83889M Mariner SCREW, IDLE MIXTURE

Illustration 1 g00286266
Boiling point of water
Remember that temperature and pressure work together. When a diagnosis is made of a cooling system problem, temperature and pressure must be checked. Cooling system pressure will have an effect on the cooling system temperature. For an example, refer to Illustration 1. This will show the effect of pressure on the boiling point (steam) of water. This will also show the effect of height above sea level.
At operating temperature, the engine coolant is hot and under pressure.Steam can cause personal injury.Check the coolant level only after the engine has been stopped and the filler cap is cool enough to touch with the bare hand.Remove the filler cap slowly to relieve pressure.Cooling system conditioner contains alkali. Avoid contact with skin and eyes to prevent personal injury.
The coolant level must be to the correct level in order to check the coolant system. The engine must be cold and the engine must not be running. After the engine is cool, loosen the pressure cap in order to relieve the pressure out of the cooling system. Then remove the pressure cap.Test Tools For Cooling System
Table 1
Tools Needed
Part Number Part Name Quantity
4C-6500 Digital Thermometer 1
8T-2700 Blowby/Air Flow Indicator 1
9S-8140 Pressurizing Pump 1
9U-7400 Multitach Tool Group 1
Making contact with a running engine can cause burns from hot parts and can cause injury from rotating parts.When working on an engine that is running, avoid contact with hot parts and rotating parts.
Illustration 2 g00286267
4C-6500 Digital Thermometer
The 4C-6500 Digital Thermometer is used in the diagnosis of overheating conditions and in the diagnosis of overcooling conditions. This group can be used to check temperatures in several different parts of the cooling system. Refer to Operating Manual, NEHS0554, " 4C-6500 Digital Thermometer Group" for the testing procedure.
Illustration 3 g00286269
8T-2700 Blowby/Air Flow Indicator
The 8T-2700 Blowby/Air Flow Indicator is used to check the air flow through the radiator core. Refer to Special Instruction, SEHS8712, "Using the 8T-2700 Blowby/Air Flow Indicator" for the test procedure for checking blowby.
Illustration 4 g00286276
9U-7400 Multitach
The 9U-7400 Multitach Tool Group is used to check the fan speed. Refer to Operating Manual, NEHS0605, " 9U-7400 Multitach Tool Group " for the testing procedure.
Illustration 5 g00286369
9S-8140 Pressurizing Pump
The 9S-8140 Pressurizing Pump is used to test the filler caps. This pressurizing pump is also used to pressure test the cooling system for leaks.
Illustration 6 g00439083
1U-7297 Coolant/Battery Tester or 1U-7298 Coolant/Battery Tester
Check the coolant frequently in cold weather for the proper glycol concentration. Use either the 1U-7297 Coolant/Battery Tester or the 1U-7298 Coolant/Battery Tester in order to ensure adequate freeze protection. The testers are identical except for the temperature scale. The testers give immediate, accurate readings. The testers can be used for antifreeze/coolants that contain ethylene or propylene glycol.Making the Correct Coolant Mixtures
Adding pure antifreeze as a makeup solution for the cooling system top-off is an unacceptable practice. Adding pure antifreeze increases the concentration of coolant in the cooling system. This increases the concentration of the dissolved solids and the undissolved chemical inhibitors in the cooling system. Add the antifreeze and water mixture in the same concentration as your cooling system. The following chart assists in determining the correct concentration of antifreeze and water. Refer to Operation and Maintenance Manual, "General Coolant Information".
Table 2