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Still leaking oil

ok...so what vacuum exists on the PCV hose? Is the correct PCV valve installed?

Have you hooked up a manometer to the vent side hose to see if it has positive or negative pressure?
 
Took valve covers off to check condition of baffles under the cover they are clean. PCV valve and vacuum hose clear and sucking strong. what next???
 
I'd do a compression check; Also, your high vacuum at low rpms goes away at heavy loads, higher rpm in gear. Blowby may be overwhelming your PCV system, developing crankcase pressure, and causing oil leaks out dipstick and other seal deficits.
 
I'd still encourage you to hook up a manometer...if the condition DD describes exists, that will be verification...and if it does, a leak down test would indicate the source(s)...
 
That engine has a PCV valve hose on one cover leading to the intake manifold and a breather hose on the other cover leading to the flame arrester. I would think that the breather hose (which has no restriction) would vent any blow by and keep the crankcase from developing any significant pressure. Plus the dip stick tube leads to a "t" fitting below the bottom of the pan, meaning there can be no venting though the dip stick tube unless all of the oil exits the engine first. So I suspect the dip stick being pushed out is a vibration issue, not a pressure issue. Still, I suppose any pressure pulses would make a small leak bigger so it can't hurt to look for blow by, but that is unlikely to be the fundamental problem. I think the dye and the black light are still the way to go to find the leak.
 
makomark said:
I'd still encourage you to hook up a manometer...if the condition DD describes exists, that will be verification...and if it does, a leak down test would indicate the source(s)...
Click to expand...
What is a manometer?
Compression test on both engines (350's) 1969 vintage. Are consistent. Taken with all plugs out. Cold. 113 to 117 pounds across the board on both engines.
 
CaboJohn said:
That engine has a PCV valve hose on one cover leading to the intake manifold and a breather hose on the other cover leading to the flame arrester. I would think that the breather hose (which has no restriction) would vent any blow by and keep the crankcase from developing any significant pressure. Plus the dip stick tube leads to a "t" fitting below the bottom of the pan, meaning there can be no venting though the dip stick tube unless all of the oil exits the engine first. So I suspect the dip stick being pushed out is a vibration issue, not a pressure issue. Still, I suppose any pressure pulses would make a small leak bigger so it can't hurt to look for blow by, but that is unlikely to be the fundamental problem. I think the dye and the black light are still the way to go to find the leak.
Click to expand...

Hose from breather/pcv valve in the valve cover to vacuum source in the manifold. Breather on oil fill tube in the front of the manifold. No hoses going to flame arrester.
 
OK, so it is an older engine without the hose from the breather going to the flame arrester (it is done in more recent engines so that if the hose releases gases [as it might at high rpm when the lack of vacuum makes the PCV useless] the fumes will still re-enter the engine to be burned). But the comment is the same. The PCV system, whether new or old, is designed to suck air, blow-by gasses, moisture, etc. out of the crankcase and there is (somewhere) a breather designed to let air in so there will be a flow though effect. If the PCV is not drawing correctly the breather would serve as a vent to allow gasses to exit the crankcase, thereby preventing it from becoming pressurized. So you should not have a crankcase pressure problem. And the dip stick tube on your engine likely is connected to the pan by a fitting on its side, but the principle is the same as the bottom connect as it still comes in below the oil level and therefore will not serve as a vent. So the dipstick being pushed out is likely a false clue to your problem. But unfortunately advice on what is not causing your leak is not a lot of help.
CaboJohn
 
SAME Problem......Purchased 1996 boat which had the 350 motor rebuilt 2 yrs. ago with 405 hrs on Engine.
Previous owner said the mechanic told him the spec sheet stated not to use gasket seal
on the chain cover, and said that was where the oil leak orginates on my engine.
Is the dye test the best way to verify this is the leak?
Tks..... Ivey
 
The dye test work well and does best with a clean engine.

Somebody is clueless with respect to the sealer...also, on the newer SBC's, GM says NOT to reuse the timing cover if removed...you may a a combination of issues...
 
..."on the newer SBC's, GM says NOT to reuse the timing cover if removed"

What's with that? They must wanna sell new parts!

Jeff
 
jclays said:
What is a manometer?
Compression test on both engines (350's) 1969 vintage. Are consistent. Taken with all plugs out. Cold. 113 to 117 pounds across the board on both engines.
Click to expand...

Isn't a manometer something that measures your manhood???
I'm sorry I know that doesn't help the problem at all, but I wondered the same thing, and thought this definition made complete sense...
And, I thought it was funny.
 
Thanks Scott...i didn't see the post with that question.

Compression test is OK per GM's revised spec...but that doesn't mean the rings aren't leaking....

A manometer is the fancy word for a pressure gauge but one that is very sensitive...usually calibrated in inches H2O vs inches Hg....a good HVAC tech will have a digital one....and they are much easier to use than the conventional Dwyer Magnahelic gauge...
 
Real head scratcher... Had time after the holidays. Cleaned the engine of any dirt/oil. Added dye to the crank case oil and ran the boat at the RPM range that causes the leak. She doesn't leak at lower RPM's. When the engine cooled I removes the water pump and pullies around the area where I suspected the leak. The dye showed the leak running down the front of the timing chain cover from the seal around the harmonic balancer. Dang...I've changed this out twice already. Since everything was apart again I once more replaced the seal, ran the boat.....Same leak, Same amount, same RPM range. Nothing changed...BTW I had also changed the harmonic balancer the last time around to give the seal a fresh surface to run on.
 
Is there a chance that it is the cover leaking in such a way that it looks like the seal? I would think that if you have replaced the seal and the balancer that might be worth looking at. Maybe a pin hole in the cover it self. Good luck.
 
I had a similar problem with one of my '90 454 Crusaders. Replaced the seal and added a sleeve to the HB but it still leaked. Bought a new cover with seal already installed and installed that being careful to follow the directions regarding sealant at the bottom edge next to the oil pan. Had the old timing mark bracket removed and welded to the new cover. No more leaks
 
jclays - went back thru the thread a few times ... when you put the new seals into the timing cover, did you install them bare or did you put locktite on the outer surface of the seal? also, were any helical grooves on the seal between its lips?
 
i agree.....oil dipstick pushed up is classic crankcase pressure. just having a pcv on one valve cover does not cut it. there must be a way for air to circulate inward from the oposite valve cover. this is always a hose that goes to spark arrestor. the easiest way to explain this.....is like trying to suck a small amount of liquid out of a coke bottle. you can't unless you have anothe air inlet. if this inlet is blocked or removed on your engine, the when it is up to speed, the compression that can bypass your rings eventually builds up pressure and starts blowing out oil, gaskets....and dipsticks.
 
makomark said:
jclays - went back thru the thread a few times ... when you put the new seals into the timing cover, did you install them bare or did you put locktite on the outer surface of the seal? also, were any helical grooves on the seal between its lips?
Click to expand...
Not Locktite but permatex black mouse type compound. Yes to the groves on the seal.
 
crankbait said:
i agree.....oil dipstick pushed up is classic crankcase pressure. just having a pcv on one valve cover does not cut it. there must be a way for air to circulate inward from the oposite valve cover. this is always a hose that goes to spark arrestor. the easiest way to explain this.....is like trying to suck a small amount of liquid out of a coke bottle. you can't unless you have anothe air inlet. if this inlet is blocked or removed on your engine, the when it is up to speed, the compression that can bypass your rings eventually builds up pressure and starts blowing out oil, gaskets....and dipsticks.
Click to expand...
Engine has always been vented this way. Started to leak about one and a half years ago. Never leaked before. Starboard engine same set up no leaks yet.
 
Unfamilar with the permatex "black mouse" compound...I learned a long time ago that those seals are best installed with a liquid sealant on the outside of the seal's case...in the case of permatex, they have a blue "thread locker" liquid that would be adequate.

The helical grooves, i an referring to are on the ID of the seal, where the crankshaft would ride...some have refered to them as ribs. if they exist, they are engine rotation sensitive. they are an older design part; the newer design is engine rotation insensitive. The older designs work just fine, they just need to be matched to the engine rotation. if you pick the wrong orientation for the grooves, the seal will ALWAYS leak.

I will check later to see if I can get a pic from a manual that is sized for posting.
 
View attachment front seal.pdf

hopefully the drawing for the "grooved" front seals is attached.

if you get the wrong seal, with the grooves "tilted" the wrong way, they will permit the oil to exit vs "pushing it back into the pan". May not be your issue but never hurts to check.

If the dipstick is still "popping out", I'd suggest getting a manometer (very low pressure gauge) and seeing how much pressure is building up in the crankcase.

good luck!

ps - the pic is from a mercruiser manual - MIE = inboard, MCM= outdrive (LH only)
 
The leaking engine rotates counter clock wise when viewed from behind. I bought the seal for that rotation at our local marine store. It had the ribs. Almost bought the seal for the opposite rotation engine because it had no groves but the literature with said the wrong rotation would cause severe oil leak. Hmmmm dont think that having zero groves would cause a leak. Almost worth a try at this point.
 
Just thought of this: Is it possible that the crank snout is running out? That would cause a leak that no seal could stop.

Jeff
 
even if you fix the oil leak.....you still have the issue of the oil dip stick being pushed up. that....is excessive crankcase pressure.
 
Might give the seal for the opposite rotation engine a try. Marina manager said he's used them before, No groves, seals better. What could it hurt. Engine already leaks. No groves should not pump out oil.
 
if you mean the "no groove" seal, it should work with either rotation...the only caveat, like crankbait said, if you have a lot of crankcase pressure building up, no seal will hold the oil back after a certain pressure develops...
 
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