Basic Auto Mechanics – Week 5

Another week with no classroom instruction, and it seems that we have lost a couple of our students.  We now have around 5 guys that are showing up regularly.  They may have been more advanced than the class, but I don’t really think that is the case.  I feel that I could have taken a more advanced class but I am still learning something every week by going.  Experience and diagnostic skills seem to be the pieces of the puzzle that I am missing so the more I am exposed to this trade, the more experience I will acquire and the better I will become.

This class was all about the cooling system.  We started off by going over the water pump and there were a whole bunch of water pumps on the bench for demonstration.  The impeller, the actual part that is rotating in the block, was shown to us and it was explained to us that the shaft it is connected to is riding on bearings that are in the water pump itself.  It is blocked off by a mechanical seal which, as he explained to us, is like two pieces of glass pushed together which keeps the water from entering the bearing chamber.

If for some reason the water does enter the bearing chamber, we were shown the hole in the water pump that would allow the water to leak out in front of the bearings to prevent damage.  We then started talking about how people troubleshoot leaks and some people will plug this hole.  Unfortunately this creates a kind of “bomb” in the motor.  Eventually the anti-freeze will wash away the bearings lubricant and seize the pump.  At this point, something would break and possibly destroy parts of the engine.

We were also shown a radiator.  The teacher had cut open the top of the radiator for us to see what the inside of it looks like.  I was unaware that there were tiny tubes that ran down the length of the radiator that are extremely small; I always thought that the water passages were much larger.  These tubes are surrounded by the fins that you see which radiate the heat away from the fluid.  There can be as much as a 40 degree drop in temperature from when water enters the radiator and when it leaves the radiator depending on the design and vehicle that it is in.

We then went into thermostats and their function.  We learned that they work on the principals of a thermal spring.  When the spring reaches a certain temperature, it compresses to open the valve.  Once this valve is open, the thermostat lets a certain volume of fluid through it to be cooled by the radiator.  The teacher mentioned that taking a thermostat out and running open hoses to test it is a bad test.  The reason for this is that the volume of fluid is no longer restricted and the pressurized system is allowing the fluid to run to quickly through the radiator.  This makes the cooling function of the radiator less efficient and that 40 degree temperature drop no longer occurs and the engine continues to run hot.

At this point we moved on to heater cores.  There were a whole bunch of them on display and they work on the opposite principal as a radiator.  The coolant enters and leaves the same side of the heater core and the heat from the fluid radiates out through the device.  This is what allows your car to have heat in the winter and keep you warm.

Next we were going to be shown how to use a torch.  Unfortunately the Oxygen and Acetylene bottles were nowhere to be found.  The cart with the lines and torches were there, but we could not use them.  However, we went over some safety and what the equipment actually was.  We were instructed on the use of the regulators and that they should always be shut on the low pressure side when starting and that the high pressure side reads automatically.  We were shown that the threads on the lines spin opposite ways and that it is an international standard that keeps the Oxygen and Acetylene running through the correct lines.  He taught us how we would go about heating up a nut to remove a stuck bolt and how to heat metal to bend it the way we may need it.  This was all done by demonstration without the actual torches working.  The teacher was visibly upset by this but did the best he could with what he had.

Overall it was another great class.  With the bottles missing for the torches it was a little bit of a letdown but the teacher made up for it with some stories and explanations that were more than satisfactory and actually quite entertaining.

 

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