rear main seal or valve cover gaskets leaking??

[1972BlueC20]

I'm getting oil droplets on my driveway....I thought the valve covers where leaking and maybe they are still. They were very loose so I tightened them up and didn't see any more droplets for a few days. I cleaned up the engine below a little so I could see where it was coming from. It does look like the valve covers were leaking or are still leaking. There is oil from the spark plug area all the way down and back...

I did an oil change the other day and wiped the bell housing off real good and the oil pan.....now I got droplets all back on the bell housing.

Does this sound like a rear main seal? or?

How much should a rear main seal job cost from a mechanic shop?

I just need a reasonable ballpark so I know I'm not getting ripped off when I go to get quotes.

I'd do it myself, but I don't currently have the equipment or proper space.

[Blazerowner]

I think you have to pull the motor to do a rear main seal replacement. I don't think you can get the pan off with it in the truck. The rear main seal is inside the bell housing so the leak should be coming out around the bottom of the engine or inspection cover on the tranny. I went with rubber valve cover gaskets when I built my motor in my Chevelle. No leaks and they last forever. Not cheap though but you get what you pay for.

[NoNeck]

I would try replacing the valve cover gaskets before replacing the rear main seal. The gaskets are cheap and easy to replace.

Also, it is very easy to OVERTIGHTEN stock steel valve covers. Especially if they are tightened again and again. The metal underneath the bolt holes deforms and actually causes the valve covers to leak because of loss of clamping force over the entire cover.

When you remove the valve covers, lay them on a flat surface and lightly hammer the holes flat if they are deformed. This might do the trick.

One other thing to look for is the oil pressure sending unit (or oil line) that screws into the back of the engine block near the distributor. The stock ones are notorious for cracking and causing a leak similar to what you described at the back of the motor and the bellhousing.

Just remember these old trucks never were completely leak-free and will always drip. Someone on the forum once said they are just marking their territory.

POP

[twouvakind]

I am ditching the OEM bolts going the stud and spreader thingy route on my valve covers.

[i82much]

Try the UV dye, it works great.

[Fitz]

Originally Posted by 1972BlueC20

I'm getting oil droplets on my driveway....I thought the valve covers where leaking and maybe they are still. They were very loose so I tightened them up and didn't see any more droplets for a few days. I cleaned up the engine below a little so I could see where it was coming from. It does look like the valve covers were leaking or are still leaking. There is oil from the spark plug area all the way down and back...

I did an oil change the other day and wiped the bell housing off real good and the oil pan.....now I got droplets all back on the bell housing.

Does this sound like a rear main seal? or?

How much should a rear main seal job cost from a mechanic shop?

I just need a reasonable ballpark so I know I'm not getting ripped off when I go to get quotes.

I'd do it myself, but I don't currently have the equipment or proper space.

Since the rear main seal is underneath the bell housing I don't see how a leak there can get oil on the upper outside of the bell housing. To get to that seal you must remove the transmission, bell housing, clutch and flywheel then loosed the motor mounts so you can raise the motor high enough to get the pan off or just pull the motor. That leak is far more likely to be a valve cover gasket which would allow oil to run down the outside of the bell housing..

[jocko]

It really does sound like a valve cover leak - and Pop is spot on, do the easy/obvious first, because a rear main seal is not a fun, or inexpensive if you let someone else have the fun, job.

If you saw oil up by the spark plug, then the rear main seal is likely not the culprit. The rear main seal is actually enclosed in the rear of the rear main bearing cap. To do it right, the cap needs to be pulled and the crankshaft removed. To do it "sorta right" and cross your fingers, you can leave the crank in, remove the bearing cap, and use a sneaky pete tool to try to snake the old upper seal half out and the new one in, but it's very easy to damage the new seal. Bottom line, it's sometimes best to live with a rear main seal leak until you do a rebuild on the motor. A few drops, while it drives me nuts, isn't sufficient for a full teardown.

Pop's description is perfect - flatten the mating surface (gently, and on the edge of something, don't just whang on it with a hammer - it'll ruin the curved edge of the valve cover), especially around the bolt holes because that is where they get distorted the most, get new gaskets, and do not over-tighten them, this allows the gaskets to work on the full perimeter and keeps them from tearing. Hopefully that's your only problem.

[magwakeenercew2jh]

Originally Posted by i82much

Try the UV dye, it works great.

What UV kit do you like?

[asolde]

The rear of the intake manifold could be leaking at the rail to. Some guys use a rubber gasket there, I use a bead of the right stuff sealant along the rails. Look at your distributor base could be a leak there. The oil pressure sending unit or fitting is back there to. The valve covers always leak if they have been on there any time at all. The oil pan gasket could be leaking at the rails. The rear main seal most likely is leaking and the timing cover could be leaking. You can buy the uv kits at any parts store. That works good when you get everything sealed up and your looking for small leaks.

[1972BlueC20]

Great, thanks guys!

Do you recommend cork or rubber gaskets for the valve covers?

Use RTV or not?

Also, if the valve covers are warped badly, can you recommend a good set of aftermarket valve covers?

[Tx Firefighter]

As far as rear main seals, changing one is much simpler than you're being led to believe. I unbolt the motor mounts and fan shroud, jack engine up and put blocks of wood between mounts and frame stands. From there its just a matter of dropping the pan and doing the seal.

For valve cover gaskets, go FelPro Permadry and forget about it. They install dry, and are completely reuseable multiple times. This gasket I'm holding in my hand has been on two different engines. No sealant, nothing. Just put them in place and tighten the valve covers. They are multi layer rubber, steel composition.



Use good gaskets and proper workmanship and your stuff won't leak a drop. The old yarn about all old trucks leaking is a falsehood. Come to my place and I'll show you a line of trucks that don't leak or seep even a trace amount.

[70STOVEBOLT]

Fel-Pro Permadry is the only way to go. They have built-in torque limiters to prevent overtightening of the bolts. They are very expensive, but as Kevin stated above, they
can be reused several times, and no sealant is required.

[1972BlueC20]

are these the felpro permadry gaskets your talking about??


http://www.autozone.com/autozone/par...33253_35483_0_

[Tx Firefighter]

That's the ones. Painful to buy I know, but they never fail and in the long run are money well spent. Just lay them in place dry, right out of the box and bolt the cover down.

[1972BlueC20]

cool, what are those extra pcs in the picture on the autozone website??

[Tx Firefighter]

Those are little load spreader plates that you use with each bolt. It spreads the bolt's tension out over a wider footprint on the valve cover to give more even clamping force.

[i82much]

Originally Posted by magwakeenercew2jh

What UV kit do you like?

Can't remember, I got some at NAPA and some off of Amazon, both worked pretty well. I thought I had a rear main leak but it turned out to be the dipstick provision (long story). It is amazing how oil can be completely invisible until it forms a drop and this can make it very misleading trying to determine where an oil leak is actually coming from. I had drops coming right off the center of my bellhousing, but once I got the UV dye I realized the oil was going down from the dipstick provision, around the oil pan, and forming drops right in the center of the oil pan. My rear main is fine.

[1972SUPERSB]

Like mentioned previously. I've had an engine leak from the back of the manifold by the distributor. I thought it was the valve covers. Make sure and use high temp silicone installed of the gaskets on the front and back of the manifold.

[franken]

If there are oil leaks, I'd also look at the front of the engine. The timing cover/crank/damper seal is often toast, and a groove worn in the damper. You can get a sleeve cheap.

If the pan is coming off it makes no sense not to spend another $15 for the sleeve, timing cover, and WP gaskets. Then again mine seemed to be leaking from the front.

This was on a 71 Camaro and I popped the dist cap, jacked up the engine and dropped the pan. Pulling the radiator, accessory drives off the engine and so on was probably more work.

Cleaning and repainting the parts is the most work. I used colors and finishes that mimicked the "original" stuff so after a few miles it looked the same. But no more oil spots

[msgdsrf]

The rear main usually show a leak only at the bottom, at the dust sheild and back. If the leak is on the bellhousing, I'm guessing you mean higher up, it's from A. most likely oil gauge line connection on block. B. Intake rear seal (use RTV) or C. disrtibutor (if leak is on passenger side).