Oil pressure

[techspy]

Hello all. well, I finally picked up my baby and we have been having a great time! What a difference from my pervious 83 turbo! I have a question though. First, I know that the oil pressure guages are known to be inaccurate, but when the engine is warm, especially idling in hot weather in traffic, it reads really low. So much so that some times the oil pressure warning light flickers. But when I give a little throttle, it comes up just a tad and the light goes off. Then when back on the highway, the temps drop and the pressure comes up. The pressure never shows more than say one third on the guage. So, I was thinking about installing a nice electronic oil pressure guage just to see the actual reading. I am not removing or disconecting the stock guage, but wanted to just install the electronic sending unit and just use the second guage to monitor the ctual pressure for awhile then disconnect it, leaving the sending unit for future readings. So, any suggestions on where and how to connect an additional sending unit? Also, does the low pressure warning light receive its "instructions" straight from the sending unit or does it get info from the oil pressure guage or ecm? If it is from the sending unit, maybe the unit needs replacing if it is that far off?


Thanks

John
94 S4

[lotusespritworld]

I'm looking at doing the same with my 92 SE, thinking of replacing the dial or adding one where the stereo goes. Mine reads really low as yours. Not had the time or money as yet, but it's on my long list.

kato
Lotus Esprit World

[dictys]

How do you know whether or not the gauge is correct at present?

Maybe the reading is correct?

just being the devil's advocate

[lotusguy]

Hi,

On the 9XX engine, the oil pressure is really sensitive to the type/weight oil you're running. Be sure to use the manufacturer's spec or you'll get lower readings. Also, the filter yoiu choose can make a difference as well...Jim'85TE

[sanj]

The oil pressure sender on the S4 is a dual unit. One terminal, which gives a variable output, feeds the gauge, the other turns the warning light on. There is a relay in line with the latter, which is supposed to prevent the light from ever coming on below 1600 rpm. Evidently the acceptable hot oil pressure at idle can be low enough to trigger the low-pressure switch, so Lotus put this (rather dangerous) bypass in place to avoid alarming the driver. Why your oil light flickers at idle bears investigating, perhaps the relay is not functioning.

Cheers,
Sanj

[lovemonkeysd]

I have the same problem as techspy on my '90 SE. When idling in warm weather the pressure seems really low, but upon resuming driving it will go back up, but never gets above about halfway on the gauge. Is this drop in oil pressure standard, or is it indicative of something going wrong (or already wrong)?

Thanks,
Dan

[techspy]

After talking to my local Lotus mechanic, he believes that it may be a faulty sending unit. I am going to have it replaced when it goes back to the shop for storage. Unfortunatly I won't be able to give any info on the results for about 6 months when I return.

John
94 S4

[cnh1990]

On my 90 SE in hot weather with the engine temp at 90 I read 2 lines from the left at idle and when at speed it reads any where from 1/2-2/3 on the gauge.
Calvin 90 SE

[Lasse]

Cnh1990, What type of oil are you using?

I use Mobil 1 Rallye Formula 5W/50. I have the same low readings at conditions described by the other posters above. I have put this question forward to Lotus and the say that this is to be considered as normal values using this oil.
The meter is an "off-shelf" unit. If you have the unit without numbers on the scale you should be aware that the last mark before the red zone is 2kg. This means that the required minimum pressure at idle (0,35kg) is VERY close to "0".

Best Regards /Lasse

[lotusguy]

Lasse said:

Cnh1990, What type of oil are you using? I use Mobil 1 Rallye Formula 5W/50. I have the same low readings at conditions described by the other posters above. I have put this question forward to Lotus and the say that this is to be considered as normal values using this oil. The meter is an "off-shelf" unit. If you have the unit without numbers on the scale you should be aware that the last mark before the red zone is 2kg. This means that the required minimum pressure at idle (0,35kg) is VERY close to "0". Best Regards /Lasse

Lasse,

Using 5W-50 will give you low readings. A better oil is Mobil 1 15W-50 which is widely available. Happy Motoring! Jim'85TE

[cnh1990]

Lasse said:

Cnh1990, What type of oil are you using? Best Regards /Lasse

Castrol Syntec 5-50 with a Purolator filter.
The engine has 34K of mostly highway miles.

The 5w increases to 50 as the temp does so it should not be that much of a difference after warm up to the 15-50.

Calvin 90 SE

[Lasse]

What I'm trying to say is not that I find it a problem that I get low readings.
The Mobil 1 Rallye Formula 5W/50 is the oil recommended for the 910 engine in the Esprit Turbo. What I'm trying to say is that low readings at idle and high temeratures should be expected and is not subject to any problem. I have checked this with Lotus and that is at least their standpoint. At least not with the Rallye Formula oil since it is fully syntethic. IF HOWEVER you are using a mineral oil and get these readings there can be problems. Syntetic oils create a lubrication film (don't know if that is the correct english term) doing ther job with very little pressure and therefor are superior to mineral oils, which are fully dependent on pressure.
The only fault I can se described above is that the "low pressure tell tale" comes on below 1600 rpm, which it shouldn't.

Best Regards /Lasse

[techspy]

Actually, after a little more attention, I have discovered that the tell tale light doesnt come on until I rev to start moving from a stop, and the rpm's pass 1600. Then, just for a split second, the light flickers. But once the rpm's pass 1600, it goes off again. So the relay is good. I am having my mechanic check out all the simple stuff such as the sending unit etc. Maybe it is because of using a "better" synthetic oil. But, I can't see THAT much of a descrepancy in oil pressure reading just from the type of oil. I mean, more than a 50% difference? Thats hard to believe

John
94 S4
http://24.31.219.162/

[superdave]

Hi there, even though the manual recommends 5W/50, my mechanic recommends the 15W/50 for older engines just like Jim has stated.
The 5W/50 will give you a lower reading especially if it's an older car.
Check your sender unit as my mechanic is just changing one on a 95 S4 which showed very low readings. Good news on that car is that is was a healthy car with a good pressure.


Cheers,



Dave Walters

[Lasse]

Again...

Low readings is NOT a problem when using an Oil with Low viscosity, because why are the readings low?

Because the oil is thin and flows more rapidly! And what does this mean? It MEANS that it COOLS the engine more efficiently.

If you have oil with high vicosity and get low readings either your bearing shells are worn out or you got a bad/worn oil pump. Now this is problem!

There is no end in it self having as high oil pressure as possible. It's not necessarily good because if the oil lubrication system is working as it should then a high pressure is equal to the oil passing slower through the bearings. In the worst case the oil may actually carbonise in the bearings because the temperature gets to high!

Conclusion: Low pressure (but of course above minimum values stated by manufacturer) is NOT a problem.

Best regards /Lasse

[tlannon]

yeah, but just because the oil viscosity is lower it wont cool more efficiently if the oil is crap in the first place....if you run a very high quality fully synthetic AND the recommended grade, it will cool even more efficiently.

[Lasse]

Thankyou, that was exactly what I ment! Thanks for making it even more clear!

/Lasse