Oil presure guage

Hi, I have a 1999 C. Being new to the world of 911s, my other car being a Lotus I need to call on your knowledge. When I turn on the ignition the oil pressure gauge move round to max. It stays there even after start up and even when hot. My first reaction is electrical problems with either the wiring or the sender unit. Any suggestions would be greatly appreciated. Thanks Steve.

i've also just moved from lotus to here, not big in porsche yet, but suspect its the sender unit, if you can locate it, try unplugging and re connect, if no joy, replace.

Steve! & Bob!! Sender units are a common problem, but they usually go the other way - ie read zero, not max. Check the two wires on top of the sender are connected properly. You can find it on the top of the cylinder head, about half way back on the drivers side of the engine compartment. It points vertically upwards, and is tucked behind some pipes.

I was reading on renntech.org just today that someone had exactly the problem and that it turned out the oil pressure sender wires were connected the wrong way around. When swapped over the problem immediately disappeared. Probablgy not your solution, but you never know! Greg

Thanks for the feedback guys. Will have a look at the weekend if it stops snowing. Cheers Steve

Hi Richard, Once the snow cleared and in between the rain I had a quick look for the sender unit. I know there is not much room to work but could not locate even by feel. Would you have any pics to help as I do not want to start pulling things off while working blind. Cheers Steve

This is the only picture I have. It is buried fairly well back on the right hand side. Look for the convoluted tube and you should find it underneath it.

Richard, Many thanks that is a real help. Will let you know how I get on. Happy New Year Steve.

Richard, Your pic was very useful. I found the unit after a bit of pipe moving. It looks and feel like it is the original one. The spade conectors are different sizes so would not be able to reverse them. Well on my car anyway. As a test I pulled off one wire and started the car. This gave the same result, max oil presure. Therefore looks like the unit has failed. The car is due a service at the end of this month so will add a new one to the "to do" list. All I need now is the name of a good independent 911 garage in the south east Essex area. Many thanks Steve

The only ones in Essex I have heard good things about are HP Motorsports in Hainault, and Autostrasse in Coggeshall.

I can recommend HP Motorsport. Have used them for last 3 years and the guys are very helpful. Shahid

Hi Steve. Probably a silly question but you say that the pressure is reading high even when hot; are you sure that the oil has had time to reach it's optimum temp when you're reading the pressure? I only ask this as I know that mine takes some time to reach temp even in the summer and as such the oil pressure reads as high - until the viscosity of the oil reduces. If your water temp is reading around 90 for over ten mins or so then I think that you can consider the oil to be up to working temp. It's freezing at the moment so you might find that the oil takes ages to reach temp and for the pressure to then hover around 2.5 bar at idle speed. Adrian.

Thanks for the suggestion re servicing. Will give them a call soon. Adrian, Thanks for your comments. The gauge shows max when the Ign is on but without the engine running. So I am thinking the sender unit has failed and making the gauge show max all the time. I had a similar problem on my Lotus some years ago but would only show zero. That car is a bit more "diy friendly" so could sort that one myself. Will let you know once it has been to the garage. Thanks again.

...but the engine is well up to running temp when you get this reading - as you said initially...?

Adrian, Maybe I was not that clear in my first message. It shows as max at all times hot or cold, engine running or not. You turn the key and round to max the needle goes. Had a word with a few specialists and the cost of a replacement is not bad. Thanks again for your suggestions.

All, Thanks for your suggestions. In the end I used HP Motorsports in Hainault. They replaced the oil switch and carried out a minor / yearly service as per the book. I told them the car was new to me so they gave it had a good look over and found very little wrong. Just a few oil weeps which was good news. All this they did at a reasonable price. They are enthusiasts so we spent some time chatting about 911s etc. They seem to be good guys so will be using them again Also in the next unit is Design 911 UK. They gave me a good price on 4 Pirelli PZERO ROSSO N4s. Fitting the tyres while the guys at HP did the service. Just need to get a second key sorted. The current spare is broken and very warn. Not looking forward to that call to the local Porsche dealer! Steve