Generation III Internal Engine 1997-2006 LS1 | LS6
Sponsored by:
Sponsored by:

low oil pressure at idle

Thread Tools
 
Search this Thread
 
Old 01-05-2009, 01:55 PM
  #1  
Teching In
Thread Starter
 
crawdad379's Avatar
 
Join Date: Mar 2008
Posts: 12
Likes: 0
Received 0 Likes on 0 Posts
Default low oil pressure at idle

I bought a 6.0 2500 farm truck real cheap. Shortly after startup when the fast idle kicks off the trucks oil pressure will drop to zero and the dummy light flashes. As long as I barely bump the gas or keep the idle over 550rpm its over 25/30psi. I figured the farm use clumped up the oil with short trips never fully heating up the entire oil, so I flushed it onced with the engine flush which seemed to help alittle.
It looks like droping the oil pan to clean it out includes dropping the front diff so that last resort.
I've heard some old timers talk about draining half the oil, filling with diseal to flush the sludge out. Are there safe options without hurting seals and bearings or what?
Old 01-05-2009, 03:08 PM
  #2  
TECH Apprentice
iTrader: (5)
 
blue by you's Avatar
 
Join Date: Sep 2003
Location: Stoughton, Wisconsin
Posts: 358
Likes: 0
Received 0 Likes on 0 Posts

Default

If I were you, I would check the actual oil pressure with a good known pressure gauge before you start trying anything else. If that checks out, then I would probably start with the sender which could be partly plugged or just junk.
Old 01-05-2009, 04:25 PM
  #3  
TECH Senior Member
iTrader: (96)
 
01ssreda4's Avatar
 
Join Date: Aug 2007
Location: Turnin' Wrenches Infractions: 005
Posts: 24,241
Likes: 0
Received 79 Likes on 70 Posts

Default

i would swap oil pumps after flushing the motor.
Old 01-05-2009, 05:05 PM
  #4  
TECH Resident
iTrader: (6)
 
Lt1Porsche's Avatar
 
Join Date: May 2005
Location: Midlothian, Virginia
Posts: 795
Likes: 0
Received 2 Likes on 2 Posts

Default

The idle sounds like it may be sitting a bit low. If you increase the idle to 550rpms and pressure is fine then I think the oil pressure is fine. But isnt the idle suppost to be around 600-750 rpms.
Old 01-05-2009, 05:35 PM
  #5  
Teching In
Thread Starter
 
crawdad379's Avatar
 
Join Date: Mar 2008
Posts: 12
Likes: 0
Received 0 Likes on 0 Posts
Default

can I adjust the idle manually?
Old 01-05-2009, 05:38 PM
  #6  
Teching In
Thread Starter
 
crawdad379's Avatar
 
Join Date: Mar 2008
Posts: 12
Likes: 0
Received 0 Likes on 0 Posts
Default

O yeah, when I go on a long trip the oil pressure drops to 20 but no lower at idle.

can I reach the sending unit without pulling the intake? I do have a 5.3 sending unit
Old 01-05-2009, 11:40 PM
  #7  
On The Tree
iTrader: (8)
 
ss69's Avatar
 
Join Date: Nov 2007
Location: TN
Posts: 193
Likes: 0
Received 0 Likes on 0 Posts
Default

Similar to what mine was doing. I just pulled my engine and found sludge and dried, flaky oil EVERWHERE. There was only about 3 or 4mm in the oil pickup screen where oil could actually get through.

Might try using Trans. fluid to flush it out. Replace 1 quart of oil with 1 quart of trans. fluid.
Old 01-06-2009, 12:59 AM
  #8  
LSxGuy widda 9sec Mustang
iTrader: (12)
 
-Joseph-'s Avatar
 
Join Date: Nov 2001
Location: Texas and Qatar
Posts: 3,043
Likes: 0
Received 0 Likes on 0 Posts

Default

If its sludge it'll probably take pulling the pan off to clear it all out, but might be able to be bandaided if its not too bad. I would also recommend replacing the oil pump and pickup tube o-ring. At least with the pump off and oil pan loose you can use compressed air to blow through the pickup tube and attempt to clean it out.

Do the lifters ever get noisy from lack of oil?
Old 01-06-2009, 07:05 PM
  #9  
TECH Apprentice
 
GMTECH4's Avatar
 
Join Date: Jul 2006
Location: Columbus,Ga
Posts: 326
Received 7 Likes on 5 Posts

Default

i don't think there is anything wrong with your motor, if it is ldling that low and stalls every now and then. there is a software update to fix that. i would do the update before going any further.
Old 01-06-2009, 07:06 PM
  #10  
TECH Apprentice
 
GMTECH4's Avatar
 
Join Date: Jul 2006
Location: Columbus,Ga
Posts: 326
Received 7 Likes on 5 Posts

Default

oh ya your suppose to clean the throttle body also with the update, i would sea foam it
Old 01-06-2009, 08:37 PM
  #11  
On The Tree
iTrader: (4)
 
chevboy28's Avatar
 
Join Date: Mar 2005
Location: Minnesota
Posts: 101
Likes: 0
Received 0 Likes on 0 Posts
Default

my old 400 sbc did the same thing and it had like 500 miles on it or less it's frustrating and i gave up
Old 01-06-2009, 10:04 PM
  #12  
Teching In
 
Ls1olds's Avatar
 
Join Date: Feb 2005
Location: Waukesha,WI
Posts: 44
Likes: 0
Received 0 Likes on 0 Posts

Default

The motor i bought had the same problem, dissassembly found a spun cam bearing. Hopefully yours hasnt done the same thing.
Old 01-07-2009, 01:56 PM
  #13  
Teching In
Thread Starter
 
crawdad379's Avatar
 
Join Date: Mar 2008
Posts: 12
Likes: 0
Received 0 Likes on 0 Posts
Default

if I run it with a spun cam bearing whats the worst that could happen? eat the cam journals up?
Old 01-07-2009, 02:06 PM
  #14  
TECH Veteran
iTrader: (31)
 
bjamick's Avatar
 
Join Date: May 2006
Location: Birmingham AL.
Posts: 4,218
Received 3 Likes on 3 Posts

Default

Most likely I would say its a bad sensor. I would still do a nice seafoaming to clean everything out. Then do the ATF cleaning.




All times are GMT -5. The time now is 02:24 PM.