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Registered
Join Date: Oct 2001
Location: San Carlos, CA US
Posts: 5,523
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oil pressure safety piston baffle
I am working on a 87 Carrera case and have stripped the case to nothing, except that the oil pressure safety valve piston will not come out. This is the one installed in from the bottom of the engine, with a sleeve inside the spring.
I have noticed that the bore goes all the way to the top where the oil pressure switch for the idiot light is. So I removed the pressure switch, inserted a long screw driver inside and tried to tap out the piston but it will not come out. How would the piston work if it does not move? All the books I have read said that the piston should come out. Wayne's engine rebuild book even said that you "can get to the piston from the opposite side after removing the oil pressure switch." But, it seems to be wedged in there with some kind of a fixed screw. what now?
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Porsche 2005 GT3, 2006 997S with bore-scoring Exotic: Ferrari F360F1 TDF, Ferrari 328 GTS Disposable Car: BMW 530xiT, 2008 Mini Cooper S Two-wheel art: Ducati 907IE, Ducati 851 |
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01-30-2013, 01:45 PM
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Schleprock
Join Date: Sep 2000
Location: Frankfort IL USA
Posts: 16,639
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Well the one you're dealing with is not the safety valve. It's the pressure relief valve. There's a difference.
Vertical relief valve regulates the pressure and keeps it around 80 psi. If this is exceeded, oil is bypassed thru this valve and directed back into the inlet side of the pump. The horizontal safety valve dumps oil back into the sump when it is activated. If it's stuck, then that overpressure relief function is not going to occur and the first thing to get hurt would probably be the engine mounted oil cooler. That valve opens to the sump at 115-130 psi depending on which engine we're looking at. An '87 should open at 115. Check out this thread 304065 started. Good stuff in there Ultimate Oil Pressure Relief Valve Thread
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Kevin L '86 Carrera "Larry" Last edited by 304065; 02-01-2013 at 11:20 AM.. |
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02-01-2013, 07:51 AM
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Moderator
Join Date: Dec 2001
Posts: 9,569
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Kevin is right about the nomenclature.
You do NOT want to bugger the bore that the piston rides in. Did you try heating the case? Don't burn yourself, this will take a while, but the aluminum case should expand more than the steel piston, allowing the two to separate. With the plug and spring removed there should be nothing holding it in except corrosion. If it won't come out, I would send the case to Ollies and have them take it out, then inspect the bore for damage.
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'66 911 #304065 Irischgruen ‘96 993 Carrera 2 Polarsilber '81 R65 Ex-'71 911 PCA C-Stock Club Racer #806 (Sold 5/15/13) Ex-'88 Carrera (Sold 3/29/02) Ex-'91 Carrera 2 Cabriolet (Sold 8/20/04) Ex-'89 944 Turbo S (Sold 8/21/20) |
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02-01-2013, 11:19 AM
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Registered
Join Date: Oct 2001
Location: San Carlos, CA US
Posts: 5,523
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Success !
a 16 inch metal rod, 3/8 inch diameter, a 16 ounce hammer, three sharp and very firm blows, and the piston popped out. Bore is still nice and round, with two pits, but will be OK to use.
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Porsche 2005 GT3, 2006 997S with bore-scoring Exotic: Ferrari F360F1 TDF, Ferrari 328 GTS Disposable Car: BMW 530xiT, 2008 Mini Cooper S Two-wheel art: Ducati 907IE, Ducati 851 |
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02-03-2013, 07:56 PM
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