1972 Oil Leak cause - front of engine

[Patrick H.]

I'm working on doing some repairs on a 1972 350/200 (base motor) 4-speed car with 67000 miles. The owner notes that he was leaking oil or using oil quite a bit when he last used the car. It has been in storage for 16 years, so he doesn't recall much more than that but he wants the problem fixed if possible.

There is plenty of oil on the bottom of the motor, both front and back. I suspect that the rear main seal needs replacement and have that on my "to do" list. However, I'm wondering what the "most common" place for an oil leak on the front of the motor might be. I would think it is either the crankshaft seal or the front oil pan seal. Timing chain cover seal seems much less likely to me. When I replace the rear main seal I will, by default, also be replacing the oil pan seal and front pan seal. However, should I also think about the crankshaft seal and/or another location? I don't have the luxury of cleaning off the motor, driving the car for a few hundred miles, and then looking for the leak spot. It's a "one shot deal." But removing the balancer to replace a crankshaft seal isn't high on my list if it doesn't need to be done.

Attached are 3 pics, one of the front of the pan, one of the middle, and one of the bellhousing and trans.

Any and all thoughts are appreciated.

Patrick

[William C.]

Re: 1972 Oil Leak cause - front of engine

Just based on the first picture, it looks like the timing cover seal is leaking as the leakage seems to extend above the pan seal area a good ways.

[Patrick H.]

Re: 1972 Oil Leak cause - front of engine

Just based on the first picture, it looks like the timing cover seal is leaking as the leakage seems to extend above the pan seal area a good ways.

I don't know how much it would affect the appearance of the motor, but the power steering system is also leaking a fair amount, and will be R&R'ed. Parts are already here.

You don't know how much I'd like to just pull the motor, clean it, place it on a stand, regasket it, paint it and drop it back in.

Patrick

[Kevin G.]

Re: 1972 Oil Leak cause - front of engine

I'm sure that you will repair /replace the fuel pump but it can be a source of an oil leak at the front too. The pictures do show more then just a leak problem with the pump. Just a thought?

Kevin

[Patrick H.]

Re: 1972 Oil Leak cause - front of engine

I'm sure that you will repair /replace the fuel pump but it can be a source of an oil leak at the front too. The pictures do show more then just a leak problem with the pump. Just a thought?

Kevin

Did that last year.

[Edward J.]

Re: 1972 Oil Leak cause - front of engine

Pat, My 35* Yrs Working On Cars And Gm Dealership Exp. Common Areas Of Leaks On Chevy Small Blocks Are- Oil Pans ,rear Main Seals, If The Front Timing Cover Seal Leaks, Its Slings The Oil- Check Botom Of Water Pump , Hoses Check For Signs Of Oil Spots On Them. Of Course The Valve Covers To-sometimes The Oil Runs Down The Rear Cornors Of Cylinder Heads And Can Be Miss Dia. As A Rear Seal Or Oil Pan. My Advice Would Be To Clean Underside Of Engine, If You Dont Mind A Little Paint Missing, Brake Clean Work Well And Drys Quickly, Use In Well Vented Area. Then Drive Car A Few Miles And Recheck Yhe Areas.

[Patrick H.]

Re: 1972 Oil Leak cause - front of engine

Pat, My 35* Yrs Working On Cars And Gm Dealership Exp. Common Areas Of Leaks On Chevy Small Blocks Are- Oil Pans ,rear Main Seals, If The Front Timing Cover Seal Leaks, Its Slings The Oil- Check Bottom Of Water Pump , Hoses Check For Signs Of Oil Spots On Them. Of Course The Valve Covers To-sometimes The Oil Runs Down The Rear Corners Of Cylinder Heads And Can Be Miss Dia. As A Rear Seal Or Oil Pan. My Advice Would Be To Clean Underside Of Engine, If You Don't Mind A Little Paint Missing, Brake Clean Work Well And Drys Quickly, Use In Well Vented Area. Then Drive Car A Few Miles And Recheck The Areas.

Ed,

I'd love to, but I'm also replacing the metal fuel lines and the power steering system. The car is coming apart - once if possible - and then in drivable status it goes back to him. That's why I'm trying to play the odds by replacing the "most likely" leakers. The owner knows it may have to return here in the future for another leak but I'm trying to minimize my personal frustrations. I'm working on the car part as a favor, part for therapy.

No oil on the water pump, the pulleys or the radiator hoses. So, per your notation, front timing cover seems less likely. How about the crank seal in the center of the timing cover - does that usually leak?

Patrick

[Edward J.]

Re: 1972 Oil Leak cause - front of engine

Patrick, The Oil Seal On Front Timing Cover Is What Slings The Oil Onto Pump And Hoses, So Front Seal Must Be Good, Look At The Corners Of Intake Manifold Front And Rear, The Intake Manifold To Block Rubber Seals Sometimes Dribble Down The Front And Rear Of Block. To Be Honest With You What Doesnt Leak On A 35+ Year Car, Valve Covers Are The Most Common Leaks On Chevys Engines.the front seal on oil pan is wet, you'll need at least a pan, would rec. the rear main seal.

[Patrick H.]

Re: 1972 Oil Leak cause - front of engine

Patrick, The Oil Seal On Front Timing Cover Is What Slings The Oil Onto Pump And Hoses, So Front Seal Must Be Good, Look At The Corners Of Intake Manifold Front And Rear, The Intake Manifold To Block Rubber Seals Sometimes Dribble Down The Front And Rear Of Block. To Be Honest With You What Doesnt Leak On A 35+ Year Car, Valve Covers Are The Most Common Leaks On Chevys Engines.the front seal on oil pan is wet, you'll need at least a pan, would rec. the rear main seal.

Thanks Ed.
I'll plan on the pan seals and rear main then.
Valve cover gaskets are already scheduled.

Patrick

[Clem Z.]

Re: 1972 Oil Leak cause - front of engine

my advice clean the whole engine of the oil and start from scratch to look for the leaks.

[Dick W.]

Re: 1972 Oil Leak cause - front of engine

Hmmm. Medicine business must be slow.. I will see if I can find my old "Doctor of Motors" diploma that Perfect Circle used to issue when you attended one of their seminars. I will scan it and Photochop the name and add Patrick Hulst. I betcha Clementine has one of those

[Patrick H.]

Re: 1972 Oil Leak cause - front of engine

Hmmm. Medicine business must be slow.. I will see if I can find my old "Doctor of Motors" diploma that Perfect Circle used to issue when you attended one of their seminars. I will scan it and Photochop the name and add Patrick Hulst. I betcha Clementine has one of those

LOL!

No, but my own 72 needs no work, and I don't do fiberglass so my 71 sits in a barn 30 miles away. It gives me something to do and I get a bit of "mad money" from it.

Patrick

[Paul D.]

Re: 1972 Oil Leak cause - front of engine

It may just be the picture, but I see a dent about 1" long at the front of the pan just below the front seal. It looks like something sharp like a wide chisel or a piece of metal caused it. I know it doesn't take much to affect the sealing of that front seal (pan to timing cover). After you replace all those seals, be sure to check out the PCV/valve cover breather system to make sure there's no blockage.

[Patrick H.]

Re: 1972 Oil Leak cause - front of engine

It may just be the picture, but I see a dent about 1" long at the front of the pan just below the front seal. It looks like something sharp like a wide chisel or a piece of metal caused it. I know it doesn't take much to affect the sealing of that front seal (pan to timing cover). After you replace all those seals, be sure to check out the PCV/valve cover breather system to make sure there's no blockage.

I'll take a close look at that area once it's apart. I don't "recall" seeing a specific dent but I'll look.

Patrick

[Brian M.]

Re: 1972 Oil Leak cause - front of engine

Take a look at the fuel pump rod retaining bolt location.