Got a new used motor put in my truck, they replaced the rear main before they put the motor in. About 2 weeks later the rear main was leaking again so I took it back and they put another one in, saying there was a burr on the crankshaft. Now its been a few days since then and it is leaking once again, what is going on here? Is there a solution?

 

Might be time to look at the rear main bearing, if it's sloppy it will ruin the seal. Do you have a knock in the engine? When starting or turning it off possibly? For as far back as I can remember rear main seals in Ford motors has been a problem, the 351M/400's from the 70's among the worst.

 

Sounds like someone fudged up putting it back in...I read somewhere about when it does this with a burr...but they have already put the other one in...Wonder if they just slipped it out..ran an emery cloth over it..I wonder if they got in a hurry. If I find the link with the service procedure from Ford, I will Post back later with it. I wonder if yours is a 1-piece or 2-piece rear main seal?

Be sure they know it immediately...It's not an easy job to replace it..I wouldn't want them to plac the blame on you 3 months down the road..I don't know what length of warranty period they gave you.

 

Cody...

I couldn't find that link involving the procedure for the rear main seal, but did stumble upon a unique Write-Up on the process. If you read into the step-by-step of it, you will notice how he hit the crank with his drill. He installed a repair sleeve on the end of the crank. Also, there was mention of the difference between a 302 and a 351. One member of FSB(Full-Size Bronco) noted that the bolts for the flywheel run all the way thru the 302s' crank where on the 351, they do not. He recalled that on the 302s', a sealer was to be used to prevent oil from leaking out thru them, but didn't recommend loctite. It wasn't necessary for the 351. Also there was notable difference between (2) types of gasket material.

Give the link a look thru and then take another good look at the leak you have. Perhaps you can discuss this with the mechanic that installed the 2nd seal in your motor.

Hope this helps!
Rear Main Seal Change Write-up, What and What Not to do (56K...I wouldn't) - FSB Forums

 

Thanks very much for that write up, I glanced through it real quick since I'm short on time but I will read it more throughly later. And yes I will have a talk with the mechanic. I don't know if I can have the downtime with the truck now as I did in the winter since I just sold my second car, so I hope the leak doesn't get worse so I can drive it for at least a couple of months. I hope it's nothing too serious because I really don't want to have to go through replacing a main bearing or anything of that nature, if I have to go that route might as well rebuild the whole thing..