Misdiagnosis of a blocked radiator is an easy mistake, says Jack Biddle
A story in the Herald recently told about a young tourist couple who were forced to cut their holiday short after suffering overheating issues with their rented campervan.
Apparently the campervan developed issues when they were in the lower South Island and a local garage diagnosed the cause as being a faulty thermostat. After the thermostat was replaced, the couple continued on their journey only to have the same problem continue as they made their way up the island, which ultimately disrupted and forced them to change their original travel itinerary.
They eventually reached Taupo where another diagnosis suggested a blocked radiator as the real cause of the overheating problems.
The Austin Kimberley.
The story bought back memories of guess work and ongoing problems when I was involved in the retail side of the repair business. The golden rule in our workshop basically said “prove it before you replace it”, which meant proving to the workshop foreman why items like thermostats needed to be replaced.
The rule came about after a wheel bearing-like noise was reported on an Austin Kimberley. Mechanics chased that noise all around the car, eventually replacing every wheel bearing to no avail. The noise was eventually traced to the roof rack, which played a merry tune similar to a noisy wheel bearing when the wind passed over it on the open road.
From that day on, mechanics were often asked to show where the hardening had worn through on a particular bearing surface before they were given approval to replace to help stop any misdiagnoses.
It was a simple but effective way of clearly identifying where such noises were actually coming from and helped removed any guess work. It also potentially saved the workshop a lot of money in lost time and parts purchasing.
The same rule applied to suspected faulty thermostats, which meant placing them in water and heating a container until the thermostat’s opening temperature was reached. From my experience, there was an almost 100 per cent hit rate that the thermostat would actually open as it should, rather than stay permanently shut. That meant looking elsewhere for the real cause of any overheating issues. A blocked radiator was often one such reason.
I’m not suggesting some thermostats don’t fail at times, but in the recent case of the campervan, it obviously wasn’t the cause of problem.
In my view, thermostats should definitely be replaced as a precautionary measure when any major work is carried out on a cooling system. My reasoning is because they can actually fail to close properly or remain wide open at times and create other issues such as engines not warming up quick enough from a cold start.
As discussed in previous Car Care columns, overheating of an engine can create expensive damage. So if you happen to notice the temperature gauge rising above normal levels, especially when in traffic, take immediate action.
Be wary of being told it’s simply a thermostat issue. If the temperature gauge drops slightly on the open road and climbs again in traffic, it may well be a partially blocked radiator issue among other things.
Amusing to think back and be thankful for lessons learned from working on Austin Kimberleys!