Sab

My oil pressure shows below 1.5 BAR at idle 675 RPM and reaches 3 BAR at 3k RPM, when the car is at operating temp on a hot day.
I am running Mobil 1 SuperSyn High Mileage Formula 10W-30.

Now I think the gauge is incorrect, since my engine seems very healthy. I have virtually no oil consumption (I don't have to refill anything between 4k oil change intervalls) and I had a leakdown test performed (10 - 2 - 3 - 5 ; 1 - 5 - 3 - 10 %leakage).

My fuel gauge shows 3/4 when filled up, my voltage gauge shows 11.5 when it is really 13.5, so I guess it is just very likely that the oil pressure gauge has the same problem, no?

How could I test it and what would be the cause if my pressure is really too low. And most important what is too low for the 928 S4?

I had two 500 SL Mercedes before the 928 and one always showed 2 BAR at idle and the other 0.5 BAR, when I complained at the dealer he stated that that was within the norm.

Cheers,
Sab.

Tony

I havent tried but you can do it on other cars. Un screw the oil pressure sender and screw in an actual gauge with an extension on it. you will need the car up on the ramps im sure..

Low oil pressure at idle could be the fault othe cam shaft plugs. If they are missing they dont stop the flow of oil to the aft bearing journals for the camshafts. The S4 cams are shorter than the predecessors so they placed plastic plug across the oil holes. Many times they warp and fall out. When this happens the oil pressure drops at idle and a bit at midrange. At WOT you should always see it at 5bar.


this is what they should look like..



and this is what they shouldnt...


and they dont belong here...


heres a web page i have on it...
http://members.rennlist.com/v1uhoh/nasty.htm


HTH

MikeN

You should see the following.....

About 2 - 2.5 bar at idle
Just about anything above idle should peg the needle at 5.

When did your readings start?

Also, you really should be using a thicker oil......maybe most of your problem. I use Mobil 1 15W-50.......perfect for just about all outside temps except maybe sub-zero winters.

Jim V

Is your guage ever reaching 5 bar? Most any 928 engine,even a worn out one, will hit 5 during normal operation so if your's is maxing at 3 I'd blame the guage.

This sounds very familiar to how mine was acting before I pulled the pod and cleaned connections and grounds.

Doug Hillary

Hi,
Sab - was this a sudden thing?
You already have some excellent and meangful advice to consider. It all needs carefully looked at and especially the gauge considering your other readings ( electrical problem ?)

Oil viscosity can be an issue too and PERSONALLY I would not use the M1 10w-30 grade in my car unless I was getting down to -25C temps in winter

IMHO I would seriously consider moving up to a 0w/5w-40> grade M1 oil in any case. Such oils are thicker than M1 10w-30 at both 40C and 100C and are much more "robust" at high rpms, temperatures and loads

Regards

Sab

,
great advice, I will change the oil right away.
Tony, I hope my plugs did not fall out of the cams.
Jim, yes it does peg out at higher RPM's or when cold.
Doug, it always seemed a bit low, but I never remember it to dip below 1.5 and yesterday it did. (I used to have thicker oil before, I think Castrol 20W-50)
Thanks everyone,
cheers,
Sab.

Jerry 87 928S4

Sab, mine does the same thing. On occassion, when hot it will even drop down to 1 and the warning light will come on with low idle. I tested it with a meter connected where the oil sending unit goes. I got 18 to 20 PSI which confirms the 1.5 bar. It seems only to be a problem when it is exceptionally hot out. I did change to 15W - 50 Mobil 1 and it seemed to improve the pressure if only slightly.

My voltage guage reads 1 volt low since I also tested it with a meter. Since I have had the condition more than a year, I have assumed it is just the electrical system reading low. Oh, my gas guage reads low like everyone also.

I have always wondered if I have the problem Tony mentions. I did check one side when I replaced a valve cover gasket and all looked great.

Z

I've heard of the plastic plugs coming out on several 928s, and saw one that was out just recently when I took the valve covers off of a car with low oil pressure. The loose plastic plug was the one in the same location as in Tony's pictures, and it ended up in the same location in the head as his too. All of the other plastic plugs in that car looked fine. It may be occuring in different model years too, but every case I've heard of was on an '87 model year car.

Tony

The replacement is an aluminum pin. of the same length as the diameter of the plug, with a narrow end that extends down into the oiling hole. It wont come out! I got them from 928intl.

I f you go the with the new pins, make sure your camshaft seals are in VERY good shape as there will no longer be a physical plug to keep oil being flung around in the head from being sent back on to the cam seal. The physical presence of the plug actually helps prevent that. the pics i posted may make that a bit easier to understand. (upper right plug has the cam seal behind it...left has been removed)

My guess on all the scenarios like this (87 on wards.) one of the plugs is not seated properly. Only one of mine was missing and it gave the symptoms you indicate.

Don '85S3

Sab:

Very common problem. My fuel gauge shows 3/4 when full. Oil pressure gauge shows about 1 when idling and maxes out at 3 when at higher revs. I think the solution (as Jim stated) for all of the above is pod removal and cleaning all contacts. More work than it's worth at the moment for me.

mark kibort

As I posted many times, mobil 1 did this in my 79 track car. only on hot days, when the engine was pretty warm. (fans cycling, etc) sometimes, when really hot, the oil pressure warning light would come on, and it took 3500rpms to get 5bar. (my S4 with redline or Amzoil only needs 1500!)

We will know if its the oil for sure, when the new owner changes the oil to something other than mobil 1.

remember, Im still suspect to mobil 1 as most of the engine catastrophies have been on mobil 1!! probably fine for street use, but Im concerned about it for racing.

anyway, those numbers you have seen on hot days resemble mine on mobil 1.

mk

Nathan Valles

Possibly a dumb question but....

If you have the heads out why not just have the holes welded shut, or just tap the hole and plug them with a set screw and some locktite?

Am I missing something?

drnick

hey you guys, just bought an s4 club sport/se with lowish oil pressure at idle!

these cam shaft plugs, they can be accessed simply by removing the cam covers??