Question: Low oil psi after rebuild - Diesel Place : Chevrolet and GMC Diesel Truck Forums
 
Home Forum Market Place Garage Tuning Library DTC Tool Register Vendors
Go Back   Diesel Place : Chevrolet and GMC Diesel Truck Forums > GM Diesel Engines > 6.5L Diesel Engine
Register FAQ Forum Rules My Replies My Threads Advertise

6.5L Diesel Engine Discuss the 6.5 GM diesel engine & associated components. Automatic transmission questions & problems belong in the 4L80/85 - 4L60E - 6L90 Transmission Forum


DieselPlace.com is the premier Duramax Diesel Forum on the internet. Registered Users do not see the above ads.
Like Tree4Likes

Reply
 
LinkBack Thread Tools
Old 08-11-2019, 10:12 AM   #1 (permalink)
Knappy
Low Boost
 
Join Date: Aug 2019
Location: Fort Worth, Texas
Posts: 5
iTrader Score: 0 reviews

Low oil psi after rebuild

This is my first post on this website. Amazing knowledge here on these 6.5's. I have a 96 Chevy 3500 4x4 that dropped an oil cooler line and ended up spinning a mail bearing. The machine shop said the block was bad so I got a 99 block and rebuilt the motor with all new parts. The motor runs great with the oil psi at 40 until it warms up then it drops to 20 psi a 2000 rpm and about 8psi at 1000 rpm. Here is the kicker. I put an oil pump for a 1996 6.5 (Mellings M55I) but the 1999 motor calls for a Mellings M255-294S. Could this be what's causing the low oil pressure after the truck warms up. I know it can be a lot of things but guess I'm hoping I just need to change the oil pump. Any thoughts?

Steve

__________________
96' Chevy K3500 6.5L

Last edited by OkDually; 08-11-2019 at 10:22 AM. Reason: prefix/sig
Offline  
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Old 08-11-2019, 10:47 AM   #2 (permalink)
Tommygunner
Diesel Expert
 
Tommygunner's Avatar
 
Join Date: Feb 2010
Location: Northesat Nevada
Posts: 2,925
iTrader Score: 0 reviews

IIRC They upgraded the pump in 97 to a high volume pump because of the oil squirters in the 506 engines, that weren't in older 6.5s. 96 was a change over year. some trucks got 506 blocks, some got older version without high volume pump & squirters. You could try changing out the pump to the proper year for your engine (99). Hope it helps. Also normal pressure for oil squirter blocks runs lower than earlier blocks. Normal pressure when warm, is around 20 at idle, 40-50 at cruise RPM.
I hope you fully primed the lube system before starting up the new engine. If not, your cam bearings are most likely toast.

__________________
The beauty of the Second Amendment is that it will not be needed until they try to take it

If Americans ever allow banks to control their currency. First by deflation then inflation. The banks will deprive the people of all property. Until their children wake up homeless.
1998 GMC K1500 WT, 6.5 TD. 80,000 miles. Auto, 3.73 gears. Remote PMD mounted on the radiator support. KOJO tune WOW! Carter HD lift pump. Feed the beast, GM8 turbo with Hurricane impeller. K&N filter. Ported, gasket matched upper intake. Leroy's braded stainless steel oil lines.
New Bosch injectors. Flow matched 2200 lbs pop
3 1/2" custom Aero turbine exhaust. Nutered Cat
2" Lift RS5000 Shocks. 285 X 17 Bridgestone AT summer tires. 12.50 x 33 x 15 Procomp MTs winter. Powertrax No slip locker in rear.

Last edited by Tommygunner; 08-11-2019 at 10:58 AM.
Offline   Reply With Quote Quick reply to this message
Old 08-11-2019, 11:05 AM   #3 (permalink)
Knappy
Low Boost
 
Join Date: Aug 2019
Location: Fort Worth, Texas
Posts: 5
iTrader Score: 0 reviews

So I guess the Mellings M225-294S is the high volume version of the oil pumps?
I am going to try to remove the oil pan without pulling the motor. Not sure if that can be done on this truck.

Steve
__________________
96' Chevy K3500 6.5L
Offline   Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Old 08-11-2019, 12:10 PM   #4 (permalink)
DieselPro
Diesel Guru
 
DieselPro's Avatar
 
Join Date: Mar 2004
Posts: 7,097
iTrader Score: 0 reviews

You might want to do this as well > Pressurize the oil gallery once the pan is off and see where all the oil is going. I do this on all engine builds before the pan is installed. You can find all kinds of places where oil pressure is being lost. Several ways of doing this. Most high end shops have a oil tank that is pressurized by regulated air pressure. I use a electric driven oil pump/tank built by me for this. Could use a pump up insect sprayer or some other type pump. Places where I have seen engines leak internally. > Cam bearings, lifters, missing oil gallery plugs, bearings.
I test oil pumps as well in a drill press with thin oil to set regulated pressure.
Oil pump sounds like the problem. I would disassemble each and check pump rotor lengths. new one should be longer I would guess, if not the pump is not going to fix it.
https://www.summitracing.com/parts/slp-t40

Side note: take oil pump off and plug oil hole there before testing.

POST PICS of this for others to see.

Last edited by DieselPro; 08-11-2019 at 12:12 PM.
Offline   Reply With Quote Quick reply to this message
Old Yesterday, 06:32 AM   #5 (permalink)
dieselolds
Ronald Reagan fan
 
dieselolds's Avatar
 
Join Date: Sep 2003
Location: Newfoundland/Alberta,Canada
Posts: 3,991
iTrader Score: 3 reviews
Send a message via MSN to dieselolds

The pan can be lowered in the K series trucks with the engine in place.You just need to lower the front axle a coupe inches and that’ll give you the room you need.The high volume oil pump will fix your issue.The Melling part number in your last response is correct for high volume.
__________________
1996 GMC Sierra ext.cab Z71....with new genuine GM 6.2 660 short block,4L80E/6.5TD cylinder heads,DS4 5521S,82' 6.2 rocker arms,acdelco TP1069/Racor 20S fuel filters,4" diamond eye exhaust,3.73 G80 locker,stanadyne 37818 injectors

1996 Chevy K1500 Z71.....with '99 6.5 506 goodwrench van engine,88-93 6.2 diesel Napa y-pipe,'87 700R4,acdelco TP630F/Racor 20S fuel filters,Bosch non-turbo injectors,stanadyne blue tag 5088

1993 Chevy K1500 Z71...with 97' 6.5 TD 506 block,82' 6.2 rocker arms,stanadyne 37818 injectors,stanadyne blue tag 4911,DSG girdle,reman 700R4,Banks boost/pyrometer gauges,acdelco TP1069/TP943 fuel filter system,4 diamond eye exhaust/2 piece crossover

2008 Mercedes Benz E320 3.0 V6 turbo diesel

2013 Volkswagen Passat 2.0 TDI

Last edited by dieselolds; Yesterday at 06:36 AM.
Offline   Reply With Quote Quick reply to this message
Old Yesterday, 08:30 AM   #6 (permalink)
Knappy
Low Boost
 
Join Date: Aug 2019
Location: Fort Worth, Texas
Posts: 5
iTrader Score: 0 reviews

Man I hope so. It's a sickening feeling when you watch the oil pressure fall. I am going to pressurize the oiling system and see what happens. We did pre pressurize the motor before we started it. I'll let you guys know how it works.

Steve
__________________
96' Chevy K3500 6.5L
Offline   Reply With Quote Quick reply to this message
Old Yesterday, 11:58 AM   #7 (permalink)
Tommygunner
Diesel Expert
 
Tommygunner's Avatar
 
Join Date: Feb 2010
Location: Northesat Nevada
Posts: 2,925
iTrader Score: 0 reviews

Glad you primed it before starting. Its most likely the oil pump. The older 6.5 pumps did not have the volume needed to supply the extra needs of the oil squirter blocks. Doubt you did any harm to the engine running it with low pressure. IIRC 10 psi is the low spec at idle. As long as it did not drop to 0. You should be ok.
__________________
The beauty of the Second Amendment is that it will not be needed until they try to take it

If Americans ever allow banks to control their currency. First by deflation then inflation. The banks will deprive the people of all property. Until their children wake up homeless.
1998 GMC K1500 WT, 6.5 TD. 80,000 miles. Auto, 3.73 gears. Remote PMD mounted on the radiator support. KOJO tune WOW! Carter HD lift pump. Feed the beast, GM8 turbo with Hurricane impeller. K&N filter. Ported, gasket matched upper intake. Leroy's braded stainless steel oil lines.
New Bosch injectors. Flow matched 2200 lbs pop
3 1/2" custom Aero turbine exhaust. Nutered Cat
2" Lift RS5000 Shocks. 285 X 17 Bridgestone AT summer tires. 12.50 x 33 x 15 Procomp MTs winter. Powertrax No slip locker in rear.
Offline   Reply With Quote Quick reply to this message
Old Yesterday, 12:11 PM   #8 (permalink)
Knappy
Low Boost
 
Join Date: Aug 2019
Location: Fort Worth, Texas
Posts: 5
iTrader Score: 0 reviews

What all is involved in dropping the front axle down? I have never done that.
__________________
96' Chevy K3500 6.5L
Offline   Reply With Quote Quick reply to this message
Old Yesterday, 04:35 PM   #9 (permalink)
kmagg
Heat Sink
 
Join Date: Feb 2017
Posts: 12
iTrader Score: 0 reviews

Was the sender replaced during the rebuild? And have you verified this low pressure with another guage? Maybe a manual guage? I have had many GM oil pressure senders fail over the years. Scares the crap out of you. Usually they read fine at startup and then would slowly drop as the engine warmed up. Giving a false low reading, sometimes zero pressure! Just something to check before the hassle of dropping the diff and pan. Not saying it couldn't be a pump, you never know.
__________________
1994 Chevrolet Blazer 6.5L 4X4
200,000 miles, OPS/LP relay, new glow plugs, F style intake-EGR delete, new crank pulley, Spectra sending unit with ACDelco tank sock, new fuel & brake lines front to back, rebuilt (by me) stock turbo, new stock Bosch injectors, Heath PMD relocation with Dtech PMD, Heath fuel pump, new timing chain & crank sensor, air intake snorkel removed, new CDR, resealed engine (except head gaskets), new oil pump, Feed the Beast mod
Offline   Reply With Quote Quick reply to this message
Old Yesterday, 11:49 PM   #10 (permalink)
Knappy
Low Boost
 
Join Date: Aug 2019
Location: Fort Worth, Texas
Posts: 5
iTrader Score: 0 reviews

I did replace the oil sender at the time of the rebuild. I would like to try a mechanical gauge if I can find a good way to hook it up. I know for a fact that I put the early oil pump in so I bet /hope that is the problem. I will let you guys know what happens.

__________________
96' Chevy K3500 6.5L
Offline   Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Diesel Place : Chevrolet and GMC Diesel Truck Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

PLEASE READ! You must check your email inbox for the confirmation link to complete registration. Please check your spam box if you do not see the email in your inbox.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Insurance
Please select your insurance company (Optional)

Log-in



Posting Rules
You may post new threads
You may 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 Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -4. The time now is 11:02 PM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Shoutbox provided by vBShout v6.2.1 (Lite) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd. Runs best on HiVelocity Hosting.
© AutoGuide