Poor oil pressure or bad gauge?

[Blk95993]

I have a 79 SC that has an oil pressure problem-I think?! Car gets around 3 bars on cold start and then drops once the engine get to normal temps. I drove the car for 20 minutes in a mix of back roads, hwy, and traffic yesterday evening. The temp seemed to be increasing, but just above the 1/2 mark. Does not go in the red. AS the temp increased, the pressure decreased. Ran about 2 bars under load once temp got above 1/2 mark. Just put in 20w50 before I drove the car. It was about 80 degrees in Atlanta last night. Car does not smoke. Questions for the BB-

1.) If the car quickly overheated and oil pressure is a direct function of cooling, would that limit the issue to the oil pump. Conversely, if the car kept normal temps and the oil circulation is a direct function of cooling, would that limit the issue to the guage?

2.) Is 3 bars ok for a car w/ 200k miles?

3.) Maybe just needs a valve adj? Or does this have anything to do with it?

4.) Just put fresh oil in. If a drain a little, will the color give me any indication or information? To explain furthur-clean oil in and if it comes out black with only 20 minutes of engine time-maybe a big problem?

5.) Should I not drive the car anymore and take it to a prof before I do major damage-assuming that the guage is ok.

I have searched the bb and posted on my project thread, but can't seem to find a similar situation. Thanks for the help again. Hope everyone is having a great weekend. Curry

[moneymanager]

Oil pressure is always high when the motor is cold, declining as it warms. Looking at the oil color and/or adjusting the valves won't do much. And just knowing you have 3 bars of pressure tells us very little. We also need to know when this occurs. At operating temperature, the pressure should read 10-15lbs or 2/3--1 bar per 1000 rpm. So if you have 2.5-4 bar at 4000 rpm on a warm motor, you're fine. If it's at the low end of that scale, you might replace the sender or swap with someone else to see if yours is reading correctly before considering anything else. SC's are very tough; your motor is probably just fine. .

[Blk95993]

I purchased a new sender and can't get the old one off. It idles around 1-2 bars. Under load it does not move more than 3. I just let it sit for 30 min and the engine temp came up to the 1/2 and the bar stayed around 1-2. With a load it did not move above 3.

Are the any other indicators outside of a gauge that would tell me I am getting bad oil pressure?

What could happen if I drive the car with bad oil pressure??

On a side note, the engine pulls like no bodies business....tons of power...

[Walter_Middie]

Sounds like there is still some confusion here. Looking at it in a basic way, oil pressure is a function of temp and RPM, as said above. If you had 1-2 bars at idle, you also need to say if the engine was cold or warm (although this sounds just fine either way). What temp and RPM is it at when you get 3 bars?

When warm, you should get about 1 bar at idle, and on the freeway at 3000 RPM you should be getting about 2 bars or more. It can vary widely from there and still be OK - most engines with a lot of miles will have very little oil pressure at idle when warm, and again on the low end when the RPMs come up. This is still OK. When the red dash light comes on when the RPMs are up, that's bad. Sounds like you are OK.

[livi]

Sounds like your oil pressure is slightly on the low side, albeit not necessarily too low. It is good to see 2 bars on a hot idling engine and preferably 4-5 at high loads. Pressure is not the most important factor. Flow is. You might be perfectly OK.

What is your oil consumption ? More than 1 quart / 500 miles ?

[moneymanager]

If it pulls well and there aren't huge clouds of smoke coming out the back, it's probably a great motor. Get the sender changed at your shop. Idling at 1-2 bars is fine for a warm motor. You really want to get on a freeway with a warm car and take a look at pressure at 3 or 4k. If it meets the 2/3 -- 1 bar PER 1000 rpm rule, it's fine. Are you saying you see 5 bar? That's great.
If the oil pressure is old enough, you could kill the motor by driving it. Yours sounds better than normal.

[moneymanager]

that should be "if the oil pressure is LOW enough...." Don't know what I was thinking.

[Blk95993]

I dont get above 3 bars when warm on the hwy. Never have been able to get over that point. As far as oil consumption, the car has been a project and I have not been able to drive it enough in order to determine the oil consumption.

Is it safe to assume that if the engine is not overheating that I am getting good circulation-even with low bars? Or is that a dangerous way of looking at it?

[KNS]

It sounds like you're fine. On my '80, I'll get about 4 bar on start up and then never see it that high again. I'll criuse right around 3000-3500 RPM on the highway and see about 3 bar or little lower. On a long, hot drive it might get to around 2.5 bar but since I've added a Carrera cooler that has improved. I changed out the sender a while back and it made no difference.

[moneymanager]

Do replace the sender; it may give a reassuring result. But your car sounds pretty much like other Porsches of its age. I'd start worrying about something else.

[Formerly Steve Wilkinson]

I'm reading the poster's original post to say that his _temperature_ gauge was at 3/4 up the gauge. Am I missing something? If so, that's way too hot.

Maybe he means 1/4 of the way up the gauge...

[Blk95993]

Edit-It sits around 1/2. Does not go in the red. Just drove it again for about 15 min with traffic and it stayed just above 1/2.

[Early_S_Man]

Remove the pressure sender block BEFORE attempting to remove the sender. The block is retained by the hollow bolt that feeds the cam tower oil line.

Put pressure sender block in a vise with soft jaw inserts, and use appropriate socket on pressure sender.

[Dave (Oz)]

Originally Posted by Blk95993

I purchased a new sender and can't get the old one off. It idles around 1-2 bars. Under load it does not move more than 3. I just let it sit for 30 min and the engine temp came up to the 1/2 and the bar stayed around 1-2. With a load it did not move above 3.

Are the any other indicators outside of a gauge that would tell me I am getting bad oil pressure?

What could happen if I drive the car with bad oil pressure??

On a side note, the engine pulls like no bodies business....tons of power...

Even 1 bar is pretty normal for an SC at idle once warm. I was a little worried when I got mine because it goes even below that (although goes well above 4 under load) but my mechanic tells me its normal as does the owners manual. In fact the owvers manual even suggests that the warning light can come on at idle as long as it goes away under load. As others have said, SCs are tough motors so yours is probably fine.

[Dave (Oz)]

Originally Posted by Blk95993

Edit-It sits around 1/2. Does not go in the red. Just drove it again for about 15 min with traffic and it stayed just above 1/2.

That does sound a bit warm. It shouldn't go much above the upper end of the little square bracket marker on the bottom of the gauge in normal use.

[Gunter]

Dave said it; just above 1/2 is too hot.
Reasons for higher temps can be ignition timing, clogged fins on the cylinders, front oil cooler blocked. (Don't use a full bra)
Thermostat for front cooler faulty?
Feel the lines for the front cooler. Are they hot?
Check the timing. 5 deg at idle.
Fan belt slipping?
Keep the fan blades clean.