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odd oil pressure behaviour


raptor07GT

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so, I have a 07 HR and it's had some electrical issues which were looked into before I went away on a long weekend (without car!). Result, the car had enough power in the battery to start the car after 4 days of sitting in the rain whereas before it killed the battery dead flat in 3 days.

 

New problem, drove the car for 4 days after electrical fix (new battery cable clamps and earth strap) and no issues other than the damned hunting idle and general slop in throttle response BUT Sunday after car had been sitting for 4 days the oil pressure gauge and warning light decided to play dead (gauge) and the pressure light came on. This happened after about 5 minutes of starting car and driving off. Stopped engine and checked underneath car. No drips, oil on dipstick in correct place and the engine didn't sound like it was dying. So, being stupid (and really hating this cars behaviour) I restarted car and drove on. Once the engine had heated up the oil pressure gauge started reading normally and the pressure light went out. Same again Monday today

 

crank car - oil pressure over 90 (might even be off the scale) when idling cold but within 5 minutes it drops to zero and light comes on

ignore every fibre in my body and all mechanical sympathy and keep driving and lo the gauge starts reading properly and the pressure light goes out. 

 

Checked oil level at work in the daylight and the oil is almost at the high mark. Oil is clean and fresh with filter less than 2.5k miles in. Er, how big a problem is this? Checking some posts, a mechanical gauge check is required to see whats actually happening there but I assume the pressure light is fed differently from the pod gauge ? Really really dislike this cars way of dealing with day to day stuff (i'm sure it hates me for driving with the oil pressure light on!) :bang:

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Hopefully it's just a bad sender, but the first thing to do is as you have said - get a mechanical gauge hooked up and see what the pressure is actually doing.

As long as the readings are good get a new sender fitted.

 

Top Tip -

DO NOT over tighten the sender when putting it in, the upper sump pan is aluminium and I have seen both stripped threads and one split, that's then a major repair or replacement!

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thanks guys. Bit of an update. Both this morning cold and this evening cold the oil pressure gauge was reading 60psi BEFORE i cranked the engine which seems a little odd to say the least. I drove to work (45mile trip) and the pressure was fine until until about the last 10 miles when it dropped quite a bit and had the light coming on and zero pressure at idle. Parked the car at work then 40 minutes later cranked it back up again to take to the garage next door and lo the gauge read zero before cranking and pressure was fine no light either. Anyways, garage didn't have a mechanical gauge but they reckon its the sender. These senders are not cheap just to replace on a whim :( 

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1 hour ago, raptor07GT said:

hese senders are not cheap just to replace on a whim

They're not terribly expensive, with the right tools you should be able to do it yourself, to save a bit of cost.

 

https://www.torqen.uk/nissan/350z/engine/electronics/1019-350z-nissan-oem-oil-pressure-sending-unit-sensor-switch-25070-cd00a.html

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On 29/01/2019 at 08:35, Keyser said:

Hopefully it's just a bad sender, but the first thing to do is as you have said - get a mechanical gauge hooked up and see what the pressure is actually doing.

As long as the readings are good get a new sender fitted.

 

Top Tip -

DO NOT over tighten the sender when putting it in, the upper sump pan is aluminium and I have seen both stripped threads and one split, that's then a major repair or replacement!

The sump split when they tried to take old sender out. I'm selling this POS when I eventually get it back :bang: :bang:

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  • 3 weeks later...

So bit of an update on this one. New sump and sensor fitted and now I have a guage that moves but something is horribly wrong. At cold I now have oil pressure about 60psi and hot, well it's not even registering however no oil pressure warning light come on. Garage doesn't want to take new sensor out in case the new sump splits so what choices are there for checking the actual pressure, any sandwich plate options or other pressure locations a gauge could be plugged into?  This is turning into a Greek tragedy :(

 

 

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Faulty gauge ? Wiring fault ?

Has the gauge even been checked ?

Not 100% sure as can vary on certain cars, but if you unplug the connector that meets the sender, get a piece of wire and bridge the terminals on the gauge side. The gauge should go up to max then back to zero when the wire is removed. If it doesn't then you probably have a faulty gauge.

 

can't understand why they wouldn't want to remove the new sender to do a pressure test if that and the sump is new.....unless they messed it up and just siliconed it in.

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New oem sensor supplied by vendor on here. Will get the gauge checked by bridging terminals. Anyone know if you can put a meter over the sensor and what it reads at different pressures?  

 

I guess the garage just don't want to risk the breaking of another sump, doesn't help me though. Any 350z specialists in central Scotland or even Scotland? 

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  • 3 weeks later...

hey bud, indeed Automek would be the next on the list. Chris at Dynatune (I've used his rolling road for my previous car) seems confident he can find the fault, he is also happy to put on a mechanical gauge to see what is actually happening whereas my original garage have gone to ground and dont seem to want to investigate further.  I just want it sorted so I can move on, it is a very expensive ownership that needs ending sooner rather than later :(

 

edit: Dynatune was on the recommended garage list :)

Edited by raptor07GT
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  • 1 month later...

ok, so final line on this one. Chris at Dynatune plugged in standalone sensor / gauge and we got 25psi at a hot idle with what seemed like pretty thin oil. Took some pics of the oil pressure sensor and had it confirmed it was the wrong sensor. How on gawds green earth the wrong sensor was in has not been established but that explained the crappy pressure reading. Happy I actually had oil pressure and it wasn't leaking either, I took the car up over the Applecross and enjoyed driving it about the Highlands. Got a replacement sensor sent direct to me and Chris fitted it last week. Fresh oil and Nissan filter fitted yesterday and lo we now have cold cranking pressure and of course the all important hot pressure at idle.  So for a dodgy sensor way back in January, 2 senders and a replacement mid sump, several months of pillar and post shuffling and the best part of a grand later, I can breathe that the job is done. Seriously wtf!

 

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