rattle/noise but not what you think

[xenadu]

1995 (e36) M3. I posted this here because I don't think this is necessarily unique to the M3...


This past weekend a friend and I did a replacement of the water pump, radiator, thermostat, thermostat housing, etc which went perfectly fine (parts purchased from PelicanParts, except Aluminum thermostat housing from BMP Design).

Anyway while we were working I also changed out the primary timing chain tensioner as I was getting an engine rattle that seemed to be growing worse and it seemed a cheap fix. It did solve the noise problems on cold startup but that just amplified the fact that the engine is way too noisy when warm.

Anyway, upon cold startup it was very quiet. As it was idling in the garage I could hear the noise getting slightly louder and louder. After I drove for a few minutes and it got up to operating temp it was back to being very loud.

So far I haven't run across anyone else with the quiet-when-cold but noisy-when-warm issue. The sound does change in relation to RPM but at highway speeds it is either not present or too quiet to hear.


I finally decided no more $100+ stabs in the dark so I took it to the shop. They are reporting that I need new chain guides and a secondary tensioner (plausable).

However they also are saying that the oil pump is the real culprit/source of the noise and that when the oil heats up and thins out the pump starts to rattle.

Does this seem at all plausable to you? At first glance I don't want to believe it.

[parolof]

The previous owner of my car had the guides and a secondary tensioner changed together with the chain and primary timing chain tensioner, (looking at the old garage bill) but I've never heard of a rattling oilpump before...:-/