killain

Hi everyone, I want to change the anti-freeze and just maybe the water pump on my 79, but I was wondering what's the best way to flush the system? and how do I drain the system completely so I'm refilling with clean water and anti-freeze?

jerryp58

I don't know if it's still archived or not, but there was a thread a while back about this. I can't really remember what the concensus was, but I think the best way to flush the system is to use one of those Prestone kits and cut open the heater hose to pump water through. I think some used a metal T instead of the plastic one so that they could leave it there for future flushes (without the fear of cracking during a freeze), others might have "patched" the cut with a straight piece of pipe, and others like me, just replaced the heater hose. Be careful with that heater core end though :eek:

As far as completely draining the system, I'm not sure, but I think you need to remove the freeze plugs (I guess that's a misnomer, but that's what I'm used to calling them) to do that.

Captain Morgan

You could also do the flush a few times, running with just water in the radiator in between flushes, and keep flushing till it comes out clean (or close to it). You'll have to run until it gets up to temp and opens the thermostat and you'll also want to make sure the heater is on so you run the stuff through the heater core. However, if your radiator is too clogged, you may have to pull it and take it in to be rodded out. That's a fun job. :rolleyes: I knew mine was bad, just didn't know how bad. The entire bottom half was filled with sludge. Just make sure you take it to a shop that will do what you request. I took mine in and the guy kept trying to talk me out of rodding it, said it would only need to be flushed. I told him to rod it anyway. When I went to pick it up, he said, "I had to take it apart to fix one of the leaks and it's a good thing I did. The bottom half was filled with crud. I ended up having to rod it out" Duh, that's why I asked to have it rodded in the first place, genius. :rolleyes:

gerry c

I use the Prestone kits with good success on most everything. Here's my method, install the kit and throw a bottle of the "super flush" in, reinstall the radiator cap. Drive the car to get the engine up to normal temp, with heater on... maybe 15 minutes. Put a heavy towel over the filler cap and CAREFULLY and slowly open the cap.... the water will be very hot and under pressure so watch out. Hook a hose up to the Prestone adaptor and with the engine running turn the hose on just a little bit.... not to much to prevent temp shock and to keep the water hot so the thermostat stays open. If you have easy access to hot water with the hose, I would use it but you do not need to. Leave the engine and hose running at least 15 to 20 minutes. Since you are in PA, this would be a good time to go inside a grab a cup of hot coffee. After 15 or 20 minutes the water coming out should be nice and clear. Shut the car off and let it sit for an hour to cool off. If you have access to an air compressor, I would put air through the Prestone adaptor and blow as much water as you can out the radiator, if not, open the bottom petcock on the radiator and drain it that way. Close the petcock, leave the cap off the Prestone adaptor and fill the radiator with antifreeze. After you have all the anti-freeze in that you are going to put in put the cap back on the Prestone adaptor and finish fill with water. One problem with vettes is that the radiator is lower than the adaptor, which can prevent use of the Prestone method of letting water flow out the adaptor while filling, In this case, I raise the front of the car with my trusty floor jack.

The above works for me. One thing I also do is always put in a can of Barrs brand radiator sealer. Does it work??? I don't know but all I can say is that for the last 15 years I have been doing that I have never had a minor leak (only seams splitting at inlets) and during that time, the wife and I have put at least 70K miles a year on our cars and it has not seemed to impair cooling since we live in a desert where summer temps are always over 95 and temps above 110 have been seen on a regular basis and most of our cars see at least 150K miles before they are retired and we have two with over 200K on them(we have 9driving vechiles here, two under restoration, and the vette).

Another tip.... A two liter soda bottle with the bottom cut out makes a great funnel for anti-freeze.

Good Luck. :seeya