Nagging oil leak (a stumper for ya!)

[KShortell]

OK, it's my turn for a stumper.

I've got this nagging oil leak that I'm having trouble nailing down, but I do have it localized. This is on my stock 1986 350 SBC (LS9) engine.

Keep in mind that the valve stem seals, valve cover gaskets, oil pan gasket, rear main oil seal, oil cooler hoses, and oil filter are all new. The valve covers and rear main are not leaking at all.

Only the driver's side of the block below the manifold alongside the rearmost two cylinders is wet. I'm almost wondering if the factory oil cooler connection/adapter at the spin-on filter location has a bad gasket. It's never been apart.

It's a nagging leak, but not a hemorrhage.

There is a bolt between the middle two cylinders one either side of the block just above where the oil pan is. I'm not sure what these are. The oil starts from here back on the driver's side. I'm inclined to think that these bolts are coolant drains for the jacket in the block. My FSM and Haynes book don't show these bolts.

See the photo below for the area in question and a close-up of the bolt I'm talking about. Thanks!




Kevin

[swervin ervin]

Yes, those two bolts are plugs into the water jacket. This is the way you drain all the coolant from the system. As for the leak, I'm not sure on the cooler attachment, since I've never had one, but it would be worth a shot to replace the gasket just to see. If you are positive the valve covers are not leaking, and you sound like you are, it just about has to be something with pressure leaking, instead of a drain like a valve cover. What about the oil pressure sender? On some engines they were right above the oil filter. Does any oil run down the back of the block, or is it just on the side?

[KShortell]

To be honest, I haven't looked at the sender yet. It's on my list, though. The FSM says it's on the LEFT front side of the distributor. Hmm...time for further inspection, especially from underneath.

[swervin ervin]

The sender on my 85 is in a brass tee, up beside the distributor. In this tee, with the sender, is the oil pressure switch for the choke. I do know on the 87's I've seen the sender is down close to the filter. I've also seen some on here say their older trucks had them down there. I have no idea when, why, or the reason behind any of this.

Check the sender first. It's a good place for a leak, with pressure since it receives pressure at this point.

[KShortell]

That does make sense. My choke light's been coming on a bit lately.

It's always been prone to come on evry now and then for a couple seconds after driving a long high speed interstate distance and then stopping at the end of an off ramp. I always figured that was due to a lower idle. In fact, that happened just last week-- definitely lower idle-- voltage dropped and you could feel the lower rpms when creeping forward. Idle rpms were fine when I checked them on Saturday, though. It's only after a high speed run on open highway for 10 miles or more.

The choke is brand new-- only a couple months old and not even 1,000 miles on it yet.

It came on tonight, though after restarting the engine warm after driving a few miles, running an errand and then coming back out. It didn't immediately go off after revving the engine. It went out after a few seconds, though. I am getting the proper oil pressure readings at the gauge, though. I'm going to have to get back under there for sure.

We may be onto something...

[Grim Reaper]

Mines leaking off the back somewhere as well. It's all wet down the back of the motor. It drips. Valve covers looked sealed so I'm about conviced it's a intake leak at the back. It's got a slight seap at the front as well.