Answers
May 26, 2020 - 08:39 PM
Hi there
Coolant loss from an engine is often a mystery, especially when there are no obvious leaks to be found. Could it be that your mechanic missed a leak somewhere?
Going on historical data, those Polos are mechanically very robust, so the chances are that it loses coolant in one of the peripheral cooling system components. The first suspect would be the "radiator cap" - the blue xxxx -on cap on top of the plastic reservoir where you add coolant. This cap uses a spring-loaded mechanism to relieve excess pressure in the coolant system, by bleeding off excess coolant. As this internal spring weakens with age and repeated heat cycles, it will open the cap's pressure relief valve prematurely, and bleed coolant into a hidden channel (it's easy to miss, unless you know exactly where to look). So, first order of business will be to replace the cap with a new one (which costs less than R200 at Goldwagen), to see if the coolant loss continues. In 90% of cases with ageing cars, the radiator cap is the first item to perish, and will likely need to be replaced about every 100 000 km.
But before you do that: are you sure that it does in fact lose coolant? Overfilling the expansion tank (to the brim on a cold engine) will see the system bleed off the excess fluid, giving the impression of a coolant loss. On that overflow tank are two marks, and the coolant level must be around the bottom (MIN) mark when the engine is cold. Anything more will be expelled from the system.
If all this fails, inspect every plastic fitting attached to the cooling system (and the surrounding area) for any sign of a white, powdery residue: that's the tell-tale sign of hairline crack in the fitting, which will lead to gradual coolant loss and will require replacement of that fitting. (Sidenote: when replacing a plastic fitting, be careful to not overtighten the fitting, because that may crack the new fitting as well). If all the plastic fittings check out fine, investigate the water pump (attached to the driver's side of the engine) for signs of leaks.
With no sign of leaks anywhere, if may point to a failed head gasket or a cracked cylinder head - but those issues will also lead to loss of power and driveability, and misfires especially when cold. This will need to be verified by a pressure test at a radiator repair shop - there's a test they can do to check for combustion gas in the cooling system. If this test picks up any gas in the coolant, you're in for a big repair bill, and should only entrust the job to a very capable mechanic.
Good luck, and hope that you get to the bottom of this problem quickly!
The AskAutoTrader Team
Jun 09, 2020 - 09:09 PM
Hi there
First of all, I'm happy that they found the source of the water loss. Water pumps are wear items on cars, and the design of most of them are of such a nature that the first sign of incipient failure is a leak past the seals. This usually points towards excessive pump shaft play, which is already an indication that replacement is imminent. 105 000 km is a fair lifespan for a water (coolant) pump, and it's generally recommended that the water pump should be replaced along with the cambelt. Fortunately, VW parts aren't very expensive (except from the agents), and the chances are that the labour charge to replace the pump will be higher than the cost of the pump itself. Goldwagon will be able to supply a quality replacement pump at a reasonable price, so you could start your shopping there...
Hope this helps!
The AskAutoTrader Team
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