Would someone out there be willing to give me the short course on the procedure for purging the radiator on my 91? Thanks in advance for your help.

 

On my 95 I purged the entire coolant system several times. Not sure if it's similar to yours. There is a plastic drain plug I unscrewed at the bottom inside corner of the radiator. If there is a lot of sludge in there you may want to drain the whole thing several times. Mine was pretty bad due to someone at some point mixing the coolants. I stuck a hose in the resivoir by the firewall and let it flow for a really long time with the engine running. Be sure to keep an eye on the temperature getting too hot. I did this several times until it was crystal clear water then let it drain. I then added my premixed coolant until it started to run out the other side and then pluged up the drain on the radiator. Mine also has a pressure release valve located by the thermostat for topping off the coolant and releasing pressure. Be carefull I tightened it too much and broke it off. Hope yours is similar and this helps.

 

You can buy a kit that Prestone sells at most auto parts stores. It goes inline on your heater hose and allows you to attach a garden hose to it. You drain the radiator, turn on the hose, start the car and run till it's clear deal. Plug back up, remove hose, refill and drive. Makes it easy to do next time.

 

 

I guess I wasnt clear enough in what I was asking, but thanks for the replies. Actually, I just installed a new radiator and I understand that after filling the system back up I need to purge air from the system. That is the part I am unclear on. Any input will be appreciated.

 

One more note. My car is a ZR-1 and its thermostat is at the bottom of the system just behind the radiator. I didnt see any relief valve there.

 

I have the same question on my '94. The FSM says to close the relief valve screws (which it never says to open) when coolant starts to come out and I cannot find a picture of where they are. Maybe my eye sight is going (or too many Lites). Can somebody post a picture or give me page reference in the manual? I'm pretty sure I was able to flush the system by draining and refilling the radiator about 10 times last night. 64000 miles and I don't think it has ever been changed . My engine temp this morning was about 15 degrees lower than before. But do like to know where all the service points are on the car. Any help is appreciated as always! Thanks
-Chris

 

I just leave the cap off and run it to let air escape from the filler cap.

 

With all the flushes I did last night I'm pretty sure that's how I got the air out. There was alot of bubbling going on. Still, it would be nice to find the screws Thanks!

 

The fill procedure for the LT5 motor is different from the LT1 motor. There are no bleed valves on the ZR-1 motor.

The LT! bleed valves are located on the passneger side of the thermostat housing and on the driver's side of the throttle body at the lower corner. Thes valves are opened during the coolant fill step and closed as soon as a steady stream of coolant flows out. Make sure to keep the coolant from spilling on to the Opti!!

Flushing the ZR1- cooling system requires removing the thermostat to get the old coolant out after the radiator petcock is opened. The service manual procedure is to drain the old coolant, replace the t-stat housing (don't put the stat back in) refill with water and let the engine idle for 3 minutes. Drain and repeat as necessary until the water is clear. Then drain again and re-install the thermostat and fill with a 50% mix of coolant and distilled water. The plastic expansion tank can be removed and cleaned during this step.

The LT5 cooling system needs 7.3 quarts of ethlyene glycol coolant and the rest is distilled water. Fill the surge tank and start the motor letting it idle for about 4 minutes, filling the surge tank as necessary. Keep a close eye on the temp guage during this fill procedure.

Reinstall the pressure cap and shut the engine off. The plastic expansion tank can be reinstalled and filled with 3 quarts of a 50-50 mix of coolant and water.

For the ZR-1 only, turn the A/C to OFF and start the motor. Let it run at idle until the cooling fans have turned ON and let the motor idle for 3 minutes after the fans have turned on. Turn the engine OFF and let cool completely (to 80 degrees or so).

I'm not a fan of using the in-line hose kits. The LT1 cooling system is a reverse-flow design so if you do use this kit, it has to be instaled in the correct hose. And it does not allow for draining coolant from the block so you can add the correct amount of coolant. You hve to pull both knock sensors from the LT1 block to get the coolant in the block out.

Because the service manual recommends the use of distilled water for filing, a flush kit doesn't really allow for that. If you have tap water in your area that is high in mineral content, using tap water may cause more harm than good. Distilled water is cheap; about a buck a gallon in grocery stores and you only need 3 gallons.

 

If you want to get the coolant out without removing the knock sensors, open the radiator petcock, then open the coolant container (the black one above the engine) and put a vacuum hose from a ShopVac that has blower capability over the container.

The forced are will push all of the coolant in the system out. Hold the hose until nothing but AIR comes out of the petcock valve.

 

I had read this recommendation before and thought I'd try it but my shop vac doesn't blow. I do have a new electric leaf blower so after a couple of Lites I grabbed the duck/duct tape, rinsed out my vac hose and duck taped it to the blower output. It's amazing what 220 mph air will do when routed through your coolant/expansion tank ! It shot the petcock valve out behind the car. I don't know if it got any water out of the block but the radiator was certainly clear.

 

C4Cruiser, that was a great, detailed explanation and exactly what I needed. Thanks again.

Glenn