Oil leaks

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
3,938
Reaction score
5,687
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
Idk why I post something and doesn't appear and when I write it again. It posts twice.
 
Last edited:

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
3,938
Reaction score
5,687
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350

CWBlack71

Member
Joined
Apr 21, 2021
Posts
34
Reaction score
19
Location
Del Rio, Texas
First Name
Chris
Truck Year
1977
Truck Model
K30 Scottsdale
Engine Size
350
Yes, there is one on the side of the block on the drivers side above the #3 plug
 

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
3,938
Reaction score
5,687
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
So now you've checked them both and they're both good. Did you check on the bolt I mentioned on post 18?
 

CWBlack71

Member
Joined
Apr 21, 2021
Posts
34
Reaction score
19
Location
Del Rio, Texas
First Name
Chris
Truck Year
1977
Truck Model
K30 Scottsdale
Engine Size
350
I am no mechanic by no means, but are you talking about a mechanical fuel pump? There is a place to mount one, but there are no holes for the arm to go into. It’s like it was not made to accept a mechanical pump.
 

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
3,938
Reaction score
5,687
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
We are talking passenger side of the block low an towards the front of the engine? That would be where a mechanical pump would bolt. The factory mechanical pumps worked off a pushrod that went through the block angled up to the cam. There was a hole with a short bolt coming in from the front of the block,if that bolt isn't there it would be an oil leak.On your block maybe not around 86 is when they got really hit and miss on the machine down in the fuel pump area. See if you can find a pic somewhere on here or online sbc fuel pump pushrod bolt. Maybe you can get a visual to see where that bolt is.
 

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
3,938
Reaction score
5,687
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
Found a pic for you. There should be a bolt there with a copper washer or silicone on it.
You must be registered for see images attach
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
6,698
Reaction score
11,151
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
Lots of great suggestions have been made, and OP says checked and no leak, but still a leak persists, so I'd like to suggest a diagnostic procedure.

Run a die test on it. Very simple, not expensive and trace it down. Go to your favorite auto parts store and purchase a bottle of oil die, engine degreaser and / or brake clean. Then go to harbor freight and purchase $20 black light if you don't already own one. Drive truck home clean the engine block up as best you can particularly in the area of the leak. Install the oil die and run the engine until the leak is dripping on the ground again how ever long that takes be it minutes of running or weeks of driving. Kill the engine and wait for it to get dark, or park truck in dark garage. Shine the black light around, the die you purchased will glow either green or red, and you'll be able to follow the leak trail to the source. Pull the starter if needed to get a better view. Pull the converter cover to double check that there is no die in there.

This is what most mechanics do when the origin of the leak is not forthcoming.
 

Rusty Nail

Full Access Member
Joined
Jan 29, 2015
Posts
9,734
Reaction score
9,529
Location
the other side of the internet
First Name
Rusty
Truck Year
1977
Truck Model
C20
Engine Size
350sbc
Needs pix dude , quit screwing us around.
I'm going with distributor gasket - or rather the lack of.
 

GTX63

Full Access Member
Joined
Nov 27, 2022
Posts
708
Reaction score
2,878
Location
Tennessee
First Name
Ty
Truck Year
1985
Truck Model
K10
Engine Size
350
X2 on the die and cleaning.
Start from the beginning. Pick up the die and degreaser and head to the car wash. The motor will be good and hot. Degrease the engine and wash it off. By the time you get home the motor will be dry. Add the die.
If it is a slow leak, let the motor idle over a section of cardboard. Shut the motor off. If you don't see the leak then, you should in the morning.
 

CWBlack71

Member
Joined
Apr 21, 2021
Posts
34
Reaction score
19
Location
Del Rio, Texas
First Name
Chris
Truck Year
1977
Truck Model
K30 Scottsdale
Engine Size
350
Thanks for all the comments and suggestions. I’m going to do the dye and see how that goes
 

75gmck25

Full Access Member
Joined
Oct 13, 2016
Posts
2,018
Reaction score
1,808
Location
Northern Virginia
First Name
Bruce
Truck Year
1975
Truck Model
K25 Camper Special TH350 NP203
Engine Size
5.7
I recently resolved an antifreeze leak near the back of the intake, and determined it was because the bolts I used were about 1/4” too long.

When I swapped to an aluminum intake I reused the intake bolts. As far as I can tell, the intake flange was thinner than OEM and at least one of the bolts bottomed out before actually pulling the intake on tight to the head. It took a while to leak, but eventually started a small dribble that went down the back of the engine where it wasn’t even visible. And then heat burned it off when the engine got warm. When it finally opened up to a stream it was visible enough to see what was happening.
 

Matt69olds

Full Access Member
Joined
Jan 8, 2018
Posts
2,338
Reaction score
3,569
Location
Central Indiana
First Name
Matt
Truck Year
81
Truck Model
GMC 1/2 ton
Engine Size
455 Olds
The pvc valve is not clogged up. I can blow thru it. It seems good

Remove the breather from the other valve cover, start the engine. Put a small piece of paper over the hole in the valve cover where the breather went (opposite the PCV) crankcase vacuum should be enough to hold the paper in place with some noticeable suction. If not, the PCV system needs some attention.
 

henrym

Member
Joined
Aug 16, 2015
Posts
42
Reaction score
14
Location
Albuquerque, NM
First Name
Henry
Truck Year
81/84
Truck Model
K20
Engine Size
350
Gentlemen, I have been chasing an oil leak on a 86 350. I have replaced the rear main seal, oil pan gasket and the intake gasket. I have also replaced the dipstick tube just in case. Still have a leak somewhere and not sure where to go from here. The oil seems to be coming from the passenger side around the starter location. Any ideas or suggestions?
Excess blow by may be forcing oil out breather, follows down the valve cover by fan/angle.
 

Latest posts

Forum statistics

Threads
41,850
Posts
903,481
Members
33,363
Latest member
snoblind
Top