Oil pressure

[tulit]

On my 06 Gransport I’m seeing warmed up idle oil pressures drop to just a hair over the 1/4 mark on the built in gauge (1.25 bar, ~20psi).

Cold idle is pegged at 5 bar. And the pressure always returns to being pegged at 5 bar after revs go up slightly above idle (~2500rpm and above).

Could this be a symptom of a bad sender or possibly something else?

I see most people saying idle should be closer to 2.5 bar warm.

 

[lambertius]

I can't speak for Canada, but locally every Gransport I've driven has a low oil pressure warning on a warm day. There are a few reasons this happens:

1. The nature of dry sump systems means that oil pressure can move significantly between idle and load.
2. As oil ages it loses its viscosity, so the natural wear in the oil will make it thinner regardless of external temperature. Could be time for an oil change? Also, dry sumps shear oil much faster than an average oil pump for reasons I've never bothered understanding, so regular oil changes matter.
3. Engine mileage will see oil pressure less stable over time.
4. The OEM oil is a bit weird, normally you get more than one viscosity rating since global temperatures tend to vary. Where I am I'm running a 5W50 which 100% addressed the issue, even on 40 degree days. If you do run a non-recommended engine oil I strongly recommend not changing the winter rating, and when I did it I compared all the OEM oil specs against the oils I was looking at, as there were some cases where there was a bigger difference between two 5w40s than there was between the OEM oil and the 5W50 I picked. Unless you want to do an intentional startup procedure, I'd stick with the OEM winter rating and just try and run a bit thicker at the hot end.

Keep in mind, high tolerance engines do need thin oils to work so don't go thicker unless you need to, and the the low idle pressure is less of an issue than low pressure while running. If the oil in it is new and its still not keeping up then I'd suggest a bit of engine wear and a warm day are the issue, in which case a slightly thicker oil would help. If the oil is old, just change it.

 

[CatmanV2]

As long as it comes up fast when you press the throttle and the level is OK should be fine.

The senders do go bad, but they tend to wander all over the place. From memory the low pressure warning is also a different circtuit.

Not wanting to make a habit of disagreeing with the fine engineer that is @lambertius unless warm is a lot warmer there (yes it is, I know) than over here, actual lights are pretty rare in the UK.....

C

 

[Zep]

The main symptom of a failed pressure sender are a ticking action on the needle, but they do also go out of calibration, normally just before they start ticking. Your transition to full oil pressure at 2500 is a couple of hundred higher than it was in my car, but this does vary.

As @Catman said, lights are pretty rare in the U.K. and as I think the temperatures in your part of the world are comparable. On a super hot UK day (33C) and driven hard for some time you might see the light.

Other things to check are the engine earth strap for presence and clean connections and the connection to the post on the sender. There is a how too somewhere, I am sure someone will post it shortly if you do need to change it.

 

[Mr S]

Had it the other week on one of the hottest days we had. Gave her an Italian tune up, and stopped to get reverse and noticed the pressure drop and the light come on. No issues as had plenty of oil. However im changing the sending at some point soon. Though id be interested to know if there is a specific earth strap i need to clean up.

 

[tulit]

Thanks all. I’ve never actually gotten the low pressure light coming on and the readings are steady (no twitching). So either calibration or a real low pressure issue.

What’s interesting is I see that the f430 idles at just over one bar. Given it’s the same general engine crankcase/pump is there really any reason the 4200 should be any different?


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[Zep]

Had it the other week on one of the hottest days we had. Gave her an Italian tune up, and stopped to get reverse and noticed the pressure drop and the light come on. No issues as had plenty of oil. However im changing the sending at some point soon. Though id be interested to know if there is a specific earth strap i need to clean up.

It is between the body and the bell housing in the right hand side.

 

[Zep]

Thanks all. I’ve never actually gotten the low pressure light coming on and the readings are steady (no twitching). So either calibration or a real low pressure issue.

What’s interesting is I see that the f430 idles at just over one bar. Given it’s the same general engine crankcase/pump is there really any reason the 4200 should be any different?


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The Fezza might well drive the oil pump slightly slower due to the higher rev limit. Or the gauge calibration might be different (although the sender is the same). Your best bet is to base it on what others have seen with the same engine on the same car.

 

[tulit]

The Fezza might well drive the oil pump slightly slower due to the higher rev limit. Or the gauge calibration might be different (although the sender is the same). Your best bet is to base it on what others have seen with the same engine on the same car.

Surprisingly enough all the components from the crank to the pump are the same between the cars so the speed they turn should be the same. Of course a lot of the things driven by the pump may differ.

I guess my question then is - What’s the proper/expected oil pressure on these cars (as read from a well calibrated separate gauge not the built in one).


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[Zep]

If you find out, do let us know. What we do know is that the light comes on just below 1.25 bar on the gauge in the car, which I can verify on a new VDO sender in my car when I had it.

The pump drive is the same on the 430, but the pump itself is not, whether this has a bearing on its displacement is unknown.

It would be easy to get sucked into this, but you are traveling a well worn road, a lot of folks have had issues with calibration, flickering oil lights and to a man (well apart from one, where it was the earth strap) they have changed the sender and it has gone away. You pay your money and take your choice.

 

[hashluck]

I have replaced two senders on two cars and both times for the same issue - they were showing a reading with ignition on and engine NOT running so clearly could not be relied upon. I am not sure they can ever be relied upon though

From memory my gauge reads lower than I would like idling when warm but never to the point of showing a light and goes to 5 with very moderate throttle. Car has been into Emblem at least 5 or 6 times and never been mentioned as abnormal. Picking it up from a service soon so will remind myself how it behaves.

 

[Swedish Paul]

I thought oil pressure should be up with the ignition on and the car ready to start because of the dry sump?

 

[CatmanV2]

I thought oil pressure should be up with the ignition on and the car ready to start because of the dry sump?

I don't believe so. Mechanical oil pump, innit?

C

 

[Matt82]

The coupe GT that we’ve had for a couple of weeks now hasn’t had oil pressure less than 5 barg. Either I’ve got fantastic oil pressure all the time or I’m getting full scale deflection on the gauge due to a sender fault.

My money is on the later!

 

[CatmanV2]

The coupe GT that we’ve had for a couple of weeks now hasn’t had oil pressure less than 5 barg. Either I’ve got fantastic oil pressure all the time or I’m getting full scale deflection on the gauge due to a sender fault.

My money is on the later!

Yeah, that's a real possibility

C

 

[Zep]

The coupe GT that we’ve had for a couple of weeks now hasn’t had oil pressure less than 5 barg. Either I’ve got fantastic oil pressure all the time or I’m getting full scale deflection on the gauge due to a sender fault.

My money is on the later!

Yes, that’s deffinetly knackered!

 

[Matt82]

It’s on the list of things to sort!

Once I summon the energy I’ll write a thread with a list of all the issues I’ve discovered on it for all to see

 

[safrane]

I thought oil pressure should be up with the ignition on and the car ready to start because of the dry sump?

This was the case with my car, but Emblem informed me it is a fault. If they fault, I'm not going to argue.

 

[Mr S]

Mine only shows pressure when the engine is on, but i do plan to swap it out for a Zep special at some point soon

 

[lambertius]

All the ones I've seen, if you just put the ignition on (engine off) there is no pressure and so the warning light comes on until you start the engine.