Oil pressure gauge and water temp gauge issue

[Olivebdr]

Hello,

i would need your expertise and gentle advises please.

After 4 years of patience, my Serie II OTS just came back from mechanics and paint shop some weeks ago. Engine has been totally rebuilt with new pistons and Eiffel chassis are brand new as the overall painting. I changed the hood, rebuilt the hydraulic steering rack, fuel lines, pump and reservoir. Time to drive it But unfortunately, it still some major issues i'm trying to fix :
Water temp
The gauge is showing a very hot temperature. I take the real temp at intake manifold with an infrared camera.
- pointer is vertical at 45°celcius
- It is just below red bar at 64°celcius
- it is at the last stage of red bar at 79°. Ventilator starts at 85°.
Oil pressure
Original pressure sensor is showing 0 lb when engine is off. When contact is switched on, the pointer is going from 0 to 60 and come back to 0. Then it jumps from 0 to 30 every 10 secondes. Engine running, pointer shows 60lb whenever the engine cold or warm, and whatever the rpm is.
A new sensore, purchased from SNG, showed 50lb whatever the rpm when cold. It showed 40lb when warm at idle and 50lb at 2500rpm. it worked for 20 miles. Now it shows 50lb even the engine is not running
... With SNG sensor, Oil gauge is receiving 12.82v and sends 7.64v to the sensor, engine off. 8.65v when engine's running...

I did my homework and tested the dashboard and alternator electrical circuit.
Voltage is 12.82v engine not running
Voltage is 14.5v at idle
Voltage is 14.6v at 2500rpm
Same Voltage at battery as at volt gauge
Voltage after gauge regulators is between 5 and 10.5v.
Oil Gauge electronic filter is showing 3.2v. Any difference on gauge with or without this filter.
+ terminal post, Battery and Alternator connectors are clean and greased
0.16 ohms gap between negative battery and engine earth. Same with dashboard earth
I tried to find out if I had any power coming from oil pressure sensor to the gauge. Nothing.
I tried without cigarette lighter, radio and antena. Still the same issue.
And finally i tried with disconnecting fuses one by one... still the same.

I did not tried the fuel+matches... but i'm beginning to think about it

I'm aware the oil pressure issue could come from the pressure regulator, just below oil filter. But i do not understand why the oil pressure would not change even if oil is warm... it makes no sense for me. Anyway, I should receive a mechanical oil pressure sensor+gauge today. I will keep your in touch.

The forum already helped me a lot with several related post but i still stucked despite my actions...
Thanks in advance for your kindness and patience.
Olivier

[Olivebdr]

[malcolm]

Olivier, personally, I gave up on the oil pressure senders and had the SNG capillary guage fitted - now 100% accurate all the time.

[Olivebdr]

Here are some news for today. I’ve received my workshop mechanical oil pressure gauge.
engine cold
35 psi at idle
40 psi at 2000 rpm
engine warm 80 degrees
40 psi at idle
50 psi at 2000 rpm

a little to high at idle, isn’t it ?

[AshM]

Oliver

My S2 with 6,000 miles since a full engine rebuild idles at around 40 when hot.

Cheers
Ash

[Olivebdr]

At idle ?

[malcolm]

Mine idles at about 40 when hot. If really hot such as a fast run over a long period in very hot weather, it can drop to 25/30 at idle.
Of course, it does depend on your idle speed as well. As soon as my revs are up to 1000, I'm back to 40 if it had dropped to 25ish as above

[Olivebdr]

Thank you Malcom & Ashm,
It reassures me. I will change the oil for a thiner one and everythinh should be fine

[AshM]

Don’t go too thin. Needs to be in the 20/50 range.

I always use Penrite and they have just changed it to 20W /60.

But respect oil choice is quite a personal thing. Everyone has their preference.

Cheers
Ash

[Olivebdr]

I will keep in the operator manual range... expecting it to be 20/50 or near.
Engine has been rebuilt 2 years ago. I don't know which engine oil has been used by the mechanics and sadly will probably not be able to get the information.

[christopher storey]

Oliver - I think you are getting too worried about all this. Your pressures are absolutely fine . You would only need to change to a thinner oil if you lived in a very cold climate where cold cranking of the engine might be a problem

[Olivebdr]

Thank you Christopher.

In an other hand, i resolved my water temperature gauge issue.
I desassembled the little regulator behind the dashboard pannel. On the bench, with a little cutter and my best glasses, i cut the glue on the little harm, right of the component. Turned 360° counter clockwise and re-installed it on the dashboard, reconnected.

Previous measures was :
Real Temp // Gauge Needle
45°c // Vertical
64°c // 2mm before red
79°c // last part (right) of the red bar
Now i can read :
Real Temp // Gauge Needle
50°c // Vertical
73°c // 2mm before red
82°c // left part of the red bar
Ventilator is starting at 82° and temp is dropping to 79° before fan stop.

Thanks all for your kind help. I will let you know when i will have changed engine oil in a couple of week...
Olivier