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I’m in the middle of a road trip through the alps and have notice a similar issue.
Going up mountains passes, the coolant temp will get within 1/8th in of the second mark, and stay there. Oil pressure never goes under 0.8-0.9 bar at idle, and is typically above 1 bar, but I’m seeing drops in turns, by as much as 2.5 bar (4 -> 1.5 at 4K is the most I’ve seen), even though I’m taking thing slow. Some of it is due to the revs dropping down as the turns are quite tight, but some is definitely linked to the cars lateral movement. Also, the oil pressure seems to top at around 3-3.5 bars even past 4K in a straight line.
If I stop the car and test the oil pressure in neutral, it’s fine and shows normal progression through the rev range.
Going downhill, oil pressure is solid in straights and in the turns.
I’m running 5w40, and the fans work fine at low and high speeds. The coolant level is a smidge below min when cold and a little above when hot.
Curious, can a scavenge pump be damaged from improper orientation..?
The answer is a little complicated , but YES, it CAN be damaged, but let me explain the circumstances....
The scavenge pumps are just positive displacements pumps that pump oil and uses the oil for lubrication of itself...
..
When the pumps are oriented correctly they pump oil from the heads to the Sump ( on the opposite side of the Sump ie. bank 1 pump delivers oil to the bank 2 side of the Sump and vice versa) and every thing is fine...
If the pump is oriented 180* out of position, the pump will pump from the Sump back to the head ( although the passage size will keep it from pumping as much volume/pressure) but will get lubrication and not be damaged..
If the pump is oriented 90* out of position, the pump will not pump any oil in either direction, and also will not be getting any oil for lubrication and can get damaged in prolonged running..
So, the answer is, IF the pump is 180* out it will NOT be damaged, but IF the pump is 90* out it CAN be damaged...
Last edited by Porschetech3; 05-11-2024 at 05:46 PM.
Well I seem to have found at least part of my issue. Here are pictures of both scavenge pumps. The drivers side is mounted the wrong way around
Passenger side:
Driver’s side:
I can’t spin it here as I don’t have the tools so I’ll just head home via the motorway to avoid higher g turns.
The question is how much damage can running the engine this way have done… I’ve taken things slow and haven’t pushed the car much once we noticed the issue but we did drive a good 100 miles through mountain passes with lower oil pressure in turns.
Quick update - I’ve managed to rotate the pump the right way around. It is possible without moving the engine but is a pita.
Will drive the car a bit aggressively this pm and see what happens. It’s got good pressure an idle and sounds ok though.
Sorry for hijacking the thread
Another update: rotating the scavenge pump 180 degrees did the trick. Oil pressure stopped dipping in right (or left) hand turns anymore, and became steadier when going uphill in a straight line.
First off, that is crazy that two people found their covers the wrong way. That's a really high rate considering how many people have probably never even checked those covers.
But following up here on issue: I put my oil level at 3/4 and did a short but aggressive run through a canyon today. High revs and thus high coolant temps but no ticking when I came to a stop. The pressures also did not give me any trouble at idle when the temps were super high. I am still getting pressure big sways/drops in the twisties though sometimes down to one on the pressure indicator. Though, this was a different canyon than normal and a much shorter drive so I'll have to test on the longer Angeles crest one next.
When I came back I wanted to try to get the last of the air out of my coolant flush so I sat with the rear end of the car elevated on the driveway and revved the engine for a bit. Temp gauge went up clear past the zero and the two fans kicked on high, as expected. The odd thing though is at idle the revs were bouncing up and down and the oil light was triggering every time it hit a low. Turning on the AC boosted the revs and they were fine but why would the high-speed fans caused the engine idle to fluctuate so crazily. Normally it's very solid. Why would the fans on high cause the revs to sway like this? You can see it settle when I turn on the AC:
The moment the fans kick-in, they put strain on/load the electric system that in turn has the generator providing (charge) current. Compared to the power required to keep the engine turning at idle rpm, the generator charging is a significant increase in load that results in a dip in rpm and subsequent idle rpm control. On a cable throttle like yours, the idle control valve is slow compared to dbw-throttle idle control.
With A/C on the engine load is already higher through both the A/C compressor as well as the fact that both radiator fans are (should be) already running at low speed. When switching to high speed the fans increase the load on the engine to a lesser amount and idle rpm drop is smaller.
With all due respect, you can't diagnose moderate inconsistencies in a 20+ year old car by committee , you need very accurate testing , and in your case accurate testing of ALL the systems that are related ...
I would suggest accurate testing of oil pressure, oil temperature and coolant temperature, fuel trims and fuel controls , and a full Vehicle Analysis Log to looks for other Systems that may be out of spec...
The 996 holds up very very well to age, but due to it's sophistication takes more attention to careful testing...
A 20+ year old $80k dollar car ( 996) will require more carefull testing than a 20+ year old $20k car ( Ford ) ....All parts/systems of car have a natural degradation progression as the parts wear or age-out , but some parts/systems can degrade much faster than others and the carefull testing can determine which ones need the most attention/repair/upgrading or is causing the inconsistencies...
Last edited by Porschetech3; 05-13-2024 at 04:35 AM.
The moment the fans kick-in, they put strain on/load the electric system that in turn has the generator providing (charge) current. Compared to the power required to keep the engine turning at idle rpm, the generator charging is a significant increase in load that results in a dip in rpm and subsequent idle rpm control. On a cable throttle like yours, the idle control valve is slow compared to dbw-throttle idle control.
With A/C on the engine load is already higher through both the A/C compressor as well as the fact that both radiator fans are (should be) already running at low speed. When switching to high speed the fans increase the load on the engine to a lesser amount and idle rpm drop is smaller.
So the high so the high speed fans cause the engine to lack charge and that causes the ICV to falter? I have the higher amperage 997 alternator I guess that doesn't have an effect?
Just very curious situation.
But back to tick and low oil light. so far the extra oil (vs changing the oil weight) seems to have helped both issues. Will do a long 40 mile one way canyon drive this week and see if the symptoms really do get solved with the extra oil. I'd been vigilant about keeping it at lower end of 1/2.
Your high coolant temps aren’t helping, either. I would be panicking if my coolant temp needle went past the center of the “0” in “180”.
I apologize if you’ve covered this already, but have you performed the fan mod? It’s a switch that activates the radiator fan relays to kick on at your whim.
(I personally jumped the high speed fan relays to activate when the low speed fan relays are activated, and keep the AC constantly running to activate the fans. But I’m gonna redo it later to turn on the fans without necessitating the usage of AC.)
also, have you installed the low temperature thermostat from LN Engineering? I find the thermostat alone can help keep my oil temps cool enough to raise the pressure by about 0.5 bar (observed via the OEM dash gauge).
Your high coolant temps aren’t helping, either. I would be panicking if my coolant temp needle went past the center of the “0” in “180”.
I apologize if you’ve covered this already, but have you performed the fan mod? It’s a switch that activates the radiator fan relays to kick on at your whim.
(I personally jumped the high speed fan relays to activate when the low speed fan relays are activated, and keep the AC constantly running to activate the fans. But I’m gonna redo it later to turn on the fans without necessitating the usage of AC.)
also, have you installed the low temperature thermostat from LN Engineering? I find the thermostat alone can help keep my oil temps cool enough to raise the pressure by about 0.5 bar (observed via the OEM dash gauge).
From what i've read, right side of 0 (i don't remember the exact number but have checked via odbii dongle) is acceptable operating temp. I think it depends on where and how you drive. I drive the canyons at 5-7k rpm uphill for 30-40 miles. It's at right edge of 0 on the way up, edge of 8/left of 0 on way down. Freeway driving closer to 8. Cars that don't get pushed I think stay much cooler. Rest of country don't have mountains to climb
I am still getting pressure big sways/drops in the twisties though sometimes down to one on the pressure indicator.
If you mean OP goes to 1 bar at high rpm, on the op gauge, in the twisties,? stop doing that immediately. You are causing engine damage on extremely expensive m96 internal parts. A new crank is $6k
Originally Posted by Porschetech3
With all due respect, you can't diagnose moderate inconsistencies in a 20+ year old car by committee , you need very accurate testing , and in your case accurate testing of ALL the systems that are related ...
I would suggest accurate testing of oil pressure, oil temperature and coolant temperature, fuel trims and fuel controls , and a full Vehicle Analysis Log to looks for other Systems that may be out of spec...
The 996 holds up very very well to age, but due to it's sophistication takes more attention to careful testing...
A 20+ year old $80k dollar car ( 996) will require more carefull testing than a 20+ year old $20k car ( Ford ) ....All parts/systems of car have a natural degradation progression as the parts wear or age-out , but some parts/systems can degrade much faster than others and the careful testing can determine which ones need the most attention/repair/upgrading or is causing the inconsistencies...
Ben8jam, As you know, I've been following your problems and trying to help out when I can.
So, imo This ^ (PT3's) is the best advice you could possibly get from anyone.
05-11-2024, 03:25 AM
