catamax944

Hi,
Please help,
I recently bought a 86 na parts car in good condition.I was planing on selling the engine and other parts i dont need but it seems the engine has a problem.When i bought the car i saw the engine run and oil pressure was good but it was cold so it mislead me.When i got it home i took it for a ride and after the engine got hot oil pressure gradualy dropped to 1 bar at idle (warning light comes on also) and a max of 4 bar when driving.Otherwise it seams to be running great and i was also told by the PO that the engine has been recently serviced (timing belt ,ignition,injectors,oil and filters) .I havent examend it yet except for the oil that is on max and very clean.
What could be the problem?

KuHL 951

First I would try running 20W-50 unless you know that's what was in there now. I've seen 10W-30 oil do exactly what you are having a problem with.

F18Rep

That is a good suggestion on the oil. Another simple test (and I've mentioned this so many times I'm sure eyes are rolling) would be to get the engine running and get a view of the power steering pulley (on the crank). If it is wobbling slightly, then your problem may be that the PS pulley was not centered when it was last installed - a very easy mistake to make. Easy to fix too. Result is intermitant and occassionally low oil pressure. bruce

catamax944

I found an oil bottle in the trunk and it's 10w40.In my DD i run Castrol 10w60 and i have great oil pressure(better than any other oil).You really think 10w40 is causing this?Should i change it?
The power steering pulley on the crank is straight ,only the pump pulley is a little wobbly.

KuHL 951

For the price of an oil change it's worth a try. I live in a hotter climate and have never had any luck all with anything less than 20W-50 on the several 944's variatios I've had. These cars tend to get some serious mileage on them and light oils don't seem to agree with them IMO. Lets put it this way, 20W-50 won't do any harm.

L8_apex

Just a thought - could this be related to the Oil-pressure Relief Valve (OPRV)? When new, the release pressure is about 7 bar (so I've read). If the interior spring is cracked/broken in the OPRV, that would prevent proper build up of oil pressure. Try the search on "OPRV". There have been many threads on this. I've replaced my OPRV recently to stabilize oil pressure during cold and hot operation.

catamax944

Funny thing is that it's about 10 degres celsius here (50 F).I will try it anyway,actually i'm hoping it's the oil,it would be a cheap fix.Thanks for the help,i'll let you know how it turns out.I was thinking of it too but i didnt know how it works or not work when broken.I will do a search and see if i can find out more.

944Ross

Make sure the crank bolt is very tight; after the belt job it may not have been torqued to 175 ft-lbs.

If you are going strictly off the dash gauge, it's also worth checking pressure with a quality mechanical gauge.

GTSilver944

155 ft/lbs. not 175.

KuHL 951

If you are seeing a consistent range from 1-4 bars at operating temps I would think your OPRV is OK. A bad OPRV will stick open or closed. If you have the old 3-piece style they are more prone to problems than the 1-piece conversion OPRV for the early cars. The worst case scenario is a #2 rod bearing going bad but you should be able to hear that when it's warmed up. Do you get 5 bar at cold start in the morning?

catamax944

Yes! Why?It sounds and runs great,nothing obvius.

KuHL 951

Because that's good! It still sounds like a viscosity issue to me. Give that 20W-50 oil change a try and report back. If it doesn't change anything then you can start looking at mechanical reasons.