HELP!!! low oil pressure

boosting951 · 11-12-2008, 09:36 PM

I have a 86 944 turbo with fresh engine but only 1 bar of oil pressure, after a few minutes of starting and shutting the car off( im affraid of damaging internals by leaving it run to long) the oil pressure comes up and is fine. When i shut off and let it sit for a few hours or more it happens all over. Any help would be great, thanks scott

AaronM · 05:01 AM

It's normal for the car to take a few seconds to build oil pressure upon initial starting. 1 bar at idle is fine and if it comes up after that there's no problem.

The general rule is that an engine should have a minimum of 10 PSI oil pressure per 1,000 RPM (so 10 PSI at 1,000 RPM, 20 PSI at 2,000 RPM, etc). 1 bar is 14.7 PSI and idle is about 850-950 RPM. So if you have 1 bar at idle upon startup and the pressure comes up after a few seconds then you're fine.

When comparing to modern cars, remember that the oil pressure gauge on the 944 measures actual pressure. The "gauges" in most modern cars (that is, the gauges from the factory) are largely decorative. They are programed to go to the middle of their range as long as the oil pressure is within an acceptable range. They are essentially idiot lights in gauge form.

Aaron

2Tight · 11-13-2008, 06:22 AM

Personally I feel 1 bar after a few minutes running is way too low for a 951. You claim it's a fresh engine? Most people see 4-5 bar on cold start-up. What do you you see at start-up and what weight oil is are you using?

boosting951 · 11-13-2008, 06:27 AM

What about the lifter tap that doesnt go away until the pressure finally comes up and also when i rev it the oil pressure still shows barely 1 bar

rsrmike · 11-13-2008, 07:04 AM

I believe you have an air leak somewhere in the pick-up to the oil pump.

Been there, done that, it sucks. I had the exact same symptoms as yours.

Mine problem was caused by being a little too anal, and in a hurry at the same time.

I wiped the oil pump mounting surface down w/ solvent and waited for it to dry, unfortunately, I soaked the rag too much and inadvertently filled the oil pump mounting bolt holes w/ solvent. When I installed the pump, one of the bolts pushed enough solvent out to wash the loctite 574 away in just a tiny 1/16" wide stip, butthat was all it took for the pump to suck air...

Unfortunately, your air leak could be anywhere on the pump mount surface, the lower block "girdle", or the pick-up tube or O-ring between pick up tube and block...

boosting951 · 11-13-2008, 07:08 AM

Quote:

Originally Posted by 2Tight

Personally I feel 1 bar after a few minutes running is way too low for a 951. You claim it's a fresh engine? Most people see 4-5 bar on cold start-up. What do you you see at start-up and what weight oil is are you using?

At cold start its just below the 1 bar and i use 20-50 oil.

rsrmike · 11-13-2008, 07:23 AM

You can also try dumping a few extra quarts of oil in, just for cranking purposes, I wouldn't drive it overfilled, sometimes the extra oil will cover the airleak, if it's in the girdle or pickup tube. If you get good pressure quickly w/ extra oil, well you know the oil pans has to come back off.

I assume you've checked the torque on the crank pulley bolt and you have a working/correct oil pressure relief valve?

Techno Duck · Techno Duck's Garage

As Mike said, verify the torque on the crank bolt and make sure the power steering pulley is seated right on the crank.

1-bar @ cold start is way to low unless its 200*F ambient temp out and your using 10w30 oil. You should get 4.5-5bar on the gauge almost immediate after starting a cold engine (this is assuming your using a correct oil filter with anti-drainback valve).

I dont think idling at 1-bar is a huge deal. The factory manual actually states .5 bar is within there 'tolerance' range, albeit at the extreme low range. Personally i would not run the car with anything less than 2-bar at idle.

boosting951 · 11-14-2008, 11:52 PM

Quote:

Originally Posted by rsrmike

You can also try dumping a few extra quarts of oil in, just for cranking purposes, I wouldn't drive it overfilled, sometimes the extra oil will cover the airleak, if it's in the girdle or pickup tube. If you get good pressure quickly w/ extra oil, well you know the oil pans has to come back off.

I assume you've checked the torque on the crank pulley bolt and you have a working/correct oil pressure relief valve?

Ive tried putting 5 quarts in to see if its the pickup and that didnt work. The crank pulley is at 145lbs. I just pulled out the relief valve, but only the spring and bolt came out, is the cylinder part suppost to come out also cause i cant get that part out of the filter housing.

rsrmike · 11-15-2008, 11:28 AM

do you mean 5 extra qts?? That should cover just about any air leaks...

Yes, the piston should come out, It's possible the tool to align the oil filter housing when tightening wasn't used and the pressure piston is binding up in the housing?? That would be easier fix then pulling the pan for sure...

Maybe take some pics of what you have for the oil relief valve. Didn't the 86 have an early one piece valve?? Or was that 87? Are the block and oil pressure relief valve original?

AaronM · 11-15-2008, 11:46 AM

Quote:

Originally Posted by 2Tight

Personally I feel 1 bar after a few minutes running is way too low for a 951. You claim it's a fresh engine? Most people see 4-5 bar on cold start-up. What do you you see at start-up and what weight oil is are you using?

I'm assuming that he's starting and shutting it off immediately because it doesn't register 5 bar instantly and doing that for a few minutes.

If it's taking more than 5 seconds to come up if he leaves the engine running, then yes, I agree that there's a problem, but I can't see an issue with 20w50 taking 2-5 seconds to register on the gauge.

boosting951 · 11-15-2008, 06:25 PM

Quote:

Originally Posted by rsrmike

do you mean 5 extra qts?? That should cover just about any air leaks...

Yes, the piston should come out, It's possible the tool to align the oil filter housing when tightening wasn't used and the pressure piston is binding up in the housing?? That would be easier fix then pulling the pan for sure...

Maybe take some pics of what you have for the oil relief valve. Didn't the 86 have an early one piece valve?? Or was that 87? Are the block and oil pressure relief valve original?

Yes it was 5 extra quarts, it ran fo aout 30 seconds and still less than one bar of pressure. My relief valve is the 3 piece (pre july 86) not the one piece that people are saying is better to use, and i have no idea if its the original.

my next question is how do i get the piston free? Can it be done without removing the filter housing?

2Tight · 11-15-2008, 06:40 PM

Quote:

Originally Posted by AaronM

I'm assuming that he's starting and shutting it off immediately because it doesn't register 5 bar instantly and doing that for a few minutes.

If it's taking more than 5 seconds to come up if he leaves the engine running, then yes, I agree that there's a problem, but I can't see an issue with 20w50 taking 2-5 seconds to register on the gauge.

Agreed. I posted before he said the piston on the OPRV did not come out with the spring. Sounds stuck to me and I had exactly the same thing happen on my 86. The piston had some really small debris from somewhere and it bound up the piston in the sleeve. I was able to pull it out with my finger. I cleaned up the sleeve/bore and installed a 1-piece 86 conversion OPRV and it's been fine since. A good cleaning and realignment of the valve might be all he needs. Hopefully it isn't a cracked pick-up tube. Maybe it can be solved by a simple retorque on the crank bolt. A lot depends on what was done during the 'refresh' of the motor. Some people consider a refresh is just rod bearings and seals; others tear it down completely and replace everything without any block machining.

boosting951 · 11-18-2008, 12:35 PM

Quote:

Originally Posted by 2Tight

Agreed. I posted before he said the piston on the OPRV did not come out with the spring. Sounds stuck to me and I had exactly the same thing happen on my 86. The piston had some really small debris from somewhere and it bound up the piston in the sleeve. I was able to pull it out with my finger. I cleaned up the sleeve/bore and installed a 1-piece 86 conversion OPRV and it's been fine since. A good cleaning and realignment of the valve might be all he needs. Hopefully it isn't a cracked pick-up tube. Maybe it can be solved by a simple retorque on the crank bolt. A lot depends on what was done during the 'refresh' of the motor. Some people consider a refresh is just rod bearings and seals; others tear it down completely and replace everything without any block machining.

i retorqued the crank bolt to 155 and i was able to get the oprv cylinder out today and it had pieces of metal shavings behind it. I cleanded the oprv and opening then reinstalled it. My engine rebuild was torn all the way down then had the crank and rods polished, new rings and the head fully rebuilt, ect.

What is the most effective way to prime the oil pump.

2Tight · 11-18-2008, 06:49 PM

Quote:

Originally Posted by boosting951

i retorqued the crank bolt to 155 and i was able to get the oprv cylinder out today and it had pieces of metal shavings behind it. I cleanded the oprv and opening then reinstalled it. My engine rebuild was torn all the way down then had the crank and rods polished, new rings and the head fully rebuilt, ect.

What is the most effective way to prime the oil pump.

Was the engine 'refreshed' after a bearing failure? Hopefully if it was a rod bearing failure they followed the correct procedure to flush the block. A bearing failure will leave all sort of evil stuff in the pan as shown below.

If not it sounds like the head might had had a few slivers left in it from the machining. One method I've seen to prime the oil pump is to use a rubber tipped air nozzle over the dipstick tube opening to seal and hit it with about 5-10 psi of air pressure. The oil filter should be off at the time. Another tried and true method is to pour oil down the center tube of the filter mount with a funnel and turn the crank counter-clockwise at least two turns while making sure there's always is oil in the funnel.

Personally I would see if just the OPRV cleaning has helped first. There is no reason it shouldn't prime by itself with a few cranks and the DME relay out.