Dodge Nitro. Manual - part 529

Fig. 76: Identifying Main Spring, Gasket Retainer, Stainless Steel Swivel Top, Rubber Seals, Spring
Loaded Valve, Coolant Pressure Bottle, Filler Neck & Overflow Nipple
Courtesy of CHRYSLER LLC

The cooling system cap is located on the coolant pressure bottle for 3.7L/2.8L The cap construction includes;
stainless steel swivel top, rubber seals and retainer, main spring (1), and a spring loaded valve (5).

OPERATION

The pressure cap allows the cooling system to operate at higher than atmospheric pressure which raises the
coolant boiling point, thus allowing increased radiator cooling capacity. The pressure cap releases pressure at
some point within a range of 110 kPa ± 14 kPa (16 psi ± 2 psi).

A spring-loaded vent valve in the center of the cap allows the system to pressurize and depressurize without

1 - MAIN SPRING
2 - GASKET RETAINER
3 - STAINLESS STEEL SWIVEL TOP
4 - RUBBER SEALS
5 - SPRING LOADED VALVE
6 - COOLANT PRESSURE BOTTLE
7 - FILLER NECK
8 - OVERFLOW NIPPLE

2007 Dodge Nitro R/T

2007 ENGINE Cooling - Nitro

creating a vacuum. If the valve is stuck open, coolant will escape to the overflow hose. There is also a gasket in
the cap to seal to the top of the filler neck.

DIAGNOSIS AND TESTING

RADIATOR PRESSURE CAP

Fig. 77: Testing Cooling System Pressure Cap
Courtesy of CHRYSLER LLC

Dip the pressure cap (1) in water. Clean any deposits off the vent valve or its seat and apply cap to end of the
Pressure Cap Test Adaptor that is included with the Pressure Tester 7700. Working the plunger, bring the
pressure to 104 kPa (15 psi) on the gauge. If the pressure cap fails to hold pressure of at least 97 kPa (14 psi),
replace the pressure cap.

CAUTION: Use only the pressure cap specified for this vehicle. Use of other pressure

caps can lead to coolant loss and overheating.

1 - PRESSURE CAP
2 - PRESSURE TESTER

2007 Dodge Nitro R/T

2007 ENGINE Cooling - Nitro

If the pressure cap tests properly while positioned on Pressure Tester (2), but will not hold pressure or vacuum
when positioned on the filler neck. Inspect the filler neck and cap top gasket for irregularities that may prevent
the cap from sealing properly.

PRESSURE RELIEF TEST

Fig. 78: Identifying Overflow Nipple, Main Spring, Gasket Retainer, Stainless-Steel Swivel Top, Rubber
Seals, Vent Valve, Pressure Bottle & Filler Neck
Courtesy of CHRYSLER LLC

CAUTION: The Cooling System Tester Tool is very sensitive to small air leaks that will

not cause cooling system problems. A pressure cap that does not have a
history of coolant loss should not be replaced just because it leaks slowly
when tested with this tool. Add water to the tool. Turn tool upside down
and recheck pressure cap to confirm that cap is bad.

1 - OVERFLOW NIPPLE
2 - MAIN SPRING
3 - GASKET RETAINER
4 - STAINLESS-STEEL SWIVEL TOP
5 - RUBBER SEALS
6 - VENT VALVE
7 - PRESSURE BOTTLE

2007 Dodge Nitro R/T

2007 ENGINE Cooling - Nitro

The pressure cap upper gasket (seal) pressure relief can be checked by removing the overflow hose at the
radiator filler neck nipple. Attach the Pressure Tester 7700 to the filler neck nipple (1) and pump air into the
radiator. Pressure cap upper gasket should relieve at 69-124 kPa (10-18 psi) and hold pressure at 55 kPa (8 psi)
minimum.

There is no need to remove the radiator cap at any time except for the following purposes:

1. Check and adjust coolant freeze point.

2. Refill system with new coolant.

3. Conducting service procedures.

4. Checking for vacuum leaks.

CLEANING

Clean the radiator pressure cap using a mild soap and water only.

INSPECTION

Visually inspect the pressure valve gasket on the cap. Replace cap if the gasket is swollen, torn or worn. Inspect
the area around radiator filler neck for white deposits that indicate a leaking cap.

PUMP-WATER

DESCRIPTION

8 - FILLER NECK

WARNING:

The warning words "do not open hot" on the radiator pressure cap is a
safety precaution. When hot, pressure builds up in cooling system. To
prevent scalding or injury, the radiator cap should not be removed while
the system is hot or under pressure.

WARNING:

If vehicle has been run recently, wait 15 minutes before removing cap.
Then place a shop towel over the cap and without pushing down rotate
counterclockwise to the first stop. Allow fluids to escape through the
overflow tube and when the system stops pushing coolant and steam into
the CRS tank and pressure drops push down and remove the cap
completely. Squeezing the radiator inlet hose with a shop towel (to check
pressure) before and after turning to the first stop is recommended.

2007 Dodge Nitro R/T

2007 ENGINE Cooling - Nitro

Content .. 527 528 529 530 ..