No oil pressure on cold start

marko · 03:40 PM

Yes, I know this has been covered. I've searched and read many posts on this, but I'd like to run it by you all just the same.
Video of the problem.
https://youtu.be/1aVhZSdAuQ8

On cold start, no oil pressure for about 6 sec or so. After that, pressure reaches 4 or 4.5 bar. I hear a groaning noise up front. If I let the car idle for about 3 or 4 minutes, shut it off, then back on again, the pressure goes up to 5 bar and the noise goes away. If I do not restart the car, the noise continues. If I restart the car too early, before it warms up, the pressure goes to 4 or 4.5 bar and the noise continues. Once it hits 5 bar after a restart, the noise does not return until the next cold start.
Things I've tried with no change:
-changed oil and new Mahle filter.
-poured oil down filter mount hole.
-tightened crank bolt
-pulled OPRV and replaced the o-rings, piston moves freely
-replaced OPRV with another, but I don't know if it is good or not. Very slight binding at the bottom when pushing in the piston.
-changed oil to 10W-40. I've used this for the last 20 years. I switched to 20W-50 about 6 months ago.

One thing I haven't tried is starting the car with the OPRV out and see if oil gushes out or not. Haven't looked at the nuclear options yet, oil pick up tube or oil pump, although I would think those would give low pressure all the time.

Watchall think?

Leo944 · 09-19-2015, 03:06 PM

Hey Marko, I've had the same issue on my 86 944 for months except it would take a lot longer to get up to pressure. It got a lot worse last week to the point that now I have no pressure at all, even after 2 or 3 minutes. I'm obviously not driving the car.

Like you, I'm baffled by this and decided to upgrade my old 3-piece OPVR with the retrofit one-piece valve.

I just posted a request for help assembling the retrofit OPRV, perhaps you've had experience assembling it??

Thx, Leo

marko · 09-19-2015, 03:49 PM

Welcome to the board, you've come to the right place for help.
Here's a link about the OPRV that should help.
944 Foot To The Floor: How to remove and replace OPRV (Oil Pressure Relief Valve) on a Porsche 944

Porscharu · 09-19-2015, 04:57 PM

My understanding is the OPRV only "relieves" pressure at higher rpms. During idle the OPRV has no effect on building oil pressure.

fiily · 09-19-2015, 05:05 PM

crank bolt loose? That the only time I have seen low/no oil pressure.

155 ft lbs is porsche specs

Bradical · 09-19-2015, 06:30 PM

Your oil pump is loosing its prime. The noise is from the oil pump running dry for a bit, most likely. With the engine cold, remove the oil filter and pour a little oil down the hole and screw the filter back on. If you have oil pressure right away when you start it up, then replace the oil filter and be on your way. I would recommend replacing the oil pump drive gear because its probably a little worn from being started dry a few times.

I suspect the oil filter check valve isnt working.

marko · 07:45 PM

filly,
Already checked that, torqued to 155ftlbs plus a little more.
Bradical,
I have already tried the oil in the filter hole thing, but no change. Also put on a new Mahle filter with no change. Now that I think about it, there is a center hole for the filter and a passage to the right of that. Should I be pouring the oil in the center hole or the other passage? I filled the center hole when I tried it.

Bradical · 09-19-2015, 08:18 PM

No, its the center hole... I am hoping that someone else chimes in before I tell you that there is a service bulletin about this issue that recommends you apply LocTite 574 to the mating surfaces of the pump. I am not totally sure how difficult it would be to dismount the oil pump with the oil pan still installed... Maybe not possible.

marko · 09-19-2015, 09:30 PM

I did a front seals job, including the oil pump seals and o-ring about 30k miles ago. I did use loctite 574 to seal the mating surfaces. Didn't need to drop the oil pan. The noise does sound like it is coming from that area.

marko · 09-20-2015, 09:45 AM

I took out the OPRV this morning just to rule it out for sure, should have started with this first. Cranked the engine 5 cycles, then off, then 5 more cycles, no oil came out the hole. Guess I'm left with the oil pick up tube or the oil pump? Is there a way to determine which might be more likely the problem?

kdjones2000 · kdjones2000's Garage

The oil pump is a gear pump - don't expect that to ever fail unless there is some big trauma to your engine.

I would go with pickup tube...

John_AZ · 09-20-2015, 10:43 AM

Hi Marko,
Another post. Solved but unresolved.

http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/620006-924s-oil-pressure-gone.html

J_AZ

Leo944 · 09-20-2015, 12:07 PM

Marko-- Thanks for the link to the 944OnTheFloor, however, my problem centers around re-assembling the OPRV not installing it.

My post explaining my complete lack of oil pressure and upgrading the OPRV type from the 3-piece to the retrofit one-piece has yet to appear because it awaits approval by a moderator. I'm hoping it will be posted soon.

In a nutshell, I purchased a used retrofit OPRV & took it apart in order to clean all parts and replace both o-rings. According to Porsche, the re-assembly calls for placing the inner o-ring on the housing and pressing the components together using a vise. While doing so, it appears as though the inner o-ring (black) does not fit properly inside the screwcap when the housing assembly is pressed into the screwcap. I believe that the o-ring will be destroyed if I continue to press the vise further.

So, my question to forum members, have any of you attempted this & what is the best method to press these mothers together without cutting up the inner o-ring in the process? As we all know, they're not cheap. Anyone?

John-AZ-- Thanks for links to very informative earlier posts and your very similar issue with a lack of oil pressure. Do you have any suggestions?

Leo

Bradical · 09-20-2015, 04:27 PM

Seems odd that you build oil pressure after awhile though.

marko · 09-20-2015, 07:31 PM

I dunno guys, doesn't seem to be a clear this or that. I'll go with checking and resealing the oil pump first since it will be so much easier then checking the pick up tube.
Found this oil flow diagram while searching, makes it a little easier to visualize the oil path.
944 Oil Flow Diagram

djnolan · djnolan's Garage

After doing belts, I had a low oil pressure problem, turns out the crank pulley was off center and didn"t seat fully. It was still torqued tight, but not all of the way on the crank.

I still have nightmares.

marko · 09-21-2015, 07:57 AM

I sure wish that was the my problem. Pretty sure it's on there good, but I'll take a look at it tonight just to be sure.

John_AZ · 09-21-2015, 05:12 PM

Quote:

Originally Posted by Leo944

[So, my question to forum members, have any of you attempted this & what is the best method to press these mothers together without cutting up the inner o-ring in the process? As we all know, they're not cheap. Anyone?

John-AZ-- Thanks for links to very informative earlier posts and your very similar issue with a lack of oil pressure. Do you have any suggestions?

Leo

A vise or press should not be needed. If the black "O" rings are pre lubed, just gently pressing the cap over the "O" ring in your palm is all that is necessary for my '87-'88 924S relief valves.

Pelican Parts - European Automotive Parts and Accessories - Porsche • BMW • Mercedes • Volkswagen • Audi • Saab • Volvo • MINI

Also, I mention this again, do not use URO or any cheap oil pressure sender.

Use only OEM Porsche or Mahle oil filters with the proper oil "anti drain valve"

Check the wiring from the oil pressure sender over the WP. It cracks and gets brittle.

I did notice in Clarks TSB-19017 that there is an update to the earlier TSB 19017.

In item 4 on the repair procedure, Clarks has added a "Caution:
on some valves the damping piston may have a 45' camfer on one end. This end faces the screwcap."

Just more information.

GL
J_AZ

txhokie4life · txhokie4life's Garage

The pumps do fail -- our ChumpCar had a one go just before loading up for a race.

What we do to check oil pressure/flow is to pull the oil filter, pull the spark plug from the rotor
(and sometimes we'll pull the fuel pump relay) and turn the engine over with the starter
a few times and see if oil comes out the filter hole. We will also prime the pump by
filling the center hole on the oil filter housing.

It usually takes a few tries, but if the pump is working and there's no issues with pick-up/vacuum seal to the pump, then we get oil out the filter hole.

Mike

marko · 01:53 PM

Well, I got my oil pump out, didn't find anything exciting. The gear has some resistance to it, had to insert the small drive gear piece in order to turn it. It pumped out a little oil when I turned it. Could be normal I suppose. Is there anything I should be looking for?

Edit: Mike, I would think you would also get oil coming out of the OPRV hole when cranking. From the oil diagram it is right after the oil pump and before the filter. The oprv has a return to the oil sump when open, but I would expect to see some oil coming out of the OPRV hole.