Rear main seal leak??

[RCE1962]

Brought the 62' in for an oil change today and had them take a look at whether a new leak at the rear of the oil pan was an oil pan gasket or a rear main seal. Chances are that it is a rear main seal. The engine doesn't have over a five hundred miles on it since its rebuild in 2008 and the car has been sitting for long periods of time, with only intermittent start ups, short trips or idling in the driveway. I was out of commission for some time due to health issues and then had a few other tranny issues with the car that made it a bit unreliable for regular outings.

Having said that...a friend had mentioned to try an oil additive that may/may not assist with sealing this...if it is the rear main seal. Failing which...I guess I should start budgeting for the proper fix.

Any suggestions with regards to a recommended "brand" / "type" of oil additive for this as an interim fix?

Ron

 

[DonSSDD]

What oil are you running now?
Don

 

[RCE1962]

Hey Don..

10W 30

 

[mac1]

Mine also leaks. IMHO, if it's a small leak I wouldn't worry about it. The two piece RMS just doesn't seal that well. Just put something under it in the garage.
I use a 50/50 mix of straight 30 and 40 weight oil, non synthetic.

 

[yellow wagon]

If its just a small drip I wouldn't worry to much. Check you oil level before taking the car out, top it off if its down some and don't think twice about it. Its a Chevy motor, its called "marking its territory"

 

[poison ivy]

when the rear main seal was installed, did you or builder install the two little rubber ends in the seal?

 

[RCE1962]

Poison Ivy...I assume that the builder installed the rubber ends as well only because there was no evidence of this leak for a few years and the problem never showed up until recently..... but I could be assuming wrong.

"Marking its territory" Well Jason.... actually this dog has been pretty good at doing that lately. I don't mind a bit of oil leaking here and there...but this was a bit more than I expected. As the engine warms up the dripping slows down. So maybe with a bit thicker oil as Mac said and probably the suggestion Don was leading up to...it will help. I spoke to a few mechanics here and said that sometimes an oil additive for this kind of thing will help as well... but it doesn't always work.

I'll let you know what happens in the next week or so.

Thanks guys.

 

[DonSSDD]

I've found that if you have an oil leak, a synthetic will leak more. I've had this happen on 2 vehicles, no leak with regular oil, leak with synthetic. I try to use synthetic in everything BTW, I'm not a synthetic hater.

Don

 

[mac1]

There is a higher percentage of RMS leaks with a manual transmission car . I was told this by a reputable mechanic.

 

[W-motorhead]

Ron, Following up on Poison Ivy's comment above, I attach three photos, showing the two small seals, which fit into the rear main bearing cap. These seals are separate from the large, two-piece seal, which goes around the crankshaft journal. When I disassembled my '63 409, which had an oil leak like the one that you described, I noticed that the previous builder had failed to install these small side seals. When I raised this topic on the 348/409 website, several members told me that inexperienced w-motor builders often make the mistake of omitting these side seals. To replace them, the engine must be pulled from the car. I'm afraid you have to live with the annoying oil leak or roll up your sleeves and plan a rebuild. Dan Fults

 

[models916]

Usually when the side seals are missing it's more than a drip.

 

[W-motorhead]

In my case of the missing side seals, the oil leak became active when the engine was hot. There no leak when the car was parked with the motor shut off. The leak did not create a puddle of oil, as one might think, which might be explained by the presence of some crumbly sealant in the grooves where the side seals were supposed to be installed. Ron's oil leak slows when the engine warms, so maybe the side seals are present and his Chevy is, as Jason humorously said, "marking territory."

 

[RCE1962]

Well Mac...the car does have a manual transmission.

Dan...Thanks for the pics. I am assuming the side seals were installed since this the oil dripping never occurred until now. I purchased a RMS oil additive product to try first. I've had some folks say that it has worked its worked for them. Aside from improper installation, I suppose it can depend on a variety of circumstances, if this product can be helpful. We will see. Even if it slows to the "marking" level... I will be happy...otherwise the engine will have to be properly fixed.

Thanks everybody!

 

[RCE1962]

When I started this post the typical event was that the dripping was about one every second and started slowing to a very slow drip... maybe once every few minutes...but it did not stop all together, Before the weekend the shop verified the leak was from the RMS. Yesterday. Fresh oil change to 10W30 and Lucas RMS additive to the oil. (thought I would try the 10W30 first). Also, yesterday the car idled for about ½ hour and no drip. Shut it off and let it sit for a few hours,, then driven for about ½ hour while checking every once periodically...no leak. Today...the car left no drips on the driveway/garage. Went for a drive for over an hour...no dripping. Let it idle for awhile again...no dripping. Its an understatement that I'm thrilled that the RMS is not leaking. Anyways...so far so good.

 

[mac1]

I'm glad it worked out for you. I've got a bottle of that in my garage but was reluctant to use it. If my leak gets any worse I may use it someday.

 

[RCE1962]

Just thought I should provide an update. Still no oil leaks at the RMS.

 

[mac1]

Just thought I should provide an update. Still no oil leaks at the RMS.

Congratulations. I'm glad it has worked for you. You'll have to keep using that periodically. It swells or expands the all the rubber seals and it looses some of it's effectiveness over time.

 

[RCE1962]

Good to know. Thanks Mac.

 

['37-4D]

Just thought I should provide an update. Still no oil leaks at the RMS.

Hi @RCE1962

Glad I came across this thread.

Is this the product you are referring to?
https://lucasoil.com/products/engine-oil-additives/engine-oil-stop-leak

I also have what I think is a RMS leak. Fresh build, just around 350 miles on it. About the little tabs, the motor did not leak that much at first. I can't vouch as to whether or not he used them or not.
It leaks when I stop driving and drops a puddle the size of my hand. Then nothing when I shut off, other than the residual oil making its way down the back of the pan.
I also have to mitigate some blow by I have. The pressure may or may not be forcing a hand on the leaking.

I was suggested to switch from Comp Cam break-in oil (10w30) to Shell Rotella 15w40 zinc oil. (I have flat tappet)
I won't be driving in winter obviously either.
Any thoughts on switching and then adding the Lucas oil stop leak additive?

@Don Jacks @DonSSDD

 

[W Head]

don't believe Shell Rotella has the good stuff any longer. Feds took it out about 2 years ago.

W Head

59 Impala 409-2,4s