The main reason is every vehicle on the road today has different locations for the pressure and coolant temp sensors, not to mention thread sizes. Using oil pressure as an example, it is recommended that a tee fitting be used so you can add the new AutoMeter sender while retaining the OE sender. Please see Fittings under the Accessories section to see a selection of what we have available to help you install your gauges in your vehicle. Additionally you may be able to make a trip to your local plumbing store, or, you may need an additional metric adapter, from a performance fittings supplier (especially for late model vehicles and imports).
For the electric water temp gauges, the temp sender should be located either in the intake manifold or the cylinder head; this is not an instance where a tee fitting can be used, as coolant will not circulate past the sender. Please see our radiator and heater hose adapters under the Accessories section as another available option for mounting your gauge’s coolant temperature sender.
When it comes to mounting the sender for either a trans temp or oil temp gauge, we recommend you use a weld in bung, available separately for MECHANICAL gauges as model #2261, or for ELECTRIC gauges as #2260. The reasoning for this is simple; when the bung is mounted so it will be continuously submerged in fluid, it will give the most accurate readings.