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Old 06-15-2013, 09:49 AM
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Bad oil leak/crankcase pressure on 91 Prostar? Advice needed

So I finally got on the water for the first time since I bought my boat a month ago. Had some electrical and overheating issues that I think have been worked through. After riding for about 20 minutes I stopped to check for any fluid leaks as I replaced several water hoses and all the fuel lines. No issues but now the bilge is filled with oil. I would say probably about a quart.

It appears if the oil is limited to the right side (fuel pump side) of the engine and it looks as if it is mainly coming from high--valve cover area, front and back. I tightened the valve cover gaskets and went back to the landing; nuts were somewhat tight, but needed tightening down. I would not have thought the valve covers would have leaked that much oil in that amount of time.

The oil fill valve cover has a flat plastic push in cover that I replaced as it had no cap when I purchased the boat. Hopefully this is causing my issue. Running the engine in the yard has never shown any evidence of an oil leak. What type of oil fill cap/breather should the valve cover have? Not sure what would be the correct oil fill cap.

I plan on trying to replace the valve cover gaskets and clean the bilge somehow this morning. Any other suggestions as to where the oil could be coming from, block plugs to check, etc.?

Thanks,

Ansley
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Old 06-15-2013, 10:03 AM
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93ProStar205 93ProStar205 is offline
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Oil leaks suck to find, but given the rate it's leaking this should be an easy one. Clean up the motor/bilge with Simple Green or similar and have someone run it while you look for the source(s) with the motor box up and a good flashlight. Could definitely be the valve cover gaskets, particularly if the crankcase is overfilled. My 93 205 used to pool it in the intake valley between the runners due to a leaky valve cover. Would also check rear main seal area between the motor and trans.
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Old 06-15-2013, 10:27 AM
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SWGA Boater SWGA Boater is offline
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Quote:
Originally Posted by 93ProStar205 View Post
Oil leaks suck to find, but given the rate it's leaking this should be an easy one. Clean up the motor/bilge with Simple Green or similar and have someone run it while you look for the source(s) with the motor box up and a good flashlight. Could definitely be the valve cover gaskets, particularly if the crankcase is overfilled. My 93 205 used to pool it in the intake valley between the runners due to a leaky valve cover. Would also check rear main seal area between the motor and trans.
This is one place I noticed oil pooling which lead me to think valve covers.

I looked at alot of pictures on the web and its seems most Ford engine have a breathable oil fill cap. I will replace the nonbreathable cap with a breathable cap also.

Thanks all for the quick suggestions!
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Old 06-15-2013, 10:30 AM
Cloaked Cloaked is offline
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Originally Posted by SWGA Boater View Post
I looked at alot of pictures on the web and its seems most Ford engine have a breathable oil fill cap. I will replace the nonbreathable cap with a breathable cap also.

Thanks all for the quick suggestions!
I have had engines with both caps. Can't say that I know the difference as long as there is one there......works for me....best I recall. my last several have been solid caps....

You can check your PC valve by shaking it. If it rattles, it's (theoretically) good.

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Old 06-15-2013, 10:08 AM
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Do you have a functioning PCV valve on one of the valve covers?
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Old 06-15-2013, 10:11 AM
Cloaked Cloaked is offline
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Sometimes, tightening (over tight) can disfigure the valve cover slightly, allowing for more of a leak than less.

Don't overlook the possibility of a main seal (rear is common).

Oil can come out of the filler cap (or absence of one) but nothing to the extent of a massive oil leak per se.... You'd see more of a mess around that area without the cap...

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Quote:
Originally Posted by Thrall View Post
..Some of you give a whole new meaning to the phrase "another @sshole with a Mastercraft."

RE: Thrall, Welcome to the club....
NEW SKINS in TN... Leading Edge Marine Interior

feedback on a TN company: http://www.mastercraft.com/teamtalk/...ad.php?t=58767

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Old 06-15-2013, 10:23 AM
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Originally Posted by Table Rocker View Post
Do you have a functioning PCV valve on one of the valve covers?
Yes the left cover has a PCV valve. I will check or replace as they are inexpensive.
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Old 06-15-2013, 11:16 AM
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JimN JimN is offline
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Originally Posted by SWGA Boater View Post
Yes the left cover has a PCV valve. I will check or replace as they are inexpensive.
Pull the PCV and shake it- if it rattles, don't bother replacing it.

When you changed the oil and filter, did you crank the new filter on like it was a contest? Only tighten it 3/4 to 1 full turn after the rubber gasket makes contact with the block.

What about the hose for draining the oil- is it hanging at the front of the engine, next to the pulleys? I have seen several that wore through because they moved during acceleration and made contact with a pulley.

Remove the starter and use a small diameter flashlight with an inspection mirror to look at the flywheel- if it's covered with oil (it will have a sheen that shouldn't be on it) and looks like it's wet, you may have a bad rear main seal. Not the end of the World, but you don't want to run it this way.

What does the transmission use- Dexron or 20W? Make sure of where the leak exists- did you check the fluid levels after you saw the oil? If not, do it immediately.
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Old 06-17-2013, 12:01 AM
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Still leaking....:no face:

Replaced valve cover gasket this afternoon, sprayed down the block with brake cleaner, cleaned the bilge and went for a short test run. After a 10 minute run, right front of engine, hoses, etc. is covered in oil. I do not think it is the valve cover gasket, as I can see no leak under the gasket. There seems to be three things that it could be: oil pressure switch piping, oil filter, or dipstick tube. Also made sure oil level was ok. I'm guessing I lost about 1/2 quart as this what it took to bring the level back to the safe zone.

I bought another PVC valve and replaced my solid oil fill cap with a breathable cap also today. I plan on taking the pressure switch plumbing off and checking it and also replacing the oil filter, as well as trying to tighten the dip stick tube.

After I do this I may make a run with the dog box off to see if I can see where the leak is coming from. It is weird that at the dock with the fast idle around 2000 rpms I cannot see a leak.

Hope to get to work on this later in the week. I'll update the thread afterwards.

Thanks for all the suggestions!

Last edited by SWGA Boater; 06-17-2013 at 12:40 AM.
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Old 06-17-2013, 12:52 AM
john jones john jones is offline
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I just chased down a oil leak on my 93 maristar.

Last edited by john jones; 02-03-2014 at 11:13 PM.
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