As cars get into the higher mile range and they get older, car repairs can get more expensive. The reason for this is because as cars gain more miles certain components surpass their intended service life. For example if we have a car come into our shop for a misfire and we find the component at fault to be a leaky injector we would normally replace the single injector, but if the car is in good shape and has over 150k on the odometer we are going to advise the customer to change all the injectors. The reason for this is that at that mileage it is not unreasonable for injectors to fail. We will let the customer know that if we change the single injector they might be coming back with the same problem on another injector. Depending on the engine it could be a considerable amount of labor to get to the injectors. It just doesn’t make sense to change one injector when you consider the labor it takes to get to the injectors. We might as well change all of them if the mileage on the car is high enough.
Manufacturer Recommended Replacements
There are parts where the Original Equipment Manufacturers will not honor the warranty unless other parts within the same system have been changed as well. One of these parts are fuel pumps. If you change a fuel pump but cheap out on replacing the fuel filter, if the new fuel pump were to fail the manufacturer will not warranty it unless you can show a receipt that the fuel filter was changed at the same time. The reason for this is that fuel pumps often burn out due to clogged fuel filters.
Another part like this is air conditioning compressors. If you were to change an A/C Compressor and weren’t able to show you changed the receiver dryer and orifice/expansion tube then the company would refuse to warranty the new A/C Compressor if it failed. The reason for this is because when an AC Compressor fails it is likely to send small metal particles through the Air Condition System. The metal particles tend to get stuck in the receiver dryer and expansion/orifice tube and those metal particles will destroy the new A/C Compressor.
While you are in there type repairs
If the car is high mileage and there is something about the car that is a well known pattern failure we will always avise to change the part that is well known to fail. For example a customer comes in with a Nissan 3.5 litre V6 and it is leaking from the timing cover gasket. Even if the timing chain isn’t rattling we would advise to change it if the car had anywhere near 100,000 miles as the timing tensioners are prone to fail around that mileage. Similar with the Honda 3.5 litre V6. If the engine is nearing 100,000 miles and we have a leaking water pump then we would advise the customer to just do the entire timing belt job as it is pretty much the same amount of labor and the engine would be good for another 100,000 miles of service.
This tends to be one of the reasons as to why people end up trading in or junking their older high mileage cars. As the cars get older many components surpass their service life and problems tend to cascade. Mechanics are put in a difficult predicament where if you only replace one worn component it is likely that the next ignition coil or injector will fail shorty, but then if a mechanic suggests to change everything the mechanic runs the risk of upsetting the customer. When dealing with high mileage cars it is always difficult to advise the customer on what needs repair if the car has had some services neglected.