|The MGA With An Attitude
REMOVING The SAFETY GAUGE - DT-108
The oil pressure and water temperature gauge is often referred to as the "safety gauge" or "combination gauge". Sometimes factory documentation refers to it as "thermometer". The oil pressure signal pipe is connected with a female threaded nut. The temperature signal pipe is permanently attached at both ends and cannot be detached from the gauge. Being a rather fragile pipe, it is secured for strain relief with multiple P-clips at various points along its length. To remove the safety gauge requires removing the sensor bulb from the engine, detaching the P-clips, removing a bracket from behind the dash, then pulling it all out the front while carefully snaking the sensor line through the firewall.
James Cameron in California, USA, was doing some refurbishment work on the dash and wanted to remove the dash assembly without pulling the safety gauge out of the car. He was wondering if it was possible to remove the front trim ring (and glass), then push the gauge body back through the hole in the dash. Initially the answer is "no", because the gauge shell is a close fit in the hole, and the shell has a small flange on the front edge to key with the front bezel (red arrows below). However, where there's a will there's a way.
Jim Sterner, owner of Sports Cars Garage in Palm Desert, CA, suggested grinding a little off the edge of the hole in the dash and then carefully work the gauge out from the back (although I don't know if he was actually recommending it). Of course it works, being careful not to damage the fluid lines. For later reassembly it may be a bit of a fidget to align the gauge in the center of the enlarged hole.
There is also the matter of a sealing ring between the bezel and dash panel. This was originally a thin flat rubber ring. This may have been changed to a round section O-ring for replacement parts some time later (during production of MGB). Currently available seal rings will most likely all be round section O-rings. The O-ring will be narrower (radially) than the original flat ring. This may present a problem with the O-ring falling through the enlarged hole in the panel. If you omit the O-ring you risk chipping paint on the panel, and possible light escape around the bezel from the instrument illumination lamp.
I do not personally recommend modifying the panel in this manner (especially if it is not your car), but it's your call.