The water pump is a key component of vehicles. Its performance, together with adequate coolant, ensures that the engine maintains its optimal operating temperature. This article addresses common concerns and provides insights into understanding the water pump temporary leakage.


Temporary leakage: key aspects


First of all, it should be noted that the watertightness of all water pumps made by Industrias Dolz is checked by a calibrated machine which automatically detects It introduces air at 1 bar of pressure on the surfaces of the water pump which have been in contact with the coolant for a specific time. After a period of adjustment, it checks that the drop in pressure is less than 3.5 cm3 /min. That is why the pumps manufactured by Dolz do not leak under proper operating conditions.


Adequate operating conditions


To prevent future leaks and ensure the longevity of your cooling system, it’s essential to maintain it regularly and know what optimal conditions the coolant should meet:

1.- There must be no solid particles dissolved in the coolant of less than 0.5 mm.

These particles can get between the two contact faces of the dynamic seal and cause a temporary leakage in the water pump due to the imperfect coupling of the two friction rings. When the two contact rings of the dynamic seal are in constant rotation these particles can be expelled from them by the centrifugal force of the rotation.

2.- The main function of the spring which pushes the graphite ring against the silicon carbide ring is to balance the hydrostatic pressure of the coolant, keeping the two rings of the dynamic seal in constant contact. Temporary variations in pressure can cause a hydrostatic imbalance in the working area of the dynamic seal and produce a leak in the water pump.

For all these reasons, to avoid this phenomenon, there must be no air in the circuit. In addition, it will be necessary to check that the coolant in the expansion tank is between the maximum and minimum levels.


Cross section of dynamic seal


Coolant stains at the water pump outlet pipe


If you observe coolant stains by the water pump’s drain hole, you could think that the pump is leaking, but this phenomenon is normal. The two contact surfaces of the dynamic seal are in a state of constant rotation and friction. In normal working conditions allowed to permeate between them in proportion to internal pressure.

Under normal working conditions, a small film of coolant liquid is allowed to enter between them due to the internal pressure gradient. The coolant acts as a lubricating medium which reduces both the wear and the heat produced by the friction of the two contact surfaces. Normally the liquid evaporates before reaching the last of these contact rings, thereby not producing any leakage from the seal.


What to do if you observe small temporary leakage stains from the water pump


  • If there are small coolant stains near the water pump drain hole you may feel that the pump is leaking.
  • When small amounts of coolant, normally less than 10 cc, are coming from the water pump´s drain hole must check that there is no air in the circuit and there are no residue particles in the car´s coolant expansion tank.

If you carry out these operations and the leakage persists, then you must remove the water pump to be analyzed at the factory.


Related content: Discover the DOLZ Total Quality Control Process

Dolz, without limits


At Industrias Dolz we guarantee the quality of our products through the different phases of their production. Our extensive experience as manufacturers of water pumps together with the constant improvement and innovation of our production processes allows us to ensure the perfect adaptability of our products.

In this way, we ensure that the water pumps comply with all existing regulations for adaptability and functionality, always equivalent to OE Quality (art. 1 EC Category Exemption Regulation 1400/2002).