Oil pressure switch

[dafix]

Hello,

I have oil leaking from the engine of my DAF 46 after each drive, and I suspect it comes from the oil pressure switch. I removed it and noticed that the plastic part (with the electric pin) is a little loose (maybe oil was sprayed around from a gap between the plastic and metal part). I bought a new switch but I have some doubts about the mounting. According to the workshop manual, there is no gasket required (and this is how the old switch was installed). To be sure that there will be no leak, I wonder if a copper ring gasket (like the one for the sump plug) would improve the sealing. Or perhaps some PTFE tape or loctite around the thread (but that might be a problem for the electrical contact with the engine block). So, any experience with oil pressure switches is welcome...

[andrew]

I had an identical problem with my oil pressure switch! PTFE tape didn't help one bit, and the solution was to fit another switch, sourced from E-Bay, which fitted perfectly and stopped the leak! I can't explain why the second switch stoppod the leak, but it did! The use of a washer might help-after all, Daf use them in the transmission lubrication seals. Good luck!

[starider]

Hi, just for information,the threaded part of the switch has a tapered thread, so as it is tightened, the increase in the thread diameter, prevents any leakage. Just about every oil pressure switch which screws into an engines cylinder block, uses this method.PTFE tape is great for plumbing but little else.
If you want to make sure there is no longer a leak,apply a smere of gasket cement[Hylomar for instance] to the threads. It is important not too over tighten as the threads in the Aluminium casing could strip.

[dafix]

Hello, I have installed the new switch with a copper ring. After having thoroughly cleaned the engine (to remove any trace of oil), I drove my DAF a few kilometers and once back in the garage I put a sheet of paper on the floor underneath the engine. After a few hours, no spot of oil was noticed on the paper, so I think the problem is solved now.

[dafix]

Just a note for whomever might encounter the same problem: to remove/re-install the oil pressure switch, just remove the plastic grille at the front (2 screws at the bottom at each corner and 5 clamps in the engine bay that hold the grille to the body. These ones are sometimes not easy to remove), then the switch can be accessed from outside of the car. I used a 24-mm double-end spanner (the ring end) to unscrew the switch, but the new one required a 22-mm spanner.

[andrew]

I've bought an oil pressure gauge, which I've yet to fit to my engine. Ideally I should like to insert a flexible pipe or hose into the opening in the engine block and, using adaptor, fit the oil pressure switch AND the gauge at the other end. I need to work out the thread dimensions in order to buy the correct threaded part to fit into the block.

[bobdisk]

Perhaps one way of doing it would be to get a faulty switch and clean out the faulty plastic switch and leave the brass body empty. You will then have the correct fitting into the block. Then solder in an adaptor to take a suitable length of copper 3/16 brake diameter brake pipe, bent to clear the dipstick and any other components in the way, and leave the end behind the starter motor, and solder another adaptor to take the gauge/switch adaptor on at the end.

[starider]

Could use an old sender switch as suggested, but importantly do not use soft solder on any part of the conversion. Silver Solder is the recomended jointing medium. Silver solder is a lower melting point brazing rod due to a percentage of silver alloyed with the brass to allow a joint which is almost as strong as a brazed joint. As an apprentice trained sheetmetal worker and welder, I have used silver soldering when brazing is too high a temperature and if you are not used to using pure brazing rods, it's easy to melt both parts being joined,where as using silver solder melts far sooner than brass.If the old sender body is mild steel there is no problem.
As with brazing dis-similar metals can be neatly joined with silver solder,although I only use it on smaller jobs due to the much higher price of SS rods than pure brazing rods.
The problem with soft soldering is that if used on joints subject to any sort of vibration there is a chance of failure as the joint is nowhere as strong.
I anyone is not sure or wants further advice,please ask.