Grumpy

I have a 72 Cutlass 350 and have a minor oil leak that I am having a problem fixing/finding. The engine was rebuilt by a performance engine builder 10,000 miles ago and runs great. I always find oil on the top of my intake manifold and have replace the valve cover gaskets using rubber gasket tightened the bolts hand tight plus 1/4 turn and still find oil. I do use Mobil 1 oil which I know will find a place to leak. Is there any other place that oil can leak and find its way on top of the intake other than from the valve cover gasket?

Olds64

Perhaps your valve covers are warpped from overtightening. If they are then a new gasket won't do the trick. You have to take them off, straighten them where the bolt holes are, and reseal them with a new gasket.

Grumpy

Before replacing the new rubber gasket I did check and adjust the pull down holes with a straight edge. The covers are after market chrome but seem to be in very good shape that's why I am puzzled. I don't think I torked them down to tight but if I did would it be possible to back out the bolts and retighten them to be sure without replacing the gasket. Sure would hate to take the air condition bracket off again but if necessary I will. I did notice that whith the engine running a very small air bubble around the intake at the head and also the bolt that hold the intake down which I did tighten. Don't see how oil could come out at that area but I do see a small buble probably a small vacuum leak.

Allan R

Olds 350 should have a valley pan below the intake. If it wasn't installed, I'm wondering if that could be the source of your leak. Is there a lot of oil? Or is it just a little smudge? Is it on both sides or just one spot all the time? If it's just one spot, you might have a bad gasket. It's unlikely a performance builder would make an intentional mistake. Why not take the car back to them and ask them what they think the source of the leak was. If the same mech who worked on it is still there, that would be a good starting place.

Grumpy

The leak is minor may be a half teaspoon full after driving for an hour or so, just enough to be annoying. The leak is mostly on the passenger side of the car with a smaller leak on the drivers side. The strange part about this is the oil a slight amount at the bottom edge of the intake manifold which is normal for a VC leak but don't understand how the oil pools up on top of the intake manifold because the oil would have to get over the thickness of the manifold to pool up on the top. The engine was rebuilt about 8 years ago but only has about 10,000 miles on it so I can't take it back. I had the car about four years which I bought from my neighbor the original owner. The engine runs perfect, in fact I don't see how it could run any better than it does so I don't think it is anything major, just annoying. I am not a mechanic but can do jobs like this and learning every day about this car which I really enjoy. It is a convertable and runs and looks almost new and without a rattle which is surprising for a convertable so that's why little things like this are annoying.

Oldsguy

Is the positive crankcase ventilation system working well? Valve? Hoses? Routing?

Grumpy

The PVC Valve is on the drivers side and everything looks like new. In fact when I took the valve cover off the engine the top of the head and everything inside of the valve cover looks like brand new absolutely no dirt or deposits, looks like it is a new engine. I've been thinking about taking the V cover back off and putting RTV around the top, what do you think.

Let me ask you this, I put the new gasket on and went out for a small ride about 10 miles and did find fresh oil not much, does it take time for the gasket to seat itself? I also have to say this sight is GREAT it helps me a lot and I just sit and read Q&A from other people and learn a lot. I'm sure a lot of other do the same.

Olds64

Did you scuff the chrome on the valve cover before putting the gasket on? I had a friend with a SBC engine. Whenever he ran chrome valve covers he had difficulty with sealing them because the oil would spill out between the valve cover and the gasket. He finally had to take them off and scuff the chrome with sand paper before sealing them again with RTV and a new gasket.

I suggest using RTV to adhere the gasket to the valve cover and then torquing the valve cover down. You could also put a thin film of Permatex on the head when putting the valve cover on to have sealant compound on both sides of the gasket. The only problem with this is that it would be a PITA to take off again. Good luck!

Grumpy

Yes I took a piece of sand paper and did scuff the VC before putting on the gasked but did not put anything on the head. I also put a straight edge over every bolt hole and did have to ping out a little though not much. It's at the point where the idea of the leak bothers me more that the leak itself. It's not a major leak but it's a leak and annoying. I was just looking at it again and where the oil is on the intake I don't know how it could get into the area where it is getting with out a major leak.

Modern Motoring

you did say the PVC system "looks" new, but you didn't say that it was working to the best of your knowledge. I would bet it's the PCV system pressurizing the valve cover area.

Redog

Well if you think valve cover gaskets, just buy new valve cover gaskets.

I when thru serveral sets before I just said "F" it and bought the Fel-Pro reusable ones. They don't need any RTV and they are designed so that you cannot overtighen the bolts

$34 from Summit, but the leaks stopped

Grumpy

How do I know or how do I check to see if the PVC is pressurising the system? Keep in mind that A lot of this is new to me.

Grumpy

I was just thnking would the oil pressure gauge always being high have anythng to do with the PVC pressure causing the leak ?

Modern Motoring

An over zealous oil pump could be dumping more oil in the upper head area than could be drained back down to the oil pan.

Now as far as the PCV test, the PCV valve should rattle when you shake it with the engine off. It should be pulling a good vacuum when the engine is running, it should have a whistle to it. The other have of the system is the ventilation side with a pipe that runs up to the air filter assembly. This should have a good air flow going through it, but not big enough it blows you away. If there is too much flow thru this side it would indicate a ring problem as compression blow by is pressurizing the crank case.

Bluevista

This is a real longshot but my 350 heads have weird casting areas on top where the intake manifold attaches. They look like holes just on the edge of the intake gasket, I looked at other Olds and a lot have them. I wonder if the oil could be coming from there somehow from under the manifold, or if it is even possible? Those thing freaked me out when I first saw them on mine while I was cleaning the sludge off . That is strange, usually the top edges of valve covers don't leak in my experience, maybe it's sloshing up there somehow but that would be pretty obvious I would think unless it's burning off, smell burning oil? If the breather is clogged up or the PVC is bad you could blow or suck oil out of weird places.

Allan

Grumpy

I just checked the PVC, PVC filter and vacuum hose that comes from the intake to the PVC valve and everything appears to working properly. I so have a K&N filter With Holly carb so no tubes going to the filter to check. Went out for a ride about 10 miles came home and have oil at the edge of intake by gasket. I took a clean white rag and run it down the edge of the VC and absolutely NO oil came off on the rag, dry as a bone. I checked the gasket as ALLAN mentioned about the small holes in the head just at the edge of the intake manifold gasket and can see a very slight bubble. I think the oil is comming from the holes under the intake gasket. I have no idea what this is or what to do about it. The leak is not bad enough for me to take the intake off unless this will cause a problem.

Any suggestions?

Modern Motoring

So you have a PCV valve on one valve cover, but no vent off the other valve cover ?? The Crankcase HAS to vent off somehow. In the old days it was via a "road tube" usually coming off the intake valley area, and two open breathers on each valve cover. You should still vent the case to the air filter assembly, one to keep from having oily air in the engine area, two to keep those fumes from polluting the environment.

Grumpy

I do have a oil breather on the passenger side valve cover of the engine, no tube going to the carb. The PVC and filter are on the driver side of the engine on the valve cover with a hose going to the intake. Both are clean and in working order. Still don't know what the little holes in the head under the intake gasket do. I think the oil is comming out of those holes because the vc gaskets are not leaking.

Bluevista

The breather system sound fine, as long as the air can get in and out. I still wonder how oil can get up there on the heads, the "turkey pan" gasket should prevent anything from splashing up but who knows? The air cleaner doesn't have oil sitting in it and it's dripping? I have seen that from lots of vapors from the breather but you have no hose to it? I'm just shooting in the dark here, there are much more knowlegable guys that should know what those head things are and what effect they can have if they chime in. I attached a pic of my engine without the intake. I don't know what those things do but you can see where they are.

Allan



http://farm4.static.flickr.com/3021/...249d4b65f8.jpg

petty

Probably the most common symptoms of oil leaks is on the valve cover gaskets. The valve covers are located at the top of the motor and they are a common source of engine oil seeps and leaks. Check at the PCV, it may require you to replace it.

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mugzilla

The Right Stuff is da kine RTV ...

How about a pic of the oil accumulation ...