I am getting ready to install the new rear main seal in a 300 and was wondering if it would be ok to use some sort of sealer where the seal will go to prevent any leak by around the outside of the seal? I have some silicone and also some gasket sealer from napa that I brush on.

 

I wouldn't. The higher quality seals are fully overmolded in a silicon rubber, so there shouldn't be any leaks. Using a sealant might let it pop out-

 

I don't want to contradict those with more knowledge than I, but when I was replacing the crank in my 300, the rear main seal went in place so easily that I was afraid it would fall out. I pulled it back out, put a generous bead of blue rtv around it and then pushed it back in...seems to be ok so far. About 14k miles.

 

Is there a break in period on this? I just replaced the rear main seal on my big six and now it is squealing.

 

What years?

I once read a trick. Guy stated that on the one piece seals, as you know, the seal can cut a groove in the crank and cause the new seal to not work well. He suggested using a seal from a newer mod motor, he stated these have dual contact points vs the one. I have no idea if he was correct or not but if your at the parts store, might be a good idea to compare the two and see what your options might be.

 

I've got about 10k on mine and it leaks about 1 quart of oil in two weeks. I am getting ready to tear into it again. I have heard that it is the nature of the beast with these motors?

 

I am about to replace the real mian seal in my 77 F150 300 I6. While bringing this back from the dead, it developed a leak that runs down across the inspection plate on the transmission. In about two minutes there is a sizable puddle of oil on the floor.

I though while I go this far, I might as well replace the pan gasket, which seems to be leaking too. I read to put some grease around the seal if you are not going to fire it up right away. If you are going to run it the same day then to put a coating of oil around the seal before putting it on.

The motor has 80,163 original miles, but has been setting in a barn for nearly 20 years! I fear as I resurect this I will need to replace the front main seal, as well as the valve seals too!! Now to locate a transmission jack!!!!,.....

Also if anyone has any inpute or advise on this task, please feel to speak up, it is greatly appriciated, and THANKS!!