When I very first had my TJ around 4 years back, the oil pressure gauge on the 4.0l used to just go up and down like a yo-yo, but this was soon fixed with a new pressure sender unit from Lighthouse. (I subsequently discovered that this is a common problem). Since then the gauge has been fine and has always shown a stable reading; that is until I had the drain-plug blow out the bottom of my radiator back at the Turkey Hunt and the oil pressure switch was blasted with hot water and loads of steam. Once the radiator plug was fixed, I noticed the oil pressure gauge going up and down again, so another £30+
later I fitted a new oil pressure switch from Lighthouse. But before I fitted it I took a look at the ruined one and with hind sight I reckon I could have easily salvaged it.
The plastic covering sleeve can quite easily be prised off to expose all the innards. Now, I'm assuming water/moisture must have found its way in here and I suspect that had I thoroughly dried out the inside and re-assembled it, I would have probably had a working sender unit. The only way I could see moisture getting in was via the orange rubber/silicone seal, so I decided with the new one to give this area a careful smear of Locktite Silicone Seal to hopefully prevent water/moisture ingress in the future.
If anyone else has a gauge yo-yoing, then you might just save yourself having to buy a new one.
Here are a few photos, which might help in my explanation:
The old one already prised open
My unopened new one - just sealed
