Zongshen RX3: Engine Cooling System

[SpudRider]

Overview

The engine cooling system employs antifreeze and mechanical components which work together to prevent engine overheating, and which optimize engine performance. The engine cooling system is comprised of the following components.

Radiator Cap
Radiators
Coolant Overflow Bottle
Water Pump
Hoses
Radiator Fans
Thermal Switch
Thermostat
Engine/Coolant Temperature Sensor
Coolant

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Radiator Cap

The radiator cap is a pressure relief valve. The engine cooling system is a closed system. As the engine transfers heat to the antifreeze the coolant expands, creating water pressure in the system. When the water pressure reaches 16 psi (1.1 Bar), the radiator cap protects the system by venting coolant into an overflow bottle to reduce excess pressure. At the same time the radiator cap maintains moderate pressure in the closed system to increase the boiling point of the coolant, and to prevent air voids from being introduced to the coolant. When the temperature of the coolant decreases, the pressure in the system also decreases. At this point the radiator cap allows coolant to be drawn from the overflow bottle back into the system.



The following video describes how a radiator cap operates.

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Radiators

The Zongshen RX3 is equipped with two radiators. Each radiator also has a protective grille which directs airflow over the radiator. Never block airflow to the radiators, or you will risk engine overheating, and engine damage.

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Coolant Overflow Bottle

When the radiator cap vents coolant to reduce system pressure in the engine cooling system, the coolant is collected in the overflow bottle. When engine heat is reduced and system pressure decreases, the coolant in the overflow bottle is returned to the radiators.

The coolant overflow bottle has markings for minimum and maximum levels of coolant. When the engine is cold, the coolant level in the overflow bottle should reach the minimum mark. When the engine is hot, the coolant level in the overflow bottle should reach the maximum mark.

If the coolant level falls below the minimum mark when the engine is cold, you should add more coolant until the level reaches the minimum mark. Maintaining the minimum level of coolant will prevent air voids from forming in the cooling system.

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Water Pump

The water pump circulates antifreeze throughout the engine cooling system. The RX3 water pump is powered by the engine's counter balancer. In the following image the connection for the water pump shaft on the engine counter balancer is shown inside the red oval.



The right end of the counter balancer protrudes through the right crankcase half, where it attaches to the water pump shaft. In the next image the counter balancer connection for the water pump shaft is shown inside the orange oval. The end of the counter balancer is supported in the right crankcase half by a sealed bearing.



The water pump shaft is supported inside the right crankcase cover by a bearing, an oil seal, and a water seal. Below is an image of the water pump shaft with its bearing and two seals.



Inside the right crankcase cover, the water pump impeller screws onto the end of the water pump shaft.

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Hoses

The radiator hoses are designed to meet specific standards for size, temperature rating, and pressure tolerance. Inspect the hoses regularly for loose connections, cracks, or other defects. Replacement hoses must meet or exceed the original hose specifications.

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Radiator Fans

The radiator fans dissipate heat by drawing air through the cooling fins of the radiators. The fans are activated by a thermal switch located at the bottom of the left radiator. The switch closes when coolant temperature reaches 82 degrees Celsius.

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Thermal Switch

The thermal switch is open at room temperature. The switch closes, and activates the fans when the temperature exceeds 82 degrees Celsius. The operating temperature of the fan is inscribed on one face of its hexagonal locking nut.

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Thermostat

The thermostat is installed inside the thermostat housing, which is located in the radiator hose above the engine. This hose descends and connects with the right side of the engine cylinder. When the engine is cold and coolant temperatures are low, the thermostat remains closed, allowing antifreeze to remain inside the engine. This allows the engine to warm to operating temperatures.

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Temperature Sensor

This sensor contains a temperature-dependent resistor with a negative temperature coefficient.



The temperature sensor is inserted into the thermostat housing.

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Coolant

The recommended coolant is low-silicon antifreeze which is specifically recommended for aluminum engines.

Coolant is drained from the system by removing the bolt with a copper washer, which is located at the bottom of the water pump housing.

[Lkhangee]

Excellent write up.

I have Chinese Cg200 water cooled 163ML. Its mixing oil with water. I resurfaced the head and cylinder using 220,300,400,800 grit papers. Now I need to check water pump if it's leaking. Is there any test one can do on it to see if its leaking water to oil from there?

Regards

[Jay In Milpitas]

Originally Posted by Lkhangee

Excellent write up.

I have Chinese Cg200 water cooled 163ML. Its mixing oil with water. I resurfaced the head and cylinder using 220,300,400,800 grit papers. Now I need to check water pump if it's leaking. Is there any test one can do on it to see if its leaking water to oil from there?

Regards

Oil in water and water in oil is usually the water pump seal problem.
http://i442.photobucket.com/albums/q...psgdtiogez.jpg
Good luck.

[Citroenjunkie]

Hi there, dumb question time.

Is it normal for the gauge to fluctuate. I suppose I'm used to car gauges which hit the middle of the scale and stay there.
On my ride home I had to cross a pretty high pass and one hill in particular was about 5 km long. To climb it I was pegged flat out in fifth the whole way and as I neared the top I could feel the hot air flowing past my legs, then I noticed the gauge was showing four bars not the usual three. At the top of the climb I hooked sixth and in about 30 seconds the gauge dropped back.

Today sitting idling while a friend did a slow turn on loose gravel I noticed it head back to four bars, but as soon as we got moving dropped down again. I checked today, the fan wasn't going.

I'm guessing that all of this is quite normal and I'm overthinking again but "checking saved many a man money!"

[rjmorel]

Mine does that also on hot rides . I can watch the temp gage go from 3-4 bars going up hills and come back down when going down other side of hill. For piece of mind though remove radiator cap when it's cooled off and see if the coolant level is up to top. It took several refills to get mine topped off when new because of air trapped in the system. rj