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:
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

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.