Sudden Oil Pressure Drop
10-14-2009, 10:37 AM
#16
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So will running 1.5-2 qts low and driving in an enthusiastic style, will it introduce air bubbles into the oil passage as the oil inlet is uncovered in lateral load maneuvers.
Really hope they don't stop making the 'classic' oils with the push of modern blends of low ZDDP flow like water viscosity oils. Think 0W-20 was the thinnest Mobil One I saw.
Really hope they don't stop making the 'classic' oils with the push of modern blends of low ZDDP flow like water viscosity oils. Think 0W-20 was the thinnest Mobil One I saw.
10-14-2009, 10:46 AM
#17
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Maybe a situation where the engine was fully warmed up, clearances were at their widest tolerances (within reason not compared to track use) yet the oil was still chilly?
Also, if this theory is true, a hotter thermostat would warm up the engine further and may have very little effect on the oil temp which could accentuate the issue. I'm not sure, just thinking out loud.
If this theory with the oil not fully warming up holds any merit, I've been thinking about trying a 10w-40 next year. Kind of split the difference a little. It's a damn expensive oil for an experiment, but I'm thinking since my replica Cobra uses 10w-40, if I end up dumping it out of the 928, I can always re-use it in the Ford
10-14-2009, 11:41 AM
#18
Indeed, low oil level and lowered spec'd viscosity are the first avenue for corrective action. Failed oil pressure/bypass/thermostatic springs are not likely suspects for such a sudden, near catastrophic pressure failure in my opinion. From intimately personal experience, human error and wrongful action are more likely suspects. It took nearly a year for oil pressure to noticeably drop after a paper towel had been left hidden in the forward part of the oil pan, following an OPG job.
From my limited experience; the oil pressure trouble-shooting hierarchy would essentially include:
1) Resolve the possibility of a human decision related error (oil viscosity issue or previous maintenance related issue)
2) Unless a credible lead suggests an internal cause to the problem, absolve any possible external causes. That is, take the path of least resistance. Replace the oil thermo/bypass/pressure springs simultaneously. Check for any improvement. Check the oil cooler circuit for clogging.
3) Internal causes: This is the fork in the road for us that do not have 4-poster lifts. Each approach involves a different type of labor intensive work. Likely suspects may include the oil pump, a pickup tube related issue, or a failed cam bearing plug. Use intuition in deciding which avenue to initially take. Oil pressure that varies between operating stages might indicate a cam bearing plug failure. The lack of either pump noise or chewed belt teeth may suggest dropping the oil pan first. There are plenty of threads on all of these operations. Proceed thoughtfully, so as not to take every wrong action before finding the right one.
Good luck.
From my limited experience; the oil pressure trouble-shooting hierarchy would essentially include:
1) Resolve the possibility of a human decision related error (oil viscosity issue or previous maintenance related issue)
2) Unless a credible lead suggests an internal cause to the problem, absolve any possible external causes. That is, take the path of least resistance. Replace the oil thermo/bypass/pressure springs simultaneously. Check for any improvement. Check the oil cooler circuit for clogging.
3) Internal causes: This is the fork in the road for us that do not have 4-poster lifts. Each approach involves a different type of labor intensive work. Likely suspects may include the oil pump, a pickup tube related issue, or a failed cam bearing plug. Use intuition in deciding which avenue to initially take. Oil pressure that varies between operating stages might indicate a cam bearing plug failure. The lack of either pump noise or chewed belt teeth may suggest dropping the oil pan first. There are plenty of threads on all of these operations. Proceed thoughtfully, so as not to take every wrong action before finding the right one.
Good luck.
Last edited by mj1pate; 10-14-2009 at 11:58 AM.
10-14-2009, 07:11 PM
#19
By Hacker
I did do some research but I must admit I don't like the fact that RP doesn't disclose exactly what is in its oil, I did actually ring the States and the local agent for RP and they both assured me of high levels of ZDDP. I agree there is a lot of smoke and mirrors when it comes to oil and their tests, that goes for Amsoil too, I don't buy all tit for tat type oil tests that they run.
The other factor that seemed to make sense, was that RP didn't make oils to the latest standards such as SM as they said when you get to a SM oil ceratin agents are removed that are good for preventing engine wear. They didn't want to go down that path. I suppose what made me happy with RP was the gearbox oil.
I have the early LSD set to the higher lock ratio, Porsche in the service bulletins and maybe in the workshop book talk about the revised design and the fact that it is not noisy like the early designed LSD I have fitted. Well I have never heard a sound from it. Porsche also revised the clutch plates for better lubrication which I suspected was also related to noise, my car still uses the non grooved plates and as I said, not a peep.
Back to the RP engine oil, oil pressure always good almost no blowby, it is a new engine though, no noises of course and a cam with low lift i.e 0.472", RP does say to use their racing oil if the lift is over 0.525". I also did read the oil study conducted in North Carolina by a Govt authority and it didn't seem to have any holes in it.
I would be interested to hear what happened when these engines went south though. Was the oil used the right oil for the job? I.e the right viscosity. As to the very low milage engine that died. From approx 10K miles it always used Mobil 1, it was always a 40 weight oil but I can't be sure of the first number, it was not 0 though. This is when it has suspected noise tappets. That mechanic put that oil in all his Porsches I am told.
The car was involved a bad accident and the engine was removed, within 6K miles the engine was finished. Was it stuffed before it went back in, or was it ruined over the course of the 6K miles,(due maybe to the incorrect installation of the torque tube) we'll probably never know. I wasn't aware that the Mobil 1 grade he switched to had such a high level of ZDDP, I have to admit I have never investigated it as I never have heard anything good about Mobil 1. I have heard though of higher levels of ZDDP though in the 1500- 1700 range.
As to viscosity and I don't know if I should even be discussing this, as it is quite complex and I may get something wrong, but I have read an article about oil and friction in the slipper bearings. It is a fine balance between flow and pressure. The higher flow, sure more bearing cooling but there is also the ability to support the journals under load.
If I get time I will look it up and verify, but from memory there is 3 stages of lubrication in the bearings. What you want for low friction is when the bearing is surfing the boundary layer of the oil. Fully grooved bearings are bad for this. Changing viscosity will throw the balance out I believe. I wont go any further without referring to the article because it is quite complex.
Changing the oil has never been so dangerous and that new standard Hacker refers to which is GF-5 may actually be improved over the previous due to so many failures that are being seen. It looks like the authorities have seen they have gone too far, we'll see about that.
Greg
First off, I would do some more research on Royal Purple before recommended it to anyone. I was a "fan" of their oil until I recently saw the aftermath of a few high performance cars using it. I have also seen oil analysis reports from RP that shows less than stellar ZDDP numbers. This is from their street oil, not the XPR racing blend.
As for Mobil 1 and ZDDP, they are one of the few motor oil manufactures that openly shares their ZDDP levels:
http://www.mobiloil.com/USA-English/...duct_Guide.pdf
Assuming this is the same for all markets.
As for Mobil 1 and ZDDP, they are one of the few motor oil manufactures that openly shares their ZDDP levels:
http://www.mobiloil.com/USA-English/...duct_Guide.pdf
Assuming this is the same for all markets.
The other factor that seemed to make sense, was that RP didn't make oils to the latest standards such as SM as they said when you get to a SM oil ceratin agents are removed that are good for preventing engine wear. They didn't want to go down that path. I suppose what made me happy with RP was the gearbox oil.
I have the early LSD set to the higher lock ratio, Porsche in the service bulletins and maybe in the workshop book talk about the revised design and the fact that it is not noisy like the early designed LSD I have fitted. Well I have never heard a sound from it. Porsche also revised the clutch plates for better lubrication which I suspected was also related to noise, my car still uses the non grooved plates and as I said, not a peep.
Back to the RP engine oil, oil pressure always good almost no blowby, it is a new engine though, no noises of course and a cam with low lift i.e 0.472", RP does say to use their racing oil if the lift is over 0.525". I also did read the oil study conducted in North Carolina by a Govt authority and it didn't seem to have any holes in it.
I would be interested to hear what happened when these engines went south though. Was the oil used the right oil for the job? I.e the right viscosity. As to the very low milage engine that died. From approx 10K miles it always used Mobil 1, it was always a 40 weight oil but I can't be sure of the first number, it was not 0 though. This is when it has suspected noise tappets. That mechanic put that oil in all his Porsches I am told.
The car was involved a bad accident and the engine was removed, within 6K miles the engine was finished. Was it stuffed before it went back in, or was it ruined over the course of the 6K miles,(due maybe to the incorrect installation of the torque tube) we'll probably never know. I wasn't aware that the Mobil 1 grade he switched to had such a high level of ZDDP, I have to admit I have never investigated it as I never have heard anything good about Mobil 1. I have heard though of higher levels of ZDDP though in the 1500- 1700 range.
As to viscosity and I don't know if I should even be discussing this, as it is quite complex and I may get something wrong, but I have read an article about oil and friction in the slipper bearings. It is a fine balance between flow and pressure. The higher flow, sure more bearing cooling but there is also the ability to support the journals under load.
If I get time I will look it up and verify, but from memory there is 3 stages of lubrication in the bearings. What you want for low friction is when the bearing is surfing the boundary layer of the oil. Fully grooved bearings are bad for this. Changing viscosity will throw the balance out I believe. I wont go any further without referring to the article because it is quite complex.
Changing the oil has never been so dangerous and that new standard Hacker refers to which is GF-5 may actually be improved over the previous due to so many failures that are being seen. It looks like the authorities have seen they have gone too far, we'll see about that.
Greg
