Being told based upon a video I took of the om606 that the uneven sound is a loss of compression on a cylinder, and to check valve clearances. Sounds pretty catastrophic to me? Is it?

Well, you should probably check compression and try to figure out where you're losing compression.

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Milan Brown 1979 240D, rebuilt OM617.952 turbo diesel, rebuilt 722.315 transmission (my only daily driver)

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You can live with it or as mentioned. The first thing would be to do a compression check.


Catastrophic is putting the horse before the cart. It can be several things. Also you can loosen off one injector line a little at each injector. One at a time to see if you have a weak or dead cylinder. The 606 has hydraulic lifters. Depending on the results of a compression test. You may want to remove the valve cover and look at the valve train.

Could simply be one or more dead hydraulic lifter.

How many miles on the engine?

You could get a used engine oil analysis for a better idea of engine health.

IMO go STRAIGHT to a leakdown test.

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1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

Also, going back to your previous thread, no one told you to check valve clearances, I don't know where that came from. OM606 has hydraulic lifters.

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1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

One test won't help much. If someone neglected an engine by not changing oil / leaving the air filter off then at some point get back on schedule, an oil test won't show prior neglect.

Do a compression test and then a leak down test.

Why did you start a second thread? Keep all your troubleshooting in one place.

99 E300d hard cold stsrt

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It has 240k miles, was well taken care of and did have rebuilt injectors. It was run on a steady diet of home brew fuel though

Broken /stuck glow plug leaking compression ?

Do you have all of the service records to confirm this?

Did you install these or was that from previous owner?

For how long and what specific fuel?

Uneven sound while cranking is low compression, IMO OP will waste time with a compression test. We already know that cylinder isn't contributing.

Once the leakdown test is done, we'll know immediately just how severe the situation is. As in, whether the valve train failed or the piston failed.


















By the way, what exactly was the fuel it was given?

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1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

That information should have been given right at the beginning. Changes the whole equation. Depending on the home brew setup, it can cause a host of issues not found in an engine run on straight diesel. Stuck rings, delivery valves, and all sorts of other issues associated with running alternative fuels.

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96 E300d

I like leak down tests however, a compression test is a quick way to determine what cylinder is low and a leak down why it is low. Looking at starter amp draw on a scope is also a quick way to determine relative compression.

We don't know if the cranking goes RRRR , chug , RRRR, chug , RRRR , chug or RRRR , chug , RRRR , RRRR , RRRR , chug

The first could be a battery with a shorted cell ( actual shorted not what some throw at any electrical problem ) causing the cranking to be weak overall. This kind of battery failure is like installing a 10 V battery in a 12 V system , it will crank for long periods of time but cranking will be slower than normal.

The second would be a cylinder with low compression.

A worn cam lobe / rocker / large valve lash can increase compression, this is something that a leak down won't detect. When valves open late, close earlier and intake / exhaust overlap is reduced, compression readings will rise.

While we are on the subject. there are two kinds of compression ratio calculations, static and dynamic. Static is a calculation using swept volume and minimum combustion chamber volume and Dynamic that also takes into account valve events / intake ram effect / forced induction.

Can't be, that is a myth perpetuated by those evil oil companies / car dealers / manufacturers to prevent the masses from using " free " fuel and not having to pay road tax associated with real on road fuel.