I have an old (1983) chevy 305 engine in my truck.I replaced the valve cover gaskets and cleaned the engine so I could see if anything was leaking. After driving for about an hour I checked the engine for any new leaks and I found 2 small puddles of oil around 2 of the intake manifold bolts on the driver side. I wiped my finger all the way around the valve cover gasket and there was no oil leaking from there.
so, where the heck could that oil be coming from?
Here`s a stock photo of a 305 with green arrows pointing to the 2 manifold bolts that had puddles of oil around them:
What you might be mistaking as an oil leak is actually coolant.
There’s no reason for oil to be pumped into the intake manifold because there are no mechanical moving parts that require lubrication.
But hot coolant needs to be pumped into the intake manifold to prevent icing of the carb and intake manifold during cold weather.
ok, thanks. I
ll check it again tomorrow.it did seem to be a bit thin for oil but it was dark in color like dirty oil. it does have a small coolant leak on the other side of the manifold where the heater hose connects to the engine,im going to replace that hose tomorrow and I`ll check those “oil” puddles again to see if they are oil or coolant.
sounds like the intake gaskets may be leaking
I agree. While the intake manifold doesn’t itself require lubrication, the head that it’s attached to the side of does. The oil may be coming from that used to lubricate the rockers. Once the oil lubricates the rockers, it squishes out the sides and runs down into “galleys” from where it then runs back down to the oil pan through return channels. Being open to the oilpan, these return channels allow pressure from the crankcase to pressurize the cavities under the valvecover gaskets, and the oil is also subject to turbulence (splashing around).
I checked again and it was definitely oil, really dirty oil. I wiped everything off with a rag and I`m going to check it again the next time I drive it.It may have just been left over oil that leaked from the valve cover gasket before I replaced them.
Those spots on any Chevy smallblock collect a bit of oil flying around, always. Those 2 bolts don’t go into an oil passage, they seal off the exhaust crossover passage passing under the manifold to warm up the incoming air. I’ve had oil in those spots on my race engines (with a blocked exhaust passage) with no explanation for the presence. It never collects very much but it’s always a bit wet with oil. I could never get it to stay completely dry but any little valve cover gasket leak will end up there.
I checked it again and there was some oil there, so I wiped it off and let the truck idle for about 5 min
s and I saw oil started to puddle again. I took the bolts out and they both had oil on the threads. I put some silicone gasket sealer on the threads and around the top and put them back in. If it continues to leak I guess I wont worry about it,it
s just a little oil. I dont know how oil is getting to those bolts, unless the head is cracked?
I still think you may have leaking intake gaskets
The middle intake manifold bolts pass through the cylinder head casting and the tips of the bolts are in the valley of the engine (see the bottom view in the picture). A dab of RTV should do the trick, oil puddling in that area on the old Chevrolet engines is not unusual and is not serious.
The RTV did the trick, i checked it after driving a couple hundred miles and no more leaks.