Rear Main Seal....Do I Need To Pull Engine?
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Senior User
Joined: Apr 2004
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From: Chicagoland Metro area
Rear Main Seal....Do I Need To Pull Engine?
Hi all! I rebuilt my '68 390 a few years back. Got it all back together, and found the rear main seal leaks (not to mention those cool-but-pesky "Power by Ford" valve covers). Been living with it for a year or two, and it's bugging the heck out of me. I really don't want to pull the engine and/or trans to replace it, but, I may have to.
Anybody here had luck replacing the seal with the engine in the truck? Also, would you install the rms with the offset, or even with cap? I think I did with the offset, even though my engine machinist said do it straight. I cant't remember if I put a dab of black RTV on the ends of the rms or not, but, I have read that is important to do. Would like to hear your tricks/opinions/stories on doing the rms.
Thanks!
Dave
Anybody here had luck replacing the seal with the engine in the truck? Also, would you install the rms with the offset, or even with cap? I think I did with the offset, even though my engine machinist said do it straight. I cant't remember if I put a dab of black RTV on the ends of the rms or not, but, I have read that is important to do. Would like to hear your tricks/opinions/stories on doing the rms.
Thanks!
Dave
Hotshot
Joined: Jul 2005
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From: Middle Tn.
Yes, an over fill could cause excessive crankcase pressure.
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Thanks for your reply 69. I have the dust shield off of the bell housing right now, and I cannot see any oil leaking down the front of the flexplate, or dripping from the center of the engine where the trans and engine mate. However, I do see an oil drip on the under side of the passenger valve cover which is right above the starter motor. I also see oil on the starter motor which looks like it blows around down there and finds its way to the bottom center of the bell housing. So, the source of the leak may actually be the valve cover. I have tried rubber, and cork gaskets, and beads of TPV with both. Nothing seems to seal it up. I am wondering if I ever do get that leak stopped if my rear main seal leak will miraculously go away too.
Anybody tried stronger/stiffer valve covers to solve leaking?
Anybody tried stronger/stiffer valve covers to solve leaking?
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From: Chicagoland Metro area
When you say the rear manifold, do you mean the rear of the intake manifold? I do believe I did use cork when I rebuilt it a few years ago. Also, I did tighten down the passenger side valve. I took the truck out for a drive last night, and went out and looked for leaks this AM. There were no drips on the bell housing, or coming down from the rear corner of the passenger valve cover.
I am starting to wonder if I overfilled the oil last time I changed the oil, and due to the higher pressure it may have been blowing oil out. I did have to make my own filler tube, and it could be a bit too long, causing me to put too much oil in to hit the full mark on the dipstick. I am going to change the oil this week and see how much comes out, and then put exactly five, maybe six, quarts back in.
I am starting to wonder if I overfilled the oil last time I changed the oil, and due to the higher pressure it may have been blowing oil out. I did have to make my own filler tube, and it could be a bit too long, causing me to put too much oil in to hit the full mark on the dipstick. I am going to change the oil this week and see how much comes out, and then put exactly five, maybe six, quarts back in.
Hotshot
Joined: Jul 2005
Posts: 13,834
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From: Middle Tn.
The metal valve covers and rear intake manifold are prime leak areas and one can be confused with the other the way the oil moves around once warm. I ended up going to cast valve covers. I even tried the rubber on steel gaskets and they didn't work.
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From: Chicagoland Metro area
Glad you made the comment about the cast aluminum valve covers. Been thinking about putting a set of those on. After driving the truck some more this AM, I think that tightening the valve covers up helped the leakage from the top end.
However, I still have a small trickle of oil leaking down the bell housing. I tracked it up, and it does look like the leak is coming from the rear main seal. It drips down the metal separator plate (between engine and trans bellhousing), runs over to the passenger side, and then drips down the right side of the bellhousing. If it was a gusher I would proceed to replace the rms. However, not sure it is worth the effort for a relatively small amount. I am going to continue to watch it and see what happens.
However, I still have a small trickle of oil leaking down the bell housing. I tracked it up, and it does look like the leak is coming from the rear main seal. It drips down the metal separator plate (between engine and trans bellhousing), runs over to the passenger side, and then drips down the right side of the bellhousing. If it was a gusher I would proceed to replace the rms. However, not sure it is worth the effort for a relatively small amount. I am going to continue to watch it and see what happens.
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From: Chicagoland Metro area
Hi guys! I got busy installing relays to fix my flickering headlight problem on the '68, and am now busy working on the rear tail light wiring....very weak turn signals. I have not had a chance to work on the rear main seal yet.
Valve cover gaskets.....I have tried rubber and cork. They all seem to leak. However, I have cork ones on there now. They seem to be working better, but, I think they still leak in the lower corners, especially on the passenger side. I did not trim the cork. But, I did use some sealer adhesive for good adhesion on the valve cover side of the gasket.
While the rear main is leaking a little, the power steering gear and pump is leaking A LOT!!! I will probably focus there before I focus on the rear main. I may end up putting a Red Head gear in.
Now that the old gal is 50 (built in Sept. '67), she is really falling apart on me! But, she still runs better than trucks half her age, and looks a damn sight purtier too! She really turns heads when she is strutting her stuff down the road. Even pulls my 5000 lb. boat/trailer down the road like a champ.
Valve cover gaskets.....I have tried rubber and cork. They all seem to leak. However, I have cork ones on there now. They seem to be working better, but, I think they still leak in the lower corners, especially on the passenger side. I did not trim the cork. But, I did use some sealer adhesive for good adhesion on the valve cover side of the gasket.
While the rear main is leaking a little, the power steering gear and pump is leaking A LOT!!! I will probably focus there before I focus on the rear main. I may end up putting a Red Head gear in.
Now that the old gal is 50 (built in Sept. '67), she is really falling apart on me! But, she still runs better than trucks half her age, and looks a damn sight purtier too! She really turns heads when she is strutting her stuff down the road. Even pulls my 5000 lb. boat/trailer down the road like a champ.
Laughing Gas
Joined: Jul 2010
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From: Chico, Ca.
The stamped steel valve covers get distorted from over tightening. If the metal looks dimpled at the bolt holes, hammer them flat. I use the cork gaskets with some permatex between the cover and the gasket.
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