BB OIl leak - The 1947 - Present Chevrolet & GMC Truck Message Board Network

stope4 · 03-24-2008, 08:30 AM

O.K. I've done everything I know possible to try and stop an oil leak on my 71 BB 402. I replaced the valve cover gaskets, oil pan gasket, intake manifold gaskets, rear main seal, and distributor gasket. I used the black gasket maker along the front and rear of the intake manifold. The leak is occurring somewhere above the oil filter. It's not coming from the oil guage line, or any of the above areas where I replaced gaskets. I know this cause when I rub my fingers at the intersections of these, I do not get fresh oil, it's dry crap. Is it possible the heads could be leaking oil out between the head and block? The vehicle does not burn oil. I noticed theres a screwed in plug on the back of the drivers side head. Could this plug leak oil? Any advice is welcome. Short of pulling the heads, not sure what's next.

JimKshortstep4x4 · 03-24-2008, 04:25 PM

The plug is probably for the water jacket. I would still suspect the valve cover gaskets as they are hard to seal and the covers could be warped.

Try shining a light up at the rear corner of the covers to see if that is where the leak starts.

Jim

stope4 · 03-24-2008, 09:33 PM

I ran the car for an hour and am getting oil leaking. I've run my fingers along the edge where the valve covers meet the heads and where the intake meets the block and heads with no evidence of fresh oil. Is there any way you can get an oil leak between the head and block without the vehicle burning oil?

JimKshortstep4x4 · 03-25-2008, 03:33 AM

I guess it is possible to leak oil between the head and head gasket but I have never seen it happen.

You may want to try a color additive to the oil which leaves more of a trail.

Jim

stope4 · 03-25-2008, 07:39 PM

Jim, thanks for the suggestion. I may try that before I remove the intake again.
Is it possible to leak almost in the rear corner and just under the head. I put sealer along the rear edge where the intake meets the block, but I do not believe I ran it along the head and block for a an inch or two. Is it o.k. to run sealer along the head and block from the back of block to say the middle of the first port or water jacket hole? If this is infact where the leak is occurring, will this solve the problem?

jhow66 · 03-25-2008, 07:54 PM

If the oil is dripping off of the flywheel dust cover, it could be the rear cam plug.

stope4 · 03-26-2008, 01:39 AM

I do get leakage at the flywheel dust cover. I haven't had it on since I started down the oil pan gasket, intake manifold gasket route. Where is the rear cam plug? What does it look like? Is it repairable while the engine is in the vehicle?

stope4 · 03-26-2008, 07:35 PM

When I got home last night, I checked on the back of the engine for a cam plug. When I didn't find it, I thought maybe I was the victim of a good joke and you had me searching for something that didn't exist. I even began to laugh at this possibility. Before I said anything, I looked at my Rebuilding a BB book and sure enough it mentions a Cam Plug so I new you weren't pulling any fast ones on me. Unfortunately the cam plug is under the bell housing so inspecting it while the transmission is in the car is not an option. But more than this, I don't think this is where the oil is coming from unless the oil can escape out of the side of the bell housing and make it's way to the back lower head and oil filter. The oil filter is where I see the oil leaking to the ground. When I trace it up, it's coming from the rear lower head area by the exhaust manifold. I do get a little leakage at the dust cover, but this oil is old grimmy black oil. The oil leaking off the oil filter is new fresh oil.

Sinister · 03-26-2008, 08:30 PM

What kind of oil filter adapter do you have? I had a leak on my smallblock that was driving me crazy. Traced it to an older model oil filter adapter, where the oil filter seals to the adapter and not the block. Swapped it for a later model adapter.

stope4 · 03-29-2008, 07:25 AM

Think I may have solved my oil leak problem. On a hunch, I cleaned the back of the engine really well just to see if maybe oil wasn't leaking from up top. Then I decided to tighten in a aggressive manner the oil pan bolts above the oil filter. I didn't have anything to lose since I have the one piece felpro rubber gasket. I heard you can tighten these way more than the regular style. What do you know, I idled the engine for over an hour this evening and so far so good. looks like I may have hit paydirt. Thanks for all the suggestions, I looked seriously at all.

03-24-2008, 08:30 AM	#1
stope4 Registered User Join Date: Jan 2006 Location: Houston Posts: 434	BB Oil leak O.K. I've done everything I know possible to try and stop an oil leak on my 71 BB 402. I replaced the valve cover gaskets, oil pan gasket, intake manifold gaskets, rear main seal, and distributor gasket. I used the black gasket maker along the front and rear of the intake manifold. The leak is occurring somewhere above the oil filter. It's not coming from the oil guage line, or any of the above areas where I replaced gaskets. I know this cause when I rub my fingers at the intersections of these, I do not get fresh oil, it's dry crap. Is it possible the heads could be leaking oil out between the head and block? The vehicle does not burn oil. I noticed theres a screwed in plug on the back of the drivers side head. Could this plug leak oil? Any advice is welcome. Short of pulling the heads, not sure what's next. Last edited by stope4; 03-24-2008 at 08:30 AM.

03-24-2008, 04:25 PM	#2
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: BB Oil leak The plug is probably for the water jacket. I would still suspect the valve cover gaskets as they are hard to seal and the covers could be warped. Try shining a light up at the rear corner of the covers to see if that is where the leak starts. Jim __________________ 1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC

03-24-2008, 09:33 PM	#3
stope4 Registered User Join Date: Jan 2006 Location: Houston Posts: 434	Re: BB OIl leak I ran the car for an hour and am getting oil leaking. I've run my fingers along the edge where the valve covers meet the heads and where the intake meets the block and heads with no evidence of fresh oil. Is there any way you can get an oil leak between the head and block without the vehicle burning oil?

03-25-2008, 03:33 AM	#4
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: BB OIl leak I guess it is possible to leak oil between the head and head gasket but I have never seen it happen. You may want to try a color additive to the oil which leaves more of a trail. Jim __________________ 1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC

03-25-2008, 07:39 PM	#5
stope4 Registered User Join Date: Jan 2006 Location: Houston Posts: 434	Re: BB OIl leak Jim, thanks for the suggestion. I may try that before I remove the intake again. Is it possible to leak almost in the rear corner and just under the head. I put sealer along the rear edge where the intake meets the block, but I do not believe I ran it along the head and block for a an inch or two. Is it o.k. to run sealer along the head and block from the back of block to say the middle of the first port or water jacket hole? If this is infact where the leak is occurring, will this solve the problem?

03-25-2008, 07:54 PM	#6
jhow66 Registered User Join Date: Jun 2002 Location: Knoxville Tenn. Posts: 3,058	Re: BB OIl leak If the oil is dripping off of the flywheel dust cover, it could be the rear cam plug. __________________ 56 Chevy Bel-Air 2dr. HT (purchased new) 71 Chevy Cheyenne SWB PU (502HO) 65 GMC short bed step--work in progress and my gofer

03-26-2008, 01:39 AM	#7
stope4 Registered User Join Date: Jan 2006 Location: Houston Posts: 434	Re: BB OIl leak I do get leakage at the flywheel dust cover. I haven't had it on since I started down the oil pan gasket, intake manifold gasket route. Where is the rear cam plug? What does it look like? Is it repairable while the engine is in the vehicle? Last edited by stope4; 03-26-2008 at 01:40 AM. Reason: added last seven words to last question

03-26-2008, 07:35 PM	#8
stope4 Registered User Join Date: Jan 2006 Location: Houston Posts: 434	Re: BB OIl leak When I got home last night, I checked on the back of the engine for a cam plug. When I didn't find it, I thought maybe I was the victim of a good joke and you had me searching for something that didn't exist. I even began to laugh at this possibility. Before I said anything, I looked at my Rebuilding a BB book and sure enough it mentions a Cam Plug so I new you weren't pulling any fast ones on me. Unfortunately the cam plug is under the bell housing so inspecting it while the transmission is in the car is not an option. But more than this, I don't think this is where the oil is coming from unless the oil can escape out of the side of the bell housing and make it's way to the back lower head and oil filter. The oil filter is where I see the oil leaking to the ground. When I trace it up, it's coming from the rear lower head area by the exhaust manifold. I do get a little leakage at the dust cover, but this oil is old grimmy black oil. The oil leaking off the oil filter is new fresh oil.

03-26-2008, 08:30 PM	#9
Sinister Between Trucks... Join Date: Mar 2002 Location: Los Angeles, CA. Posts: 3,830	Re: BB OIl leak What kind of oil filter adapter do you have? I had a leak on my smallblock that was driving me crazy. Traced it to an older model oil filter adapter, where the oil filter seals to the adapter and not the block. Swapped it for a later model adapter. __________________ Beat it to fit, Paint it to match...

03-29-2008, 07:25 AM	#10
stope4 Registered User Join Date: Jan 2006 Location: Houston Posts: 434	Re: BB OIl leak Think I may have solved my oil leak problem. On a hunch, I cleaned the back of the engine really well just to see if maybe oil wasn't leaking from up top. Then I decided to tighten in a aggressive manner the oil pan bolts above the oil filter. I didn't have anything to lose since I have the one piece felpro rubber gasket. I heard you can tighten these way more than the regular style. What do you know, I idled the engine for over an hour this evening and so far so good. looks like I may have hit paydirt. Thanks for all the suggestions, I looked seriously at all.



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