Figure 6-21.  Removal of securing straps.  Figure 6-22.  Filling an oil tank. Figure 6-23.  Checking oil level with dipstick. Figure 6-24.  Oil cooler.  Oil Temperature Bulbs Pressure and Scavenge Oil Screens reaches 85 °C (185 °F), ±2 °C, the valve is closed completely,  diverting all oil flow through the cooler core. Most oil temperature bulbs are mounted in the pressure oil  screen housing. They relay an indication of engine oil inlet  temperature to the oil temperature indicators mounted on  the instrument panel. Temperature bulbs can be replaced by  removing the safety wire and disconnecting the wire leads  from the temperature bulbs, then removing the temperature  bulbs using the proper wrench.  [Figure 6-25] Sludge accumulates on the pressure and scavenges oil screens  during engine operation.  [Figure 6-26]  These screens must  be removed, inspected, and cleaned at the intervals specified  by the manufacturer. Typical removal procedures include removing the safety  devices and loosening the oil screen housing or cover plate.  A suitable container should be provided to collect the oil that  drains from the filter housing or cavity. The container must  be clean so that the oil collected in it can be examined for  foreign particles. Any contamination already present in the  container gives a false indication of the engine condition.  This could result in a premature engine removal. After the screens are removed, they should be inspected  for contamination and for the presence of metal particles  that may indicate possible engine internal wear, damage,  or in extreme cases, engine failure. The screen must be  cleaned prior to reinstalling in the engine. In some cases,  6-16