C-1 engine block leak

[Kevin T.]

I have been frustrated with a pesky oil leak from the rear main seal on the engine block of my 59 Fuelie. Since I have only owned the car for about 4 months, my history with it is limited. But it seems to have coincided with replacing the clutch and resurfacing the flywheel about 2 months ago. The transmission was also replaced 3 months ago. I did not see any signs of this leak when I first purchased it. The car and engine were restored about 4 years and 7500 miles ago. My mechanic thinks that it may be manifesting itself now that I am actually driving it versus it sitting around (he also says there are other signs that the car was not driven much by the prior owner). My mechanic has replaced the rope seal 3 times now, and replaced a higher output oil pump that was on the car with the "correct" one thinking the high oil pressure was too much for the seals - all to no avail. He now thinks it may be a wornout crankshaft that needs to be replaced. Since that task requires pulling the engine yet offers no guarantee that it will solve the problem, I am hoping someone can offer some other potential solutions or ideas. Thanks in advance for your help as always. - Kevin

[Joe L.]

Re: C-1 engine block leak

Kevin-----

Usually, the kind of crankshaft seal-surface wear that will cause the kind of problem that you have will be discernable with the crankshaft installed in the car. However, if there is any discernable wear on the seal surface such as nicks, scratches, uneven wear, etc., the crank will need to be replaced. Some especially competent machine shops may be able to weld-up and regrind the seal surface once the crank is out of the car.

Something else to try if the crank seal surface appears to be in good shape, is to use a retro-fit, neoprene-type seal. This seal replaces the rope seal and is available from aftermarket sources. However, most 1959 Corvettes originally used a neoprene-type seal and not the earlier type rope seal. If your block is a 3756519 then I believe that it was originally equipped with a neoprene-type seal. In that case, if a rope seal is being installed, that may be your problem. If you have the later style block, just use the 59-86 small block seal GM #10121044.

[ian#32567]

Re: C-1 engine block leak

kevin,make sure your mechanic is following the sealant requirements on the surface of the rear main brg.cap,and what is the crank endo?..ian

[Kevin T.]

Re: C-1 engine block leak

Thanks Joe. The casting on my block is 3737739. Even though my 59 is an early production car (9/9/58), it has an engine assembled on 3/18/58. Does that make a difference in your advice? - Kevin

[Joe L.]

Re: C-1 engine block leak

Kevin-----

You likely have an original rope seal block. Convert to the aftermarket neoprene seal and apply sealer to the block in the areas shown in 1960+ GM service manuals for engines with original neoprene seal blocks.

[Robert Willis]

Re: C-1 engine block leak

Or one of the oil gallery plugs up behind the flywheel is leaking ???

[Roy Braatz]

Re: C-1 engine block leak

Not many Mechanic's today know that as you pull the new rope seal throught the top area, you don't just cut off the ends . You must pack the seal by pushing both end up as you turn the crank, other wise your just leaving gaps in the crevasses of the crank cap, that is why the rope is longer.Also on the bottom cap it also needs to be packed tightly and not just layed into it.
Many people blam the rear seal when they have a miss align rear intake gasket seal which is hard to determine when your oil is clean in a new engine rebuilt.

[Chuck G.]

Re: C-1 engine block leak

Just a thought. I chased a supposed rear main bearing seal leak on my 63 for years. Turned out it was the front transmission seal, and that my "oil" drip was actually a transmission gear oil leak. You mentioned that the trans was recently rebuilt. Again...just a thought. Chuck

[Chuck G.]

Re: C-1 engine block leak, another thought

Another thought...I've seen people chase supposed rear main leaks, only to find one of three things.
#1. Oil leak from the valve covers,
#2. Oil leak from the distributor (intake and FI plumbing), and
#3. Oil leak from the rear of the intake manifold in the "V" created where the intake meets the head on both sides. All 3 will cause the oil to drip down the back of the block, and off the bottom of the bellhousing. If your mechanic has replaced the seal three times, I would think he could tell if the crank is scored. As others have said, if it is the rear main seal, a double lip neoprene seal should help, as it contacts the crank and seals in two different areas, whereas the rope seal contacts only one area. Hope this helps. Chuck

[Kevin T.]

Re: C-1 engine block leak

Joe, I was optimistic that the neoprene-type seal you suggested might be the answer. My mechanic was also aware of this product and had already ordered one to try out. Unfortunately, after he got it he says it will not fit my block. As I mentioned before, I actually have a 58 block (3737739) in my early production 59. He thinks the rope seal is the only thing available that will fit. He is looking into some type of a roap seal that is supposed to be a higher end one of some sort. Otherwise I guess I am back to possibly having to replace the crankshaft. Regards, - Kevin

[Roy Braatz]

Re: C-1 engine block leak

Un-less your grankshaft is chewed up were the seal goes it's OK. Read my other post as to how the seal is installed . But one other thing to check is the rear bearing wear.Have your guy plastic gage the rear bearing to determine the clearance and if it's to great the crank can flexe cousing the oil seal not to seal. If so have him replace it to the right clearance which you can get and easly remove the old one and install a new one.