Cooling System

Facts:

-Overheating on an engine is 258 Degrees F

-One sign of a stuck open thermostat is when the bottom of the radiator hose is hot and the top of the radiator hose is cold.

-For every pound of pressure added to the rated radiator pressure cap, boiling point increases 3 degrees F.

-Most causes of overheating is an inoperative cooling fan.

-Overheating can destroy or soften rubber hoses and gaskets.

-An incorrectly installed head gasket can cause overheating.

Common Causes of Overheating

-low coolant level
-Plugged,dirty, or blocked radiator
-Defective or inoperative Fan
-Incorrect ignition timing
-Low engine oil level
-Broken Fan Belt(if aplicable)
-Dragging Brakes
-Frozen Coolant(in freezing conditions)
-Defective Thermostat
-Defective water pump
-Faulty Radiator cap
-Faulty Temperature sensor
-Improper coolant mixture
-Faulty thermostat
-Restricted radiator hose(s)


Electronically Controlled Cooling Fan

There are two relays, one for low speed, and one for high speed.Voltage is supplied through a 30 amp cooling fan 1 and 30 amp cooling fan 2 fuses.

The ECM commands low speed fans when the engine coolant temperature exceeds approximately 223 degrees F or when the A/C refridgerant pressure exceeds 190 PSI.The ECM commands high speed fans when the engine coolant temperature reaches 230 degrees F, A/C refridgerant pressure exceeds 240 PSI, or when certain diagnostic trouble codes are set.

The engine coolant temperature sensor will not function properly if coolant is low,because it must be emerged in coolant to operate properly.It can only read the temperature of coolant.It cannot read the temperature of steam,or the temperature of the engine block.


Coolant

Coolant should not exceed a mixture of 70% coolant/30% water.Do not fill with 100% coolant, your engine can overheat and can freeze.

The cooling system will not function properly if air is not released from the system after a refill.


Examples of coolant mixtures:

Antifreeze Water Freezing Point Boiling Point(with 15lb radiator cap)

50% 50% -34 degrees F 265 degrees F

60% 40% -62 degrees F 269 degrees F

70% 30% -84 degrees F 276 degrees F


If overheating occurs in slow/stop and go traffic, the usual cause is low airflow through the radiator.Check for airflow blockages or cooling fan malfunction.

If overheating occures at highway speeds, the cause is usually a radiator or coolant circulation problem.Check for restricted or clogged radiator.

Coolant Temperature Warning Light

If the "hot" light comes on during driving, or the temperature gauge goes into the red(danger) zone, the coolant temperature is about 250 to 258 degrees F.If this happens, follow these steps:

Step 1 Shut off the air conditioning and turn on the heater.
The heater will help rid the engine of the extra heat.
Set the blower speed to high.

Step 2 If possible, turn off the engine and let it cool.(This may take several hours)

Step 3 Never remove the radiator cap when the engine is hot.

Step 4 Do NOT continue to drive with the hot light on, or serious damage to your engine could result.

Step 5 If the engine does not feel or smell hot, it is possible the problem is a faulty hot light sensor or gauge.

The gaskets most prone to overheating is the valve cover and intake manifold gaskets.

Gaskets and/or Vacuum hose failure often results in an air(vacuum) leak that leans the air/fuel mixture.The resulting lean mixture burns hotter in the cylinders and contributes to the overheating problems.

The vehicle computer(if aplicable) can often compensate for a minor air(vacuum) leak, but more severe leaks can lead to driveability problems,especially idle quality problems.

If the leak is severe enough, a lean diagnostic trouble code may be present.If a lean code is not set, the vehicle's computer may indicate a defective or out-of-range MAP sensor code.

Thermostat Temperature Rating

180 Degrees F - Starts to Open at 180 Degrees F and is fully open at 200 Degrees F.

195 Degrees F- Starts to Open at 195 Degrees F and is fully open at 215 Degrees F.

The common misconception is that the rated temperature on the thermostat is when it is fully open.

One sign of a stuck open thermostat is when the bottom of the radiator hose is hot and the top of the radiator hose is cold.

 

The proper operation of the starting system depends on a good battery,good cables and connections, and a good starter motor.Because a starting problem can be caused by a defective component anywhere in the starting circuit,it is important to check for proper operation of each part of the circuit to diagnose and repair the problem quickly.

Starter current can be measured by using a high-current clamp and a digital multimeter or a specialized starting and charging tester.

Excessive current draw may indicate one or more of the following:

1.Binding of starter armature as a result of worn bushings.
2.Oil too thick for weather conditions.
3.Shorted or grounded starter windings or cables.
4.Tight or seized engine.
5.Shorted starter motor


Starting System Symptom Guide

1.Starter motor whines- possible defective starter drive; worn starter drive engagement yoke;defective flywheel

2.Starter rotates slowly- possible high resistance in the battery cables or connections; possible defective or discharged battery; possible worn starter bushings;possible worn starter brushes or weak brush springs

3.Starter fails to rotate- possible defective ignition switch or neutral safety switch; possible open in the power circuit between the battery and the starter; possible defective starter solenoid

4.Starter produces grinding noise- possible defective starter drive unit; possible defective flywheel; possible incorrect distance between the starter pinion and the flywheel; possible cracked or broken starter drive end housing