Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Diesel Discussion

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 10-14-2012, 11:32 PM
Registered User
 
Join Date: Mar 2011
Location: Victoria Canada
Posts: 37
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?

Reply With Quote
  #2  
Old 10-15-2012, 12:10 AM
t walgamuth's Avatar
dieselarchitect
 
Join Date: Apr 2005
Location: Lafayette Indiana
Posts: 38,604
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.
Reply With Quote
  #3  
Old 10-15-2012, 12:12 AM
Registered User
 
Join Date: Aug 2007
Posts: 972
Quote:
Originally Posted by t walgamuth View Post
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.
A W126 has an electric oil pressure sender and gauge.

Quote:
Originally Posted by birkhoff View Post
I can't figure out a way to determine the oil level in the housing before starting since removing the cover dumps the oil.
You could intentionally drain the filter housing and see if the delay in pressure increases or remains the same.

Or, you could loosen the cover nuts slightly and see if the housing starts to overflow concurrent with the gauge responding.

Quote:
Originally Posted by birkhoff View Post
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?
At a minimum, you are overly optimistic.

Last edited by qwerty; 10-15-2012 at 12:48 AM.
Reply With Quote
  #4  
Old 10-15-2012, 12:22 AM
whunter's Avatar
Moderator
 
Join Date: Dec 2003
Location: Metro Detroit, Michigan
Posts: 17,390
Answer

Quote:
Originally Posted by birkhoff View Post
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?
The oil pressure sender or wire may have been disturbed, or taken a bath in used oil.

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/
Reply With Quote
  #5  
Old 10-15-2012, 12:39 AM
Registered User
 
Join Date: Aug 2007
Posts: 972
Quote:
Originally Posted by whunter View Post

A poor electrical contact would explain your symptom.

Consistency is seldom a characteristic of a poor electrical connection.


Quote:
Originally Posted by birkhoff View Post
Once oil pressure rises, everything is normal.
Reply With Quote
  #6  
Old 10-15-2012, 02:02 AM
A work in process...
 
Join Date: Oct 2009
Location: Texas
Posts: 985
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.
__________________
Codifex
1981 240D ChinaBlue (Got her running with a donor engine.)
1983 300DTurbo w/sunroof.
1984 300TD manual sunroof. (Electrical Gremlins)
Reply With Quote
  #7  
Old 10-15-2012, 02:10 AM
Registered User
 
Join Date: Mar 2011
Location: Victoria Canada
Posts: 37
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:
Originally Posted by qwerty View Post
A W126 has an electric oil pressure sender and gauge.



You could intentionally drain the filter housing and see if the delay in pressure increases or remains the same.

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.
Reply With Quote
  #8  
Old 10-15-2012, 03:32 AM
whunter's Avatar
Moderator
 
Join Date: Dec 2003
Location: Metro Detroit, Michigan
Posts: 17,390
Hmm

Quote:
Originally Posted by qwerty View Post
Consistency is seldom a characteristic of a poor electrical connection.
I disagree in some cases.

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.


.
Reply With Quote
  #9  
Old 10-15-2012, 05:42 AM
vstech's Avatar
DD MOD, HVAC,MCP,Mac,GMAC
 
Join Date: Mar 2006
Location: Mount Holly, NC
Posts: 26,832
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!
Reply With Quote
  #10  
Old 10-15-2012, 06:21 AM
t walgamuth's Avatar
dieselarchitect
 
Join Date: Apr 2005
Location: Lafayette Indiana
Posts: 38,604
Quote:
Originally Posted by qwerty View Post
Consistency is seldom a characteristic of a poor electrical connection.
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.
Reply With Quote
  #11  
Old 10-15-2012, 09:26 AM
Registered User
 
Join Date: Aug 2007
Posts: 972
Quote:
Originally Posted by t walgamuth View Post
He does not have consistencey. It is intermittent.
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.

Quote:
Originally Posted by birkhoff View Post
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.
Concur.

Last edited by qwerty; 10-15-2012 at 10:00 AM.
Reply With Quote
  #12  
Old 10-15-2012, 10:31 AM
Registered User
 
Join Date: Oct 2012
Posts: 5,924
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.
Reply With Quote
  #13  
Old 10-15-2012, 01:46 PM
t walgamuth's Avatar
dieselarchitect
 
Join Date: Apr 2005
Location: Lafayette Indiana
Posts: 38,604
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.
Reply With Quote
  #14  
Old 10-20-2012, 03:33 PM
Registered User
 
Join Date: Mar 2011
Location: Victoria Canada
Posts: 37
82 300SD slow to build oil pressure -- update

Quote:
Originally Posted by whunter View Post
The oil pressure sender or wire may have been disturbed, or taken a bath in used oil.

A poor electrical contact would explain your symptom.


.
Saturday, and a few spare minutes to look into this. I took off the sender wire and grounded it. That puts the gauge at 0. Ungrounding it pegs the gauge to full pressure. So, the sender must increase resistance with rising oil pressure.

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.
Reply With Quote
  #15  
Old 10-20-2012, 04:15 PM
pawoSD's Avatar
Dieselsüchtiger
 
Join Date: Oct 2004
Location: Grand Rapids, MI
Posts: 15,438
The senders themselves can also fail and read incorrectly or not at all. Have had it happen twice so far between all our cars...

__________________
-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)
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 10:54 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page