There should be no need to bleed the system, there are no complications for having air in the cooling system, as long as there is not a lack of coolant
If you are looking into getting the coolant replaced (which I personally highly recommend at least every other year, if not every year), there are different kinds of flushes.
1. Your typical classic, basic flush constitutes draining the raditor by the drain screw typically found on the bottom of most raditors, flushing it through with water, then refilling the radiator with new coolant. Far from the best way. This does not do a good job at all of cleaning out the coolant p[asses and the coolant actually in the block, hoses/lines, or heater core, thus only giving you more like 1/2 of a flush.
While this method can be easily done on your own, the next two methods are processes I used at the shop where I worked. Although you will have to go to a shop and shell out the $40 or so, these are far superior the the first option.
2. We would disconnect the upper raditor hose from the raditor, then hook up our machine filled with approx. 2 gallons of coolant (more for larger trucks), one hose to the raditor hose, and another hose the the raditor itself. Start the engine, turn on the heat. As the engine warms up and the thermostat opens up, the coolant, as it is circulating, flows into the machine, and the vacuum from the coolant leaving the engine pulls the new coolant into the engine. you can put as much coolant in the machine as you want, then just flush it through until the coolant is gone from the machine. turn the engine off, disconnect the machine, reconnect the hose to the raditor, fill the overflow tank, let the eingine run for a few minutes, then re-top off the overflow if necessary. (this is probably the messiest of the options, but more effective than #1)
3. The newest way to do a raditor flush is based entirely on vacuum. This machine hooks up the the shop hose to give it its suction, and has two cylinders; one for waste coolant and one for the new coolant. using numerous levers, you can change which cylinder is open and whether the air is on or off.
Take off the raditor cap, and plug the rubber nozzle on the end of the machine's hose into the opening. Start the engine, and as before, turn on the heat to make sure you are getting through the heater core as well. as the engine is running, you turn on the vaccuum on the machine, which then sucks out all the coolant in the raditor. As the engine heats up and sends coolant to the raditor, it gets sucked up as well. Since it is an entirly sealed system, you will create a negative vacuum in the cooling passages and hoses of the einges (you will see the upper and lower hoses collpase because of this vacuum). when the coolant has been effectivly flushed out, the vacuum is turned off, and the cylinders are switched. the negative vacuum in the engine pulls the new coolant in to fill all the passages, chambers, and hoses in the engine. Top off the raditor and overflow bottle, let the engine run to ensure that the level stays up, then re-top off if necessary.
One of the big concerns with this method is, "You're going to run the engine with no coolant in it?!"
I am still not entirly comfortable with it necessarily, but the whole process from start to finish takes just over 5 minutes, so the engine is never without coolant for more than 90-120 seconds. And as many of these as I've done, I have never encounted any proplems stemming from this, and it seems to be becoming the stand way of doing it, so there must be some grounds for its safety to the engine.
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05-17-2004, 08:48 AM
