Hello everyone, my first post so I hope you guys and gals can help. My parents have a 1999 Blazer 4.3L 4X4, I have searched and searched and have read all about oil lines and rear main seals leaking on these trucks but it seems neither of these are leaking on my parents truck. Now at first I thought it was the oil lines but after a better look it seems theres oil leaking from somewhere above the exhaust manifolds and working its way down both sides of the motor, down along the oil lines and everywhere else like the starter, oil pan, trans at the torque conv cover, pretty much everywhere under the hood from the exhaust maifolds downs is wet with fresh oil. After a short drive there will be a small wet oil spot and the truck requires a quart of oil once a month to keep the level up. Now I looked at the top rear of the engine and saw a small puddle of oil between the distributor shaft and the upper black intake plenum resting in a recessed area of the lower alum intake. I cant tell if the oil is from the distributor shaft, valve covers, oil press sender or from a bad intake rear intake seal/gasket.

What I want to know is if anyone else has has this issue where oil is leaking from somewhere at the rear top of the engine and working its way down. I dont want to replace the intake gaskets if its more likly it just a bad distributor gasket or valve cover or even leaking oil press sender. I know for a fact its not a rear main seal or oil lines as I steamed washed the motor and the leak is back from top of engine. Any help would be great.

 

As you already stated there are three major possibilities likely for an oil leak in that area.

The most likely being one of the valve cover gaskets judging by the amount of oil you are leaking. Probably the passenger side one if it is running down towards the starter.

For the amount of oil that is leaking the distributer seal is less likely but still plausible as it is in the right area. Usually they don't leak quite that badly though when they go bad on these engines.

Third is of course the lower intake gasket. This one I would say is least likely but still plausible. I consider this one the least likely simply because of the fact that I can't ever recall seeing the RTV that seals the area where oil would leak from fail before the gasket area that seals around the coolant passages. Especially if this truck still has the original gasket sets on it.
Though if the lower gaskets have been replaced in the past then someone may have put to thin a layer of RTV or perhaps the wrong type which would cause a seal failure down the line.

The best that you can really do to be certain before a repair attempt is to clean the engine as best you can. Top up the oil and have someone start it while you use a nice bright light to try and pinpoint the location of the leak better. Specifically looking in the area around each of those three seals while the engine is running.

There is always that wonderful glowing fluorescent dye stuff that you can put in the oil to highlight the leak a bit better.

 

Also check the oil pressure sending unit on the top rear of the engine by the distributor.