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82 300SD slow to build oil pressure
My 82 turbo diesel has developed a strange habit starting from a month ago when I replaced the two oil cooler hard/soft lines. On first startup after the change, it took a long time to build oil pressure. Figured I had to fill the oil cooler and lines so didn't think much about it. But since then, about 3 out of 5 cold starts lead to very delayed oil pressure at the instrument panel gauge. Other times it behaves normally, with full OP after a few seconds.
I think it is more likely to happen after the car has sat a while (like a few days). But it also happens between morning park and afternoon startup with about 8 hours between. Here is what I have done: 1. Checked the two o-ring seals on the oil filter housing shaft -- I do this at every oil change. They seem intact and not particularly hard. I have spares to change in at the next oil change. 2. Checked the electrical connection for the oil pressure sender unit. Pulled it on and off a few times -- no difference. It feels normal 3. Timed the delay a couple of times. About 30 seconds when it happens. 4. Once oil pressure rises, everything is normal. I have heard there is a non-servicable check valve in the filter housing. That's a drag -- I don't get too excited about the prospects of changing that out. Because it is intermittent, I'm thinking something electrical or possibly the check valve, but not the shaft seal on the oil filter housing. I can't figure out a way to determine the oil level in the housing before starting since removing the cover dumps the oil. I'm kind of hoping that while I wait for oil pressure to build, the bottom end is getting good flow from the pump. Maybe the piston sprayers are inactive and the turbo is lacking pressure, but otherwise, all the main bits are getting oil. Am I delusional? |
#2
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Are you sure you have an electric oil pressure guage?
If it is mechanical like on the 123 i would suspect air getting in the line that supplies the guage and the delay is in filling the line up.
__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC] ..I also have a 427 Cobra replica with an aluminum chassis. |
#3
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Quote:
Quote:
Or, you could loosen the cover nuts slightly and see if the housing starts to overflow concurrent with the gauge responding. At a minimum, you are overly optimistic. Last edited by qwerty; 10-15-2012 at 12:48 AM. |
#4
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Answer
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A poor electrical contact would explain your symptom. .
__________________
ASE Master Mechanic asemastermechanic@juno.com Prototype R&D/testing: Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician. Noise Vibration and Harshness (NVH). Dynamometer. Heat exchanger durability. HV-A/C Climate Control. Vehicle build. Fleet Durability Technical Quality Auditor. Automotive Technical Writer 1985 300SD 1983 300D 1984 190D 2003 Volvo V70 2002 Honda Civic https://www.boldegoist.com/ |
#5
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Consistency is seldom a characteristic of a poor electrical connection.
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#6
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I've not had to solve this problem on my cars yet - don't have it. But, I do have a theory.
Could there be air trapped somewhere in the lines? Maybe in the oil cooler itself? When the car is cold, the oil has a slightly higher viscosity and would not be so rapid to compress the possibly trapped air. When the car is shut down, the compressed air would displace the oil again.
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Codifex 1981 240D ChinaBlue (Got her running with a donor engine.) 1983 300DTurbo w/sunroof. 1984 300TD manual sunroof. (Electrical Gremlins) |
#7
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Quite right. This is a W126. I should also note that we have 460K kilometres showing on the clock (Canadian car) just in case this becomes relevant.
Qwerty, I like your idea of doing an intentional drain for diagnostics. My recollection is that starting from an empty housing after an oil change gives a bit of a lag, perhaps 10-15 seconds, but not as much as 30 seconds. I do wonder if the oil cooler is getting dumped too. Does anyone know if a failed check valve allows the oil cooler circuit to drain? I'll also pursue the housing overflow idea. This assumes a willing assistant, I suppose, and it could get messy, but the result will eliminate the pressure switch from the list of suspects. Hunter: I'll pull the connection and make sure the contacts are tight since that is a pretty simple thing to do but, honestly, I'm not hopeful. Thanks all. Quote:
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#8
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Hmm
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Here are a few examples: * five radios currently setting here, identical consistent symptoms. * many climate control push button units with identical consistent symptoms. * many instrument clusters with identical consistent symptoms. * etc, etc.. All are temperature related, above XX° perfect function, below XX° nothing. * A bin full of harness wire and terminals that test good with the engine running/vibrating, and bad with the engine off. ******************************* A diagnostic always starts at the most basic. The oil pressure sensor may be failing. The instrument cluster may have a poor ground issue. W123: Instrument cluster Printed Circuit Board repair Ground the sensor wire, turn the key on: Does the oil gauge react instantly? If it is slow reacting there is a wiring or cluster issue. Verify mechanical oil pressure: Remove the oil pressure sensor. Take a spare oil drain plug, drill and tap the center for 1/8 npt. Buy and install this tool. Engine Oil Pressure Test Kit I do not insist any of these are the issue, but the contact cleaning/testing is simple, costs nothing, and is a good diagnostic starting point. . |
#9
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what is the checkvalve's purpose? is it a bypass thing? or is it for the cooler lines? it almost sounds to me like the filter is draining back each shut down... that would make me think an air leak in the lid, but that would result in an oil bath out the canister... I guess it's POSSIBLE the large o-ring could be damaged resulting in air getting in, but no oil getting out, but I doubt it.
I bet it's a sender issue...
__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread "as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do! My drivers: 1987 190D 2.5Turbo 1987 190D 2.5Turbo 1987 190D 2.5-5SPEED!!! 1987 300TD 1987 300TD 1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere! |
#10
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He does not have consistencey. It is intermittent.
__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC] ..I also have a 427 Cobra replica with an aluminum chassis. |
#11
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It was described as intermittent, but the problem is consistent in that it occurs only during a cold start, 60% of the time. Hardly the hallmark of a poor electrical connection.
I would suggest that "intermittent" and "consistant" are not necessarily mutually exclusive concepts. For example, you could say that people attend church intermittently (only one day out of seven), even if they show up every Sunday. Concur. Last edited by qwerty; 10-15-2012 at 10:00 AM. |
#12
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Well I am not going to get into the area of intermitant type issues. Even though with twenty five years of intensive heavy electronic servicing in my background. I think I have seen more than my share of it..
So the first order of business from my perspective is to read the sender ohms prior to cold start, then a few seconds after cold start and after running a minute or two. The thrust being of course you do not want a delay present if it is created by no oil pressure. Not owning a pressure gauge to apply to that same port if the oil pressure sender did not reflect it was working well. I would substitute it with another. Keeping it as simple as possible and going for the easy stuff first is usually less frustrating. Thermal expansion and contraction will always be with us well. Thirty seconds or so does not sound like much when we express it as a measure of time. Still in all too many things like developing oil pressure it is a very long time. Not being a car expert I was even wondering about the possibility of a sender sludging up causing a delay in it changing it's response time. |
#13
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Yes, often you can remove the sender and screw in a mechanical guage right at the place the sender screws in.
__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC] ..I also have a 427 Cobra replica with an aluminum chassis. |
#14
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82 300SD slow to build oil pressure -- update
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Cleaned everything up, tightened up the female part of the connector and voila, perfectly normal oil pressure even though the car had sat for one week. Next start, a few minutes later, no oil pressure at all! Removed the sender wire -- still no oil pressure showing. Put it back on, full oil pressure. Took it off again, gauge is pegged as before. Methinks this is an electrical problem! Most likely something going on between the connection at the sender and the gauge. Nothing else in the cluster is behaving strangely. Here is the revised plan: Check for shorts to ground in the wire by clipping onto the connector end of the wire and ground and wiggling things around. If intermittent, that would explain the symptoms, sort of. It would not explain why I only see this at startup so far. If nothing shows, pull the cluster. Ok, then what am I looking for given that there seem to be no other issues with the instrument cluster? Thanks. |
#15
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The senders themselves can also fail and read incorrectly or not at all. Have had it happen twice so far between all our cars...
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-diesel is not just a fuel, its a way of life- '15 GLK250 Bluetec 118k - mine - (OC-123,800) '17 Metris(VITO!) - 37k - wifes (OC-41k) '09 Sprinter 3500 Winnebago View - 62k (OC - 67k) '13 ML350 Bluetec - 95k - dad's (OC-98k) '01 SL500 - 103k(km) - dad's (OC-110,000km) '16 E400 4matic Sedan - 148k - Brothers (OC-155k) |
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