Originally Posted by GrandpaDan

97-98 Blazer 4.3 4wd. Big oil leak dripping off bell-housing on the passenger side. Thought it was a rear main seal, but popping off the inspection cover showed flywheel was dry and clean, no leak at seal. Followed the oil flow up the side of the bell-housing, and saw oil in the plastic conduit covering the wires from the oil pressure sender.
The sender is at the top of the engine, just to the right on the distributor, and the electrical connection points at the passenger side, so oil leaking out (under pressure!) was flowing down the wires and inside the conduit that runs down the passenger side of the transmission, leaking out on the way.

I feel so much better knowing it's not the main seal. I replaced the sender, added a new distributor cap/rotor, distributor gasket while I was in there.

Originally Posted by mech cb

I think I found it! The valve cover gaskets were looking fine. I saw a ton of oil on top of the bell housing, and there was a little bit around the base of the distributor. It didn't look like much, so initially I accounted it to oil just getting spread around. So I pulled the distributor out and noticed a little bit of oil on the gasket. I remember replacing that gasket last time I pulled the distributor, but I didn't see any traces of an o-ring when I did that so I never put one back on. I went ahead and tossed an o-ring on it in the groove so now it has an o-ring along with the gasket. Then, I noticed the oil pressure sensor was loose. This was very well my fault. When I replaced it, I couldn't track down an oil pressure sensor socket (the one I got for the job didn't fit the oil pressure sensor), so I used a big wrench (27 mm, I believe) to tighten it down. Well, I was trying to be careful not to snap that small aluminum neck off in the hole so I didn't put as much torque on it as I probably should have. Sure enough, that thing was finger loose and there was a trail of oil on the bottom of the threads.

While I'm kind of kicking myself right now....I am SO glad I didn't have to do head gaskets!! I'm just kind of surprised though - no puddles of oil around the distributor area and the heaviest amount of oil was on top of the bell housing rather than at the base of the actual leak. Even when I checked with my UV light - no real traces in the immediate area. It didn't start showing until I got to the top of the bell housing.

Originally Posted by mech cb

I think I found it! The valve cover gaskets were looking fine. I saw a ton of oil on top of the bell housing, and there was a little bit around the base of the distributor. It didn't look like much, so initially I accounted it to oil just getting spread around. So I pulled the distributor out and noticed a little bit of oil on the gasket. I remember replacing that gasket last time I pulled the distributor, but I didn't see any traces of an o-ring when I did that so I never put one back on. I went ahead and tossed an o-ring on it in the groove so now it has an o-ring along with the gasket. Then, I noticed the oil pressure sensor was loose. This was very well my fault. When I replaced it, I couldn't track down an oil pressure sensor socket (the one I got for the job didn't fit the oil pressure sensor), so I used a big wrench (27 mm, I believe) to tighten it down. Well, I was trying to be careful not to snap that small aluminum neck off in the hole so I didn't put as much torque on it as I probably should have. Sure enough, that thing was finger loose and there was a trail of oil on the bottom of the threads.

While I'm kind of kicking myself right now....I am SO glad I didn't have to do head gaskets!! I'm just kind of surprised though - no puddles of oil around the distributor area and the heaviest amount of oil was on top of the bell housing rather than at the base of the actual leak. Even when I checked with my UV light - no real traces in the immediate area. It didn't start showing until I got to the top of the bell housing.

Originally Posted by Tyler House

glad you found it. having the same type issue. going to check my sending unit now. thanks for everyones input