newbie2vette

I am convinced that the rear main seal is the cause of the leak on my newly rebuild engine. I am informed that the seal can be removed without taking the engine out. can someone share their secret how it is done and the proper orientation of the seal when installed. first attempt doing this. thank you in advance.

tomgallucci57

i did mine last week.i did alot of research first,it was my first time also.i would tell you,for starters,too google search-corvette hacks-then click on rear main seal replacement.it gives a pretty clear understanding of what needs to be done.mine still seems to have a very small leak,but much better than it was.may have to redo,ugghh.different people say different things about where to apply the anarobic sealer,,check out that web site and see what you think.the job really isnt that hard,maybe 5 hours total.do a little bit each day. ill try and follow this thread,,best of luck with your drip....tom in cleveland,oh.

Mark Riles

Are you sure it's the rear main? Sometimes oil can leak from the backs of the valve cover gaskets and trail down the back of the block and appear to be a rear engine seal leak. Valve cover gaskets are much easier to change. If you're sure it's the rear main this is how.

Get the car in the air and supported by jack stands. Unbolt the idler arm from the passenger side frame and so long as the front wheels are dangling the steering linkages can be dropped enough to make room for the oil pan to come off. You'll have to remove the transmission dust cover and oil pan. This also means that you will be doing an oil change and will need new oil and filter and pan gasket. Once you have the oil pan off, you can remove things such as windage tray and oil pump. Be careful when dropping the oil pump. If it still has the plastic coupler shield it may be brittle. Note that when the oil pump goes back up you will have to get the notch lined up with the bottom of the distributor shaft. Once the oil pump is out you now have access to the rear main. I like to first check the main bolt torque by tightening just to make sure it is where it needs to be. Once verified simply pull the bolts and tap on the away edge to dislodge it. Use a small brass punch to push the block side of the seal around the crank and pull it out carefully. Make sure the new one is facing the right way and lubricate it with oil. Start it and slide it in but leave .25" of the block side of the seal sticking out. When you put the cap side of the seal in make sure you mimic that .25" so that when you place the cap on the block the ends of the seal meet with that rotational offset and the seams of the seal don't line up with the seams of the main cap. Retorque the cap bolts, install and torque the oil pump and windage tray, and using the new oil pan gasket seal everything up to spec. Then lift the steering back up and get the idler arm bolted back to the frame and you're ready for your new filter and fluid. Also, the oil pan gasket can leak and mislead you a bit too so it's worth mentioning to be sure it's the rear main before you do this.

7T1vette

You don't want to go to the trouble of changing the rear main, if that's really not the problem. Clean everything off....really well...and put some dye (available at auto parts stores) in the oil. Start engine, let idle and look for the beginning of oil leakage in that area. As mentioned, it can leak from the valve covers, you could have a head gasket leak, it can be leaking from the rear oil pan bolts, or even the cam-pocket plugs on the rear face of the engine block.

Don't change the main seal, unless you are certain that is the cause.

If it is, then unbolt the idler arm from the right-side frame rail, and lower the steering linkage so you can get access and remove the oil pan. Drain oil, remove pan, clean all around the bearing cap to remove dirt/grime, remove cap retaining bolts and pull cap straight down. You may need to tap on the cap as you are pulling, as it is a very tight (close tolerance) fit. Clean the seal groove in the lower and upper halves of the cap. Follow directions on how to install seal. If you do it wrong (especially in the upper cap), you will cut the seal lip and it will leak worse. Many folks offset the seal pieces just a bit in each cap so that the butt-joint of the seal halves will not be right at the cap splitline. That offset only needs to be about 1/4" to work well. And, if you offset them, put just a dab of black RTV sealant [only black RTV sealant!] at the end faces of the seals...not enough to squish out of that joint when they go together.

Good luck.

1Fordman

Make sure no oil is leaking from the intake manifold to block surface. It will run down the back just like a leaking valve cover gasket.

newbie2vette

Thank you everyone, I did find that web site with an excellent write up on the complete procedures. Yes, I've checked all the posibility where the leak is coming from, I even got the one piece pan gasket. to check the valve cover and any other leak source which I can verify. I put on some gloves with power to reveal any leak where I touch.

While I was sharing with a co-worker what I am about to do, and after I review the "how to" from the web site mentioned above. I remembered how the builder installed the seal on my egine, it was not close to what was describe on the tech tips.
From what I noticed during the seal installation, he install the top hlaf of the seal, then the crank. before putting the bottom half he pushed on one side so it is 1/4" pass the mating surface. I asked why he does that, he said he likes to off-set the seal to prevent leaking and I did not noticed him putting any kind of silicone.

Hence why I am leading to the rear main seal, I will re-verify all of the possible source to the leak before I proceed with the seal replacement. Also, the other reason I am leading to the main seal is where the oil is coming from. It is dripping from the gap between the bell housing and the dust cover in front of the bell housing.

Mark Riles

Something I want to mention is for the oil pan gasket and it is something I see a lot of people skip. In reference to the 1 piece gasket. They are awesome and I love using them. However, they do still need silicon to seal perfectly. Before the gasket goes up to the block make sure you put a glob of silicon in the corners at both the timing cover and at the rear main. Then when the gasket goes up and the pan gets tightened down the silicon will squish into any tiny areas where normally oil would leak out later.

Steve2147

What your engine builder did is the preferred method of seal install. Rolling it in like this is done to avoid having to remove the crank.

Neither the seal manufacturer nor the engine manufacturer specify rtv sealant on the ends of the rear main seal. There's as much risk doing it as not. And you can not seal the ends of the lip portion together. They are too small. The ends of the body of the seal are rubber coated and there is a "crush" that compresses the ends together, so I really don't believe you accomplish anything by using it but you do risk foreign material in the seal area. I've done it both ways and have never seen a noticeable difference. Two piece seals are an imperfect design and that's why they're seldom seen on today's engines.

The key to getting any gasket to seal properly is the sealing surfaces have to be completely oil free. Use aerasol brake cleaner to remove any traces of oil from the block areas and the pan. Keep your oily fingers off the surfaces. It will be necessary to glue the gaskets to the block for assembly. Use 3M weatherstripping adhesive. A very light continuous bead is all that's necessary. Let the rest of the gasket do it's own thing. Dab rtv in the corners. Tighten from the centre working outwards. Remember that the 4 corner bolts are 5/16" (1/2" head) and are tightened more than the smaller ones. If you're not sure how tight, use a torque wrench.

Steve g

TimAT

I posted this a couple of years ago, then someone cried because I used "his" pictures so I deleted it. I didn't get all of the threads it was linked into I guess. Here it is again

http://forums.corvetteforum.com/c3-t...-qestions.html

As Steve noted getting all the oil off is the only way RTV will stick. I make a pass with the brake cleaner, let that air dry, then go back with a rag and some alcohol.

Steve2147

I find that none of the gasket materials seal properly if there's oil on the surfaces, cork, rubber, neoprene etc, not just rtv. If you want a sweat free joint, everything has to be clean and dry. Pull apart a good oe seal and you will find the gasket materials stuck like sh.t to a wool blanket. The only way you can achieve that is on a dry surface.

Steve g

newbie2vette

I know this is now an old post and I am late to reply on any progress. I finally had the static time to replace the seal. It was not as difficult as I made out to be, I took the old seal to the builder to show him it was the rear main that was leaking. His first comment was "that is a junk", it was the gray seal vice the blue one. So if you get a complete gasket set and it contain a gray rear main seal do not use it and get the blue color seal seperately. The new engine has 2k on it and without a drop of oil. Thank you again for all the inputs.

iokepakai

Good to hear all went well.To many times we don't get to hear about the outcome in these threads......