Oil pressure question

[GreenGoddess]

Hi Guys,

 

I have noticed that the oil pressure on my car (84 Turbo) registers beyond the halfway mark and stays there until the engine is fully up to temperature even when the engine is only idling. Is that normal?

Once the engine is properly up to temperature the needle shows an oil pressure of just over 5 at idle which I believe is what it is supposed to be. Obviously the oil pressure increases up to around the halfway mark when motoring along at a healthy rpm. It is the oil pressure that is showing when the engine is cold that I am concerned about.

[drdoom]

What oil are you running?

[910Esprit]

Yes, that sounds a little unusual to me.   I would see that on initial startup, but then steadily drops to around 15psi on hot tickover.   (20/50).   TBH, I don't see much difference in behaviour if I switch between 10/60 15/50 20/50.   

If you have not changed to the oil since purchase, I'd suggest a new filter and a recommended grade.

[GreenGoddess]

Thank you. I have no idea what oil is in it although I know the oil and filter were changed less than 1000 miles ago (I've only done 300 miles or so since I bought the car 3 months ago).

I do notice that the oil filter isn't a genuine Lotus filter. Did I read somewhere that a genuine Lotus filter should be used due to a valve or something in the genuine filter?

Edited November 6, 2022 by GreenGoddess
fat fingers

[CarBuff]

1 hour ago, GreenGoddess said:

Did I read somewhere that a genuine Lotus filter should be used due to a valve or something in the genuine filter?

That is correct, in theory.

 

In practice, it is less important than using the car every week or two.😇

 

We have used the smaller-than-stock WIX #51374 (due to lack of clearance for the strap wrench) with no issues. 

 

BONUS: The smaller filter takes less time to re-fill when starting the engine.

Wrenches_Filters.bmp

[GreenGoddess]

Thanks again. I already have the new oil and a proper Lotus filter to go on. I may try your recommendation next time 😊👍

[ChrisJ]

Must be a genuine Lotus Filter.

After 35 years I still have no idea of what the actual oil pressure reading is on the gauge  (I just go by the position of the needle)

• Start up - Oil pressure is on the right
• Once warm, oil pressure is on the left (at idle)
• Pootling along, - vertical.
• Pressing on - on the right (but you are probably concentrating where you are going at this stage to be looking at the gauges)

Same with the temperature. Vertical OK, Not vertical - do I have an issue? Too far to the left - has something broken (I had a pipe burst in 1989 that gave this indication), Too hot, are the fans going to come on?

 

[GreenGoddess]

12 hours ago, ChrisJ said:

Must be a genuine Lotus Filter.

After 35 years I still have no idea of what the actual oil pressure reading is on the gauge  (I just go by the position of the needle)

• Start up - Oil pressure is on the right
• Once warm, oil pressure is on the left (at idle)
• Pootling along, - vertical.
• Pressing on - on the right (but you are probably concentrating where you are going at this stage to be looking at the gauges)

Same with the temperature. Vertical OK, Not vertical - do I have an issue? Too far to the left - has something broken (I had a pipe burst in 1989 that gave this indication), Too hot, are the fans going to come on?

 

Thanks. That's exactly what I was hoping to hear. My car seems to behave in exactly the same manner which is a relief.

[paulbrown22]

On 07/11/2022 at 00:03, ChrisJ said:

Must be a genuine Lotus Filter.

After 35 years I still have no idea of what the actual oil pressure reading is on the gauge  (I just go by the position of the needle)

• Start up - Oil pressure is on the right
• Once warm, oil pressure is on the left (at idle)
• Pootling along, - vertical.
• Pressing on - on the right (but you are probably concentrating where you are going at this stage to be looking at the gauges)

Same with the temperature. Vertical OK, Not vertical - do I have an issue? Too far to the left - has something broken (I had a pipe burst in 1989 that gave this indication), Too hot, are the fans going to come on?

 

Sounds much the same as mine!

[rgh0]

The behaviour is normal as others have observed and all dictated by hot versus cold oil viscosity, revs and thus pump delivery volume and oil pressure relief valve setting

i.e.

* The oil pressure relief valve will normally open when the oil is cold. It is set around 40PSI  i.e. at about 3/4 scale on gauge. 

* When the engine is hot and running at around 3000 rpm the pressure will normally be below the relief valve setting and pressure indicated will vary with revs, more revs more oil pumped around and higher the sensor pressure with needle in the 1/4 to 3/4 range depending on revs and oil used and oil pump and engine wear

* Hot and at idle oil pressure will drop to less 1/4 on the gauge with the reduced oil flow 

 

cheers

Rohan

[CarBuff]

9 hours ago, rgh0 said:

It is set around 40PSI  i.e. at about 3/4 scale on gauge. 

Don't forget, Lotus used different oil pressure gauges during the Esprit's  lifetime.

 

The '84 used a 5 BAR gauge, the Stevens cars used a 5 BAR gauge at first but then went up to a 7 BAR unit.

[910Esprit]

11 hours ago, rgh0 said:

The behaviour is normal as others have observed and all dictated by hot versus cold oil viscosity, revs and thus pump delivery volume and oil pressure relief valve setting

The way I read the post was that the gauge/pressure was not progressively reducing during warmup, but as if it was reading high and then 'suddenly' dropping at some point in time.  If so, such behaviour could be to do with the oil stat I guess but doesn't seem of major concern.

[CarBuff]

Well, I can say with certainty that the sender wiring could cause an erratic reading.

 

Ours had an intermittent bad crimp at a connector, and I lived with that for ~20 years.

NOTE:  High resistance causes the needle to PEG at max pressure.

[EXCEL V8]

I'm building a jig to assess the pressure at which the oil pressure release valve opens.  Think this would be handy to know before fitting to the engine.  Gives an opportunity to shim the spring if needs be.

Pete