The 3800 I'm putting in my fiero has been sitting in my garage for about 5 years. I'm debating on whether or not to replace the rear main and front crankshaft seal. On the plus side, I'll have peace of mind that it won't leak. The downside is that it calls for some expensive special tools and the rear main requires an awkward setup to replace with the oil pan off. I don't want to replace it while its hanging on the cherry picker and I don't want to set the engine down on the floor or table without the oil pan.

Has anyone here had seal problems with a sitting engine?

I'll just say this from experience: the 3800 has rear main seal leakage problems even when they don't sit. I'd suggest replacing it. Also, I suggest using only GM rear main seals as the Felpro seals tend to leak as well. Might as well get it done right the first time!

Good luck.

[This message has been edited by GS Jon (edited 12-24-2009).]

I did the rear main on a 3800 s2 without special tools. Was cheap and easy.

Never really seen either seals leak on a 3800 either.

If this is a Series 2 or 3 3800 engine you are working with; I don't really see a lot of problems with the rear main seal itself on these engines leaking as much as a leaking gasket for the rear main seal housing. The housing is an aluminum plate that the rear main seal installs into; and it is usually the gasket for this plate that leaks oil. GM put a TSB out years ago about warped rear seal housing plates. However, in every case I have seen a leaking rear main seal housing plate gasket; when I have replaced the gasket (reusing the OE housing), the leak has gone away. While you have this housing plate off it is also a good idea to replace the rear main seal.

There is a special tool they make to install the rear main seal itself into this housing, but I have been able to accomplish this with a big block of wood. NOTE: Notice the direction of the rear oil seal. The new design seal is a reverse style as opposed to what has been used in the past. "THIS SIDE OUT" has been stamped into the seal; make sure this faces out away from the inside of the engine upon installation. GM says not to use a sealant or adhesive when installing this seal. Lubricate the inner diameter and outer diameter of the new seal with engine oil before installation. Install the new seal into the housing until it is at the same depth in the housing as the stock seal was. Make sure the seal is evenly installed into the housing and is not cocked sideways, crooked, or distorted. Clean the crankshaft sealing surface with a clean, lint free towel. Inspect the crankshaft sealing surface and leading edge of the crankshaft for burrs/sharp edges that could damage the rear main oil seal. Remove any burrs or sharp edges with crocus cloth before reinstalling the rear main seal housing.

You don't need any special tools to replace the rear main seal housing plate while the oil pan is off. GM says install all bolts finger tight and then to lay a straight edge on the engine block oil pan flange and the crankshaft rear oil seal housing flange. Use a feeler gage to ensure there is no more than 0.10 mm (0.004 in) step on each side. If necessary, gently rotate the crankshaft rear oil seal housing to make the step equal on each side. Once aligned, tighten the crankshaft rear oil seal housing bolts to 11 ft/lbs. Then tighten these bolts an additional 50 degrees. Recheck the step height on each side to ensure the crankshaft rear oil seal housing did not move. If the step height is beyond specification, reinstall the crankshaft rear oil seal housing and measure the step again. Replace the crankshaft rear oil seal housing if the clearance is still beyond specification.

I do want to warn you that the factory gasket used on these rear seal housing plates is usually very brittle and rock hard when you remove it. So make sure you have a very good gasket scraper handy and take a lot of time to make sure every piece of stock gasket is removed/cleaned before reinstalling with the new gasket. DO NOT use die-grinder mounted surfacing discs to clean the block or plate; just use a razor blade or other sharp gasket scraper. The new gasket should come with some anaerobic gasket sealer already applied to it to aid in sealing; so you should not need to add any. Observe proper fastener tightening specs and you should have any troubles.

OTHER LEAKS to check for:

Lower intake gaskets: If your engine does not have the metal shim lower intake gaskets (and it has the plastic ones), REPLACE THEM with the metal ones (sold by GM). Use blue loctite on the lower intake bolts. Observe correct factory tightening sequence and torque on the bolts. DO NOT use roloc discs or any other die-grinder mounted cleaning disc or wire brush to clean the intake manifold sealing surfaces on the cylinder heads. Doing so will throw very small particles of metal and debris into the engine which can lead to engine bearing failure. Use only a razor blade to clean these gasket mounting surfaces.

Lower intake coolant bypass cover gasket: There is a small cover above where the EGR tube goes into the lower intake; I see a lot of these leak over time. I recommend you replace the gasket on yours if it is already leaking or if you are going to have the lower intake off.

Valve cover gaskets: Very common for them to leak due to age. Replace as necessary. If your engine has the composite/plastic valve covers, check for cracks in them and replace them if any cracks are found. New GM replacement valve covers (for Series 3 engines which will work on the Series 2) are black in color (supposedly a higher temp material and looks better than the factory cream color anyway).

Oil pan gasket: Factory stamped steel oil pans had an issue with the sealing rails warping/rippling. Fix is to use the latest gasket and lay a bead of RTV sealant on BOTH SIDES of it so it seals properly to the oil pan and block. Use blue loctite on the oil pan bolts and tighten to 125 in/lbs.

Good luck!

-ryan

------------------
6+ years on this same swap -- NO engine or transmission failures...

Custom GM OBD1 & OBD2 Tuning | Engine Conversions & more | www.gmtuners.com

[This message has been edited by Darth Fiero (edited 12-24-2009).]

I find that oil pan gaskets are best reused, with alot of RTV. The gaskets themselfs never seem to wear out, it is just the stamped steel pan that is the leak point.

Just wanted to add that when you go to install the new rear main seal, you can use the old seal to help seat the new one in fully (in conjunction with a wooden block) if you don't damage the old one too badly when you remove it (I just use a hammer and a drift to remove it and it usually comes out without being damaged.

-ryan