Can I replace my 383 rear main seal with motor still in the car?

-
/72Scamp

/72Scamp

Well-Known Member
Joined
Jan 20, 2015
Messages
226
Reaction score
54
Location
Hampton NH
So my motor started pouring oil today. Appears to be coming from the rear main seal. Constant flow of oil coming from rear of motor pouring down on the trans. Motor is a 69 383 and it's in a 69 valiant post car. Has anyone successfully replaced this with the motor in the car? And what seals are you guys having the best luck with?
 
it's fairly straight forward to do. getting the old rope one out is kind of tough. you will need a dent puller with a long *** screw in it. screw it in and have someone turn the crank by hand as you bump it out in the direction of the turning crank. I always use the two piece neoprene seals. offset the seams about a 1/4" or so. before you go to all that trouble check the oil fittings/ oil sending unit on the back of the motor behind the intake. a lot of times they are the bad guys.
 
BEFORE you replace the rear main replace the oil pressure sending unit FIRST. It is more likely to be the cause of rapid oil loss than the rear main and look the same from under the car.
 
Well it appears I do not have an oil pressure sending unit. One side is plugged and the other side just has a nipple on it with the pressure line running through the bulkhead to the oil pressure gauge. Doesn't seem right to me. But it is dry at the top of motor where the sending unit should be so apparently it was my worst case scenario and I will have to replace the rear main seal.
 
You are also going to need a Sneaky Pete install tool. Kind of a wire with clip on one end that grabs the new seal and helps drag it through as the motor is being bumped forward.
 
You have a mechanical gauge instead of the electric style which should be more responsive and accurate.
 
Make sure that oil is not coming from the center of the crank where they drilled it (too deep) for a pilot bushing. Yes, it happened to us.
 
other things to check=oil pan gasket loose from the bolts pulling the holes up towards block and not letting the gasket seal. the space between the rear main seal cap and the block has no rtv in it. the side seals are leaking. oil dripping sown from the valve cover gasket running down the block and along pan rail to back of motor on to the trans. pan gasket srunk from all the heat cycles and needs replaced
 
I will relate a story of my own. 318 poly fresh build started leaking bad after about 4k miles. Really dumped oil on the headers during acceleration. Thought it was the oil filter gasket. Nope, couldn't figure it out but oil was all over the headers and under the trans inspection cover. Thought it then had to be the rear main seal. Nope. Upon close inspection, the rear oil pan rubber seal had slipped out and was letting oil slosh straight out. Dropped the pan, reinstalled the rear seal with gasket adhesive and it has been 100% sealed since.
 
Huh that is interesting. Hopefully early this week I can get the car off the ground and do some more searching around. Thanks for the advice !
 
You must log in or register to reply here.
-

Back
Top