924Board.org

[ronined]

Hello All,

I have noticed recently that when I start my car after a long period of rest I have no oil pressure (according to the gauge), the low oil pressure light is illuminated and I hear some valve clack. After 30s to a minute or so O.P. shoots up and clack goes away. What could be causing this?

TIA

Ed
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'87 924S

[bcblase]

You should only have a few seconds of low oil pressure upon start up - maybe 2-3 seconds at the most. I would suspect your oil pump may not be developing pressure.

Usually these cars read high oil pressure until the car heats up. You might want to check the oil pressure sender unit also - it's right under the oil filter.

The clacking sound is the engine running with very little oil.

Brad
_________________
1987 Porsche 924S - track toy
1986 Mercedes 190E 2.3-16v - autocross
2007 F-150 5.4L Lariat Supercrew - tow beast
1994 Volvo 850 Race Wagon - 24 Hours of Lemons Car
2001 BMW 325xi - daily driver

[ronined]

I was curious about the oil pump. But I seem to run proper pressures once the system pressurizes. I read between 4 and 5 bar at cold idle, around 2 at hot idle, and between 4 and 5 cruising down the highway.

I initially suspected that the o.p. sending unit might be at fault because I know one of the studs to which one of the wires attaches has a portion of the thread stripped and so the connection is not as tight as I would like. However, the valve clack leads me to think that the valves are not getting the proper oil supply, which could be due to a lack of pressure, and, therefore, that the sending unit at least is doing its job.

Could a blockage of an oil passageway cause this problem? If so, what could block it? Could it be a faulty bypass valve in the oil filter? Or is this pointing toward the oil pump? BTW, I run Valvoline VR-1 20W-50 oil and Mahle OC142 filters.
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'87 924S

[Rasta Monsta]

Aieeee! 30 seconds to a minute with lifter noise? On cold start, my 2.5 pegs at 5 bar before it even catches.

Cracked oil pickup? Sticking OPRV? Better find out. If this is condition not corrected, your motor is toast.
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Toofah King Bad

• WeiBe (1987 924S 2.5t) - 931 S3

[bcblase]

[gohim]

Most likely a problem with the OPRV (oil pressure relief valve). Have you had the oil cooler housing off before?

Many people do not have or use the OPRV passage alignment tool when the oil cooler is removed, and the result is a hanging OPRV and low or non-existent oil pressure. Most 924S also came from Porsche with a three-piece OPRV, which Porsche has recommended removing and replacing with a newer one-piece chrome plated design for many years now.

Whatever you do, don't buy a used three piece (or even one piece OPRV from a failed 2.5L engine. There are two different length OPRVs and you need to get a new replacement that is of the same size as the one that your car came from Porsche with.

New OPRVs were around $400, last time I checked.

I would start by getting an oil cooler seal kit, AND the correct tool (there are two). Remove the oil cooler housing, and looking to see which OPRV you have. If you find a old three piece OPRV, shop for the best price you can find from a RELIABLE SOURCE for a new one-piece OPRV of the correct size/type. Reassemble using the tool for alignment, and follow the Porsche Technical Bulletin Instructions for assemble and measure the oil cooler housing stacks to set them the correct height.

The oil cooler housing was also supperceeded, and Porsche recommends only using the new design part. It's okay to use an undamaged used oil cooler housing of the new design as an alternative to buying a new oil cooler housing from Porsche, or reusing an old design oil cooler housing. There's a Porsche Technical Bulletin with photos that shows the difference between the old design and the new design.

[Rasta Monsta]

Gohim, was the 951 housing superceded as well? Bought a used one a while back. . .
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Toofah King Bad

• WeiBe (1987 924S 2.5t) - 931 S3

[John_AZ]

Rasta,
These may be the tech pages gohim refers too.

http://www.944online.com/pdf/oilcoolertech.pdf

GL
John

[bcblase]

Noticed my oil pressure light staying on longer than normal upon startup, and a little bit of lifter noise - but only for a couple of seconds.
Made go back and re-read this thread...
Not sure if it's just the hot weather, or something is starting to go south... engine runs fine otherwise.

I ran it at the local autocross for the first time in over a year.
Here's a launch video:

http://s222.photobucket.com/albums/dd218/newsvx/Autocross%20July%2011%202010/?action=view&current=july112010031.mp4

Track weekend coming up on July 24-25...
_________________
1987 Porsche 924S - track toy
1986 Mercedes 190E 2.3-16v - autocross
2007 F-150 5.4L Lariat Supercrew - tow beast
1994 Volvo 850 Race Wagon - 24 Hours of Lemons Car
2001 BMW 325xi - daily driver

[ronined]

I decided to try the cheapest potential solution first, so I drained the oil and ran some Gunk engine flush in the engine. I drained it, installed a new filter and new oil. I have not had the "low oil pressure on start up" problem since. However, I have only started the car about 5 times due to a hectic work schedule, so I don't know yet if it is a valid long-term solution.
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'87 924S

[Rasta Monsta]

John,

You rock, as per usual.


rasta
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Toofah King Bad

• WeiBe (1987 924S 2.5t) - 931 S3

[Paul]

Another thing to check is torque on the front pulley bolt.
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.