The Stovebolt Site Forums The Shop Area Engine Shop Rear Main Seal Problems

I'm going to apologize right off the bat for posting a question here regarding a F--d, but I really do depend on this rig as a parts hauling machine for my '35 Chev restoration project. Please bear with me.

I've got a '65 F-250 (2wd) with a 1970 Mercury 429 in it. Leaked oil from the rear-main like a seive so I undertook the task of replacing the old rope seal with a new 2-piece Felpro split rubber type. Had a heck of a time getting the old seal picked out of the block half but managed after about 4 hours with a piece of brass brazing rod to get it all out. The new seal slipped in nicely, put RTV gasket maker on bearing cap face, torqued everything down, and put pan back on. When I started it up the next day, the thing leaked worse than ever!

Has anyone had an experience like this before with this type of seal. I've only used the old rope style before (on my '63 Olds) and it worked fine. Any advice or sympathy is welcomed.

John Larson

I am probably going to get chastised for saying this but, I kinda like the mid '60's Ferds, a friend of mine has a 1960 **** , in sad shape, but does the job. Anyway, The only thing I can think of is, is it the right seal? It sounds like it is too small for the crankshaft. Maybe the parts place gave you the seal for the origional engine instead of the 429. thats the only thing I can think of. Good luck, theres more guys on here that know more about this kind of thing than I do.

Did you notice the rear main cap having a pointer like thing sticking up where the seal went and did you remove it. I think they were installed to keep the rope seal from moving,I changed from a rope to the rubber seal on a 302 and did not remove the pointer and it leaked. I think if the pointer (or whatever it is called) is left in and a rubber seal is put in it distorts the seal and it leaks. Jeff

Jonathan, I too will probably be chastized for liking early '60s "Ferds" as well -- in my opinion, the '61 to '66s were the only years that **** made a better looking truck than Chevs of the same vintage (the jury is still out on these new '03 Chevs though -- pretty ugly looking front headlight and grill set up). Anyway, the rubber seal set I bought was correct for the 429 (at least that's what the packaging said and the fit seemed right when I put it in).

And Jeff, I did grind down the pointer on the bearing cap with my Dremel tool (being careful not to take anything more off than the pointer of course).

I went to my local auto parts store today and found that I can still buy an old rope seal for this motor. I'm wondering if putting the rope back in there will seal whatever nooks and crannies are letting oil by. They're a pain to slip into the upper half but I figure it would be worth the effort given that the rubber seal doesn't seem to work. Any thoughts on this idea? Also, has anyone discovered a good way to get the rope seal into the top part -- I'd used fishing line tied to it while turning the crank shaft the last time I tried. I was thinking that a little sturdier wire attached to the end might work a little better. Also, now that I've ground down the pointer, will this make a difference for the lower seal?

Dont worry about being chastized by me with having a f**d most of the vehicles I have are f**rds,the only chevy I have is my 37 half ton. And it will be f**d powered if I cant get the mid eighties F150 o/d trans to work on the 235 I have in it. If a 300 six is the same length as a 235,it will go in it. The way I look at it is if its made in the states by the big three I will drive it. Jeff

Don't know if this would work or not, but I have seen "Chinese Finger Puzzle" main seal replacement tools in the shops. cost about $30 CDN. (What's that, 25 - 30 cents US?). It looks like a small piece of braided steel cable that grabs the end of the seal and pulls it around.

Good luck. My rear seal problem is a 1989 Z24. One piece seal around the crank. No idea how to fix it without pulling the engine.

Those seal tools are also know as "Sneaky Pete's" dii you get both haves of the seal are faceing correctly also check to make sure the drain hole for the slinger grove is not plugged up. Also is your distibuter at the back of the motor??? have seen a few main bearing leaks really being the rubber O-ring on the distributer running down the back of the motor..

I want to get this correct. Are you saying that FQRD/MERQ used a rope seal in 1970? No wonder they never made to the top!

Yep, a rope seal in 1970! I was a bit suprised when I got into the thing too.

I've heard of the Sneaky Pete/Chinese Fingers tool and will look for one before I try the job again.

I'm certain that I got the placement of the rubber seal correct as I checked and re-checked that before I bolted it back together. Cleaned out that channel as well. Also, the distributor is at the front of the engine on this motor so it's not likely to be leaking from that place.

Highflyer: sorry to hear about the one-piece seal problem you have. I feel comparatively fortunate. Don't they make a two piece replacement for whatever motor you're dealing with?

And Jeff: I like the 300 six too. I'm director of a museum and we have a 1957 Clard-Ross straddle carrier (underbelly lumber carrier) that has a scabbed-in 1975 F--- 300. Has bad rings so it burns a lot of oil but man is it reliable. We start it a couple times a year and it always fires right up. A fun rig to drive sitting about ten feet in the air with four-wheel steering.

Highflyer, I doubt that you will find a two piece for your leak, but I wouldn't even recommend it. The one piece seals are great. It is easier to remove the transmission though to replace it. Make sure the hole in the bottom of the seal housing is not obstructed. Make sure the pcv valve works well and don't overfill the crankcase and the new one will last. I will probably be replacing the rope seal on my 235 tomorrow if the parts have come in. Good Luck

Well, I tackled the task of removing the leaking split seal I'd put in the week before and was amazed to find that Felpro had actually manufactured the seal too small. Before starting the work, I'd purchased both a new rope seal and a different brand split seal just for curiosity's sake. When I put the Felpro and the Rol brand seal (which appeared to be factory **** ) side by side, the Felpro clearly had much less rubber in its construction. While it was the right size to slip around the crankshaft, it was too small to fill the grooves in the block and the bearing cap.

I've always had good luck with Felpro stuff before but this one really caught me off guard (the packaging clearly noted that it would fit my 429). Anyway, the thing is all back together and on the road. Thanks to everyone for their help.