noisy 603 diesel

I have an '87 300D 124 Euro version with a 603 in-line six naturally aspirated diesel engine. Mileage is 105Kms. Engine power is very good and has good emissions.

Engine runs rough & noisy, with slightly more smoke after a cold start, and smoothens out after approximately one minute. When engine heats up, noise level improves further, but it still has one isolated knocking sound which can't be attributed to a specific cylinder, even after loosening one high pressure line at a time.

Injection pump and injectors have been pulled down and serviced by a Bosch service station, and they have seen no problem. Glow plugs have been checked, and found OK too. Compression readings taken on a cold engine after one day of non-use are as follows: 1-340psi, 2-370psi, 3-380psi, 4-390psi, 5-390psi, 6-410psi.

Could noise be coming from uneven pressures? Are these pressures still OK?

I am more interested in noise removal when the engine is in normal operating temp.

Your suggestions have always been a grat help.

I have seen the #6 and #1 rods bend on this engine causing some unexplained noise. The problem is it will not show up on a compression test.

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Benzmac:
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M.B. says cylinder compression imbalance of more than 35psi can cause "hammering" type noises In diesel engines. The cylinder with the lowest reading is causing the problem. Suggest a hot engine compression test.