vitesse
Active member
Earlier in the summer,I posted on the forum a query about a whine which persisted seemingly related to engine temperature,despite having fitted a new water pump with new belts,then adding new adjuster pulleys.
During the course of this ,I stripped down & rebuilt the front end 3 times-thankfully I had made a crankshaft lock ,a pulley & adjuster spanner .
In the end mainly because my wife wanted it sorted because she didn't want to continue driving it in case the engine failed despite it always showing 5 bar oil pressure when hot, I passed on the mystery to John at Unit 11 hoping his much greater experience would solve the problem.
It was a puzzle for him ,too & after the 1st attempt which included retensioning the belts & altering the the tensioning pulleys ,he thought it was solved-but arriving home after picking the car up,the noise was still evident.
Having had the car back this last week,we thought it could be a balance shaft bearing,but running it without the balance belt-still the noise-then thought it could be the edge of the cambelt against the new pulley so more clearance was provided by removing a small amount off the stud bolt mounting-still no result.
Finally John traced the whine to the oil cooler housing,which was removed including the Oil Pressure Relief Valve (OPRV).
This 924S was 1st registered 1.8.1986 but when stripped down ,we found that the later oil cooler housing was fitted & it was John's opinion that this had been removed at some time in the car's life-but not whilst we have owned it which is since late June 1991 at 25,354 miles.
The next revelation was that the car still had fitted the original design OPRV which is a 3 part valve comprising a special nut,long spring & the cylindrical valve which seats directly onto a seat machined into the aluminium block.
By now ,I was well into Clarkes Garage where it is mainly well explained that there were failures with the early 3 part valve but doesn't explain precisely what although it becomes clear that the new housing was generally fitted along with a new design OPRV from 1987.
However ,initially a new design 1 piece self contained valve was made available as a retrofit for 924S & 944 models which could just be fitted in place of the 3 piece unit.
However a further revelation to us was that Porsche fitted a thin walled steel sleeve into the block within which the 3 piece valve cylinder runs ( to avoid pickup/wear in the aluminium block,presumably) & this sleeve in my engine was totally loose,to the extent that it's seating in the block was partially damaged.
We presume that this was the problem in the early pre-1986 engines that caused Porsche to bring out the retrofit 1 piece valve which screws into the same bore ,is spring loaded to ensure it seats against the bottom of the block bore,being a blind fit so impossible to shim,& has within it a self contained spring loaded relief valve which is not dependant on seating in the block although the OPRV housing itself does seal onto the existing bore seating with an O-ring.
Our conclusion on seeing this situation was that must be the cause of the whine ,caused by the sleeve oscillating backwards & forwards & of course also temperature related.
So new valve it had to be (£pain)-the sleeve has to be position & acts as a locator,so was glued back in with the appropriate Loktite ref & everything reassembled.
Result--noise eliminated--oil pressure up at 5bar when really hot .
The whole problem is that the whine seems rotationally related & therefore one tends to concentrate on the belts,pulleys,water pump!" doh.
Also neither I nor John have ever come across the fact that the these valves were an early problem with the new 8v Porsche engine .Since then have come across a blog about it posted from USA.
So if you have a mystery "whine" hope this might be of assistance.
During the course of this ,I stripped down & rebuilt the front end 3 times-thankfully I had made a crankshaft lock ,a pulley & adjuster spanner .
In the end mainly because my wife wanted it sorted because she didn't want to continue driving it in case the engine failed despite it always showing 5 bar oil pressure when hot, I passed on the mystery to John at Unit 11 hoping his much greater experience would solve the problem.
It was a puzzle for him ,too & after the 1st attempt which included retensioning the belts & altering the the tensioning pulleys ,he thought it was solved-but arriving home after picking the car up,the noise was still evident.
Having had the car back this last week,we thought it could be a balance shaft bearing,but running it without the balance belt-still the noise-then thought it could be the edge of the cambelt against the new pulley so more clearance was provided by removing a small amount off the stud bolt mounting-still no result.
Finally John traced the whine to the oil cooler housing,which was removed including the Oil Pressure Relief Valve (OPRV).
This 924S was 1st registered 1.8.1986 but when stripped down ,we found that the later oil cooler housing was fitted & it was John's opinion that this had been removed at some time in the car's life-but not whilst we have owned it which is since late June 1991 at 25,354 miles.
The next revelation was that the car still had fitted the original design OPRV which is a 3 part valve comprising a special nut,long spring & the cylindrical valve which seats directly onto a seat machined into the aluminium block.
By now ,I was well into Clarkes Garage where it is mainly well explained that there were failures with the early 3 part valve but doesn't explain precisely what although it becomes clear that the new housing was generally fitted along with a new design OPRV from 1987.
However ,initially a new design 1 piece self contained valve was made available as a retrofit for 924S & 944 models which could just be fitted in place of the 3 piece unit.
However a further revelation to us was that Porsche fitted a thin walled steel sleeve into the block within which the 3 piece valve cylinder runs ( to avoid pickup/wear in the aluminium block,presumably) & this sleeve in my engine was totally loose,to the extent that it's seating in the block was partially damaged.
We presume that this was the problem in the early pre-1986 engines that caused Porsche to bring out the retrofit 1 piece valve which screws into the same bore ,is spring loaded to ensure it seats against the bottom of the block bore,being a blind fit so impossible to shim,& has within it a self contained spring loaded relief valve which is not dependant on seating in the block although the OPRV housing itself does seal onto the existing bore seating with an O-ring.
Our conclusion on seeing this situation was that must be the cause of the whine ,caused by the sleeve oscillating backwards & forwards & of course also temperature related.
So new valve it had to be (£pain)-the sleeve has to be position & acts as a locator,so was glued back in with the appropriate Loktite ref & everything reassembled.
Result--noise eliminated--oil pressure up at 5bar when really hot .
The whole problem is that the whine seems rotationally related & therefore one tends to concentrate on the belts,pulleys,water pump!" doh.
Also neither I nor John have ever come across the fact that the these valves were an early problem with the new 8v Porsche engine .Since then have come across a blog about it posted from USA.
So if you have a mystery "whine" hope this might be of assistance.
