I have 2003 Blazer 4.3 V6 with 123,000 miles since new....runs great!! never any major issues...But every time I change oil or get under it to look...there is oil /wet all over the oil pan and tranny pan!..not dripping so much tho...always a little oil getting ready to drip at the oil plug...I always wipe everything off pretty good as possible and in no time the oil seepage comes back...I can not see where it is coming from.always seems dry topside??? I even replaced the oil drain plug thinking maybe the rubber washer was compressed/worn out and leaking thru the threads!....New one same way,always wet at the plug which I understand is the lowest point...Tried Lucas,Blue Devil and ATP202 stop leaks,still wet under there!! and I guess it blows back on the tranny pan keeping it wet....no drips on the ground as I can see?? Anybody else having this problem or know exactly where the oil is coming from on these Blazers???? Any info is gladly appreciated.....BTW I have also looked under other Blazers,one being my friends,and his is the same way,wet with oil everwhere! looked at one the other day at a shop brought in for other service...same thing,wet all over the bottom end!....hard to believe the rear main seal is leaking with only 123,000 miles and I change oil on a regular basis and filter....Is this common with the 4.3 V6???? I have replaced the oil cooling lines 3 different times for leaking at the crimps in the past...they look okay now,oil filter is snug,new PVC valve(thought maybe it was not relieving crankcase pressure enough and forcing oil out the seals?) Distributor seal looks dry and oil sending unit as well.....

 

First off, are the remote oil lines not leaking? Those are known for leaking at the crimps. I also on a 92 had the o-ring for the adapter that goes between the block and the remote oil lines fail. That caused a large loss of oil.

I also read a post about someone identifying that the two hidden nuts that secure the oil pan on either side of the rear main seal can come loose. It took him a couple attempts at a thorough cleaning to get the thread locker to work to keep the nuts torqued down. These nuts are accessed by the semi-circular openings at the front of the transmission.

I had similar symptoms and found my two same nuts a bit loose. I tightened using my inch torque wrench to spec (I can't remember what that is) and I think it has slowed the oil. Being winter I don't get under there much so I can't be sure. I think what I might try is to re-torque the nuts and then add some ny-lok nuts to the studs to keep the original ones in place. As I write this I guess I could just use the nylok nuts but the torquing of the oil pan is a bit delicate so I might as well keep the originals.

I suspect I also have a leak at the front and/or rear block rails between the heads that I did not seal with RTV sufficiently well when I replaced the LIM gaskets. I also suspect the timing-chain cover might be leaking. But, I'm in no hurry to fix those.

As long as it is not the rear main seal, I'm good.

 

On almost every 4.3 I've seen, they leak oil at the junction between the timing cover and the oil pan. Sometimes at the back of the pan, too. Also, check your valve cover gaskets. It can be hard to see that they're leaking because the top of the engine will still be dry.

 

tku for your input....i swear it looks like the oil is coming right out of the drain plug threads! wet today again and a drip hanging off the oil plug..that is a new one in there and I went so far as to teflon the threads on the new one too...and everything past the plug is wet like it is blown back there onto the tranny pan...beats the hell out me!?????

 

tku for the reply....think you are right on the common oil leak at the timing cover and oil pan areas....

 

Try cleaning the drain plug area well with brake cleaner (preferably when the oil is warm) and let it sit overnight without driving it. Check the next day to see if it's dripping again. It's possible there's a tiny crack at the drain hole.

 

Do you have the nylon washer on the drain plug between the pan and the plug itself ?

 

I got one just like the origional GM with magnet...it only has a rubber like o-ring made into the flange....,no nylon washer?....

 

It sounds like a former DIY or fast lube shop may have over tightened the oil drain plug and damaged the plug threads or even the pan threads. Then someone may have replaced the oil drain plug with the 'close but wrong size' plug. I would replace the oil drain plug with an OEM GM plug, not an auto shop version. Then use a new GM drain gasket with the rubber insert like you are using. I think GM recommends replacing this gasket at each oil change. Yes, I know not everyone does that. I recommend buying a plastic bag of these rubber insert gaskets so you will have them on hand.
I am recommending focusing first on the leak being caused by the plug and/or plug gasket because it is so difficult to replace the oil pan and gasket, especially if it is 4WD. The pan seems to be aluminum and the drain plug is steel. This is a dangerous combination especially when the fast lube places and even the dealership service bays want to over tighten the oil drain plug. I think this is due to a paranoid fear of a 'comeback' due to leaks. It is ironic that an over reaction to this fear may be causing the leak. I have seen several YOUTUBE video's showing the next guy having to use a breaker bar to loosen the drain plug for an oil change ! You shouldn't have to do that.