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Catastrophe! Oil pressure dropped to zero at highway speed.
Halfway home from Sharks in the Badlands, 9 more hours to go. Everything going well, A/C blowing cold, car running cool, etc. At 80mph, Central warning starts flashing, oil pressure gauge drops zero, engine starts clacking. I pulled over quickly and shut it down. Oil was 1 qt low, but I have been burning/losing that every 300 miles or so on this trip. On the way up, car got 2 qts or so low one time and the engine got noisy. It eventually went away, mostly, and I kept a close eye on the oil level. It has always been a noisy engine. I pulled the fuel pump fuse and cranked it a little after it had sat for 30 minutes, still zero pressure. We were sitting on the side of the interstate, so I had AAA get us a flatbed to the next exit. Once off the flatbed, I cranked it again and I had oil pressure so I started it up and had 5 bar, but engine is very clackety sounding. I am going to have it transported the rest of the way home to Nashville.
So, once I feel like digging in, any suggestions on what to investigate? Oil pickup, pump, is there a relief valve or the like somewhere in these engines?
Brett, there is an oil check valve in the heads.
I think I might check the pins in the cams at the back of the engine that will make you lose oil pressure if they haven't been replaced previously. You will have to remove your cam covers to check them.
If they are still functional, I'd go for the oil pickup seal.
Good luck
Last edited by soontobered84; 07-21-2020 at 01:01 PM.
Reason: missing word "lose"
There are a couple of pressure relief valves. Front drivers side of the block, I think. Also, if you search you can find flow diagrams that show the pump, uptake, relief valves, etc. I'm worried about your clanking noise, though. Too loud to be lifters?
The safey valve lifts at 8 barg as I understand. The oil sender maxxes out at 5 barg so that is the highest pressure one can see on the display.
Oil pressure is lost immediately if the level drops too much. You have a supercharged engine as I recall- I did read some details about your motor some time ago but I cannot remember such. I have no idea what breather design you are using but if the cam tower is retaining more oil than it should you logically could get a low pressure situation if the sump is too low and especially if superimposed on top of an already low oil level to start with. Stop the car to check oil level and some oil then drops out of the cam gallery and gives the impression the oil level is higher than it was when running. Whether such has happened remains to be seen.
Obvious things to do are compression test and leak down test. If oil pressure appears normal then the mains/big ends have possibly survived as they do not last long with no oil pressure [as in no more than a few seconds I would think]. If you were going through oil at 300 miles per quart then something was wrong to start with -be it the engine or the breather [or both].
^^ The oil control pins are only in the 87+ engines.
The oil pumps rarely fail, especially intermittently. It would be an all or nothing with that.
The valves above the oil filter can go bad if a spring snaps or gets weak. Similar issue in the 944 with its oil control valve in the oil cooler.
Does this only happen with a hot engine or while it is cold as well?
S4 engine IIRC
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
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Prudence dictates a crank bearings inspection at minimum.
Your description of having good pressure after the car sat a little is consistent with low sump level, especially if you were "at speed" with load; Your vent and breather system governs combustion gas flows between the crankcase and the heads. If not managed well, oil wont drop back from the heads due to high gas flow in the return passages. The problem may be more acute in your compressor engine that might have even more piston blow-by. You should see a low oil level alert for this before you see the oil pressure warning. You didn't mention that in your posts here.
Isn't the most likely problem due to bad oil pressure sender or wiring? That's the type of intermittent problem that comes and goes.
Separately, one can have noisy lifters if they are worn out, defective, gunked up with sludge, head check valve is defective, or if there's an oil flow problem to the heads.
An 5.0L S4 engine with S4 heads would not have oil drain drain problems when leisurely cruising at 80 mph. 160 mph maybe, but not 80 mph. For the sump to run dry, there would have to be some sort of serious mismatch issue in the drain channels between the S3 heads and S4 block. Even if the displacement is larger (what's the bore and stroke there?), I'm still skeptical.
With supercharger and stroker, how much power does this car/engine produce, by the way? I'm curious.
Certainly the gauge can be wrong, but with noisy lifters at the same time, that means something "real" occurred.
I'd start with the oil pick-up.
Pull the pan and look at the pick-up. I've seen pickups broken, pickups that had the hardware come loose, pick-ups completely blocked with sludge, and even pickups with a shop towel plugging them up.
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Certainly the gauge can be wrong, but with noisy lifters at the same time, that means something "real" occurred.
I'd start with the oil pick-up.
Pull the pan and look at the pick-up. I've seen pickups broken, pickups that had the hardware come loose, pick-ups completely blocked with sludge, and even pickups with a shop towel plugging them up.
Pickup broken or loose at the top could explain the intermittent total loss of oil pressure at mid range rpm, if the pump suddenly starts compressing air instead of pushing oil.
Pickup broken or loose at the top could explain the intermittent total loss of oil pressure at mid range rpm, if the pump suddenly starts compressing air instead of pushing oil.
Even tiny leaks in the pickup or the pickup seal will keep oil from being drawn from the pan.
I drained the oil today and cut open the oil filter. First, I noticed the oil was thick and "goopy". Granted, it was cold oil, but shouldn't be this thick. Also, my oil cooler is external to the radiator, so I don't think it's mixing with any coolant. https://photos.google.com/photo/AF1Q...eOwyWxdMaAuKeG
Second, the oil has a lot of fine specs of metal. I see copper color on some larger specks, but can't tell if the rest is silver, copper, or a mixture.
The engine did have as much oil pressure as the goopy oil would allow. I only ran it for 10-15 seconds, but it had 4 bar. The engine was still noisy, "clackity". I didn't want to run it long enough to pinpoint the exact location with my stethoscope.
Next steps, drop the oil pan and inspect what's in there and inspect the crank and bearings?
Pull the cam covers and inspect there?
Run some ATF through it to clean out the oil passages and oil cooler and such?
Or ????
I drained the oil today and cut open the oil filter. First, I noticed the oil was thick and "goopy". Granted, it was cold oil, but shouldn't be this thick. Also, my oil cooler is external to the radiator, so I don't think it's mixing with any coolant. https://photos.google.com/photo/AF1Q...eOwyWxdMaAuKeG
Second, the oil has a lot of fine specs of metal. I see copper color on some larger specks, but can't tell if the rest is silver, copper, or a mixture.
The engine did have as much oil pressure as the goopy oil would allow. I only ran it for 10-15 seconds, but it had 4 bar. The engine was still noisy, "clackity". I didn't want to run it long enough to pinpoint the exact location with my stethoscope.
Next steps, drop the oil pan and inspect what's in there and inspect the crank and bearings?
Pull the cam covers and inspect there?
Run some ATF through it to clean out the oil passages and oil cooler and such?
Or ????
07-20-2020, 10:27 PM
Catastrophe! Oil pressure dropped to zero at highway speed.
George Layton March 2014
