Oil Leak Help

[winnipeg69]

I have an oil leak on my 69 SB 4spd car. It is a leak that is worse when running. It leaks into the bellhousing then drips to the ground. How can I tell if it is the main seal?? The oil pan seems OK but hard to tell at the back of the motor. The top end is not spotless but I can see no obvious leaks when the car is running. The engine was rebuilt about 5 years ago and has very low miles. It has sat a lot more than it has been driven.

Thanks in Advance
Mike

 

[Stallion]

A sitting engine is not better than a running one, and in many cases, it is worse. Gaskets and seals dry out. Therefore causing leaks. Your leak sounds like it might be the rear main seal. Probably not the most fun job, but it's not too bad. Change the clutch while you are in there.

Wipe everything down, put some baby powder over the 'possible' areas, and then you'll be able to see the trails, and the origin of the leak. That's a little trick you will hear of.

 

[bradfordsvettes]

i think your best bet would be to clean it down and use a uv additive in the oil and check it with a uv light. it is just about fool proof all your leaks would be able to be identified with this process. they show up a yellow color best of luck steve

 

[The73vetteman]

I had a leak that sounds similar to yours after I rebuilt and reinstalled my cyl heads back in December. Started it up and had a trickle of oil at the back of the engine. Shut it down and the leak stopped.

After an hour or so of looking I found it was coming from the back of one of the valve covers. Turns out I hadn't installed the gasket quite right.

Stallion makes a good point about sitting engines. Maybe the valve cover gasket is leaking. Something to consider anyway. Clean it all up and have a good look round.
John

 

[AKRAY4PLAY]

Mike,

look at the back of your flywheel. if it is covered in oil, then you most likely have a rear main leaking or the oil gally plugs around the camshaft. if the flywheel is dry, then look to the valve covers and intake-to-block seal near the distributor. Brian

 

[BeaterShark]

It's really hard to tell the difference between a rear main seal leak and an oil pan leak. Eliminate everything else first, with the dye as mentioned above. If it looks like it is from the rear seal/oil pan, go ahead and change them both. The rear main seal is just a few bolts and brass punch away once the pan is off anyway.

Change the clutch while you are in there.

Do you really pull the tranny to change the rear main seal? Are you thinking of the 1 piece rear seal?

 

[goingballistic]

My '81 started leaking oil last year from the rear main. I told my wife I had to pull the motor to fix it , since I was going to pull the motor, I might as well rebuild it since I was going to rebuild it I'd like to drive it as well so I might as well buy a new block and start from scratch so I can take my time and do it right .......and I might as well keep the original motor in tact ( value of the car when sold thing ..... and this is a learning process and a project my boys and I can do together ( bonding) ....I am in the process of building a 383 stroker from the ground up to be dropped in next spring ........425 HP


She's gonna kill me if she ever finds out the truth........ad and the money that is going out the door ( actually in my engine)

( NO offense ladies )

 

[Stallion]

It's really hard to tell the difference between a rear main seal leak and an oil pan leak. Eliminate everything else first, with the dye as mentioned above. If it looks like it is from the rear seal/oil pan, go ahead and change them both. The rear main seal is just a few bolts and brass punch away once the pan is off anyway.

Do you really pull the tranny to change the rear main seal? Are you thinking of the 1 piece rear seal?

Hmm, I thought that you had to pull the tranny to change the rear seal, but now you have me doubting myself. Anybody verify this?

 

[JohnZ]

Nope, you only need to pull the tranny on the mid-80's-up engines with the one-piece rear seal.

 

[76okievette]

I have never done it but I read up on it in the repair manual and all you have to do is remove the oil pan and then use a punch to slid the seal out enought so you can get it with a pair or pliers to pull it out. Then slid in the new one reinstall the rear main bolts and the oil pan, of course this sounds simple but as most things go any thing can happen. I am going to attmpt this on my 76 SB this winter.

 

[Stallion]

Nope, you only need to pull the tranny on the mid-80's-up engines with the one-piece rear seal.

But is it easier to work around if you have the tranny out? I heard somewhere that it was recommended. I know not the source nor the time.

 

[bossvette]

My '81 started leaking oil last year from the rear main. I told my wife I had to pull the motor to fix it , since I was going to pull the motor, I might as well rebuild it since I was going to rebuild it I'd like to drive it as well so I might as well buy a new block and start from scratch so I can take my time and do it right .......and I might as well keep the original motor in tact ( value of the car when sold thing ..... and this is a learning process and a project my boys and I can do together ( bonding) ....I am in the process of building a 383 stroker from the ground up to be dropped in next spring ........425 HP


She's gonna kill me if she ever finds out the truth........and the money that is going out the door ( actually in my engine)

( NO offense ladies )

Well thats the way all projects start out, you may as well put in a OD trans to use all that low end torque, you will love the 383

 

[JohnZ]

But is it easier to work around if you have the tranny out? I heard somewhere that it was recommended. I know not the source nor the time.

Nope, tranny has nothing to do with it - you drop the pan and the oil pump, then the rear main cap; nothing else is in the way.

 

[nocrap]

Tool

Nope, tranny has nothing to do with it - you drop the pan and the oil pump, then the rear main cap; nothing else is in the way.

Don't you need a special tool to pull the new seal in over the crank?
I don't think you can just push it in the slot.

 

[Whiplash]

Don't you need a special tool to pull the new seal in over the crank?
I don't think you can just push it in the slot.

No special tools required although a small brass punch helps. Unless the seal is really trashed it's likely a drip from the valve covers when the oil comes to the top of the engine. I replaced both the valve cover gaskets and rear main on mine this winter and the car is now bone dry.

The rear main seal is not so much hard but rather a little intimidating.

Here's what I did...

1) Jack the car up and put on stands. Get it high enough so you can work well at the back of the motor.

2) Remove the bolt on the end of the power steering cylinder and the two bolts that hold the idler arm to the frame so you can push the steering linkage forward and away from the oil pan.

3) Drain oil and remove oil pan.

4) Carefully remove oil pump with pick up attached. I'd make a mark on the pickup near the pump to ensure alignment when you put back in. Also not a bad time to replace this entire unit as it's cheap and I had to go back and replace the pump after. For less than $30 you know you've got a good pump and you don't have to do the work again. Also get a steal sleave for the pump rod to distributor shaft assembly. A few more bucks but sure beats the nylon connector.

5) Remove rear bearing cap. Be careful with the bearing and keep this piece CLEAN.

6) I took a small piece of brass rod stock and rounded one end on my grinder to make it blunt and smooth. Gently tap one side of the top half of the rear main seal (still on motor) You should see it start to slide around. Gently grab the end that is coming out with needle nose pliers and pull clear. Some people rotate the crank here I didn't have to.

7) Read rear main seal installation instructions from the kit to reinstall. There's a little tab that comes in the kit that you place between the cap and seal to keep the cap from tearing the new seal. Notice the correct orientation and you slide carefully back in. Install the other half on the cap as instructed in the kit.

8) Replace cap and torque to specs.

9) Reinstall oil pump with pickup and torque to spec.

10) You need to make sure the pickup is positioned properly. It rotates easier than you think. I took the oil pan with no gasket and taped 3 quarters to the bottom of the pickup. I then place the pan without gasket on the motor to test clearance. With the pickup (quarters attached) just touching the bottom of the pan you know it's down low enough but also high enough to pick up oil. Now you can reinstall the oil pan with gasket. The added width of the gasket plus the extra space from the quarters (now removed) gives you a good clearance.

11) Reinstall oil pan. I went with a 1 piece Felpro gasket. The kit comes with handy trick tabs for alignment and positioning and doesnt require goofing with the goofy rubber end gaskets and alignment. Put a little gasket sealer at the proper spots where the caps meet the block and install to proper torque.

12) Replace the valve cover gaskets.

13) Replace oil filter

14) Fill with oil

15) Turn over a few times with coil wire off to help get oil pressure going.

16) Install coil wire and start her up. You should have a bone dry motor now.


I also did the front timing chain cover while I was at it. This eliminates the front seal from the equation.

Make sure you power wash the motor before or after this. The bell housing will hold some oil for a while and you'll worry about drips that aren't really there anymore.

Patience, attention to detail, time, and a little know how allows this to be done. You don't want to do it twice for sure. Good luck.

Whiplash