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High Oil Pressure

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Old 02-06-2003, 01:16 PM
  #16  
Randy V
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I'm back.

Ran a separate test gauge an determined that oil pressure is high. Specs indicate should be 72 pounds @ 4000 RPM - my car is pumping up to 92 pounds @ 4000 RPM.

Replaced the oil pressure relief valve spring - (located in the front horizontal port forward of the oil filter).

No change! Oil pressure is still too high.

What the heck is going on? What else could be causing this high oil pressure condition?
Old 02-06-2003, 03:06 PM
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WallyP

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You replaced the oil pressure relief valve spring - but no mention of disassembling and cleaning the oil pressure relief valve. Did you do that?
Old 02-06-2003, 03:28 PM
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Randy V
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Sure did Wally. Removed, cleaned and inspected. No scoring or buildup on the piston that would indicate a binding condition.

When you say 'relief valve' I assume you are referring to the entire piston assembly?

Any clues?
Old 02-10-2003, 01:27 PM
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Randy V
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Stumped ya, eh Wally?

Guess I'll have to place a call to the left-coast guys and see if they have any suggestions.
Old 02-10-2003, 01:56 PM
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WallyP

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The oil pressure relief valve on your car should limit the max oil pressure to 8 bar (115 psig). Since you aren't getting that much pressure, I would assume that the relief valve is OK.

The minimum oil pressure at 4000 rpm is 5 bar (73 psig), with no maximum specified.

I doubt that you have an oil pressure problem.

I think that you have a valve spring or lifter problem (as suggested earlier by Jim Bailey).
Old 02-10-2003, 03:00 PM
  #21  
Randy V
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Well, sounds like my guy misinterpreted the data spec, didn't he.

Thanks Wally, that really helps clear that one up.

Time to pull the cam covers...
Old 02-11-2003, 06:40 AM
  #22  
John Struthers
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Randy,
I'm interested in this one.
Any associated noises, floating, straining sounds?
Hard to believe that the German God's of steel would have crafted a valve spring made of the finest Solingen metal available that went belly-up after a mere 100,000 - 200,000 miles.
Is nothing sacred? Miles on the Odo.?
Hope its a worn lifter, as I would not want to change just one spring set without compression, tension testing all of them -time and money-.
Good luck on this one Randy. Take Pics if you do the work.
John S.
Old 02-11-2003, 02:31 PM
  #23  
Randy V
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140K John.

Engine runs great except for this one problem - no noises, misses, etc. at lower RPMs. Will be pulling the cam cover and checking/replacing the #3 cylinder lifter spring(s).

My mech bit himself in the head with a hammer when he realized he was interpretting the tech data as max pressure instead of min. Wally pulled the rabbit out of the hat yet again!

I'll drop back in when complete and report results.
Old 02-11-2003, 07:13 PM
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Oh ya, thanks to Jim B. too for his earlier note on the MINIMUM oil pressure reading.

Sorry Jim - I'm losin' it...
Old 07-24-2012, 10:18 PM
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pcar928fan
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(holy thread resurrection Batman!)

Guys,

I tried to find a similar (though opposite) thread and failed... Maybe some of you have better search skills than I...

My '95 has a bit of a problem and I am not sure if it is a gauge problem or an actual REAL problem I should be worried about.

The short and long is that the oil press and fuel gauges do not seem to be reading correctly... The OP at cold start up is just a touch over 4 and even with rpm's does not go over that. When really hot it drops to just under 1... That, of course, is WAY TO LOW and it sets off the "insufficient oil pressure" warning on the digital dash (as it should). This does not happen when the revs are up but when at low idle (in gear, at a stop...the cars idle is a touch low as well...which if brought up to spec would at least eliminate the warning, but perhaps not the problem!) That said, when fully hot at high rpm the OP is never over 3.5 bar...again this differs from all my other 928's but the range from idle hot to high rpm or cold start is the same as the other cars. In this case it is just low...instead of being 2-5 on the gauge it is 1-4...

The car runs fine and does not act like this is a problem...my '81 has had issues with low OP and when it drops below 1 it will actually die. The GTS does not die or even act like it is upset by the situation at hand.

The fuel gauge (just below the OP gauge on the GTS) also reads incorrectly... When the tank is full it shows just slightly above 1/2 full... Goes down as you drive but not correctly. By the looks of it, when the tank is actually half full the gauge will likely read empty... The distance to empty reads off the gauge so when the tank is full it will say something like 170 miles to empty... that is about correct except that the tank is in fact full and you really have about 320 to empty or way more if you are on the highway at a reasonable pace.

Are these problems related to a ground issue on the cluster itself or should I be worried about low OP when hot and if so what should I do about it? I really don't have any way to do any of this work myself but would like to be able to offer direction to the shop if I choose to take it in for this.

On the other side of the cluster when fully hot and in traffic it seems to read that it is running hot... As in the needle goes WELL in to the read and nearly to the top of the red... To say that is disconcerting would be an understatement. Considering the PO of this car spent $37k on it over the last 9-10 years he got RIPPED OFF! All work done (and normally TWICE!) at the Stealership and he didn't pitch a fit about it! UNREAL! For the money spent this car should be perfect! I will spend a hell of a lot less than that and it WILL BE!

SO, thanks guys for any insight you can provide on these issues as I get '95 GTS #51 of 77 sorted!
Old 07-24-2012, 10:46 PM
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ROG100
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Your oil pressure readings are consistent with GTS cars in high ambient temps in TX.
My car does not trigger the low light unless really really hot.
What has helped --- use 20w 50 - Royal Purple is what I use.
Add an extra oil cooler to the rad and combine the air cooler with the water cooler.

As for your water temps - something really bad going on there - you should see maybe third white line after hard driving in 100F+ temps. Are both the fans working? Normal for GTS to burn out the two fan fuse blocks - need replacing with heavier fuse connections that stand proud of the central electric.
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Old 07-25-2012, 03:04 AM
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Thanks Rog, I do know that one of the fans is NOT working. Have never seen oil press like that in either of the other two GTS's though... I'll move to heavier oil and and get that second fan going ASAP!
Old 07-25-2012, 05:35 AM
  #28  
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James, your '95 has the digital dash, so you can use it (by bridging pins 5 and 13 on the 19 pin socket under the carpet on the passenger's door sill and wobbling the left hand stalk in a secret manner) to have the digital dash read out analogue codes that can be correlated to engine temperature, oil pressure and so on. Years since I've done it but hugely useful for determining whether the problem lies with the gauge itself or is more likely a real problem. You'll need the 'diagnostic' section of the manual for instructions on this. Easy to do once you now how.

In addition I'd suggest you get an infra red gauge and check the block to radiator radiator hose to see how hot the water really is. Similarly take some cam cover readings. Compare these with other 928s.

You can also use a multimeter to test the water temp sender. Remove the sender unit, put it in boiling water, and record the water temp as it cools against multimeter reading, and compare against control values. Is it sending accurate signals?

Are your fans turning? Both with AC on? And, are they turning the correct way? Running in reverse won't help at all. Is your radiator blocked? Is there rubbish restricting airflow through the radiator?

If you finally determine that everything really is OK, via the above and other means, that the oil pressure is OK but the gauge is reading wrong, that the water temp is OK but the gauge is reading wrong, then you'd need to gett he gauges recalibrated. There are at least two ways to do this. One way is to send it to a Bosch agent and spend lots of money. The other way is to remove the needle and put it back on so that it reads accurately.

Good luck
Old 07-25-2012, 11:03 AM
  #29  
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A lot of good info in what Dave says to establish real reading v gauge.
My GTS never reads more than 4.5 bar - when cold.
I am pretty sure that the "low pressure" light is triggered seperatly to a gauge reading so very accurate.
If one of your fans is out you will run into the red very quickly - happened to me a few times.
Old 07-25-2012, 12:44 PM
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Just to clarify, this thread was started regarding my previous 1979 convertible.


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