5.3 Z 71 lost oil pressure
03-06-2008, 09:48 PM
#1
Registered User
Thread Starter
iTrader: (1)
Join Date: Mar 2008
Posts: 0
Likes: 0
Received 0 Likes
on
0 Posts
5.3 Z 71 lost oil pressure Hello, I would hoping to get some advice? I had driven home and went in to have dinner, when I came back out and cranked my 1999 Z71, the oil pressure light came on soI switched it off and a minute or so later I cranked it and the light came back on . I figured it might be the sending unit, so I bought a new oil pressure sending unit and installed it . When i cranked the engine this time the lifters went to chattering so I switched it off. I checked to make sure I had plenty of oil . I thought it might have an external oil pump but have did a little studing and have found it runs off the front of the crankshaft. I have taken the damper off and can see that the keyway is not sheared. My other guesses were the oil pickup tube is broken or sucking air or the pressure regulator is stuck fully open and my last guess is that the pump is worn out? This engine has 170,000 on it and has been a good engine with no problems other that the ticking when its first cranked. I was wondering if there might be any other suggestions out there as to the cause? I wondered about oil galley freeze plugs popping out or mains, rods or cam bearing ? Anyone willing to jump in here and help me out ? Thanks Robert
03-07-2008, 06:43 AM
#5
My Dads 2005 80k mile 2500 pickup had an issue with the oil pressure. Cold mornings, the oil pressure would not build up. Tap the throttle, and it came up and was fine. Till you turn the truck off for a long period of time. Then it would do the same thing.
Turned out to be the oil pump pickup tube seal. GM has upgraded all the new seals to a blue viton oil seal from a red oil seal.
I replaced the pump as well being in there. But both the pump and relief were taken apart and checked. Nothing was wrong.
The oil seal had a flat spot from the housing. It allowed air past during initial startup.
With your miles. Just get a new seal and LS-6 pump.
Where are you located?
Turned out to be the oil pump pickup tube seal. GM has upgraded all the new seals to a blue viton oil seal from a red oil seal.
I replaced the pump as well being in there. But both the pump and relief were taken apart and checked. Nothing was wrong.
The oil seal had a flat spot from the housing. It allowed air past during initial startup.
With your miles. Just get a new seal and LS-6 pump.
Where are you located?
03-07-2008, 09:58 AM
#6
TECH Junkie
iTrader: (11)
Join Date: Jan 2002
Location: Paxton, Ma.
Posts: 3,489
Likes: 0
Received 0 Likes
on
0 Posts
Hmm, not to hijack, but I've got a 5.7 Vortec in a 2000 2500 Express Van w/197k and been forever faithful w/oil changes every 3k. Still runs awesome, but notice lately that pressure runs just around 40psi while driving hot and goes down to 20psi at idle when hot....used to be higher, like 35-40 at idle and 50 on highway....maybe time for me to think about a new pump as well....Probably have to pull the motor to swing a pump into a van chassis, no? WJ
03-07-2008, 10:52 AM
#7
LS1TECH Sponsor
iTrader: (4)
Join Date: Apr 2002
Location: RI
Posts: 5,650
Likes: 0
Received 0 Likes
on
0 Posts
warren, if you can drop the pan your good to go. yours is an old school chevy 350 pump in the back of the motor in the pan not front crank mounted like the lsx motors
i wouldnt worry about it to much though . it could be bearings i know the old 350 "k" motors were notirous for cam bearings at high mileage
i wouldnt worry about it to much though . it could be bearings i know the old 350 "k" motors were notirous for cam bearings at high mileage
Trending Topics
03-07-2008, 03:08 PM
#8
TECH Junkie
iTrader: (11)
Join Date: Jan 2002
Location: Paxton, Ma.
Posts: 3,489
Likes: 0
Received 0 Likes
on
0 Posts
warren, if you can drop the pan your good to go. yours is an old school chevy 350 pump in the back of the motor in the pan not front crank mounted like the lsx motors
i wouldnt worry about it to much though . it could be bearings i know the old 350 "k" motors were notirous for cam bearings at high mileage
i wouldnt worry about it to much though . it could be bearings i know the old 350 "k" motors were notirous for cam bearings at high mileage
WJ
03-07-2008, 07:26 PM
#9
Hmm, not to hijack, but I've got a 5.7 Vortec in a 2000 2500 Express Van w/197k and been forever faithful w/oil changes every 3k. Still runs awesome, but notice lately that pressure runs just around 40psi while driving hot and goes down to 20psi at idle when hot....used to be higher, like 35-40 at idle and 50 on highway....maybe time for me to think about a new pump as well....Probably have to pull the motor to swing a pump into a van chassis, no? WJ
03-07-2008, 10:33 PM
#10
Registered User
Thread Starter
iTrader: (1)
Join Date: Mar 2008
Posts: 0
Likes: 0
Received 0 Likes
on
0 Posts
Hello guys, you have been great to help out with advise! I pulled the pump off after dropping the rearend and pan. The gears looked very good , It looked like the plunger was partically stuck open just a little but when I took the plug out to remove the plunger , it would not move. I had to bump the pump down on the table to get the lunger to come out . Also the O ring looked square in shape instead of being round . I still have to drop the rearend down further to get the pan off completely, then I can inspect the pickup tube for any problems in that area . I had it in my mind, if the pressure relief valve could be the problem, it would be stuck open further than it was. It looked like it was open maybe a 1/64 of an inch the best I could tell. Again Thanks very much! I'm still open for suggesations and comments ?
03-07-2008, 10:37 PM
#11
Registered User
Thread Starter
iTrader: (1)
Join Date: Mar 2008
Posts: 0
Likes: 0
Received 0 Likes
on
0 Posts
Hello 454mag , I welcome that offer , let me know how and when we can do that , I need to get this think back up and running asap. you can give me a call at 912-278-4725 or email me at robdjay@bellsouth.net and will get and address to send the shipping money and give you an address. Thanks s Very Much Robert
03-08-2008, 04:26 PM
#12
Just pm me your address and I will send it out monday and get back to you with the ship cost. should only be 3 or 4 bucks. I have a couple extra o-rings also. I will throw one in
Ted
Ted
