The water pump is the heart of the vehicle cooling system. Its job is to continuously circulate engine coolant throughout the cooling system. In today’s article we focus on the water pump replacement and the best practices to increase your pump’s lifespan.

It is considered essential to maintain a good condition of the system and always use suitable coolant liquids. So, to ensure tightness and prevent liquid leaks to the outside, the water pump has a dynamic seal.

The seal is performed by the continuous contact between two highly polished flat sealing surfaces:

  1. a hard material (ceramic or silicon carbide – 95% of the pumps manufactured by DOLZ have a dynamic silicon carbide seal) and
  2. another self-lubricating surface (natural or synthetic graphite).

Both are held in contact by the controlled pressure of a spring, one of the surfaces turns in unison with the pump’s shaft, and the other is held hermetically attached to the body of the pump.


Water pump replacement


The excellent quality of DOLZ water pumps with the highest reliability and durability (claim rate less than 0.05%) is not enough if special care is not taken with two very important aspects:

  1. The old coolant must be drained, and the coolant expansion tank cleaned or replaced if heavily soiled, including the upper radiator until the outflowing water is clear and deposits have been removed.
  2. Make sure the air that has entered in the system is removed by bleeding. Always follow the manufacturer’s maintenance recommendations found in your vehicle’s owner’s manual. The presence of air pockets in the circuit, in addition to decrease in cooling capacity, generates overpressure that can exceed the pressure of the spring that regulates the contact of the surfaces of the dynamic seal. Under these conditions, the dynamic seal acts as a safety valve, opening the contact of the surfaces and allowing the escape of liquid until the interior pressure of the circuit has normalized.
  3. Remember, only it is necessary the use of sealant paste in those references where the water pump is not supplied with gasket. Some pumps are sealed with O-rings on their inlets and outlets and, in most cases, no sealant is required.


Related content: Why check the antifreeze in summer?


Garage good practices: water pump’s lifespan


Manufacturer recommendations:

  • Avoid mixing different types of coolant (mineral, organic and hybrid).
  • Never use distilled water in your cooling system, much less tap water, into the expansion tank.
  • Recommended monoethylene glycol (MEG) concentration for freezing and boiling point is 50%.

Otherwise, it will start to leak and therefore lose coolant agent. This will result in corroded solid particles or deposits that can clog or be carried away as suspended solids due to agitation caused by the flow of the water pump and, as a result, destroy the mechanical face seals of the water pumps.


Types of residues

  • Iron oxide: brown in colour and very obvious to the naked eye, this oxide blocks radiators and wears out pumps. A descaling solution must be used,
  • Aluminum oxide: coolant becomes brown or completely black, it blocks the radiators just like iron oxide. A descaling product must be used,
  • Oil residues: Oil residues located in the upper part of the expansion vessel or in the radiator cap. Caution: check the condition of the sleeves. A descaling solution must be used.

In the following pictures we can see how affects this correct or incorrect use to the water pump:

1. SUITABLE coolant


The alkaline PH of these coolants and the accumulation of these acids lowers the pH of the engine coolant composition gradually darkening the water pump surfaces that have been in contact with them. This effect is normal and indicates it’s the suitable coolant.

2.  UNSUITABLE coolant: appear of solid residues in the cooling system



Yellowish and reddish colouring, white spots, incrustations, the presence of white or red rust, indicate the use of an unsuitable coolant which will damage the two contact surfaces of the dynamic seal and cause the pump to leak.

The weep hole drains also provide information on the conditions of the coolant used as we can see below:


DOLZ water pumps, tested quality


Now that we know how to replace the water pump to ensure its durability and good performance, let’s see what benefits DOLZ-GGT water pumps offer:

  1. 95% of the water pumps are manufactured with a silicon carbide seal.
  2. Design according to OE specifications.
  3. Optimal leak tightness and longevity of all water pumps through rigorous calibration tests.
  4.  2-year warranty from the date of purchase or 50,000 km.

How do we guarantee the water pumps competitiveness and quality?

Dolz offers its customers a tried-and-tested product for an optimum performance.

Different quality controls are defined in all production stages. All of them, are integral to ensuring success – be it in manufacturing or delivery of services. These are: Aluminium pressure die casting / Product operations (shot blasting, stamping, grinding, etc.) / Machining / Assembly / Packaging.


Keep reading: Edless quality. Discover DOLZ Total Quality Control Process.


All this controlled in accordance with the most demanding quality standards, always matching Original Equipment Quality, to ensure that safety, performance, and quality are outstanding.

Furthermore, these quality tests involve every stage of the manufacturing process. This helps to identify where a problem is occurring and the corrective steps you require to prevent it in the future.


cta water pumps