Dolomite engine oil pressure switches

[Richard the old one]

I believe that the original pressure switches fitted are, part number GPS117 and cost about £6. These bring up a warning light if the oil pressure falls to below 5psi but I am now aware the there are replacement switches that can be fitted and these will operate at either 20 psi or 35psi and cost about £35.

When the normal running pressure is 40 to 60psi it seems to me that to bring up a warning when it has dropped to as low as 5 psi is leaving it too late so should I consider fitting at least the 20psi warning switch. What do other owners think and if you have fitted a higher value pressure switch what value have you fitted and has it raised any problems.

I know it is quite a simple job to fit an oil pressure gauge at a cost of about £110 but is it really needed?

[cliftyhanger]

I have a 20psi switch I plan (one day) to fit to one of my cars. If I do so it will be in conjunction with with te original one. The 20psi one will have a bright LED fitted, and the idea is to wire it so only comes live once the car is running (not while cranking)
Incidentally, there is an adjustable switch, preset at 20psi and only £20 from Demon Tweeks https://www.ebay.co.uk/itm/141714467969 which may be an idea if you plan to pursue this.
But better is an oil npressure gauge if you have concerns about oil pressure or are inquisitive. I have never bought a new one, and had a number of used ones, mainly Smiths or Yazuka. Not all accurately calibrated but within 10% of each other, mostly closer from memory.

It was useful when I had a 1500 engine in my Toledo. With std mineral oil, when hot at idle, the pressure was about 25psi. This increased a little by changing to the much-acclaimed VR! 20/50, but went over 30psi with millers CSS 20/60. When running this equated to 60psi, against the mineral 50psi.

Anyway, I digress. A 20 psi oil switch may trigger at idle on a slant engine. I have had a few cars where the std one would flicker at idle, but were fine when running (usually the fix was a new set of BE shells).

I am not sure if any of that helps.... But I try to avoid extra "worry gauges" as they are so damn distracting. So for me the 20psi switch may, just may, be the way forward for me. Jury is still out.

[new to this]

I have fitted a MGB dual oil and temp gauge to my Sprint

Dave

[Carledo]

I too would recommend a guage!

An older, standard, OHV engine may well drop to sub 20psi oil pressure at idle, stinking hot after a long run. Many of those i've owned have behaved like this. It's not really a problem as it will usually get back where it should be as soon as you blip the throttle. Tellingly, the factory approved oil pressure is 50psi stinking hot AT 2000RPM. So long as you have that, idle pressure is next to irrelevant.

30 or so years ago, I bought an 1850 (stole it is nearer, I paid for the MOT it failed and the guy didn't want to fix it) When bought, besides one or two minor things mechanical and rust related, the oil light came on bright at idle as soon as it was warm. But it ran fine otherwise. I did the necessary work for the MOT and adopted it as a daily driver. But within a day or two, the oil light started to bother me. So I invested in a new switch and PRESTO! Problem solved!

About 6 months later the same problem returned. I thought, this time it must be the crank, I even thought I could hear a bit of main rumble developing. Times were, however, a bit tough. So I kept driving it, gently, until I could afford to do something about it, the oil light gradually came on longer and at higher revs and my lizard brain said the noises were louder. But it kept going. It somehow never occurred to me that the "new" switch could be duff (D'OH)

Eventually the stress of driving it like this got to me and, as a last ditch resort, I bought yet another new switch and would you believe it, normal operation was resumed! I had literally worried myself silly for months for no good reason. I moved the car on a couple of years later, still running strong.

Steve

[Richard the old one]

Many thanks for taking the time to respond with so much detail as it may save other dolomite owners spending a lot of money when their engines would continue to run for years with the odd flicker.

I do have a oil pressure gauge and the necessary pipework and fittings to fit it so I think at some point in the future I will temporarily fit it to check the pressure and then remove it if the pressure looks O.K.

Over the years I have had one pressure switch fail but in general they do seem to be quite reliable.

[dursley92]

I think you may find a 20psi warning light switch is going to be pain.
We used to use them on rally cars but my Sprint engines would generally bring the light on at tick over!