strange oil leak

[red69ss]

I have been fighting an oil leak for about a month now. Its on a 305 out of a 84 c10 that I put in my 72 c10. I can run the truck in my shop revving it up and just letting it idle and it doesn't leak a drop, when I take the truck down the road it starts smelling of burnt oil and sprays the windshield with oil (it doesn't have the hood on yet) and when I get it back home the whole passenger side of the motor below the head is soaked with oil, also the pass. inner wheel well is covered in oil, also the fuel pump and all hoses and lines on this side. This is on a half mile ride.

I can see no obvious place its coming from when I get under it. I do so immediatly after getting back trying to catch the leak.

I first thought it was the front pan seal ,it looked like it may be leaking so I put a new pan gasket on it, that changed nothing. It had a chrome timing cover on it so I thought that might be it , so I changed the timing cover to a stock one and put another new pan gasket in and that changed nothing.

Next it appeared the gasket at the fuel pump may be leaking so I changed both fuel pump gaskets and put on a new pump. still there was no change.

Now I'm thinking maybe the block is cracked and it only starts leaking when the motor is under strain.? I thought about the head gasket but nothing looks off there. I thought maybe its building crankcase pressure and blowing out the front pan seal, but I have a good pcv and good vaccum.

Have any of you guys ever seen this or have any ideas ? I guess its possible I'm just missing something simple, but I am about ready to pull it and put in another motor. thanks for any help.(sorry for the wordy description)

[butch86]

valve cover gasket maybe?

[clinebarger]

This 3/8"-16 hole (arrow) needs a needs a 1/2" long bolt in it.

[red69ss]

Originally Posted by butch86

valve cover gasket maybe?

no its dry fom the bottum of the head up , so I don't think so?

Originally Posted by clinebarger

This 3/8"-16 hole (arrow) needs a needs a 1/2" long bolt in it.

As soon as I saw this pic I remenbered seeing this plug on other engines and wondering what they were for, so I put on my shoes and headed to the shop to see if it was there. this engine doesn't have that hole. I did notice two raised areas on the block that were threaded , maybe one of them goes thru? they were even with the fuel pump, I'll put a bolt in them tommorow and try it.

thanks for the help

[butch86]

i have a 3/8 pipe plug in mine i forgot about that hole it will drive ya nutz if you leave it open. hope thats your issue. let us know if thats it.

[red69ss]

ok so I missed the arrow the first time I looked at clinebargers pic and thought he was talking about the plug above the timing cover.

Those are the holes I'm talking about, I hope thats my issue even though I will fill stupid for not seeing this earlier, I'll let you guys know....... thanks

[clinebarger]

Bigger arrow The bolt hole is open to the fuel pump rod/bore.

[red69ss]

thanks , so the lower hole doesn't go through?

[fastwillie 696969]

Engine Oil Dye Blacklight Test - YouTube

[68gmsee]

Yeah, let us know what you find on it.

I once had a leak that stumped me for a few days. It was the oil sending unit on another vehicle I had oozing out under higher pressure only.

Also, on hard to find cases I wash the engine thoroughly and then check again after a short run.

[Wrenchbender Ret]

Also check the engine for blowby & check the crankcase ventilation system.

[red69ss]

thanks fast willie that was an interesting video, the whole pass. side of the truck would have been glowing.

Originally Posted by 68gmsee

Yeah, let us know what you find on it.

I once had a leak that stumped me for a few days. It was the oil sending unit on another vehicle I had oozing out under higher pressure only.

Also, on hard to find cases I wash the engine thoroughly and then check again after a short run.

I have been cleaning everything up with a rag between runs to try and find it, the engine is pretty clean since I just installed it....thanks

Originally Posted by Wrenchbender Ret

Also check the engine for blowby & check the crankcase ventilation system.

I checked the pcv and the vaccum to it and everything checked out ok. thanks



I put a bolt in the hole that clinebarger pointed out and that fixed the problem (as far as I can tell). I cleaned everything up and took it down the road a couple of times and everything was dry like it should be.

Thanks to everyone who helped , that's what I love about this board something that I have been struggling with for a month you guys fix in ten minutes.

[mknittle]

I had a oil sender leaking intermittenly like that once.Drove me nuts.