Waterguy

Slight clarification. Porsche Technical Bulletin: "Early productioon 1987 engines from production date July 1986 received pressure relief valve PN 944 107 035 01. This [one-piece] valve was not anti-corrosion treated. The engine numbers are as follows:

43 H 01920 924S/944 Manual transmission
43 H 60385 924S/944 Automatic transmission
42 H 00140 944S
45 H 00086 944 Turbo

1987 engines from production date October 1986, the oil pressure relief valve PN 944 107 035 01 received an anti-corrosion treatment. Installation in production began with the following engine numbers:

43 H 05373 924S/944 Manual transmission
43 H 61268 924S/944 Automatic transmission
42 H 02847 944S
45 H 01256 944 Turbo

When repairs are made to engines which fall between the above mentioned engine numbers, the oil pressure relief valve must be replaced with pressure relief valve PN 944 107 035 01. "

Over 8,000 early build 1987 944s received an defective one-piece OPRV which will corrode. If your engine was made during this period, this could be the cause of your problems. Some people wet sand the rust off the valve, otherwise replace it with a new one.