Oil Pressure Switch (leak)

[svenedin]

I had a small oil leak from the oil pressure switch (to speedo oil pressure warning light) that screws into the block. Leak at the union of switch and block.

I had also noticed that occasionally but not consistently the speedo warning lamp would flicker briefly.

On investigation, I found a very elderly oil pressure switch that was indeed leaking oil at the union with the block and by the crud it has been leaking slowly for a long time. It was very easy to undo so obviously loose.

Just as a point of interest really, I had thought that all of these switches were tapered thread but the ancient one I took off was screwed all the way in with a copper crush washer. The new one (from ESM) is tapered thread with no washer required (only screws in part way into the block and becomes tight).

Had the wrong switch been fitted for decades or is this an older type?

A quick test and the oil light goes off instantly on start up as it should. No leaks

Stephen

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[myoldjalopy]

See this thread, especially the last four posts. It seems parallel threads with a washer were used at some point: viewtopic.php?p=686898&hilit=oil+pressu ... ch#p686898
In any case, as you have found, its a nice, easy fix - we like them!

[svenedin]

Thank you. So the conclusion is that was the original oil pressure switch that I just removed. Not bad service, 55 years. Of course I have kept the old one on the pretext "It might come in useful one day".......How exactly a faulty old switch will magically become useful is yet to be seen

Yes very easy job. At first I thought I would have to remove the distributor to get a spanner on the old switch but actually I could get a spanner on coming at it from the front so it really was a genuine 5 minute job. Those are quite rare for me!

The new switch is marked 0,60. Is that 0.6 Bar? This would be 8.7 psi which is really low. If the light comes on would be in trouble unless of course it is a faulty switch.

Stephen

[myoldjalopy]

My old switch didn't have the shoulder like yours, so I was able to use a box spanner to remove and fit the new one - even easier!

[svenedin]

I tend to over look into stuff. Been a bit bored as the weather has been terrible today. The Lucas part number for the oil pressure switch was SOB103 but this too was taper thread not parallel as with my original switch. I managed to find some NOS ex-MoD stores Lucas SOB103 switches as I am not sure I entirely trust the modern replacement.

Stephen

[Bill_qaz]

Oil pressure switches are useless by the time your oil pressure is low enough to put the light on the damage is done. There only useful on start up to know pressure is being produced. Always prefer a gauge especially on an old vehicle.You can still keep the switch and light for your originality.

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[svenedin]

Oil pressure switches are useless by the time your oil pressure is low enough to put the light on the damage is done. There only useful on start up to know pressure is being produced. Always prefer a gauge especially on an old vehicle.You can still keep the switch and light for your originality.
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My car has never had an oil pressure gauge and has managed 55 years. I don't like the look of cars with extra gauges. It spoils the simplicity of the interior. I like the Spartan look or minimalist or whatever it is. Besides, there is nowhere to mount a gauge anyway!

Stephen

[oliver90owner]

Bill is generally correct, but that is because usually the oil pressure has suddenly fallen to zilch. Plain bearings only need about 5psi to keep them apart; old pressure switches were typically 7psi.

Stick with the idiot light. Ignorance is bliss, as they say.

[svenedin]

Bill is generally correct, but that is because usually the oil pressure has suddenly fallen to zilch. Plain bearings only need about 5psi to keep them apart; old pressure switches were typically 7psi.

Stick with the idiot light. Ignorance is bliss, as they say.

I get the idea but unless the oil pressure gauge was mounted somewhere where I could actually see it and glance at it with reasonable frequency it really isn't a great deal of use. It might be useful for detecting a problem that is happening gradually but if it's a sudden thing it won't make any difference at all. Even the oil pressure light might be missed in bright sunlight especially with the roof down. A modern car with a flashing warning light and warning gong is going to work but this isn't a modern car.

There are oil pressure switches that are adjustable so that they will operate at a pre-set oil pressure (15-60 psi) considerably higher than the standard switch (7-10 psi). Of course to set such a switch you would need an oil pressure gauge. That would give a lot more warning. There are other switches available that are not adjustable but will close at below 20 psi. Again, more warning. Both types are sold by Minispares.

I know that some people make a panel for the driver's side glovebox and fits lots of gauges there. That is just too modified for me. The reinforcing arches and reinforcing lip under the dashboard on my convertible mean there is very little space and little depth to fit any gauge at all. In fact, I do not think it is possible so it is academic really and not just me being an idiot purist about it. I have considered it and I cannot work out how it could be done.

Stephen

You see there's no space for gauges here. It took me forever to find a hazard switch that would fit!

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[oliver90owner]

You miss my point. Oil pump/lube failure at high rpms is usually an unavoidable (by then) catastrophic failure. Deteriorating oil pressure cannot be monitored if it remains just above the warning level. Oil warning lights are considered as ‘idiot lights’, while gauges are fitted for useful information - at least for those that actually understand these things.

[les]

————but you said, ignorance is bliss !

[Bill_qaz]

Stephen you have an open driver side glove box, the gauge bracket could be hung from upper lip in line of sight and so could your hazard switch.The opening still useable, at the end of the day it's your car to do as you wish "to each his own"
Just ideas you may not of thought of

[svenedin]

Thank you for your suggestions gentlemen. The thread was not intended to be an argument about gauges.

I fully understand the utility of being able to monitor oil pressure over time be it hours, days or weeks.

I will consider it some more. I don’t tend to rush into changes on my car. It took me 34 years of ownership to fit a hazard switch and in the 35th year I am still resisting changing to negative earth even though it is becoming rather archaic to navigate with paper maps due to lack of power for a phone.

Stephen

[philthehill]

As regards negative earth for phones etc.
Just run a corrected earth dedicated lead direct from the battery via a fuse and the jobs done.
I ran for several years a 12v electric positive earth cooling fan on my 24v negative earth Landrover direct from one of the two batteries installed via a dedicated lead.

[svenedin]

As regards negative earth for phones etc.
Just run a corrected earth dedicated lead direct from the battery via a fuse and the jobs done.
I ran for several years a 12v electric positive earth cooling fan on my 24v negative earth Landrover direct from one of the two batteries installed via a dedicated lead.

Hello Phil. Yes if I was going to do it I would use a fully electrically isolated USB socket which would not earth through the casing of the unit but would require 2x wires and of course fusing. There are sockets for sale that meet these requirements (used on boats etc).

Over the years I HAVE done modifications to the car but they are all hidden. They were done to improve "turn key" reliability and only on bits that had persistently been trouble and that could be swapped back easily. It would actually be expensive for me to change to negative earth. I did a spread sheet calculation. For instance, I would need a new battery (so that the terminals are correctly at the back); new battery leads; a negative earth module for my positive earth electronic fuel pump; a new module for my positive earth electronic RB106. I worked it out at £350 some years ago. That is what it would cost to convert to negative earth electronic equivalents but I could actually do it much cheaper by re-fitting points based equipment that I still have. What I should have done of course was convert to negative earth more than 30 years ago. All of my friends with Minors did change at that time because they wanted radio/cassettes/cd players and it was rare by then for any of them to work with positive earth. I even recall, when I was 18, one of my friends had a Minor with an alternator which I regarded with tremendous suspicion but then he'd fitted all kinds of gadgets that needed a lot of power. Even way back then I was extremely reluctant to change anything or at least anything that showed.

Stephen

[svenedin]

There was a post on the Facebook group prompted by my photo of the 2 types of switch, parallel and taper.

A customer of a garage refused to pay the nominal charge to fit the new switch saying he would do it himself. He did not know the new one was a taper thread and tightened it in all the way flush with a great big spanner. Then the engine started to leak oil horribly. He had cracked the engine block. The block is quite thin at that point. So refusing to pay to fit the switch and not knowing what he was doing resulted in a new engine........

Stephen

[Bill_qaz]

Hi Stephen my socket is two USB +accessories socket, it's wired directly to the battery via fuse link. Charges phones and power electric tyre pump or Garmin. The body is plastic so insulated, I used 1 existing heater screw an velcro so no effect on car. The pos and neg direct to battery means you pos earth is irrelevant in this case.As Phil suggests

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[svenedin]

Hi Stephen my socket is two USB +accessories socket, it's wired directly to the battery via fuse link. Charges phones and power electric tyre pump or Garmin. The body is plastic so insulated, I used 1 existing heater screw an velcro so no effect on car. The pos and neg direct to battery means you pos earth is irrelevant in this case.As Phil suggests
20240323_125740.jpg

Very good. I shall have a look at doing something like that.

Stephen