TECH ADVISER’S CHOICE DISAPPEARING ENGINE COOLANT

I own a 2004 BMW 525i (E60). The car is in excellent condition and has done just over 111 000 km with a full-service record [Sipho, if you’re looking to sell your E60, I’d like to be top of the list, please – editor.]. It performs very well; however, what bothers me is the way it consumes engine coolant. I have to top up at least a litre of engine coolant every three weeks and I nd this a bit much. Kindly advise if such coolant consumption is normal and, if not, what could the problem be? SIPHO DUBE Mbabane, Swaziland

In our opinion, this rate of coolant consumption is abnormal. There are only a couple of possible root causes.

Leaks

If there is a leak, the coolant will make its way out of the closed system. The noticeable leaks can be found on a pipe, joint, Welch engine plug or the weeping hole of the water pump when the seals are gone. This type of leak will leave a puddle on the oor of your garage where the vehicle is parked and is easy to trace.

A more dif cult leak to nd can occur at the pressure cap of the radiator if the seal allows gases (water vapour) to escape when under pressure. Check the seal of the cap.

Any reputable radiator specialist can perform a pressure check on the system; air is pumped in and the pressure is monitored over time.

Head-gasket failure

A more serious problem is when the head gasket fails or partly fails. This would allow the coolant to enter the combustion chamber(s) and exit via the exhaust while the engine is running. In a worst-case scenario, the water can mix with the oil and is easy to spot when a milky substance is evident on the oil dipstick.

A technician can perform a compression check (and leak-down test) on each cylinder while a radiator specialist can test the coolant for the presence of combustion gases. If so, a head-gasket replacement is needed. It may be necessary to have the cylinder head skimmed (to ensure a perfect mating surface) and the head bolts replaced to guarantee the correct clamping force.