250 inline 6 mystery oil leak - The 1947 - Present Chevrolet & GMC Truck Message Board Network

68blackc10 · 09-28-2014, 12:40 AM

Hi guys I'm fairly new to the forum, so bare with me. I have a 68 c10 with 250 ci inline 6 and a 3 speed on the tree.
My problem is every since I bought it almost a year a good I've had a pretty good oil leak on the passenger side of the motor. I've tried changing gaskets on the valve cover and side covers, still leaked. Then I put a set of aluminum valve cover and side covers from a mercruzer motor with another set of new rubber gaskets, still leaks. So yesterday I pulled them back off and added silicone to the gasket, still leaks profusely. Is there something I'm missing with these motors? This is the first inline 6 I've own. It's hard to tell where it's leaking from because it coats the whole side of the motor from the distributor all the way back, and from the side of the valve cover down to the oil pan.
I was told the head was rebuilt right before I bought it. which it was real clean. Is there any plugs that might be missing? Cracked block? It runs real good so I don't think the head bolts are loose, but I should check them anyway.
Any help would be appreciated.
Jared Vicker

Gumby · 09-28-2014, 02:30 AM

Wipe down the area well and spray it with ladies dedorant with baby powder in it. will leave a white film that you can trace the oil leak path in.

68gmsee · 09-28-2014, 10:28 AM

^ Agree. Make sure the area is spotless.

Also, welcome to the site. Lots of good info here and if you can, post a pic of the area where it's coming from. Someone may have already experienced it or knows where it's coming from.

I clean my engines a couple of ways. I use engine spray cleaner and then wash off with water hose or I spray with engine cleaner and use my power washer. Just be careful and prevent water in distributor or carb. I've used plastic grocery bag to protect them before. Duct tape keeps the bags in place.

Wrenchbender Ret · 09-28-2014, 01:30 PM

It could be leaking at the fuel pump or mounting gasket. Possibly the gasket under the dist. Check your crankcase ventilation system. You need a good PCV valve & a vented oil cap or tube from valve cover to the air cleaner.

68blackc10 · 09-30-2014, 11:59 AM

Thanks for the welcome and for the help guys. I didn't think about the fuel pump gasket. I'll definitely check that one out.

storm9c1 · 09-30-2014, 02:25 PM

Quote:

Originally Posted by Wrenchbender Ret

It could be leaking at the fuel pump or mounting gasket. Possibly the gasket under the dist. Check your crankcase ventilation system. You need a good PCV valve & a vented oil cap or tube from valve cover to the air cleaner.

+1!

A clogged or non-existent PCV system will push oil out from every gasket...

68blackc10 · 10-05-2014, 11:20 PM

Figured it out, the breather hose from the valve cover to air cleaner was plugged.
Thanks for the help guys!

09-28-2014, 12:40 AM	#1
68blackc10 Registered User Join Date: Nov 2013 Location: Washington, IA Posts: 3	250 inline 6 mystery oil leak Hi guys I'm fairly new to the forum, so bare with me. I have a 68 c10 with 250 ci inline 6 and a 3 speed on the tree. My problem is every since I bought it almost a year a good I've had a pretty good oil leak on the passenger side of the motor. I've tried changing gaskets on the valve cover and side covers, still leaked. Then I put a set of aluminum valve cover and side covers from a mercruzer motor with another set of new rubber gaskets, still leaks. So yesterday I pulled them back off and added silicone to the gasket, still leaks profusely. Is there something I'm missing with these motors? This is the first inline 6 I've own. It's hard to tell where it's leaking from because it coats the whole side of the motor from the distributor all the way back, and from the side of the valve cover down to the oil pan. I was told the head was rebuilt right before I bought it. which it was real clean. Is there any plugs that might be missing? Cracked block? It runs real good so I don't think the head bolts are loose, but I should check them anyway. Any help would be appreciated. Jared Vicker

09-28-2014, 02:30 AM	#2
Gumby Registered User Join Date: Dec 2008 Location: NW-Ohio Posts: 2,525	Re: 250 inline 6 mystery oil leak Wipe down the area well and spray it with ladies dedorant with baby powder in it. will leave a white film that you can trace the oil leak path in.

09-28-2014, 10:28 AM	#3
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: 250 inline 6 mystery oil leak ^ Agree. Make sure the area is spotless. Also, welcome to the site. Lots of good info here and if you can, post a pic of the area where it's coming from. Someone may have already experienced it or knows where it's coming from. I clean my engines a couple of ways. I use engine spray cleaner and then wash off with water hose or I spray with engine cleaner and use my power washer. Just be careful and prevent water in distributor or carb. I've used plastic grocery bag to protect them before. Duct tape keeps the bags in place. __________________ 68 GMC 250/3 speed Saginaw p/b p/s 69 Chevy 350/350 currently in pieces still lookin for a cab 06 Trailblazer I just want a vehicle that I can work on, that won't talk to me, leave error msgs or keep track of how I drive...

09-28-2014, 01:30 PM	#4
Wrenchbender Ret Registered User Join Date: Oct 2005 Location: Overland Park, Ks. Posts: 5,228	Re: 250 inline 6 mystery oil leak It could be leaking at the fuel pump or mounting gasket. Possibly the gasket under the dist. Check your crankcase ventilation system. You need a good PCV valve & a vented oil cap or tube from valve cover to the air cleaner.

09-30-2014, 11:59 AM	#5
68blackc10 Registered User Join Date: Nov 2013 Location: Washington, IA Posts: 3	Re: 250 inline 6 mystery oil leak Thanks for the welcome and for the help guys. I didn't think about the fuel pump gasket. I'll definitely check that one out.

10-05-2014, 11:20 PM	#7
68blackc10 Registered User Join Date: Nov 2013 Location: Washington, IA Posts: 3	Re: 250 inline 6 mystery oil leak Figured it out, the breather hose from the valve cover to air cleaner was plugged. Thanks for the help guys!



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