Why do I have low oil pressure?
01-29-2010, 12:52 PM
#1
Burning Brakes
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Why do I have low oil pressure?
Ok, so I had this engine apart about 700 miles ago now, the rod and main bearings looked perfect. Its an S engine, I was rebuilding the head, pulled the motor out of the car. The PO had a service history on it - tons of oil changes, usually at the dealership since the day it was new. Every 2-3K miles. The pan was (nearly) spotless. Its at 100K now. It idles at an indicated 1 bar, and on the highway at 70mph it runs 3 -3.5 bar. It also sometimes has a faint lifter tap at idle on the #1 intake. So far my list of things to check will be:
The gauge - could it be giving a false reading? When I turn the car on - the needle jumps from 0 to .5 bar before I even start it.
Is it the OPRV - I didnt have an alignment tool when I put it in....but I thought if it wasnt aligned it would jam and spike the oil pressure not cause a steady low issue?
Worn out oil pump?
Oil pickup in the pan is cracked?
Any suggestions on how to check these things or where to look first would be great!
The gauge - could it be giving a false reading? When I turn the car on - the needle jumps from 0 to .5 bar before I even start it.
Is it the OPRV - I didnt have an alignment tool when I put it in....but I thought if it wasnt aligned it would jam and spike the oil pressure not cause a steady low issue?
Worn out oil pump?
Oil pickup in the pan is cracked?
Any suggestions on how to check these things or where to look first would be great!
01-29-2010, 01:06 PM
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Burning Brakes
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Pulled them out and put back in. I bought new rod nuts since the Porsche manual said I should replace them if I remove them. Anyways, they appeared as if they had no wear at all. I've seen quite a few rod bearings too. These looked almost new. No record of the PO ever having them changed, but he was one of those meticulous owners ..
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01-29-2010, 02:17 PM
#6
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No change in balance shafts/bearings or turbo?
It could just be the sensor... in my VW VR6, I started getting low oil pressure... I was expecting the worst - cam chain tensioner failure and the pieces damaging the oil pump. But it turned out to be a $20 sensor.
It could just be the sensor... in my VW VR6, I started getting low oil pressure... I was expecting the worst - cam chain tensioner failure and the pieces damaging the oil pump. But it turned out to be a $20 sensor.
01-29-2010, 02:35 PM
#7
Burning Brakes
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I have a mechanical oil pressure gauge I can check it with, problem is figuring out how to install it. Its either 1/8 or 1/4 NPT with a little snap fitting like the ones at autozone.
V2 - Thats always a good question to ask! It's full on VR1 20W50. When I keep it topped off I do get significantly better oil pressure. Still peaks at only 4 bar and idles at 1.3 or so though. Im really thinking the sensor isn't reading right, or there's corrosion at a wire connection for it or something along those lines.
V2 - Thats always a good question to ask! It's full on VR1 20W50. When I keep it topped off I do get significantly better oil pressure. Still peaks at only 4 bar and idles at 1.3 or so though. Im really thinking the sensor isn't reading right, or there's corrosion at a wire connection for it or something along those lines.
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01-29-2010, 04:15 PM
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i am yet to understand why keeping oil topped off on these cars is so important. but it seems to keep keep the valves quiet. my valves got noisy a couple of times just before oil changes when i was about a 2/3 of a quart down after 5,000 miles... i topped of oil and the noise went away. weird.
i change oil right around 5-6,000 miles. this one might be more serious...
http://www.youtube.com/watch?v=HnQwkcIsVAg
i change oil right around 5-6,000 miles. this one might be more serious...
http://www.youtube.com/watch?v=HnQwkcIsVAg
01-29-2010, 05:56 PM
#9
Rainman
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i had oil pressure gauge reading low and my oil light coming on right as i was setting out for a 400 mile road trip...said i only had 2 bar of pressure at 3000rpm cruising and idling it was under 1 bar... car was fine though, when i got home i switched pressure senders and it read 3.5 at idle and pegged at over like 2000rpm
01-29-2010, 06:03 PM
#10
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could be a gauge problem but light lifter noise on idle makes me think its actually low on pressure. My car idles at 4.5 bar cold and like 3 hot- like just off the track after one hour beating it hot. One bar is wayy low. Make sure your crank pulley is tight and pull your OPRV to make sure it moves nicely. I had mine stick on the track resulting in no oil pressure and i bought the one piece update to cure this.
Last edited by xsboost90; 01-30-2010 at 03:17 PM.
01-29-2010, 06:29 PM
#11
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Was the oil pressure fine before you had the engine apart? Or did this happen after opening it up? You really should have replaced the rod bearings if you had them out. Even if they looked fine, they are pretty worn after 100k miles. I'm with xsboost90 on this one. If you hear lifter noise, you really do have low oil pressure.
01-30-2010, 03:09 PM
#12
Burning Brakes
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I bought the car for parts mainly for the motor, so I don't know what the previous oil pressure was. It had a good looking chain tensioner in the head and there wasn't much buildup of sludge. It turned good compression and leakdown #'s, had full service records etc etc so I went for it.
I think ya'll are right about the lifter. It sure does make it more likely that low pressure is the problem. However it is just ONE lifter that makes noise and always the same lifter - so it's possible that lifter is bad / weak. Wouldn't the other ones occasionally make noise too if the pressure was low? Like wouldn't it affect all the lifters?
It has the one-piece OPRV, but if it wasn't lined up just right could it be a possible cause? I just tinkered until I could get the OPRV to slide / thread in easily, then tightened the oil cooler housing down...
I think ya'll are right about the lifter. It sure does make it more likely that low pressure is the problem. However it is just ONE lifter that makes noise and always the same lifter - so it's possible that lifter is bad / weak. Wouldn't the other ones occasionally make noise too if the pressure was low? Like wouldn't it affect all the lifters?
It has the one-piece OPRV, but if it wasn't lined up just right could it be a possible cause? I just tinkered until I could get the OPRV to slide / thread in easily, then tightened the oil cooler housing down...
01-30-2010, 04:59 PM
#15
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could be a gauge problem but light lifter noise on idle makes me think its actually low on pressure. My car idles at 4.5 bar cold and like 3 hot- like just off the track after one hour beating it hot. One bar is wayy low. Make sure your crank pulley is tight and pull your OPRV to make sure it moves nicely. I had mine stick on the track resulting in no oil pressure and i bought the one piece update to cure this.
This stuff always confuses me....if you look at clark's garage, it clearly states that it is not at all unusual to have under 2bar after a very hot drive.
I have posted before that my car pegs when cold...and drops to about 4.5 to 4 bar when warmed up.
When I come off a hot run at the track it will be around 1 to 1.5 bar...by the time my next run rolls around it's back up to 4bar.
My oil is generally always topped off...I check it 2x per day at the track.
This is from clark's garage:
The 944's oil pressure should run 4-5 bar at idle when the engine is cold. It will gradually decrease to 2-3 bar at idle as the engine oil warms to normal operating temperature. Once the oil is at normal operating temperature, the oil pressure should indicate around 4 bar at 5,000 rpm. It takes the oil longer to reach its normal operating temperature than the coolant. Therefore, don't be surprised if oil pressure continues to decline after the coolant temperature has stabilized at its normal operating temperature. Occasionally, you may see your oil pressure drop to less than 2 bar. This may happen on very hot days when the car has been driven particularly hard. You should be extremely concerned if the oil pressure dropped to less than 1 bar. This is indicative of an problem with the oil pressure indication or the oiling system itself. Under these circumstances, the car should not be driven until the cause of the low oil pressure indication is determined and corrected.