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  #1  
Old 11-08-2002, 09:43 AM
mallen
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Pressure Related Oil Leak??

Anybody,

'86 560SL with recent engine work (timing chain & related, oil pump sprocket & chain, front & rear main, valve cvr gaskets, oil pan gasket) driven easy & parked - no oil leak.

Take it out one week later, warm to operating temp & then run in third gear variable 3000 - 3600 RPM, 55 to 80 mph for 10 or so miles. Back to normal driving tooling around town, park & go in store @ 30 minutes. Come back out, oil leak - silver dollar size puddle. About dusk last nite, so I haven't had chance to try to ID origin yet.

Is it possible to build up pressure somewhere that would cause a leak to develop under these circumstances?

Puzzled in Ft. Worth,

M
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Old 11-08-2002, 10:24 AM
Jackd
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nope
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  #3  
Old 11-08-2002, 10:54 PM
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No
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  #4  
Old 11-09-2002, 05:22 PM
ILUVMILS's Avatar
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Why not? Simply because most gaskets and seals are not subject to system pressure. The valve cover gaskets, front and rear crankshaft seals, and oil pan, are subject to CRANKCASE pressure. The oil filter seal, pressure sending switch, and filter housing, are subject to SYSTEM pressure. I think what mallen wants to know is if a leak can develop under hard driving conditions but not when driving normally. If all systems are functioning normally, such as crankcase ventilation, then no oil should leak from anywhere. I'll bet the leak is always there, it just gets worse when driven hard. Keep us posted
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  #5  
Old 11-09-2002, 10:42 PM
Jackd
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Oil pressure is not dependant on RPM once it has reached a certain value. There is not more oil pressure at 4,500RPM than at 2,500 RPM.
In this case, the leak is not RPM related.
JackD
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  #6  
Old 11-10-2002, 10:23 PM
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There is an oil pressure releife valve. Once the engine is turning over about 1,500, there is a constant of about 3.5 bar of oil pressrue. Running an engine harder than normal should not have any bearing on leaks IIIIIIIFFFFFFFF the crankcase vent system is working properly.
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  #7  
Old 11-11-2002, 12:01 AM
Jackd
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You'll have higher oil pressure on start up with a cold engine at idle because the oil is thicker. As it warms up, oil pressure will drop down at idle because the oil is thinner.
In both cases, when it reaches a certain value (a bit over 3 bars), it will not get ant higher (cold or hot)
Basically, all parts of the engine (including head gasket) will never be subject to a higher oil pressure than what has been designed by the engine builder.
If you have leaks, I would completely forget about high oil pressure (hot or cold) as being the reason or cause for the leak.
There is a defective gasket or oil seal somewhere. Do not look further.
jackD
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  #8  
Old 11-12-2002, 09:50 AM
mallen
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In the Light of Day

Thanks for all the comments. What looked like oil at dusk became trans fluid at dawn. The trans was removed during the course of earlier work and front seal, filter, fluid replaced. Prior to this being done there was a very small leak that would yield a drop or two after extended driving - didn't expect to see it after the trans was serviced.

Old girl is back in the shop - did get the right response when I took the car back - sorry, I'll check it out ASAP, fix the problem and get you back on the road, no cost to you.

Consensus on the original question (could oil leak be pressure related) was no, IF everything was functioning properly. Crankcase vent system was highlighted as a possible culprit which made sense to me and while the car is being worked on I'll make sure that is looked at specifically even though it is a non-issue for now. You guys were great.

Many thanks.

M
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  #9  
Old 02-19-2003, 02:49 PM
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tkamiya - help!

Quote:
Originally posted by tkamiya
Then, can someone please explain to me why my oil pressure guage reads over 3 bars when oil is cold and at idle, then when oil heats up, it drops to 2.2 or so bars. THEN... when I raise the RPM, it goes back to over 3 bars?
tkamiya, I am just curious. I was searching for answers to an issue i have and found your comments i quoted here. I have exactly the same problem and I am wondering if you were able to fix it or not. My oil gauge goes above 3 bar and drops to about 2.2 once i drive for a while and at idle then goes back above 3 bar at high rpm. What did you find to be causing this. Thanks.
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