Oil Pressure comes up slow - PeachParts Mercedes-Benz Forum

arcticathlon · #1 05-30-2007, 05:44 PM

so my 1980 240D always clatters loud when i start it up and this louder sound happens for about 2-3 seconds. it then quiets down to its normal clatter when the oil pressure come up and the needle pegs.

so what can i do to fix that? i want the least amount of wear occurring during startup, and need to know how to fix the oil pressure lagging.

i have the correct amount of oil in the car, as a i have just replaced the oil pan gasket, vacuum pump gasket and done an oil change.

what do i need to check?

barry123400 · #2 05-30-2007, 05:53 PM

The rubber o rings on the filter stem? Ever been replaced? The responce of you gauge may be normal. Others will know.
I would change out those rubbers if you have no ideal when last done. I though they were a periodic change item anyways. Become very hard with time. Possibly a case of should be changed out anyways even if not the problem.

jaoneill · #3 05-30-2007, 06:03 PM

In addition to changing the o-rings, FWIW I have found that Mann filters seem to be manufactured to closer tolerances than most of the others; especially noticable when inserting the center tube. Pressure to 1 bar is almost immediate and spikes very quickly (after sitting overnight).

Jim

rs899 · #4 05-30-2007, 06:05 PM

This car has 712K miles on it??

I think its time to think about bearing clearances.

But one cheaper thing to look at would be the oil pump.

My 77 240D takes about 8 seconds to register any oil pressure. But - I only start it about once a month. I noticed that when I start it everyday the pressure comes right up.

arcticathlon · #5 05-30-2007, 07:47 PM

ya, my 300D pegs right away, while the 240D just takes a few seconds longer. i am not sure what you are referring to when you said "filter stem." every morning it sounds like it does not have any oil in the engine until the pressure comes up. i am not familiar with the internals of the engine, but it seems odd to think that all the oil drains back down into the pan.

rs899 · #6 05-30-2007, 08:45 PM

The filter stem idea is - look at the center prong of the oil filter lid. On it are two black o-rings. They should be soft and pliable. If they are not ( and many do look like plastic ) replace them- this may improve your oil pressure at idle.

Was this a gradual thing? That's a lot of miles, champ!

How about some more data? What is your hot oil pressure like at idle? Does the needle peg when you step on the pedal?

My VW rabbit was getting painfully slow to develop oil pressure. Sometimes it would take 20 long seconds although both the pump and the engine had less than 150K miles since the last rebuild. I replaced the pump and presto- great oil pressure. Even with the old pump, I had good pressure at hot idle and at speed. The new one improved both a bit, but really made a difference in building pressure from a cold start. I took the old pump apart and didn't see anything wrong.

#7 05-30-2007, 09:11 PM

BTW, what weight oil are you using?

barry123400 · #8 05-30-2007, 09:47 PM

Over seven hundred thousand on original unrebuilt engine? If so the oil has probably got good circulation and pressure. Perhaps the general clearances may be somewhat larger than the average engine out there. Plus the oil residue is not enough to keep it quiet until pressure comes up and gets established and cushions things. It would be reasonable to have quite a bit of wear if that engine is the original. That is a fair amount of miles afterall.

cyoung · #9 05-30-2007, 10:22 PM

My '78 240D with 79k miles takes 1 or 2 seconds to register full pressure when first started for the day. The rest of the day the pressure immediately shows on the guage.

In really cold weather (<20 degrees F) it may take 4 or 5 seconds to show full pressure.

I have wondered if the oil drains back down the thin line that goes to the guage and the time delay is just the time it takes the oil to hit the guage again.

arcticathlon · #10 05-30-2007, 10:58 PM

thanks for all your responses.

Quote:

I have wondered if the oil drains back down the thin line that goes to the guage and the time delay is just the time it takes the oil to hit the guage again.

Well it is not that it drains back down the tube or line, because it is confirmed by noise, vibration and smoothness that once oil pressure comes up that the all the symptoms disappear.

Quote:

Over seven hundred thousand on original unrebuilt engine? If so the oil has probably got good circulation and pressure. Perhaps the general clearances may be somewhat larger than the average engine out there. Plus the oil residue is not enough to keep it quiet until pressure comes up and gets established and cushions things. It would be reasonable to have quite a bit of wear if that engine is the original. That is a fair amount of miles afterall.

I dont know if it is rebuilt or not, all i know is what i have in the driveway. it burns some oil (smokes at night when looking in rear mirror), clatters heavily on startup, is a car that looks like a beater from the outside (that i have rescued), has quite a lot of blow-by compared to my 300D(cap barley moves), but i love the car...

Quote:

BTW, what weight oil are you using?

Rotella 5W-40 Full Synthetic, are you thinking that 15W-40 being thicker might make it stick to the organs more? do they even make a full synthetic that is 15W?

Quote:

How about some more data? What is your hot oil pressure like at idle? Does the needle peg when you step on the pedal?

Once the first 3 seconds have passed it performs just like my 300D in terms of oil pressure behavior. it will idle around 2, and when i rev it up it pegs.

I think i will take a video of what i mean so you can see and hear what i am referring too. Thank you all for your input.

Gurkha · #11 05-30-2007, 11:01 PM

Bravo OM616......................

712000 miles and still ticking, long live OM616/617.

vstech · #12 05-30-2007, 11:22 PM

so do you change your own oil, or have it done? M1 15W40 is only CF rated, but it would be thicker at startup.
seriously pull the oil filter lid tonight and look at the end of the shaft, if it does not have two o-rings on it's end, you have found the problem. if it has two, but they are hard as nails, you MAY have found the problem.
if they are recently changed, or nice and soft, keep looking.
John

barry123400 · #13 05-30-2007, 11:26 PM

I might have forgot an important item earlier. That tube in the filter gets obstructed with gunk. Clean it out if it has. I am not sure it is delaying things but another thing that cannot hurt to check. It does have some effect I remember. Perhaps someone else can remember exactly what it is. Hope your car gets to a million miles.

arcticathlon · #14 05-30-2007, 11:42 PM

Well i wish i did not give the camera to my wife, but i have no camera in the house(she is in California). Do you guys mean the two small black gasket looking rings at the end of the shaft that goes through the oil filter? they are not rubber like, smoothed down to the width of the shaft with no sealing ability, and hard as plastic.

Soooo where do i get these rubber rings because i looked in all my extra oil filters (i took the old one out tonight and stuck a new on in there) and they only had the large lid ring.

slarson80 · #15 05-30-2007, 11:48 PM

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=22H17A47H23J1EZ3PW&year=1979&make=MB&model=300-D-002&category=A&part=Oil+Filter+O-Ring