Oil leak - possibly rear main seal?

[Red 83]

I have discovered a fairly good sized oil leak on my '83 C10. It looks like it's either the back of the oil pan gasket, or the rear main seal. That brings me to my question: If it is decided that it is the rear main seal, how hard is it to replace? I've heard that you have to disconnect the engine from the transmission. Can it be done just by droping the oil pan? If that's the case, I can do it myself.

Thank you.

[bd]

Welcome to the site from California, Red!

As long as you have a pre-1986 gas engine in your truck it has a two-piece rear seal that can be serviced by dropping the oil pan.  However, oil leaks from the oil filter, valve cover gaskets, rear intake valley seal, the rear cam plug, rear oil galley plugs, or oil pressure switch can mislead diagnosis by dripping from the same spots as a leaking rear main or oil pan, especially if there is a lot of oil accumulation.  Clean the area well and look carefully before you tear it apart.  How many miles on your engine?

[VileZambonie]

Welcome to the site from California, Red!

As long as you have a pre-1986 gas engine in your truck it has a two-piece rear seal that can be serviced by dropping the oil pan.  However, oil leaks from the oil filter, valve cover gaskets, rear intake valley seal, the rear cam plug, rear oil galley plugs, or oil pressure switch can mislead diagnosis by dripping from the same spots as a leaking rear main or oil pan, especially if there is a lot of oil accumulation.  Clean the area well and look carefully before you tear it apart.  How many miles on your engine?

This, bd is spot on.

[Red 83]

I was told my engine is a '76. I don't know how many miles it has. The whole bottom half of the engine is covered in sludge. It would take a lot of cleaning to get it clean. If it sits overnight it leaves two puddles about 6-7" in diameter. After it has run for a while (up to operating temp) it drips fairly fast.

[Lt.Del]

I echo what's been stated.  Once you clean it up, you'll have a better idea where it's leaking from...if you want to see what the rear main looks like, click here....you fortunately have a two piece, thus, dropping the oil pan is the hardest part....

http://forum.73-87chevytrucks.com/smforum/index.php/topic,3950.msg18334/topicseen.html#msg18334

[Red 83]

I was looking at the engine earlier today and I noticed that there is sludge all over the engine. It's even up on top of the intake next to the carb. Without disconnecting the engine from the tranny, (or pulling the engine) is there anyway to see the backside to see if any of the things you guys mentioned are leaking? I'm just thinking about the hours it would take to clean off the entire engine, not to mention the crossmember and framerails and tranny (they are all caked in sludge).

[bd]

Red, welcome to the world of truck repair.      Is the "sludge" you mentioned wet, or dry & cakey, or a combination?  If the engine, tranny and undercarriage are dripping with oil, you're going to have to clean up at least the engine and bellhousing areas, and maybe the tranny, (as best you can with limited access) to pinpoint the source(s) of the leak(s).  Concentrate on the areas that are wet with oil and adjoining areas that are immediately above (oil runs downhill).  While you're cleaning, pay attention and become familiar with the engine, where parts are located, and how it's put together.  Leaks generally occur where parts/components join together.

After it's cleaned up a bit, run the engine and focus your attention on areas that are wet (dripping) with oil and work your way "up" toward the source.  Take your time and look carefully; fluids can drip several feet from the source of the actual leak.  Keep safety in mind: wear eye protection, use safety stands, set your park brake, and be mindful of moving/rotating assemblies, keeping fingers, clothing, tools, etc away from them.  It's best not to work alone!

There's an inspection cover (auto trans), or flat sheetmetal plate (std trans) fastened to the bellhousing, between the engine and transmission.  Removing the cover/plate gives limited visual access to the back of the motor.  You can use a mirror and flashlight to peer up between the flexplate/flywheel and engine block to see (if barely) the rear main, cam plug, and oil galley plug areas.

Two related questions:  How is the fluid level in the transmission?  What color is the dripping fluid?

[Lt.Del]

I'd go to a nearby car wash--the self serve kind that has power washer hoses.  Run your truck at idle and pop the hood and start spraying.  I do this with engine running because if i hit a delicate spot, the idle will decrease and I quickly refrain from putting too much water in that area.  But, especially underneath it, i'd spray the heck out of the engine with the high pressure water.
Once clean take a small point and shoot digital camera to take pics of areas that you cant put your head, just your hand and camera and take a billion pics to diagnose where the leaks are.  If your camera has a flower setting on it (usually the sympol for macro lens) use it so the close up shots are in focus.

[bd]

I'd go to a nearby car wash--the self serve kind that has power washer hoses.  Run your truck at idle and pop the hood and start spraying.  I do this with engine running because if i hit a delicate spot, the idle will decrease and I quickly refrain from putting too much water in that area.  But, especially underneath it, i'd spray the heck out of the engine with the high pressure water.
Once clean take a small point and shoot digital camera to take pics of areas that you cant put your head, just your hand and camera and take a billion pics to diagnose where the leaks are.  If your camera has a flower setting on it (usually the sympol for macro lens) use it so the close up shots are in focus.

Great idea, but check local ordinances first, in some communities this is citable.  Take some Engine Brite degreaser with you.  Don't point the nozzle at the distributor!  Remote pix are a clever idea, SgtDel! 

[zieg85]

I was really hollered at for leaving a mess one time... OOps...  and it was just mud, I couldn't imagine leaving a greasy mess somewhere the way ordinances is as far as EPA is going.   I am surprised there are still self service unmanned ones still out there.

[jaredts]

If theres a lot of sludge up top I'd check the oil pressure sensor/sending unit at the back of the intake (I've had these leak sooo many times).  Sort of next to and behind the distributor with a wire plugged into the end of it.  If you don't see it oozing out somewhere obvious like this when you start it up you'll have to do as said and clean it up pretty thoroughly to find the source.

[Red 83]

Ok, that's going to take a long time to clean.

The color of the fluid leaking is dark brown/black. It gets larger the longer it sits. It is leaking from two areas close together.
I will go to the car wash next week.

[Red 83]

Ok, I just had a thought. When I'm spraying down the engine at the car wash, how do I keep the water away from the air filter. I have an open Edelbrock air cleaner setup (cover over the filter, that's it) . If water gets in there, you know what happens.

Also, I don't have a bellhousing. They just bolted the flywheel/flexplate directly to the torque converter. If I were to crawl under there I could see the entire bottom back half of the engine. I just don't feel comfortable having it up on stands with the engine running.

[bake74]

     You be very careful, or you wrap it in plastic which means not running your engine while washing it.

[Red 83]

Awesome idea! I know where I can get ahold of some shrink wrap. That will work great. I have never cleaned an engine before, so this will be interesting.