Oil Pressure Problem After Rebuild

Hello everyone, I'm after a little help with a sight problematic 996 4S. I bought this as a project as the engine was suffering with scored bore. It's the 3rd 996 engine I have rebuilt but this one has been extremely problematic. The car is a 2005 C4S in Atlas grey, Tiptronic with a lot of factory options and just 98k. The engine was stripped and the block was re-sleeved by a well known company in Bolton (UK). The engine was re-assembled by myself with no issues but when it got to hot idle after the engine was re-installed, it indicated an oil pressure issue at 0.5 bar which tripped the lights. A mechanical gauge was fitted directly to bank 2 which showed the same reading. Some oil was removed and it had a distinct shimmer to it with flakes in the oil filter. I nearly cried as it had only 30 mins of idle on it! Engine was removed again and partially stripped. I found that bank 1 intake cam had picked up on the bearing seat and worn. It looks like like the oil way had become partially blocked with RTV during rebuild. The engine was completely stripped down again to the crank, extensively cleans and rebuilt with a replacement cylinder head, refitted and it started up. Oil pressure is very good until its at hot idle and the pressure dropped back down to 0.5 bar, 6-7 psi and rises with revs. I'm running through a list of areas that could be of concern but I could do with some help as its becoming quite frustrating. The engine sounds great, even when at 0.5bar, no ticks, knocks or anything and no CEL (oil is clean) During the rebuild, it had new main/big bearings, pistons, chains, guides, IMS, gaskets, AOS, oil cooler, oil pressure sensor, oil filter housing, oil pump relief valve was replaced with the upgraded parts and bolts. The oil pump shows no wear inside and the crank was within specification during re-build. Current oil is a quality 5W-40. I have found that bank 1 chain tensioner is faulty but not effecting tension and no apparent oil pressure loss but I have a new one on order. Does anyone have any ideas on this? - next on the list of areas to check/replace are the sump oil returns/seperator and change the oil pump (incase there is an issue that I can't see with the current one) I feels like I'm just throwing parts at this now - any help is greatly appreciated.

Always start with the simple stuff first.....check the oil filter to see if it has crushed...( you never mentioned having replaced or checked it ) Remove the sump and check to make sure the pick-up tube is not blocked with excessive sealer ( you mentioned a blocked port in the head to cam bearing). I know you mentioned a new oil pump by-pass valve and spring......but didn't say when ,before or after the first or second attempt .......make sure the new one is working properly and not sticking.... Pull the cover off the oil pump and inspect the main oil pump gears and housing, ( you can also check the by-pass valve while the cover is off much more effectively) If you don't find the problem after these things, then you will have to go into the engine again looking for the loss of pressure...

Is your current observation based on the OP gauge of the car only or have you confirmed it with the external pressure gauge? If the former, then it could be the sender reading too low.

Quotes source post: 19286608

Sorry, should have mentioned that. Yes, the filter is in perfect condition and is genuine Porsche filter that came with the new filter housing and the sump is clean. The pump gears are showing no wear and are clean. I'll take a look at the bypass valve/spring later this week and put a borescope camera up. Thinking about it, it could be getting stuck if its even slightly damaged.

I've hooked up a manual gauge on bank 2 where the sender usually sits and its reading 0.5 bar (6-7 psi) at idle. Pressure at cold, warm and even with load applied to the engine is reading very good oil pressure.

Any chance the scavenge pumps are oriented incorrectly? Would that cause oil pressure to be low?

Quotes source post: 19287315

i was thinking the same thing.

Quotes source posts: 19287315, 19287552

It would have to have both scavenge pumps oriented wrong to have low pressure at idle, but it would be even worse at RPM's and the OP is stating the pressure is ok at rpm's and cold...(?) I have seen engines run for 10k miles with only one pump oriented wrong, albeit was probably driven like a Granny... It would be smart to verify them though... We really need an accurate oil pressure data at full temp and 4k rpm to ensure the pressure is at least 50 psi at the head @4k rpm.. If the pressure is only low at idle, I would suspect the piston oil squirters are stuck open....they are spring loaded to not operate at hot idle to keep the pressure from being low, they only start squirting when the pressure is ~ 30psi..

Quotes source post: 19287315

Both pumps are set to the correct orientation but I've been thinking. How much should usually drain from the engine when bank 1 tensioner is removed? - I estimate 2-2.5 litres drained out which seems excessive. is it possible the oil is pooling in bank 1 head?

Quotes source post: 19287696

At hot idle, the pressure goes to 4 bar (50ish PSI) at 4k revs. It increases/decreases nicely with no jumps on either gauge. I'm really hoping its not the oil squirters as I'm rebuild no 3 within 2 months is hard work!

Quotes source post: 19288627

squirters were replaced during first or second build?

Quotes source post: 19288655

They weren't replaced. Ive never replaced them in previous rebuilds. I've never checked the price of them but I've recently discovered they cost next to nothing........

Quotes source post: 19286393

With your (re?)sleeve job, did you get the Capricorn pistons with 2 piece spiral wound springy thing oil rings..? What size is your engine..?

We’re the squirters removed from crank carrier to clean oil passages?

Quotes source post: 19288692

They were re-sleeved with nikasil liners using Mahle OEM pistons

Quotes source post: 19288994

No they weren't

any sealant was used in the mating surfaces between the case and the crankshaft bearing case?

Can you verify that all of the oil squirters are/were in place on reassembly?? Missing one or two will cause problems like that (been there done that on an old bmw m20). also, just for S&G�s, can you take the oil pressure reading via mechanical gauge from another port?

I realize this is way out there but, are the brackets on the valve lift control solenoids on the valve cover? Ask me how I know......

This is what I was referring to. The one on the right is missing.

Quotes source post: 19289808

No

Quotes source post: 19291068

I checked that all squirters were in place for re-assembly. This weekend I'm planning to put the mechanical gauge on bank 1 to see if there if it gives a different reading. I should have the new tensioner on Friday so I'll install that and drop the sump to check the pickup/oil returns. Hoping to sort this soon, really want to drive it!

It could just be that the engine is just loose after the rebuild. If that�s the case, switch to 5w50 oil and maybe that�s just enough to get another 0.25 bar. If that�s not enough, then press the AC button and leave it pressed so it idles at 800 RPM instead of 675. That�s if there nothing actually wrong with the engine, which is possible.

The tensioner didn't make a difference but it needed replacing anyway. Its still reading 0.5-0.6 bar. Once its cooled down, I'm going to remove the sump and check that everything is ok in there. the amount of oil that came out when I removed the tensioner is a concern though, about 3 litres drained out - isn't that excessive?

Once its cooled down, I'm going to remove the sump and check that everything is ok in there. the amount of oil that came out when I removed the tensioner is a concern though, about 3 litres drained out - isn't that excessive? That does seem excessive. When I removed my tensioners, no more than an ounce or 3 came out�

I checked the sump and pickup and air/oil separators. No issues at all, not a single speck of anything in there other than oil. I put in the old pressure relief valve/spring and moved the mechanical gauge from bank 2 to bank 1 with the OEM sender refitted to bank 2. The car is now showing 1.5 bar on the instrument panel and 0.7 bar on the mechanical gauge. this was after 1 hrs of idling so the car was at max temp. This seems strange. My brother who rebuilds agricultural machinery/engines is bringing over a new gauge during the week to use to see what it shows. Its possible that the mechanical gauge I've been using is no longer calibrated and this issue is now resolved.

Quotes source post: 19299633

I wonder if the scavenge pump isn't pumping very well.

Quotes source post: 19299779

I was thinking the same thing.

� �The car is now showing 1.5 bar on the instrument panel and 0.7 bar on the mechanical gauge. this was after 1 hrs of idling so the car was at max temp. This seems strange. My brother who rebuilds agricultural machinery/engines is bringing over a new gauge during the week to use to see what it shows. Its possible that the mechanical gauge I've been using is no longer calibrated and this issue is now resolved.� Letting these engines idle for long periods of time is not good for them (especially if you�ve got low oil pressure at idle). You�d be much better off driving the car to get it up to temp�(or if it�s in a undriveable state, running it at 2500-2800 rpm for 15 min. /full operating temp).

Symptoms: -low oil pressure at idle -cam tensioner bank 1 not actuating -cam has been replaced? Possible fault could be the 'bearing washers' (as porsche calls them) missing on the end of the cam where the variocam adjuster sits on, causing oil pressure to bleed off hence the low pressure and the cam adjustment not to work as the car warms. Happened to me when fitting schrick cams and accidentally missing them off: 996 4s - diy 3.9 x51, reworked heads, schrick etc | Page 5 | Porsche 911UK Forum Took me a while to figure out as the adjustment worked fine when tested cold.

I've just finished checking the oil pressure with a very accurate digital gauge. At cold start, max oil pressure is 7.2bar and then gradually drops to 1.4 bar where it sits for about 6 mins and then drops to a steady 0.9 bar. @tim s - I remember checking these during re-assembly. I've not had chance to drive the car yet so any issue with the variocam hasn't become evident but the car does idle perfectly. Not sure what to do now. My company car arrives in 2 weeks, when it arrives, I can get the Porsche road legal (insured/tax) and give it a road test which may help point out any issues.

Quotes source post: 19306760

Just observed another forum member install those washers. Jake calls them 'diamond washers' iirr.

The diamond washers go between the sprocket and the cam. The parts on the UK web site are only on 996.2 (and 996 Turbo) and they are three little piston rings that fit on the snout of each intake cam. If they are missing then #1 variocam won't work and #2 there is a direct leak path from the oil gallery.

Quotes source post: 19312836

I had to replace one of them during the rebuild as I damaged it whist cleaning it. The rest were checked and no problems found.

I dont have any usefull help but i can offer moral support. I just spent an extra 4 weeks getting my truck motor sorted out due to a defective part. Its worth the effort to find the root cause and I hope u find it soon.

Sorry for the lack of updates. All 3 pumps have arrived from Porsche and I'm finishing fitting the main pump tomorrow. I pulled the inlet manifolds off to get to bank2 tensioner and found the manifolds to have a lot of oil in them.

All 3 pumps are changed and didn't make a slightest bit of difference to the oil pressure. Managed to take to take it for a small drive and it didn't drive well. it felt very down on power and 'lumpy' to drive. idles just fine. Need to check the variable timing solenoids. Oil pressure issues is once again leading to the the oil jets not closing at idle or losing oil pressure at the variable timing parts

Sorry for the lack of updates, I just left the car in the garage until this week as I had run out of enthusiasm to fix it! Plugged the car into a diagnostics (TEXA) and found error code 0012 camshaft position bank 1 which explains why the car didn't feel right when I took it for a test drive. Here are some details of the data it was reading. I think that the camshaft adjust numbers are the cam deviation which at those numbers indicates a timing issue. but when I changed the pumps/tensioner, it as set perfect. Or its an issue with a component of the VVT system. Any thoughts or advice? - could a loss of oil pressure to the VVT/cams case this and therefore both issues linked?

Looks like the issue is now fixed. Pulled bank 1 timing solenoid and found that the keyway was slightly damaged which meant it wasn't seated correctly. This caused the bad running as the solenoid wasn't getting oil and loss of oil pressure as it was bleeding out oil pressure where the supply goes through the strainer and into the solenoid. looks like those 3 pumps were a waste of time/money. Road testing went well but I did 10 miles before it blew a power steering line........

Glad for you that you found the cause without having to throw more parts at it. Too bad you've run into your next challenge almost straight away, that sucks. Thanks for taking the time to report back with the cause for your troubles!