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Old 09-11-2006, 01:13 PM
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Join Date: May 2006
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75 240d 10 second oil pressure delay on start-up

Hi! I have a 1975 240d automatic and the oil pressure upon start-up takes about 10 seconds to move. Then it spikes and everything seems to be fine except for a few times when the oil pressure dropped at a stop sign.
She has other issues but I don't think they are related: no vac assist on brakes and no automatic door locks, also I think it needs to have the injectors cleaned (engine runs pretty rough)
I did just change the oil and I thought I put all the proper components back in place.

Other than that I think maybe it could be the oil pump?

Any help would be appreciated as I am not driving the vehicle until I fix this problem.

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Old 09-28-2006, 06:39 PM
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Posts: 9
Still no luck

Ive deceided to remove the oil pan and check the check valve.
We'll See.
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Old 09-28-2006, 06:44 PM
Cabernet red, actually
Join Date: Jan 2006
Location: Willamette Valley, OR
Posts: 503
Does your car have those little O rings on the oil filter housing stem? If they're hard the oil pressure will take longer to go up on startup. I doubt it would account for 10 seconds, though.

I have no idea if your car even has those, however.

1985 300D Turbo, CA model
248,650 miles and counting...
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Old 09-28-2006, 06:51 PM
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Also check to ensure that the pressure tube is filled with oil, and not air. Air in the line will delay the reading, especially with cold oil.
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Old 09-28-2006, 07:07 PM
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Location: Nova Scotia, Canada.
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After you pull up to a stoplight with an operating temperature engine how far does the oil gauge drop? I assume it stays at three when driving. On the basis of that alone I do not think the relief valve is out of the pump. Especially if the engine maintains 1 1/2 -2 bar at hot idle. It sounds more like your filter is draining down and has to be refilled before pressure comes up when cold. Are those two rubbers on the shaft the cause? They might even have disapeared. I know there is some effect if hard and bad alone. I also suspect it could take 10 seconds to fill a filter that large but might be wrong again. If it were say the relief valve it would still take at least 5 seconds seconds or more to get pressure again if you let the car sit for 30 seconds and restarted. The oil is thinner and will fill the filter faster. Or it has not had time to drain down. If instead you have almost full pressure immediatly it pretty well has to be the filter draining down with time. I reserve the right to be wrong but it does make some sense to me. But make allowances for me as a young lady many years ago sold me on the ideal two could live as cheaply as one.: The equation got kind of messed up after there were six of us.

Last edited by barry123400; 09-28-2006 at 07:26 PM.
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Old 09-28-2006, 08:42 PM
Palangi's Avatar
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Location: Republique de Banana
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Guys, this is a 115 240D. Entirely different oil filter than a 123 240D.

Andrew, how long have you owned the car? Have you changed the oil filter yourself? If so, does it have the plastic filter disk and the spring in place?

FYI, it normally does take a few seconds for oil pressure to build, but 10 seconds seems excessive. Oil pressure dropping to mid-scale on a hot engine at idle is normal also.

2004 C240 Wagon 203.261 Baby Benz
2008 ML320 CDI Highway Cruiser
2006 Toyota Prius, Saving the Planet @ 48 mpg
2000 F-150, Destroying the Planet @ 20 mpg

0BAMA .......... OUTHOUSE
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Old 11-20-2006, 04:38 PM
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Work is underway.

Thank you guys for your replies. I was beginning to think nobody was out there. So from the threads posted until this date I've come to the conclusion that the oil filter is the cause of this problem:
When I changed the oil I did not see the white disk that is supposed to be there. That is the first thing I am going to check, along with the seals.
Also, It seems to drain very slowly which leads me to believe that the check valve is OK.
Be back soon, hopefully with good results.
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Old 11-20-2006, 05:17 PM
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mmmmmm Diesel...
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Location: Royse City Tx
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Also check your vacuum pump. Brakes and locks require proper vacuum to operate.

70's Southern Pacific #5608 Fairmont A-4 MOW car

06 VW Jetta TDI 133K miles-replaced the other '06 that quit after 300k miles. (did not catch the bad cam in time)

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 195K

90 Dodge D250 5.9 Cummins/5 speed. 400K
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Old 11-20-2006, 05:45 PM
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On this engine would a failed vacuum pump diaphragm permit oil to be sucked into the intake?
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13
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Old 11-20-2006, 06:21 PM
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That might be correct as it looks like oil has been going into the intake. I don't know for sure though on the mechanics of it yet.
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Old 11-20-2006, 06:27 PM
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I've not owned the car more that a year. And I did change the oil recently. I just checked the oil filter again and the white disk is there along with a seal for the filter canister.

Barry, the filter actually didn't drain. It was still full of oil.

The injection pump, however, was not full of oil.

This leads me to think that the check valve on the oil pump is bad. So I guess I should make clear what the check valve is on the oil pump. This would be so that oil doesn't drain from the system (injection pump and oil lines) right?

Thanks again
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Old 11-21-2006, 07:03 AM
Admiral-Third World Fleet
Join Date: Feb 2002
Location: Central FL
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I have the same slow oil pressure build up issue on my 77 240D. I did change the o-rings on the oil filter spike. This car is a back-up, hence it only gets occasional starts. The few times I have started it within a day it behaved normally. I suspect it could use a new pump. Someday I will pull it and check it for wear.

My VW diesel Rabbit, which, I think has the same type of oil pump was acting even worse. It would fail to keep prime over the course of a day. I would start it and NOTHING for 15...20.. seconds. Finally, I bought a new one and it is like a new engine. Boom- oil pressure right off. And 10-15 psi higher pressures while running. I didn't really see anything wrong with the old one when I tore it down.

I also note that in the PPO's maintenance log on my other (1982) 240D, he replaced the oil pump due to low oil pressure at something like 80K miles- so maybe these things do wear out?

Just my experiences ..

80 300SD (129k mi) 82 240D stick (193k mi)77 240D auto - stick to be (153k mi) 85 380SL (145k mi) 89 BMW 535i 82 Diesel Rabbit Pickup (374k mi) 91 Jetta IDI Diesel (155k mi) 81 VW Rabbit Convertible Diesel 70 Triumph Spitfire Mk III (63kmi)66 Triumph TR4a IRS (90k mi)67 Ford F-100 (??)
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Old 11-21-2006, 11:08 PM
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Location: Puget Sound, Washington St.
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I had a similar issue with my mechanical oil pressure gauge on my 76 240d.
It was slow to read, then pow! 3 bar. I cleaned out the line and the
gauge itself to remove 30 year old oil sludge. All was fine afterwards.

Try that if nothing else works!

Dr.Diesel -
Shop Foreman
Master Guild Mercedes-Benz Technician.

Think the dealer is expensive? Do you know how much it costs to train a dealer tech? Or buy the required MB special tools to have on hand?
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Old 11-22-2006, 06:46 AM
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Originally Posted by DR.DIESEL View Post
I had a similar issue with my mechanical oil pressure gauge on my 76 240d.
It was slow to read, then pow! 3 bar. I cleaned out the line and the
gauge itself to remove 30 year old oil sludge. All was fine afterwards.

Try that if nothing else works!

This is what I was thinking was going on could hook up a gauge directly to the fitting on the engine to test the theory but I'd bet it is your gauge that is faulty.
Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz
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Old 11-23-2006, 07:27 PM
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Location: Nova Scotia, Canada.
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On the possibility of a slow oil gauge line. If it takes ten seconds to register when you kill the engine it should take longer than normal to drop the needle back if engine still cold. Problem here is what is normal I guess. Also you might have a friend start the car and see if you are getting oil up top in a second or two through the filler cap. If you are and it is pronounced I would just live with it. If not you know the oil line is okay and the check valve is the primary suspect. I cannot see the oil pump itself unless car carries almost no pressure when hot. Could be wrong though I guess.

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