Oil pressure reading 0 from idle when hot

[willy3ams]

This has been well documented in the past but I would really like to find out why?
I get good pressure from cold, and when I rev the car.
When the car gets hot and is idle the reading is zero. No warning light so can't be serious.
I've always had this issue with my car but I intend to figure this one out now.

Possible cause?

Faulty oil pressure sensor?
Faulty gauges?
Blocked on faulty oil pump?
Oil too thin? I may have 0w 40 mobil one in.. although i usually put 15w 50
Fitted champion f136 filter (no change)

Any help or advice is appreciated. I plan to do a guide on this issue soon.
cheers
J

[northy]

When the engine is hot (really hot) the oil is that thin the pump isnt having to work as hard to push it around so the presure drops down what the gauge can read.

On a trackday my cars presure drops right off when its being worked hard!

[16v_paddy]

The gauge lies anyway so don't worry about it

[willy3ams]

is there a way to get the actual pressure checked with an external device?

[16v_paddy]

http://www.defi-shop.com/installatio...ion/defi-link/ not cheap though

[willy3ams]

I have some good news!
The last few weeks i decided to buy the following.
1. Brand new oil pressure sensor £73.00
2. Mobil 1 10w 60 (thicker oil)
3. BG Quick clean (Engine flush)
4. Replacement 'Oil gauges'
5. Brand new oil pump with GrN spring (keeping as a spare if problem gets fixed)

So from cold my oil pressure was good as shown below.



but when te engine started to warm up to te point the fan kicked in the pressure would then drop.



and as the oil became hotter the reading would eventually read zero.



So the first thing i decided to do was to do an engine flush and put Mobil 1 10w 60 Extended Life.
and remove the old sensor and clean it with carb cleaner.





I had to remove the OSF wheel and get my arm under the wheel arch to undo the pressure sensor.







It's a bit tight in there!





but i eventually managed to remove it. You'll need a small wrench and a 3/4 spanner





check the loom on the other side for loose contacts below the ABS block



1st thing I noticed was how black the oil was after the engine flush (BG Quick clean)
I must have done an oil change about 4 times in the last 5 years until the oil was like treacle, but after the oil flush - black.

Once I replaced the oil sensor and the oil replaced I checked the pressure again from hot.



From this picture the Oil pressure reading was no longer zero but a slight improvement. Before at this temperature the reading was zero and moved as you feathered the throttle.

A week later i decided to replace the oil sensor altogether! As this may be the cause.



amazing a 400% improvement! To think that crappy sensor was the cause.
then i replaced the oil gauges.



and at 1000 rpm from a hot idle i get 1.2 bar pressure!

So yes a combination of faulty gauges and sensors and using thin oil is the cause. Problem solved....

Happy Days

[cliokiz]

Good effort!

Mine read fairly low but it's a high mileage engine - never see the oil pressure light flickering so it doesn't bother me. I've given it death and it's fine so plenty of oil pressure

[willy3ams]

Thanks.

If the engine isn't noisy/tappety then it must be producing more pressure than the gauge indicates, also the oil has to be at 7psi to float the bearings, if it isn't it would've seized by now or caused other pretty terminal damage.

Like you said the red oil light on the dash would be on. It was one of those niggly things I wanted to sort out.

I've read so many issues about oil pressure on here with people experiencing the same symptoms. The infos here now incase anyone else wanted to fix their's.

Cheers!

[Wobba]

Good effort there, and thanks for sharing :D

[willy3ams]

Thanks Wobba!