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justinboyd

low oil pressure

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Hi all lotus dudes

i have a lotus esprit turbo Lc and have a oil pressure problem.

oil pressure on start up cold is 60 psi and after 15 minutes of idling with water temp at 80 degrees c oil pressure drops to 20 psi,at idle 1000rpm

i rev the car to 3000 and oil pressure is 25 psi

Do the esprit^s have a oil pressure relieve valve hidden somewhere and does anyone have suggestions on this problem .

Thanks

jussy

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With the engine hot the idle oil pressure can be as low as 5 psi. At high revs, 6000 rpm, it should be 45 psi or more.

Does the engine knock or rumbel when it starts from cold indicatiing worn big ends? Do you have a mechanical gauge or an electical one with a sender on the engine?

I would imagine that there is a pressure relief valve built into the pump and it's possible that it could be stuck but I would think that would drop the idle oil pressure to nothing.


S4 Elan, Elan +2S, Federal-spec, World Championship Edition S2 Esprit #42, S1 Elise, Excel SE

 

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The oil pressure figures you have listed sound normal for a 9XX engine.

The fact that the pressure limits to 60 psi when cold indicates the relief valve is working.

If it was stuck open you would next to no oil pressure at idle.

Hilly


1981 S3 4.2 V8 6 speed (The Mutant)

Mutant V8 Conversion Thread

Knowledge is power .................... apparently.

 

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Hi all lotus dudes

i have a lotus esprit turbo Lc and have a oil pressure problem.

oil pressure on start up cold is 60 psi and after 15 minutes of idling with water temp at 80 degrees c oil pressure drops to 20 psi,at idle 1000rpm

i rev the car to 3000 and oil pressure is 25 psi

Do the esprit^s have a oil pressure relieve valve hidden somewhere and does anyone have suggestions on this problem .

Thanks

jussy

Hi Jussy,

I want to concur with what Hilly and Trevor said, and elaborate a little bit.

The relief valve is in the oil pump casting and is visible when the oil pump is unbolted from the auxiliary housing. It is a little metal plunger that is spring loaded to be closed; when there is too much oil pressure, it pushes the plunger in and oil is allowed to escape past the annulus and rotor. It is a very simple, zero maintenance design that I'd be shocked to ever see go bad.

Personally, I think your oil pressure numbers are a little lower than on a new engine, but nothing to be concerned about. The first question I have is what weight of oil are you using? This has a noticeable effect on oil pressure in the 9XX engines; if outside temperatures stay above freezing, it should pretty much be something in the range of 15- or 20W50. If outside temperatures go below freezing, see what the owner's manual says.

The second question I have is are you reading from the gauge on the instrument panel, or are you hooking up a calibrated gauge directly to the engine? I would make sure to verify the accuracy of the gauge first (yours has a mechanical Smiths gauge, right? -- I've seen a couple of those read 0 at idle when a mechanical gauge read 15).

With that said, a newer, tighter 9XX engine in a comfortable climate with somethingW50 oil will make between 70-80 psi on idle at startup, unless of course the relief valve is letting it go at something a little lower, which is absolutely fine. After driving (not just idling) the car normally for 1/2 an hour, 1000 rpm usually gives you anywhere between 15-25 psi. Agressive driving will result on the lower side of that. The numbers stated in the service manual (5psi at idle) are MINIMUMS; you should only see these when the car is driven excessively hard (i.e. track use or a very spirited run) and the oil is really heated up.

Personally, I like to see 50psi give or take when cruising on a highway in summer (3k rpm) and 20+ psi at idle (1k rpm) after cruising 1/2 hour in summer. But as the engine wears, those numbers will inevitably drop a little. That's part of the normal wear of the engines. Ultimately, the thing that is important is that it does not go below the factory stated minimums; just be mindful that you will first see those numbers when the car is driven hard. So drive your car hard in warm weather with the proper weight oil and measure your pressure with a calibrated gauge. If it is below the numbers stated in the manual under those conditions, then it's time to be worried, and make plans to replace the bearings before you end up with a rod knock and an ovaled crankshaft journal, or worse. Until then, don't worry.

One more note -- Trevor mentioned listening for a knock or rumble when it starts. When you start the car for the first time in a day or more, watch the oil pressure gauge while you listen for the knock or rumble. If your bearings are worn and you have a knock starting, you will only hear it in those few seconds before oil pressure builds up; once oil pressure registers on the gauge, you won't hear the beginnings of a rod knock any more.

Hope this helps!

Edited by Tony K

Tony K. :)

 

Esprit S1s #355H & 454H

Esprit S2.2  #324J

1991 Esprit SE

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Hi and thanks for the valuable info.

I am using 20w50 oil and it is hot here in south africa with a average temp of 35deg c

I am reading the pressure off the instrument pannel and will search for a calibrating instrument to make 100perc sure thanks.

I only here rattling noise on the cam box after driving hard and the temp is fairly hot but nothing on start up .

Thanks for the help

With the engine hot the idle oil pressure can be as low as 5 psi. At high revs, 6000 rpm, it should be 45 psi or more.

Does the engine knock or rumbel when it starts from cold indicatiing worn big ends? Do you have a mechanical gauge or an electical one with a sender on the engine?

I would imagine that there is a pressure relief valve built into the pump and it's possible that it could be stuck but I would think that would drop the idle oil pressure to nothing.

Hi ,i rev the engine to 5000rpm when hot and get 40psi and i luckily dont here any rumbles or knocking yet but do get a rattling noise on the cam box when the engine is hot.

i have a mechanical pressure guage.

Thanks for the info

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