Author Topic: oil leak  (Read 976 times)

Offline jstatic77

  • Newbie
  • Posts: 16
  • Newbie
oil leak
« on: December 27, 2017, 10:05:43 AM »
Hi this is Joe,
I have a 75 C10, edelbrock intake and carb, motor was rebuilt 15,000 miles ago. i have redone intake gasket due to bolt loosening, now its good, i bought Milodon oil pan, redone rear main while pan off, valve covers no leaking, oil pressure no leak and distributor no leak, all i can find or see is rear main but only when i get on it, i have a breather on one side and new PCV on other. i am thinking it is pressure when i get on it forcing oil out rear? should i run two pcv's and get rid of breather?

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 4796
Re: oil leak
« Reply #1 on: December 27, 2017, 11:12:33 AM »
With symptoms occurring only during hard acceleration, the oil leak is probably the result of slosh against the back of the Milodon pan - either the end seal or the inner corners where the rear main hump and pan flange meet.  A seeping rear main will leak continuously, so remove the converter dust cover and run the engine while inspecting the rear main area using a bright flashlight.  Stay clear of the rotating assembly.  If the rear main seal is the source of the leak it should be obvious with the vehicle not moving.  Did you use a one-piece or three-piece pan gasket?  The one-piece gasket provides a better seal with fewer chances for error and subsequent leakage.
Rich
It's difficult to know just how much you don't know, until you know it....
In other words... if people learn by making mistakes, by now I should know just about everything!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline jstatic77

  • Newbie
  • Posts: 16
  • Newbie
Re: oil leak
« Reply #2 on: December 27, 2017, 12:11:40 PM »
i used Felpro one piece oil pan gasket, caulked corners. used anerobic sealer on main cap.it weird it doesn't leak at all if i dont get on it.
i will clean off, remove flywheel cover and run to see.
motor has like 15k on rebuild from local shop.
how do i heck for pressure at valve cover/PCV system?


Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 4796
Re: oil leak
« Reply #3 on: December 27, 2017, 01:01:52 PM »
Remove the breather and run the engine.  If the PCV system is overwhelmed, you will observe vapor puffing out of the breather hole in the valve cover.
Rich
It's difficult to know just how much you don't know, until you know it....
In other words... if people learn by making mistakes, by now I should know just about everything!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline jstatic77

  • Newbie
  • Posts: 16
  • Newbie
Re: oil leak
« Reply #4 on: December 27, 2017, 01:15:00 PM »
10-4 i will check that too

and it has an rv cam also
shouldn't that generally lower the vacuum?
maybe i should get a vacuum gauge and check at source of PCV, front of edelbrock carb

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 4796
Re: oil leak
« Reply #5 on: December 27, 2017, 01:28:17 PM »
An "RV" cam won't affect engine vacuum appreciably.  But, don't go chasing strays.  The oil leak you've described is a simple mechanical failure of a gasket or seal.
Rich
It's difficult to know just how much you don't know, until you know it....
In other words... if people learn by making mistakes, by now I should know just about everything!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline jstatic77

  • Newbie
  • Posts: 16
  • Newbie
Re: oil leak
« Reply #6 on: December 27, 2017, 02:50:15 PM »
10-4
will check vapor puffing and remove flywheel cover and check, get back to ya..
thank you for the info
Joe

Offline jstatic77

  • Newbie
  • Posts: 16
  • Newbie
Re: oil leak
« Reply #7 on: December 28, 2017, 08:00:43 AM »
well its really weird...... i pulled flywheel cover cleaned up oil, looks like either oil pan rear over cap or rear main. I checked PCV and no puffing, valve is working great, I ran in driveway for 1/2" hour idling and revved up, put in gear with break on and revved up and nothing no leak, drove around block and nothing. went down a little hill and drove little hard back up and when i got back a tiny bit of oil on back of pan with a drip on back near cap/oil pan. cleaned and tried to see where and nothing. ran again same procedure around block normal, around block a little harder, in driveway revved up hard and nothing, put in gear and tried to power brake it and nothing, went down hill normal and back up and nothing, went down hill and drove hard back up and nothing, now no sign of leak.
i am stumped!!!! I did put 5/30 oil in for winter with a bottle of the Rislone with Zinc when i did pan and everything, not sure if that could be too thin and would push through.
Joe

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 4796
Re: oil leak
« Reply #8 on: December 28, 2017, 09:32:41 AM »
Don't overthink it.  The oil you used isn't the cause of the leak.  Essentially, there's a gap somewhere, however slight.  Maintaining patience and careful observation, you'll discover the source of the leak.  Just bear in mind that fluids naturally migrate downward and rearward.  Really difficult to evaluate leaks can be easier to identify using fluorescent dye, a UV light, and filter goggles. 
Rich
It's difficult to know just how much you don't know, until you know it....
In other words... if people learn by making mistakes, by now I should know just about everything!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline jstatic77

  • Newbie
  • Posts: 16
  • Newbie
Re: oil leak
« Reply #9 on: December 28, 2017, 11:00:47 AM »
i previously had truck steam cleaned and they died the oil and checked, they said no leak. but then i left and a couple weeks later there was leak, it was either main cap or oil pan at main cap. i looked at it with the dye in and black light at night, had mirror to look at rear behind flywheel and only spot was at cap/oil pan lip. so i pulled the junky steel pan and replaced with Milodon and fel pro one piece. here we are...... intermittent leak
could it be a tick too much oil i put in? 5 Qts plus the almost 3/4" qt of rislone
i did notice last night flywheel has slight wobble, not perfectly true/straight when spinnig. could it be this? slighty moving seal
i couldn't tell if crank end was doing same thing or not

 maybe i just die again and try to see :-\

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 4796
Re: oil leak
« Reply #10 on: December 28, 2017, 03:19:11 PM »
Overfilled with oil isn't a good thing, but for different reasons than causing a leak.  When the engine is running, the oil level drops because the oil is circulating through the engine.  Hence, too much oil is more likely to cause a leak while the engine is turned off with the vehicle sitting static. 

Unless the oil was drained after the dye was added, you shouldn't need to add more dye.  Dye doesn't wear out.  Using the appropriate filter goggles makes UV detection far more effective.

Again, oil is leaking due to a failed seal or gasket, so you need to pinpoint from where the oil is leaking and address that.  It's not some mysterious or esoteric cause.
Rich
It's difficult to know just how much you don't know, until you know it....
In other words... if people learn by making mistakes, by now I should know just about everything!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Jerr-conn

  • Newbie
  • Posts: 92
  • Retired tool maker
Re: oil leak
« Reply #11 on: January 10, 2018, 07:55:04 AM »
Jstatic77--- I agree with BD.  Couple more things, are you sure the rear main seal is installed
Correctly and did you clock the seal? 
Jerry

Offline jstatic77

  • Newbie
  • Posts: 16
  • Newbie
Re: oil leak
« Reply #12 on: January 12, 2018, 10:34:25 AM »
Yes i checked seal to make sure and clocked about 3/8"
only leaks sometimes.
I am going to check compression when i change spark plugs to see if compression ring installed upside down. maybe i will see something there?

Offline Jerr-conn

  • Newbie
  • Posts: 92
  • Retired tool maker
Re: oil leak
« Reply #13 on: January 14, 2018, 10:21:09 AM »
Joe----after re-reading this topic, you mentioned a wobbly flywheel. I would check to see if it may be cracked ? This could be your problem. Under hard acceleration , it could possibly cause A
Balance problem, causing crank to wobble enough to leak oil by the seal, especially with any
Crankcase pressure. It may be a remote possibility, but maybe somebody here may or may not
Agree. Also, with the flywheel cracked , it could be dangerous and could possibly explode.
Just trying to help.
Jerry

Offline Jerr-conn

  • Newbie
  • Posts: 92
  • Retired tool maker
Re: oil leak
« Reply #14 on: January 14, 2018, 05:44:41 PM »
Joe--- it's not that my memory is bad, it's just full. No, I just remembered a few yrs ago, I had
A 69  Z 28. If I ran it hard, when I brought home it would leak a few drops of oil on floor.I figured it
Was crankcase pressure. So I went to auto parts store and bought a pcv valve with a 1/8" hole all the way thru. Never had any more oil on floor. Can't remember what pt # was . Would be a cheap
Fix if it works for you.
Jerry