Oil Leak Top Rear Engine
 

I have an oil leak coming from somewhere on the top rear of my engine. About 6 months ago, I replaced the distributor seal and the oil pressure sensor. It doesn't look puddle up around there, but I do have enough oil pouring down that after one trip to work and back there is oil pouring down the back of the engine and dripping off the transmission. I don't think it's my rear main just based off how high it is, and I'm on the fence about it being a valve cover gasket. Are there any other seals in that area I should be aware of? I'm hoping this is something I can do without pulling the engine so I can avoid shop fees.

If its coming from the top back of the engine I would check valve cover gasket, Intake gasket, distributor gasket and oil pressure sender. if you are loosing that much oil, you might just be able to stick your hand behind the engine and feel where its wet.

Classic lower intake gasket leak. 4.3 is NOTORIOUS for it. Do a quick search on the forum, heck even Google, you'll bring up tons of info and a few in depth how-to's on changing the gaskets yourself. Expect to put almost a full day's work into the job if you've never messed with such a thing before. Absolutely very doable without pulling the motor out.

If I may make a suggestion; do the valve cover gaskets while you're at it. While everything is out of the way, you're only 6 bolts away from changing them and it's good cheap easy insurance ;)

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The engineer that designed the lower intake gasket on these 4.3 need to be beat with a stick.
Especially for the silicone bead serving as a "gasket" on the intake front and rear.

Thank you for your speedy and right to it responses guys. I do have a good amount of experience tearing down and rebuilding engines, but I'm not as familiar with the one in my own vehicle as I should be. I've done a lot of CAT, Detroit, Cummins, and even some Mercedes (screw those guys, btw). I've also done a lot of small engine work. I just haven't gotten into automotive engines as much as I probably should. Looks like I'll be getting into it this weekend. Luckily, it seems like a pretty basic engine to work on, so I may be able to actually have this knocked out in 1/2 day if things go right. I'll go ahead and be sure to order a case of brake-kleen along with those gaskets.

I've made it a little over 200,000 miles and it's now needing that gasket change, so I guess that's not bad. One thing that suprises me about this is I know they do pull some oil from the PCV, but I didn't realize it was enough to leak like that due to a bad intake gasket. I mean, it may wind up being the valve gasket - I'll see when I pull them this weekend - but if it's all coming from the intake gasket...wow.

Well, between work and my wife having a major surgery, I'm just now getting around to popping the hood. Wow. After taking off my intake and looking closer with a few extra lights, I definitely see what y'all mean by the lower intake gasket being the likely problem. It is wet all the way up to the bottom of the intake most of the way around. I even have some oil sitting under my A/C compressor for some reason. I'll double check that my p/s cap is tight. I don't remember it having half the wires and hoses going to it last time I worked on it (P/S pump, Distributor, Water Pump). I guess I was working all around them and wasn't paying much attention. It looks like I'll be doing a partial coolant drain, and relieving pressure in the fuel lines so I can disconnect the spider harness. Are there any wires I should avoid unplugging to prevent having to reflash the system? I plan on leaving the intake plugged in, but I also see a few boxes I'm not immediately familiar with. I SHOULD be able to leave the a/c system alone and just move the compressor out of the way. I'm seeing where this could turn into a 12 hour job for a first run. I'll still try and stay under that! :D

You can move the A/C compressor and bracket forward on it's mounting studs (to the front of the head) enough to get at that one intake manifold bolt. Remember there are 5 fasteners holding that bracket on the engine. Two you will have to remove. One at the driver's side bottom of the timing cover, and the other at the driver's exhaust manifold. The three studs have nuts recessed into the bracket.

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Pretty clean, i dont see any heavy corrosion trails.

https://cimg0.ibsrv.net/gimg/blazerf...9ec5cce87a.jpg

Overall, they're still decent. I see some early signs of failure, but nothing major.

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Clean valves

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Not even any buildup under the covers

I don't know what happened, but something in the air came in the garage and has given me one heck of a sinus infection while I've been working. Not something I've had happen for at least 6 months now. Anyways, between taking breaks to clear my sinuses, checkin in on and helping the wife recover from her surgery, and the occasional visitor stopping in - I'm plugging away at it. I had to stop for a min because my plenum was catching and with it being plastic I wanted to look online for any tips before I crack it. I've been following one blog in particular for occasional steps during this process, and it's so good that I think y'all should post it if it isn't already being shared somewhere else. Check this out:

How To Replace Intake Manifold Gaskets On A GMC Jimmy 4.3 Liter V6 To Fix A Coolant Leak - GM Truck Engine Repairs

Just spot on. He doesn't go into any extra crap not related to the job, he doesn't miss any minor steps, and he's very thorough in his details. It's not very often I find instructions for any job that are done like this.

After tediously going back and looking for missed hoses, connectors or bolts and not finding any, I went ahead and gravity bled the cooling system. Once all that and the oil change was done, I cranked it at 11 pm. It started right up, no problem or leaks. Its revving and idling correctly too. Once you factor in all the stops for my so,uses, helping the wife, and visitors...I would say it was a solid 8 - 9 hours of labor. I guarantee next time I can cut that in half. Hopefully there won't be a next time! Now I just need to go for a test drive and see if it still doesn't leak. I'm gonna give that RTV a little more time to set first.

Tomorrow - knock sensor on the wife's 04 Tacoma supercharged.