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Engine 302 oil leak when running

  • Thread starter Thread starter AlexM556
  • Start date Start date Sep 8, 2026
A

AlexM556

Member
Sep 8, 2026
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North little rock, AR
Sep 8, 2026
#1
  • Sep 8, 2026
  • #1
I have a 67 mustang and I recently changed the oil and filter and also replaced the gasket, pan, and rear main seal on my 302 since it has had a slight leak for a while and I wanted to finally fix it but it seems I created another problem. I drained a bit less than 5 quarts but when I filled it up, it only took 4.5 quarts before the dipstick shows oil almost at the "max overfill" line which is odd especially since the new pan is the same capacity as the original if not slightly more. I let it idle for a while but the oil level stayed the same. There was no sign of a leak and everything sounded fine so I didnt think much of it. I got in to take it for a short test drive and it reversed out of the garage no problem. I put it in drive and made it about 5 feet before smoke came up from under the hood. Oil was leaking on the driver's side somewhere and it dripped down onto the exhaust header and caught fire. I was able to put it out before it did any damage as far as I can tell but I have no idea as to what the problem is. The entire driver side of the engine bay now has a nice coat of new oil on it and the leak stopped after I shut off the engine so I never saw where it was coming from. My guess is that the breather/filler cap on the driver side valve cover started to purge oil but I thought that only happened when it is severely overfilled. Anyone know what to do? Thanks!
 
B

Butchd88

Member
Feb 10, 2026
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33974
Sep 12, 2026
#2
  • Sep 12, 2026
  • #2
Are you sure the old oil filter gasket came off when you changed the filter?
 
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nickyb

I gotta say i never painted my nuts, Never Ever
15 Year Member
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nevada
Sep 12, 2026
#3
  • Sep 12, 2026
  • #3
Have someone start the car with you looking at the drivers side for the leak. P.s. have a fire extinguisher on stand by.
 
A

AlexM556

Member
Sep 8, 2026
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North little rock, AR
Sep 12, 2026
#4
  • Sep 12, 2026
  • #4
I checked the oil filter and its fine, so the old gasket must have come off with the filter. I started it up and looked under the hood and after a few seconds it started smoking so I shut it off. It looks like the leak is coming from the valve cover on the bottom corner closest to the firewall since the smoke appears to be coming from the top of the exhaust header right beneath it. I took off the valve cover to get a better look in this area and sure enough, the corner of the gasket has some oil on it and the rest is dry. At this point Im going to replace the gaskets and see what happens. I will post an update when I get those in and test it.
 
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AlexM556

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Sep 8, 2026
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North little rock, AR
Sep 20, 2026
#5
  • Sep 20, 2026
  • #5
So I replaced the valve cover gaskets and tested it out. Theres no leak from the valve covers now but theres still another leak somewhere. I started it up and it immediately starts leaking. Give it some gas and it leaks more and starts smoking. Turn it off and the leak stops. Since it appears to be somewhere on the back of the engine on the driver's side somewhere I cant see anything but I did feel around back there and found some oil on the engine just in front of the bell housing and it runs down and drips from the steering linkage/hoses area since thats the lowest spot but that's all I can tell. At this point Im wondering if it's coming from the intake manifold but Im not so sure and I would hate to start pulling more stuff apart without being sure Im on the right track here. Any thoughts? Thanks
 

Blackhawkxx

Mustang Master
Mar 3, 2023
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Sep 20, 2026
#6
  • Sep 20, 2026
  • #6
If you think it may be coming from the rear of the intake, I would try to clean that area well using brake clean. Make sure it is clean and dry and hit the area with some baby powder, start the car and look.
 

horse sence

15 Year Member
Nov 29, 1999
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Wile Coyote's stunt double
Sep 20, 2026
#7
  • Sep 20, 2026
  • #7
If you did the oil pan from underneath you may have let the gasket slip if using the 4 piece gssket it could have pulled back just enough to let oil between the cork and rubber gasket. Let it cool ,and maybe wait over night then start it up again and look once more
 
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horse sence

15 Year Member
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Wile Coyote's stunt double
Sep 20, 2026
#8
  • Sep 20, 2026
  • #8
Did you put the rear seal in the correct way ,if not it will spray oil ,can you see in the bell housing ,if the inside is coated with oil its probably the rear seal . Also did you grease the lip on the rear seal when installed ? If not it may have already burned up ,installing a seal dry will burn it with friction quickly!
 
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AlexM556

Member
Sep 8, 2026
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North little rock, AR
Sep 21, 2026
#9
  • Sep 21, 2026
  • #9
horse sence said:
Did you put the rear seal in the correct way ,if not it will spray oil ,can you see in the bell housing ,if the inside is coated with oil its probably the rear seal . Also did you grease the lip on the rear seal when installed ? If not it may have already burned up ,installing a seal dry will burn it with friction quickly!
Click to expand...
I actually went with a felpro one piece gasket on the pan and it appears to be sealing fine. As for the rear main seal, the inside of the bell housing is dry so I think its good there too.
 

horse sence

15 Year Member
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Wile Coyote's stunt double
Sep 21, 2026
#10
  • Sep 21, 2026
  • #10
This just came up on face book haha ,I think they are listening !
https://www.facebook.com/View: https://www.facebook.com/reel/3250412968681974/?mibextid=CDWPTG
 
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DadLife0724

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Mar 22, 2024
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Cooperstown, PA
Sep 21, 2026
#11
  • Sep 21, 2026
  • #11
They are always listening
 
A

AlexM556

Member
Sep 8, 2026
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1
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North little rock, AR
Wednesday at 10:17 PM
#12
  • Wednesday at 10:17 PM
  • #12
I cleaned off the intake manifold as best I could, started it up and its dry as far as I can tell so the leak must be coming from somewhere below but it's not really obvious where it could be. Ive seen uv dye used to help find oil leaks. Never used it before but I think I will give it a shot on this.
 
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A

AlexM556

Member
Sep 8, 2026
7
1
13
North little rock, AR
Saturday at 3:10 PM
#13
  • Saturday at 3:10 PM
  • #13
I ran the engine with dye today but this leak is either very well hidden or I must be blind because the only thing new im seeing with the UV light is oil on the bottom of the driver's side motor mount. Looking at it from above Im not picking up any trail of oil so I cant trace it. I pulled off the spark plug wires to try to get a better view but that didnt seem to help. Of course one of them just decided to fall apart so I wont be able to run it again until I get that fixed. I hoped that residue from the dye would stick around long enough for me to trace it after I shut the engine off since it's a fire hazard to idle it more than a couple minutes at this point but I wonder if the dye is just burning off with the oil and disappearing. It seems crazy that the dye is clearly visible on the bottom of the motor mount but seems nowhere to be found above it. I spent a long time looking all over the place and came up with nothing. Is there a specific spot I should be looking?
 

manicmechanic007

5 Year Member
Sep 26, 2017
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Roy, Utah
Saturday at 5:28 PM
#14
  • Saturday at 5:28 PM
  • #14
The crankshaft will move forward in gear
Maybe check the crankshaft end play
Excessive or even normal end play may put the seal lip in a deeper groove on the crank at either end
 
A

AlexM556

Member
Sep 8, 2026
7
1
13
North little rock, AR
Saturday at 7:48 PM
#15
  • Saturday at 7:48 PM
  • #15
manicmechanic007 said:
The crankshaft will move forward in gear
Maybe check the crankshaft end play
Excessive or even normal end play may put the seal lip in a deeper groove on the crank at either end
Click to expand...
I should have updated the title of this post earlier. It has started leaking any time its running, even just idling in park. Still good info to know though
 
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