Larry Bible said previously, is not just compression levels alone, but consistancy between cylinders...he said that all should be within 10 percent for smooth engine operation. Outliers beyond 10% may result in "fud, fud, fud, fud" or "bang, bang, bang, bang" type of engine operation.



Good Luck

Mark

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1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)

200 psi will probably make it hard to start when cold, but I wouldn't panic yet. Get the valves adjusted, and have them left a little loose. Try a change of synthetic oil -- at the very least, it will be easier to start. It may free up dirty rings and raise compression, and it may not.

If it doesn't use oil, and the valves are fine, just drive it. When it won't start is when I'd think about an overhaul.

And have the timing chain checked -- if it is really streched, you may have valve timing late enough to reduce compression -- this is only a maybe, I'm not sure. Chain stretch causes other trouble, too, though, so get it checked.

You may also want to get a leakdown test done -- this will tell you why the compression is low and give you more to base a rebuild decision on.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

A cold engine test will show low scores, was the engine warm when your test was done?

Harry
86 300 SDL