Go Back  Offshoreonly.com > Technical > General Q & A
Results of changing oil bypass springs on Gen VI 502 >

Results of changing oil bypass springs on Gen VI 502

Notices

Results of changing oil bypass springs on Gen VI 502

Old 06-26-2003, 09:25 AM
  #1  
Registered
Thread Starter
 
Join Date: Feb 2001
Posts: 1,519
Likes: 0
Received 29 Likes on 8 Posts
Default Results of changing oil bypass springs on Gen VI 502

I was getting low oil pressure (<10 psi) at idle, immediately after a hard run. After fast idling for a few minutes the pressure would come back to 25 psi at idle. Cold starting pressure and WOT pressure were fine. When I changed the oil it was BLACK!

When I talked to my engine builder he said they had the same problem on another 502 (in a truck) and the owner of that engine had found out from Scoggin-Dickey (a GM Performance Parts dealer) that it might be the oil bypass springs in the oil filter pad on the block. If they were opening at WOT then the oil wasn't getting filtered or cooled. All Gen VI engines come off the assembly line with 11 psi springs installed.

I figured that in the marine situation the extra back pressure of lines, fittings and oil cooler could cause this bypass valve to open as though there were a plugged filter on the filter pad. Hot oil and no viscosity would be the result, then low oil pressure. The temperature sender in the side of the block was not picking up high temperatures but since they have never shown more than 180F I wasn't sure if I could trust them.

I had to remove the engines to look, but sure enough there was an 11 psi spring where there should have been a 30 psi spring (PN25161284). This spring is installed in the outer hole of the filter pad.

I also removed the bypass spring that was installed in the center hole. All this bypass does is divert oil to the oil cooler holes in the block. It only opens if an oil cooler (plumbed to these holes in the block) is plugged. Since my oil cooler is plumbed in line with the remote oil filter, as Mercury does it, these holes are not used and removing the bypass valve and spring allows the oil returning from the remote line to enter the main oil passage without taking three redundant 90 degree turns.

I also noticed that for some reason the oil line leaving the block and going to the remote filter had three 90 degree brass fittings and a short section of hose. I had never questioned this before but now I was "educated" and saw these as redundant. I replaced them with straight fittings and a long sweeping bend in a longer hose.

So what was the result of these changes? I have 35 psi at idle immediately after a hard run. Problem solved I think.

When I bought these engines as rebuildable cores I was told that they were warranty returns to one of the smaller engine marinizers. Guess what the problem was? Yep, wiped out bearings due to lack of lubrication.Something to think about when you are doing your oil lines/system.

For more information contact Scoggin-Dickey Parts Center at 1 (800) 456-0211 and ask for their Tech Sheet on BBC Gen VI Oil Systems.
tomcat is offline  
Old 06-26-2003, 09:38 AM
  #2  
Official OSO boat whore
Charter Member
iTrader: (2)
 
Join Date: Oct 2000
Location: Mequon, WI
Posts: 6,157
Likes: 0
Received 0 Likes on 0 Posts
Default

Thanks for the tip!
Cord is offline  
Old 06-26-2003, 11:18 AM
  #3  
Registered
 
blue thunder's Avatar
 
Join Date: Nov 2001
Location: Pennsylvania
Posts: 3,385
Likes: 0
Received 0 Likes on 0 Posts
Default

Any idea Tomcat if the mark IV 454s have the same situation? I get similar results to your before changes made scenario.

Dave
blue thunder is offline  
Old 06-26-2003, 11:28 AM
  #4  
Registered
 
Turbojack's Avatar
 
Join Date: Sep 2001
Location: Houston, TX, USA
Posts: 2,287
Likes: 0
Received 0 Likes on 0 Posts
Default

I believe this is only a genVl block problem.

TC- I am guessing the oil was not going thru your filter also.
Turbojack is offline  
Old 06-26-2003, 12:41 PM
  #5  
Registered
 
Krumbsnatcher's Avatar
 
Join Date: Jun 2003
Location: Newport Beach / California
Posts: 588
Likes: 0
Received 0 Likes on 0 Posts
Default Gen VI problem

I have a Gen VI and a common problem that is all ways overlooked is in the lifter alley there are 3 1/8" NPT plugs that need to be plugged, if not that will cause lower oil pressure.

When you have your block at the machine shop they usually remove all those nice little plugs, unless you have them replug them or do it yourself, they are usually overlooked.

I also plug the cooler holes in the block and run an oil pad to a remote filter then cooler.

Just a thought.

Last edited by Krumbsnatcher; 06-26-2003 at 12:43 PM.
Krumbsnatcher is offline  
Old 06-26-2003, 03:47 PM
  #6  
Registered
 
blue thunder's Avatar
 
Join Date: Nov 2001
Location: Pennsylvania
Posts: 3,385
Likes: 0
Received 0 Likes on 0 Posts
Default

Thanks Turbo.

BT
blue thunder is offline  
Old 06-26-2003, 08:29 PM
  #7  
Charter Member #818
Charter Member
 
MACDAD260's Avatar
 
Join Date: Jan 2001
Location: West Michigan & Higgins Lake
Posts: 644
Likes: 0
Received 0 Likes on 0 Posts
Default

Tomcat, You are correct. I did the exact same things as you did when I installed my rebuilt Gen V 502 last year.
MACDAD260 is offline  
Old 06-26-2003, 09:16 PM
  #8  
Charter Member
Charter Member
 
Cignificant's Avatar
 
Join Date: Oct 2000
Location: Richmond, VA
Posts: 1,679
Likes: 0
Received 0 Likes on 0 Posts
Default

Ditto. I have 3 Gen VI 502s and I've replaced the oil bypasses on all of them. It's amazing that a $3 part can cause such pain....
__________________
Steve Gresham
'03 Donzi 33ZX
Cignificant is offline  
Old 06-27-2003, 07:30 AM
  #9  
Charter Member #30
Charter Member
 
Scott's Avatar
 
Join Date: Oct 2000
Location: Bellville,Oh
Posts: 2,163
Likes: 0
Received 14 Likes on 5 Posts
Default

I just changed mine a week ago. I could only find one on the filter pad the center return had nothing in it. The engines use the Merc remote set up so I am not sure how this change effected my oil system. What I do seem to have is lower than I would like to see oil pressure on that side (especialy after a run) and the oil seems to darken fast. I also changed to a Mellings HV pump. Any ideas or thoughts?
Attached Thumbnails Results of changing oil bypass springs on Gen VI 502-engine-rebuild-042.jpg  
__________________
I have Steps & Bubbles!
Scott is offline  
Old 06-27-2003, 08:11 AM
  #10  
Registered
 
28Eliminator's Avatar
 
Join Date: Dec 2001
Location: Rapid City SD
Posts: 809
Likes: 0
Received 0 Likes on 0 Posts
Default

I have a similar problem on mine, but how do I know what I have? Gen VI or Gen V
It is a 97MPI without the fuel pump mount, but it has v belts. So How can I look at it and tell which it is, so I know if I should dig into the oil spring. Do you just buy the spring from any GM dealer?
28Eliminator is offline  

Quick Reply: Results of changing oil bypass springs on Gen VI 502


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.