Oil Pressure Switch

[fussydave]

Great news, the Stag has passed the MOT with flying colours. While under the car we have identified where an annoying oil leak is coming from, it appears to be the oil pressure switch. The oil is running down from the switch, spreading across the front of the auto box and along a pipe to the middle of the auto box giving the impression of leaks from differant places. I have not had any appreciable loss of oil since the engine rebuild so I think it is a case of a little oil going a long way. I have the car booked in for next Friday to swap the oil pressure switch. When doing a search I note that all the usual suppliers list a part number GPS117 switch for around £5. However, Rimmers also list an uprated, 20lb switch at £29. Is there any advantage to fitting this switch or is the standard switch OK?

Thanks, Dave.

[mjheathcote]

Personally, I would fit the higher rated switch.
The original low pressure gives a 'your engine is now broken' warning.
The higher switch point could give you a warning of low pressure, hopefully because of a fixable problem, before it has dropped to a point of no return!
I fitted a high pressure switch, actually a 35 psi one, so only a slight drop from normal tickover warm pressure will give me a warning light.

[fussydave]

Hi Mike,

I see the logic in that, however I note that the uprated pressure switch has two terminals as opposed to the one terminal on the standard switch. What is the function of the second terminal?

Dave

[dasadrew]

The casting which the oil pressure switch is screwed into is known to occasionally exhibit a hairline crack if the switch has been screwed in too tight at some time. Might be the cause of the leak and thus a new pressure switch wouldn't help in that respect.

Drew

[fussydave]

Hi Drew,

Is this cast the whole cylinder block or a separate component?

Dave

[dasadrew]

It's just the top cover of the oil pump.

Drew

[fussydave]

The oil pump was replaced with the engine renuild, so hopefully it is not that.

Dave

[wilf]

If your hot idle oil pressure is well north of 20psi, then the "uprated" (bit of a misnomer, but never mind) pressure switch would indeed give an earlier warning than the standard one.

If however, your hot idle pressure is 20psi or lower, then you will get worrying flashes from the warning light which mean little.

I remember someone proudly telling me how they had fitted an "uprated" switch to their pre SD1 RV8, but wondering why the warning light always came on at tickover. Not really surprising , as 5 to 10 psi was a perfectly adequate tickover oil pressure for that engine.

[DJT]

It's just the top cover of the oil pump.

Drew

Oil transfer housing 214020, not pump.

GRID005136.jpg

The OE type switch, GPS117, is specified because the Stag is a 'low pressure' engine and it is set to come on around 7psi ISTR. Many healthy Stag engines will go on for years with a hot tickover around 15psi or slightly lower. If yours is like that, fitting a 20lb switch will cause unnecessary worry when it comes on after a longish high speed run.

[dasadrew]

just testing Dave!

[mjheathcote]

Hi Mike,

I see the logic in that, however I note that the uprated pressure switch has two terminals as opposed to the one terminal on the standard switch. What is the function of the second terminal?

Dave

I can't answer that, mine has just the one, but at a guess it is probably an earth, instead of earthing through the body of the switch like the single terminal switch.

[GDPR]

It's a separate earth for fibreglass engine blocks

[thebadleys]

Just Googled it and it appears it could well be one terminal is normally open and the other is normally closed.

Hope this is useful

Nigel

[GDPR]

The other terminal used to switch a fuel pump

[richardthestag]

Oil pressure switch or oil transfer housing?

I think the only way a switch could leak would be if it was loose or broken

more likely that the transfer housing is loose, needs a quick tug on the central bolt. either way not a difficult fix



My oil leak needs a sump gasket. I use kitty litter and check the oil level to fix