I have an 87, so I don't have any nifty coolant bleed screws. But, I found some great advice on how to flush and fill the coolant system from previous posts... I tell ya, this forum is a great resource!

My upper radiator hose sprung a leak the other day, so while I'm at it, I figure it would just be a good idea to flush the whole cooling system. I've had a helluva time getting air out of the system, though.

I've drained it and filled with water, then warmed it up until the thermostat opened, but it heated up quickly... which tells me that there's air trapped in the system; especially since the oil temp was barely 150* at the time.

So, I tried running it at about 1,400-1,600 RPM and adding water that way (BTW: I found that a piece of cardboard worked really well to stick in the throttle to keep it about the right RPM). The coolant temp still went well over 260*, while the oil temp was around 200*. I'm going to drain it and go through the process again, but thought I'd see if anyone has any sage advice on getting the air out of the older systems?

I thought about just opening up the hole in the upper radiator hose to bleed the system :D (I have it taped over while I flush the system, then I'll replace the hose after it's cleaned out).

 

Well, I got determined and just disconnected the upper radiator hose at the thermostat housing and then filled the radiator... I could hear the air seeping out, and it took a while, but it displaced the air in the engine.

I went through a couple more flush/drain cycles, then went to fill it up for good. I decided to try the fill method again by running it about 1,500 RPM for a while and then putting the cap on when it was full. It seemed to be OK for a bit, but then the coolant temp got over 210* and the coolant just started boiling out the radiator filler neck and making a helluva mess. So, I guess that technique might work, as long as it doesn't get too hot.

I think I'll follow the advice I've read and drain the block from the knock sensor, pull the radiator out and clean behind it and also replace the lower radiator hose... but all that will have to come another day :rolleyes:

 

It's a bit harder with a high temp stat, but start it with the rad cap off, and as soon as the stat opens, the level in the radiator will drop.

Fill it up, and then rev the throttle and top it off and put the cap back on. Shut it off and let it cool down below the stat temp, and then repeat the second step. Make sure the overflow is filled up. Hell, fill it up all the way. The next time you get the car really hot, it'll force out what you don't need (so don't be surprised when there's antifreeze dripping from the air dam.) When it cools off, it'll suck what it does need back into the system, and then you can be sure you have no air pockets.

 

:iagree: Based on my experience yesterday, I think you're right... this will work the best (as long as there's no huge pocket of air in the engine). There was a post I was trying to follow, which said to let it run for 10 minutes with the throttle at 1,500 RPM, and let all the air bubble out, but that just didn't work very well for me.

 

After a few full heat cycles.... 80 degrees to 230 degrees, there should be no air in the system if your overflow tank and radiator cap are working properly. the overflow should be open to atmosphere through the cap.

 

As someone said here I DO NOT think you want to run the engine at 1,500 rpm for 10 minutes if the coolant level is not full. I will wait til the thermostat opens after maybe 3 minutes and you will see the water level drop. At that time fill the radiator with 50/50 distilled water and anti-freeze and when it will not take anymore coolant THEN with your left hand move the trottle to run the engine up to 1500 or 2000 rpm and you will see the water level then drop again. Then keeping the engine speed up put more coolant into the rad.(If you let the engine speed drop then coolant will pour out of the radiator) Speeding up the engine more will make the level drop more as the water pump applies more pressure and forces more coolant into the block. You have to work fast and have the radiator cap ready to put on once the coolant starts coming out of the rad (after it will take no more coolant at the 2000 rpm level) . Put the cap on only while the engine is at the 1500 to 2000 rpm speed. That will get most of the air out. 3 to 5 FULL cooling cycles will do the rest. Just start from 80 degrees and go to 228 degrees then turn it off before it goes any higher than 228. Going to 260 may cost you a cylinder head or gaskets. And don't add cold coolant to a hot engine unless you like to gamble with your engine.Cold water going into a hot engine CAN warp or crack it.

 

:iagree: I couldn't have said it better myself.

 

Yep, Skeet, I agree right down the line. What you described is what worked best for me by the time I was done with all the flush/drain cycles. I realized, later than I should have, that the reason the coolant temp sensor got so hot was because of the air that was trapped... and it still makes me nervous thinking about it :eek: It's been running fine for the past couple of days, I just hope it stays running fine!

I get to go through this all over again when I replace the lower radiator hose.

Thanks for all the help! :cheers: