79' 350 merc odd oil leak

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stupidhawk

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79' Scarab with twin 350s. the Port engine has had a leak all summer. Only does it over 3k RPM. While idling or cruising below that RPM it doesn't leak. Oil leak very near crank or main pulley. Pulley is slinging oil around the engine bay can see it in the floor of bilge and engine hatch. I pulled the harmonic balancer and replaced the main seal. I thought that would be it, but a brand new seal and I had the same problem this last weekend. Seems to have made no difference. When pulling the harmonic balancer there was a fair amount of oil behind the main bolt and sitting between the crank and the balancer. After running it, there is always a small pool of oil resting on the inside of the grooves of the main pulley. Any idea where this could be coming from?
 
Bondo

Bondo

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Re: 79' 350 merc odd oil leak

Ayuh,....

Is the Timing Cover Rusty,..??

Is the seal surface contact area Clean,+ Smooth on the hub,..??

Did you pre-Grease the Seal at installation,..??
 
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KJSmitty

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Re: 79' 350 merc odd oil leak

stupidhawk said:
When pulling the harmonic balancer there was a fair amount of oil behind the main bolt and sitting between the crank and the balancer. After running it, there is always a small pool of oil resting on the inside of the grooves of the main pulley. Any idea where this could be coming from?
Click to expand...

Are you stating that you think the oil is seeping out between the balancer and crank shaft - IE, as in where the crank key is etc?? The fact you mention oil on the inside of the pulley is a definite giveaway. If so your front main seal probably isn't the issue - but you now have a new one. :)

I would inspect your harmonic balancer very carefully for any cracks. I had this on my old Pontiac 455 and it was due to a crack resulting on a loose fitting balancer that continued to get looser until it started leaking.

Something you could try temporarily is swapping H balancers between your engines. See if the leak moves to the other, stays at the current engine, or develops on both.

Good luck
 
mkast

mkast

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Re: 79' 350 merc odd oil leak

KJSmitty said:
I would inspect your harmonic balancer very carefully for any cracks. I had this on my old Pontiac 455 and it was due to a crack resulting on a loose fitting balancer that continued to get looser until it started leaking.
Click to expand...

You have a unique way of phasing things, how can a harmonic balancer leak?
 
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KJSmitty

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Re: 79' 350 merc odd oil leak

mkast said:
You have a unique way of phasing things, how can a harmonic balancer leak?
Click to expand...

Please read his post then mine..

I did not state that the harmonic balancer itself had a leak.
OK -"It" as in the crack/"loose" fitting balancer resulted in a leak.

He stated:

"When pulling the harmonic balancer there was a fair amount of oil behind the main bolt and sitting between the crank and the balancer. After running it, there is always a small pool of oil resting on the inside of the grooves of the main pulley".

I questioned:

"Are you stating that you think the oil is seeping out between the balancer and crank shaft - IE, as in where the crank key is etc"??

I believe he is describing what very well sounds like a leak due to a poor "fit" between crank shaft and balancer. A poor "fit" issue, if fact, is commonly caused by a cracked balancer. Been there had that. For whatever reason I suspect he has a fit issue due to his description of oil in the pulley not to mention around the crank / pulley bolt when removed. I had, and have seen the same. Most Chevy SB's have snug fitting balancers. I would question his.
 
mkast

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Re: 79' 350 merc odd oil leak

KJSmitty said:
I had this on my old Pontiac 455 and it was due to a crack resulting on a loose fitting balancer that continued to get looser until it started leaking.
Click to expand...

As per your instructions, I reread this.
 
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stupidhawk

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Re: 79' 350 merc odd oil leak

Yes, it really does seem like it might be leaking between the fit of the crank and the inside of the balancer where the key is. I just assumed it wasn't possible to leak there due to the friction fit. How much should the bolt be torqued to? I have it to about 60 lbs now, is that enough? i might switch the balancers and see if the leak switches over with it. Is replacing the balancer the only way to fix this issue if that is the problem?

Thanks guys,
 
mkast

mkast

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Re: 79' 350 merc odd oil leak

If you remove the damper, inspect the seal. No uncommon to damage the lip of the seal during installtion or when installing the damper
 
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hard-3

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Re: 79' 350 merc odd oil leak

look at the seal surface on the balancer if it has a ring or groove in it , can cause new seals to leak. Fix with speedy sleave or replace balancer. A little silicone on the balancer when installed can seal the oil from coming around balancer bolt>check timing cover real close also could be leaking around seal mounting boss. also front oilpan bolts could be blowing oil out of pan and spinning balancer spreading it around making it look like oil seals leaking. Also when putting on balancer don't drive on with a hammer, I've seen it done. Will beat crank against rear thrust main bearing and destroy. Instead install with balancer installer , not using center bolt either, it pulls threads from crank. get an installer tool from autoparts store for about $10 . Sure wouldn't be fun to try to put helicoil in end of crank while in boat cause threads stripped out!
 
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stupidhawk

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Re: 79' 350 merc odd oil leak

I think i am going to pull the balancer again and replace the timing cover seal for good measure. Maybe see what that does. Never heard of using silicon between the crank snout and the balancer, seems like the friction fit should be more than enough to seal it if everything is as it should be. Anyone else ever done that before?
 
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hard-3

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Re: 79' 350 merc odd oil leak

not a lot of silicone just a drop and wipe it on as a thin film
 
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KJSmitty

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Re: 79' 350 merc odd oil leak

stupidhawk said:
I think i am going to pull the balancer again and replace the timing cover seal for good measure. Maybe see what that does. Never heard of using silicon between the crank snout and the balancer, seems like the friction fit should be more than enough to seal it if everything is as it should be. Anyone else ever done that before?
Click to expand...

You should easily be able to see whether the oil is "slinging" off the back of the harmonic balancer/pulley or if it's coming from the front/inner portion of the pulley etc. (maybe its both :) ) Can't say I have ever had a timing cover crank seal sling oil into the front of the drive pulley. :)

Did the balancer come off by hand or via puller? Your SB 350 would normally require a puller.

The silicone is an option but as you mentioned semi unorthodox. If the "fit" of the balancer is in question there most likely is a reason. I would have no issues using the silicone as a temp repair or diagnostic tool however.

Cheers
 
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stupidhawk

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Re: 79' 350 merc odd oil leak

No i had to use a puller, it was on nice and snug just like it should be, key iin proper position etc. Nothing seemed out of place except when taking the bolt out the very first time there was a good amount of oil behind it. When i pulled the balancer off there was a good amount of oil inside the balancer where it fits onto the crank snout. I can't really think of any other place that it could be leaking from that would get oil up in there and leave a pool inside the grooves of the main pulley. Since the pulley faces forward and it cupped 2-3 inches forward from the mounting surface of the balancer it seems almost impossible that oil could be leaking from anywhere else and getting inside cup of the pulley. Anybody have any other ideas? Would kind of like to fix it right, don't mind spending the money to fix it properly but I also don't care to just throw time and parts at it and still have an oily mess inside my engine bay.

Thanks again
 
Bondo

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Re: 79' 350 merc odd oil leak

Did the balancer come off by hand or via puller? Your SB 350 would normally require a puller.

The silicone is an option but as you mentioned semi unorthodox. If the "fit" of the balancer is in question there most likely is a reason. I would have no issues using the silicone as a temp repair or diagnostic tool however.
Click to expand...

Ayuh,... Great Question,.....??

I Agree,... There should be No reason at All to be Sillysealing the crankshaft.....
If it's Loose enough to Leak oil,.... It's Too Loose,+ the Reason has to be found,...
Whether the Hub, or the Crankshaft,... Something would be Very Wrong...

I pulled the harmonic balancer and replaced the main seal.
I think i am going to pull the balancer again and replace the timing cover seal for good measure. Maybe see what that does.
Click to expand...

I'm afraid I'm alittle confused by That,.......

The Seal in the timing cover IS the front Main Seal,..??..??

If you're talking about the timing cover Gasket,.... That requires pulling the motor......
 
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stupidhawk

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Re: 79' 350 merc odd oil leak

Sorry, yes I mean pulling the timing cover and water pump and replacing the timing cover gasket. Why would it require pulling the motor? There is room enough in front of the engine to sit down, can't see why the motor would need to be pulled
 
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hard-3

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Re: 79' 350 merc odd oil leak

timing cover has a lip inside of oil pan requires removal of pan to get to seal correctly. it can be done without removing oil pan but it is very prone to leakage best advice remove oilpan as service manual indicates
 
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KJSmitty

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Re: 79' 350 merc odd oil leak

stupidhawk said:
Sorry, yes I mean pulling the timing cover and water pump and replacing the timing cover gasket. Why would it require pulling the motor? There is room enough in front of the engine to sit down, can't see why the motor would need to be pulled
Click to expand...


As stated above it can be done. Just takes a little more finesse to keep the lower rubber seal/gasket sound while you coerce the cover down and onto/over the two dowels sticking out of the block etc..

Swapped many a cam that way with the engine still in the car - oil pan intact.


-BUT, if it's not leaking and the front crank/balancer seal doesn't visually look like its leaking, then I wouldn't take that on just yet.

Oil in the front of the pulley still has me thinking something is amiss with your harmonic-B. Unless you can definitely see how a seal leak is getting oil in there... :confused:


Cheers
 
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