FCSFrank

Help - Here is the story- Its a nice day today so I though I'd take the p car out for a drive. its currently 33 degrees, no wind and the sun is out and the car has been sitting about a week and a half. I'm running Doug Hillary's suggested oil of a full syn 5w-40. so I get in and start the car. The car idles for about 10 sec (seems like forever) before any oil pressure is recognized. no low oil pressure warning lights or anything during that period. ***What could be the problem? I don't want to not drive the car until spring... It doesn't do this when its warm or warmer. only on start up when its dead cold and been sitting for a bit??? it didn't do this in the summer with 20w50 dino oil..

the cars outside getting warmed up a bit right now

Any suggestions or help would be great and appreciated

Thanks
Frank
91S4

hacker-pschorr

No oil pressure is bad - assuming the gauge & sender are working. My car is running 5w50 Syntec right now. Upon startup the needle pegs almost instantly.

So, during this 10 seconds, is it at 1 bar? or even lower? If lower than 1 bar, the low pressure warning should be on (lots of flashing lights, found out the hard way on that one).

FCSFrank

no bars at all - no lights - - Help!!!!...............

Mike Frye

Probably a silly question, but did you check the dipstick? Is there enough to run?

Bill Ball

If this were REAL, you would have a good amount of engine clatter during that 10 seconds.

WallyP

The 928 has two almost independent oil pressure indications. If you have a zero gauge reading, but no warning light, there are two possibilities:
- You have zero oil pressure, and the warning light is faulty.
- You have normal oil pressure, and the gauge or sending unit is faulty.

Needless to say, door number two is a better choice...

If you truly have zero oil pressure, the valve lifters should start clickly loudly in a few seconds. Absent any noise from them, your chances get better - but ten seconds may not be long enough to be certain.

Some possible approaches include:
- Replacing the oil pressure sending unit. (Oil Pressure SENDER '89-'95 P/N 928.606.203.03) Not a good choice unless you know that it is bad - it costs $95!
- Try to hook up an oil pressure test gauge to see if you truly have low oil pressure.

There are several possibilities for low oil pressure, but first you need to find whether you have a gauge problem or low pressure.

Mike Frye

Wally and Bill,

I think you're both right. Bill said he'd hear something within 10 seconds, and I think after it was sitting for over a week, he's probably right. Frank said it was in the driveway warming up a bit though, so he would surely have an indication by now if it was a real oil problem.

On to electrical issues? Check for power at the sender?

He's not on any more, I hope we haven't lost him.

Frank?

FCSFrank

Thanks for all the input - Just got back from my drive..... During start up the last few seconds of no oil pressure I thought the car was kind of noisy. After oil pressure is seemed to quiet down??? no lifter noise though just more noisy?? it may have been me listing to closely??? I hope its just a sending unit issue - the garage is not heated so maybe it was just really cold??

Thanks
Frank
91S4

Bill Ball

Hmmm...let's say the oil pressure is taking its sweet time building up. What would be the potential causes?

A dry oil filters after an oil change will cause this kind of pressure delay and noise (so always fill the filter). But in this case the oil filter is filled, of course. I'm not sure in our oil systems where, say, a faulty check valve might be a factor. There are check valves in the head, but that would not affect pressure build-up on cold start. The pressure would be good, but you might have noisy lifters at first. That is not what is going on here, and I don't know what would delay oil pressure. Something wrong with the bypass wouldn't account for this, would it?

Anybody?

If the noise truly coincides with low pressure and clears when the pressure rises, this is potentially very bad for the wear parts. I would garage the car until this is cleared up.

Gretch

The above is the part I am most certain of.

FCSFrank

Thanks again ------ I may not start it until the temperature reaches 50 or 60 or so. well see what happens.. suppose to have a high of 18 tomorrow and cold the rest of the week - we'll see what next week brings.

also note Bill B. oil pressure does fine after sitting an hour or two - today I drove it 75 min and let it sit for about 2 hours, restarted with no pressure issues and drove home (45min)??? it didn’t do it in the summer. I've only owned the car since march 06. it was a CA car and an NV car before that??? just some history....

Thanks
Frank
91S4

dr bob

The check valves leaking in the heads would be my instant thinking. They are there to prevent leak-down of the oil in all the pressure galleys in the head, so that exactly this symptom doesn't happen. When those valves leak back, the pump has to fill the galleys up to the heads before oil pressure comes up. No leaks, and the system is already packed and you quickly see pressure right after engine start.

Solutions: Fix the check valves, or drive the car more so there's always oil in the heads.

The choice of 5W-30 may be contributing. The same 5W cold-flow characteristics help you on start-up, hurt you on leak-down once the engine is stopped.


My two sense...

Bill Ball

I didn't know this was true. I assumed that as long as the pump, pan and filter is full, the pressure would be good as it is measured at the filter outlet, I believe. Thanks, dr. bob!

ZEUS+

Do you have a quality oil filter installed ? If it is the check valves, CRC makes a good product for cleaning, unless extremely varnished and gummed up. Then mechanical repairs are necessary.

danglerb

Sender or check valve is my bet. Dunno how it is on a 928, but on my Mustang when the mechanic failed to use the filter I told them to (Motorcraft) I had some startup engine noise I guess from lifters, and I am sure it was related to the oil filters poor quality check valve. Lifter noise was within a second or two of starting the motor and didn't last more than a couple seconds.

Oil is typically 30 wt base stock with goop added for high and low temperature stability, its not like its "not" going through the pump because its this or that when its barely freezing outside.