75 240d 10 second oil pressure delay on start-up - Page 2 - PeachParts Mercedes-Benz Forum

vstech · #16 11-23-2006, 08:44 PM

where do you live? how cold is it? what oil did you replace the old oil with? 15W50, in 10*F would be pretty thick and could cause some problems with pressure building up quickly...
Just a thought...
John

Hatterasguy · #17 11-23-2006, 08:51 PM

Its an old engine with a lot of time on it, I'm sure the clearances are lose and the seals all leak a bit.

If the oil filter is installed properly, and she runs well in all other respects I say just drive it.

Did MB publish a min oil pressure build time in the FSM for this engine? If so how far off are you from it?

Wallknight · #18 11-23-2006, 10:36 PM

At the risk of sounding way too simple, did you happen to check to see if the gauge was working properly? My speedometer will sometimes stay flat for a while, then jump up to 30mph. My temp guage used to get wacky at times, too. All just lose connections. Is it possible that the oil gauge is just "sticking"? Sorta like the guy who rebuild his engine to remove the source of rust on his oil dipstick, only to later find that the problem was merely a rusty old dipstick!

AndrewB · #19 11-26-2006, 04:01 PM

I just thought of a way to test the check valve. So I noticed that there was no oil in the injection pump after it has been sitting for a day. This leads me to believe that if I put oil directly into the pump and it drains over the course of a day, then the check valve is bad. What do you think?

JimSmith · #20 11-26-2006, 04:57 PM

I checked the arrangement of the flow paths through the OM616 engine, which is a 1975 240D engine. This unit is "upside down" in the area of the oil filter compared to the 1977 and later W123 models, and the general arrangement of by-pass and full flow filter elements are significantly different.

There are no leak down prevention O-rings on the oilfilter housing center threaded stem. In fact, as I vividly recall, changing the oil on this model was a real PITA. Changing it hot, as Larry Bible recommended was an act of masochism. The "pod" with the filters in it is nestled between the front suspension arms, and as you loosen that center threaded stem, the oil runs out all over your hand and arm since it has no where to drain to, so there is no need for those O-rings that exist on the W123 versions of the same engine.

In those days the oil pressure gage was fed oil pressure from the filter housing through a very small diameter tube routed through the firewall. With whatever oil is in this tube now, in cooler weather there will be a time lag as the pressure has to push oil through this line, not much, but enough to straighten out a little Bourdon Tube gadget. How long that time lag lasts is not documented anywhere to my knowledge, but if you let the car warm up, includng the interior, and the whole line is at a more comfortable 20 degrees C or so, the oil pressure should rise much faster (won't be instantaneous though) when started again immediately after a shut down. If this is the case, I would ignore the delay at lower temperatures. It has been too long since I retired my 1975 240D - and I used Mobil 1 oil even back then (it was only available in one viscosity, but it made the engine startable at under 20 degrees F) - so I do not recall if this was a seasonal thing, or maybe just a sign of the oil being very dirty and clogging the lines up. Good luck, Jim