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Oil leaking


71MonteCarloMD

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It’s for my 1972 GMC C15 with SB350-it was leaking oil as I took the first step by replacing the valve cover gasket and cleaned up engine to detect leaking.  Still see oil spots on  driveway as did not find any leak around the covers as it seems to be leaking somewhere in rear top.

Question here is if the distributor (HEI) has gasket that might need to be replaced?  If not, where else should I look for leaks?

i read on other forum to use oil dye with black light to detect leak, I never used this method before, would you recommend doing this or not?

Rick 

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I've also had bad oil pressure sending units that leaked. Located right in the rear, near the distributor, screwed into the engine block. Leaks right where the black plastic part of the sensor is crimped to the metal body of it.

I've used the dye for A/C systems with good results. With an oil leak, I usually try to clean the area real good with a solvent like brake clean or something. Get it nice and clean and then try to find the oil leak from there.

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Thanks Dennis and Joe, will check if it’s tightened or not.  Is there a generic gasket for them or must I know specifics to get right gasket?  Like this? https://shop.advanceautoparts.com/p/felpro-distributor-mounting-gasket-70194/5785529-P?searchTerm=Distributor gasket

As for the oil sender unit, is it a gasket that I’m looking to replace or replace entire unit?

 

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That would be the right gasket, same for a small or big block.

The switch screws into the block with 1/8" NPT (pipe thread). It usually leaks at the point where the arrow is pointing. That's if yours even has that type of switch.

ado-d8050_ml.jpg

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  • 1 month later...

HI again, I decided to pull oil pan out and replace the rear main seal, no issue there.

One issue is the oil pan gasket as the front seal is thin comparing to the old one which is thicker.  I went to Advance Auto Parts to discuss with them - they weren’t sure the difference “w/o” or “with” exhaust pipe packing as we identified that the “w/o” doesn’t fit but what is the difference if it’s “with”?  Do you know what is the exhaust pipe packing is?

And am curious about the front gasket thick vs thin as it shows that I need a thick front one as Advance Auto Parts seems not to have it, am searching for other local auto parts - am curious the difference between thin and thick front seal, any reason for this difference?

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The last time I had my engine apart I went with a one piece pan gasket from Felpro. was really happy with the results. My only problem was I forgot to put the dip stick pipe through the hole in the gasket and could not get the pan to bolt up until I realized what I had done. DUH what a dummy 

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3 hours ago, 71MonteCarloMD said:

Thanks Dennis - is it safe to assume that this is not what it came from factory?

Not necessarily. A lot of the felpro kits come with both to make them universal. I personally think felpro got it wrong. Go with the one piece suggested. No gap leaks or cork

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  • 2 weeks later...

Larry, that happened to me as well.

I did go with Felpro one piece gasket but it wasn’t thick on front as I found one piece with thick front seal by Moroso, which fit much better and seems to be holding leaks on bottom.  See attached picture prior to install.

i am still working on valve covers as it’s leaking regardless what I try to do!  Even with gasket maker/sealant with rubber gasket.  Not sure it’s the valve covers that I need to replace as I evened it out before installing.  Any advice?

Also when working on straightening the valve covers, I noticed spots on inside as I’m not sure what this means?  It’s on both valve covers on both ends - see attached pictures.

E490EA50-6F69-4FC1-BE01-9ED4841AF837.jpeg

4FE18E32-D7F0-42DA-B75C-00623930BCBE.jpeg

A36C2CC4-1F9E-49BA-B1BA-5A51A415B1EF.jpeg

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I also had leaking valve covers. The 350 had Eldebrock covers when I got it and I never could get them to seal correctly. I bought some of the genuine GM Logo covers and still had minor seepage no mater what gaskets I used cork, rubber and another one I forget what it was. Finally bought some really thick cork gaskets and it has seemed to stopped. I think another thing that may have caused a problem I used the studs instead of bolts on  the covers and there are chrome plated. Still have the studs but keep checking the nuts  and they seem to be staying tight. The GM covers are of a thicker metal so they don't torque out of shape when tightened down. On the thinner covers I even tried those long bar like things on the studs and bolts that I see on quite a few cars and they did not help. Once the valve covers are bent where the holes are I have never had any luck getting them to not leak.

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To me they do not really look that bad at least as bad as some I have had. I used Kendall oil in one of my cars and after about 6,000 miles there was a sludge build up on my rockers and inside the valve covers. Switched over the Valvoline 10W 30 and in in two oil changes the sludge was pretty much gone.  Is that a rust one the one cover by the E in Chevrolet? Or a reflection also see something in the other pix that looks like the chrome is flaking. If it is flaking then it is time to replace those covers because if it gets into the oil iit could really mess up you engine. I am no expert and very far from being one, I am a jack of all trades and mater of none.

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What you are seeing on the inside of your valve covers is condensation/moisture from sitting.  A few heat cycles and it should go away. If not or gets worse there is a possibility that water is getting into the oil from the cooling system. That does NOT look like the case at this time. 

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2 hours ago, MC1of80 said:

What you are seeing on the inside of your valve covers is condensation/moisture from sitting.  A few heat cycles and it should go away. If not or gets worse there is a possibility that water is getting into the oil from the cooling system. That does NOT look like the case at this time. 

Good catch Thomas I never thought about condensation

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usually, a good PCV system will clear out any condensation. My old project motor has a a road draft tube, and it likes to create sludge.

I have a set of silicone rubber reusable valve cover gaskets and thye have sealed well time and time again, even with the flimsy Moroso covers I use,

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  • 4 weeks later...

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