99 C2 Tip - Oil Pressure

So, I've posted before about my oil gauge reading around 0.7 bar when idling in the summer time while stuck in traffic, most of the advice I received was as long as the warning light didn't come on it was fine. When idling at 0.7 I get about 3.5 bar at 4k rpm which exceed what the manual states which is 3.5bar at 5k rpm I believe. A few weeks back I had my mufflers fistered by a local shop and put them on, it was 30+ Celsius and after driving in heavy traffic I saw the oil can flicker a few times when coming to a stop light, gauge was reading 0.5 bar. Right after that day it got cold and I haven't seen the light since. Temps have only been up to the low 20s Celsius since. Last oil change was May, I have about 4000km on the 0-40 Mobil 1. Was no particles in the oil. Engine has 123,000km on it. Anyway, I bought a mechanical gauge and finally got some time to install it and go for a drive. I got the following: 5.5 Bar at cold start 3 Bar idle after a few mins before leaving garage After a 20 minute drive, water temp around 200F Idle 10PSI (0.7bar) 2000 RPM 2 Bar 3000 RPM 3 Bar 4000 RPM 3.75 Bar 5000 RPM 4 Bar So in conclusion my in dash pressure gauge seems to match the mechanical gauge almost spot on. Any thoughts on what to check for?

0.7 psig is too low. Something is not right. Drop the oil pan and check the oil pick up mesh. The next thing is replace the pressure relief spring on the main oil pump. Stock oil filter?

I replaced the spring last oil change, i forgot to order the piston but found that the PO had already change the piston and presumably the spring. I put in the new spring anyway. Stock filter, I figured the next step was to check the oil pan pick up tube

decent running hot thread for an mk1 https://rennlist.com/forums/996-foru...erature-2.html

Honestly, I would drop the pan. Just because nothing is in the filter doesn't mean something is not blocking the pickup tube. Could be plastic from a chain rail. I had a piece of aluminum wedged in mine.

I dropped the pan this evening. Nothing clogging the pickup tube. Filter was clean, no rubber, or metal. Sump pan had no metal, sludge, rubber, etc. So....I dunno where to go from here. I do recall that there was some black rubber bits in the filter last oil change. I concluded it was sealant as I had the pan dropped during the PPI, and it seemed like there was some extra sealant on the outside of the pan pressed out. Pulling off the pan today I could see sealant on the inside of the pan, but the pickup tube was clean. I also took out the swirl pots and they didn't have any debris in them either.

It could be excessive bearing wear.

Go with a third radiator , it will keep temps down and bring pressure up a bit?

The car has a third radiator from the factory(Due to being a tiptronic I think). I too suspected temperature as the cause of the low oil pressure, last week I did the radiator fan mod so I can turn on the fans to high with a switch. This did drop/stabilize the temps in traffic but the oil pressure is still low. Stopped at a light this week with temps in the low 20c I was around 198 to 204, but as soon as I got moving even in traffic it would drop down to 192 to 195. Those temps don't seem overly high to me?

Ok if your confident your coolant circuit is ok maybe you can try the millers oil I'm running it's millers nanodrive cfs 10w50 , Hartech who did my cylinder work, in the uk and are highly regarded,recommends this oil especially for the earlier cars as they tend to run a bit hotter, I was running a 5w40 oil in mine and getting the oil pressure running a bit low in hot conditions after my rebuild (all new bearings etc) and saw an improvement when I went up to the millers but I don't have a third rad and I notice only a few degrees higher on the temp gauge and the pressure drops off, now on my car as I said all new bearings, crank was checked for clearences, new oil pump , the only thing I didn't do now and wish I had in hindsight was lifters, and I do get lifter noise for like ten seconds on cold start, my engine is coming out again this winter so I'm going to get the lifters done , only other thing I can think of is cam wear where it's cut into the head with no option for replacement , my machine shop said they could machine the head to accept shell bearings like in the crank, i think we might see more of this as engines get older and have had the crank bearing done a few times, have sleeved cyljnders that have been replaced but the poor old cam bearing are the standard machined in ones getting a bit loose? After all they are at the end of the line on lubrication from the pump and there's. Fair bit of load on the end of the cams where the chain is!

You might have an oil passage clogged with sealant. Have the cam covers ever been taken off? https://cimg3.ibsrv.net/gimg/rennlis...0eb1330fc2.jpg

So, it seems my low oil pressure isn't any of the common causes such as a broken relief spring or clogged pickup. Now what? Is this a button it back up, refill it and drive making sure to monitor the temperature/pressure and do frequent oil changes? or maybe run a higher visocity oil in the summer, and 0-40 in the winter(I do daily drive it in the winter) Looking for some feedback, not really sure how to progress from here.

You could switch to a thicker oil. I saw an increase of 0.3bar when switching from Motul 5w40 to Millers 10w50 NT. I think it is better to look at the relation between oil pressure and oil temperature rather then rpm. From your rpm/pressure values it seems to me that correlation is ok. It would be more interesting to see what temperature your oil has when it is hot and have 0.7bar at the gauge. If the oil temperature is moderate you need to look to some other reasons for the low readings. If the oil temperature is on the high side you know at least the pressure is low because of the high temps. Then you could try to look at possible wys to bring the temp somewhat down. Did you replace the waterpump already? Low temp thermostat? Cleaned the radiators? 190's with mild 20degC ambient temperature seems ok.

Put a good quality 5w40 in it & replace the hex drive in the oil pump with the 997/chromoly unit. See if that does anything. I've seen pressure in my C2 go below 1bar at idle but after updating to the 997 piston & spring it stays over 1bar. https://lnengineering.com/products/o...hex-drive.html

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You can switch to Mobil 1 5w-50 oil (not a typo for 15w-50!) in the summer months. 5w-50 is an approved oil. I would not run a non-approved oil. Remember Porsche calls for 0w-40 oil if winter temps drop to 025C or lower. You can switch to 5w-50 but I can tell you after having run 0w-40 for a long while in both my cars (Boxster and Turbo, which has an oil pressure gage) then after I switched to 5w-50 oil I really didn't notice any difference at the Turbo oil pressure gage. The hot idle oil pressure varies a bit but it varies due to differences in ambient temperature not the oil viscosity. As best I can tell 0w-40 vs. 5w-50 hot idle oil pressure is the same under the same ambient air temperatures. A 2 bar on cool to cold days. A bit under 2 bar on hot days. And maybe "1.7 bar", based on the needle being below the 2 bar hash mark but not quite halfway between the 2 bar and 1 bar hash marks. Still switch and give it a shot. You can even add two bottles of Swepco 502 oil improver. Don't run the oil too long. I find 5K miles is plenty and I live/drive in a much warmer milder climate. Real cold areas can have the oil collect a lot of water and this makes for diluted oil which means reduced oil pressure. It is rather amazing that even after 5K miles how quiet the engine is, both engines, after an oil change even after the engines are fully up to temperature. The low oil pressure doesn't have to be due to excessive clearances. My 2002 Boxster engine has over 315K miles and it gets plenty hot -- the coolant can reach 226F -- and I have never seen a low oil pressure light. The oil pressure can be low because the pressure valve that controls oil flow to the piston jets may not shut off oil flow at the desired low oil pressure. The intent is if oil pressure drops too low -- I don't recall the threshold -- oil to the jets is cut off which helps preserve oil pressure/supply for the main/rod bearings and the cams and lifter hardware. There can be an internal oil pressure leak. This can arise if where the cases seal together or the cam covers seal to the heads if the sealant has a "gap" this can let high pressure oil leak out. It leaks into the crankcase so there is no outward sign of an oil leak. If the leak was under some camshaft cover you might (might) with a stethoscope detect a bit of increase in valve hardware noise compared to other areas of the camshaft covers as this leak could possibly reduce the oil pressure and supply to a portion of valve hardware. A camshaft cover removal and reseal is a rather expensive operation though and one probably would prefer some more definitive "evidence" this is required.

So I think with winter coming up and the cooling fan hack I've decided I'm going to just refill and monitor going forward. It seems there isn't a clear path forward to inspect the possible causes of the low oil pressure that don't involve some pretty invasive things, which I don't really think makes financial sense based on what i'm into the car for. I've found a Canadian supplier of Millers CFS 10W-50 NT, does anyone have any insight if this is too heavy for winter driving? We regularly see temps below -30C. My thinking is it will be too thick for cold starts. Also with the cost of this oil, (120$ plus shipping for 5L, so over 250$ for an oiler change) is it still recommended to change every 6 months or 5k miles? The other choice I'm looking at is Motul Xcess 8100 5-40, which is Porsche approved, and seems to have a good reputation. Mobil 1 5w50 isn't available in Canada as best as I can determine, nor can I find anyone selling it that ships here. In the spring, I'll most likely install a LTT, new water pump, and replace the coolant.

Millers CFS NT is also there in a 5w40 flavour. But I think with that cold weather a good 0w40 would be safer.

So I got everything back together tonight, filled up with Motul 8100 x-cess 5w40 and went for a drive with the mechanical gauge. It was alittle coolor tonight over the last test. Idle pressure is maybe 0.1 or 0.2 higher, not much, and most likely just temperature differences. However from 2k to 3k I had 0.5 bar more and at 4k 0.25 bar more. Tomorrow i'll be driving to work my usual route and will have the pressure sensor hooked back up, I don't expect to see any change but we'll see.