Coolant Change

[MAC]

I know this topic’s been discussed before, but I just want to make sure I got it right. I have two gallons of the green antifreeze and I want to do the change myself. I remember that Guru said that all that is needed is to disconnect the lower radiator hose—drain—top off with 50/50. That’s it—nothing more until the next change a couple of years down the road? Is that right?

I went to do the job and I noticed that the bottom radiator hose on the left side is not really located at the bottom, but more like 2/3 down. So I’m hesitant to do just one drain because I’m a bit skeptical that one partial drain will do the job.

Question: has anyone drained and refilled this way? And did you only drain once or more than once to make sure enough fresh antifreeze replenishes the system?

Also, I noticed that it’s not the easiest job to disconnect the bottom hose—there all kinds of stuff in the way and unless the bottom shield is removed the antifreeze is going to hit everything on the way down.

[Ranger]

If you can get at the drain plug on the radiator (easier said than done) use that. If not, after you pull the lower hose, use as shop vac and put the hose on the exhaust side and use it to blow air into the cooling system by putting the hose in the surge tank and using your hand to seal it. That will blow out most of the residual coolant. Don't forget to add the sealant tabs to the radiator hose before you button it up.

[JimD]

The radiator drain is the lowest point in the cooling system. If you can stand the mess and the cleanup, that is your best bet to drain as much as possible. You will want to do it hot so the thermostat is open and remove the pressure cap to allow air to replace the coolant.

Or, you could do a partial drain via a hose and then do it again after a few hundred miles.

[Bill K]

Are you sure you really want to do it when its HOT?

I have never changed fluid that I didnt get it spilled on myself. For that reason I do it cold.

Green - two yrs. Dexcool - 4 yrs.

But thats just me.....

[MAC]

I took the bottom radiator hose off and drained the coolant. The most difficult part was loosening the clamp screw (regular screwdriver). It's in an award position and tough to get at with a regular length screwdriver because the transaxle cooler lines block the best angle to position the screwdriver. The best way to get at it is with a long screw driver with a larger driver surface so the screwdriver has a better chance to remain on the screw when it's moved due to the awkward position. I used a screwdriver socket fitting and put together both a long and short extension to make it long enough. I drained about 1-gallon give or take. As dumb luck would have it, I accidentally left the expansion tank cap loose so about another gallon evaporated out of the system. Finally, the Check Coolant Level warning flashed and temperature was fluctuating up and down between 205 and 230. When I checked the cap I found it was loose. So all in all, I put 1 gallon of distilled water and slightly over 1 gallon of antifreeze into the system. I think that should be good for a couple of years. I also put 3 Bar's Leaks tablets (the HDC) into a half gallon of water and let them break up then poured it into the expansion tank.

http://www.barsproducts.com/origin.html

[KHE]

I also put 3 Bar's Leaks tablets (the HDC) into a half gallon of water and let them break up then poured it into the expansion tank.

http://www.barsproducts.com/origin.html

Why didn't you add the bars leaks pellets to the lower hose when the system was drained??? They will plug up the surge tank.

[MAC]

GM states that pellets can be put in through the surge tank. See Below excerpt taken from the 1994 Service Manual, p. 6B2-8 (4.6L):

The full factory fill capacity of the system is 11.8 Liters of 50/50 mixture of coolant.

If draining in the following order these locations will yield the following quantities:

A. Radiator or drain at lower left hand end tank: 3.50L

B. Left hand block drain: 3.75L

C. Right hand block drain: 1.90L

D. Heater circuit: 1.50L

Approximately 1.15L will remain in the system after a complete system drain. The above quantities can be used for cooling replacement when cooling system service is performed.

7. Start the engine and check for leaks.

8. Enter diagnostics (See Section 8A) and monitor BCM parameter BD21 for coolant temperature. The temperature should not exceed 116C during an idle at 75-80 degrees Fahrenheit ambient.

9. With the system at operating temperature (approximately 108C), the heater core circuit and the upper left hand corner of the radiator core should be hot.

10. If the heater core and radiator left hand upper corner remain cold, raise engine rpm to approximately 2000 rpm to increase flow.

11. Shut off engine and allow system to cool.

12. After system has cooled sufficiently, add three (3) cooling system pellets P/N 3634621 and add sufficient coolant to the surge tank in order to bring the level slightly above the weld line visible inside the bottle.

13. Install the surge tank pressure cap.

[gc_caddy]

GM states that pellets can be put in through the surge tank. See Below excerpt taken from the 1994 Service Manual, p. 6B2-8 (4.6L):

The full factory fill capacity of the system is 11.8 Liters of 50/50 mixture of coolant.

If draining in the following order these locations will yield the following quantities:

A. Radiator or drain at lower left hand end tank: 3.50L

B. Left hand block drain: 3.75L

C. Right hand block drain: 1.90L

D. Heater circuit: 1.50L

Approximately 1.15L will remain in the system after a complete system drain. The above quantities can be used for cooling replacement when cooling system service is performed.

7. Start the engine and check for leaks.

8. Enter diagnostics (See Section 8A) and monitor BCM parameter BD21 for coolant temperature. The temperature should not exceed 116C during an idle at 75-80 degrees Fahrenheit ambient.

9. With the system at operating temperature (approximately 108C), the heater core circuit and the upper left hand corner of the radiator core should be hot.

10. If the heater core and radiator left hand upper corner remain cold, raise engine rpm to approximately 2000 rpm to increase flow.

11. Shut off engine and allow system to cool.

12. After system has cooled sufficiently, add three (3) cooling system pellets P/N 3634621 and add sufficient coolant to the surge tank in order to bring the level slightly above the weld line visible inside the bottle.

13. Install the surge tank pressure cap.

My FSM says the same... but in this case, I'll yield to the experience and wisdom of the forum regarding where to add the coolant pellets.

I've been through many coolant changes (every year in fact, as added precaution) and each time I added the pellets (Gold Seal tubes) into the hose that connects to the thermostat/waterpump. That location is the easiest to access and I've never had a problem. On each coolant change, the coolant is uniformly brownish - a good sign since that means the pellets were distributed properly throughout the system.

[KHE]

GM states that pellets can be put in through the surge tank. See Below excerpt taken from the 1994 Service Manual, p. 6B2-8 (4.6L):

The full factory fill capacity of the system is 11.8 Liters of 50/50 mixture of coolant.

If draining in the following order these locations will yield the following quantities:

A. Radiator or drain at lower left hand end tank: 3.50L

B. Left hand block drain: 3.75L

C. Right hand block drain: 1.90L

D. Heater circuit: 1.50L

Approximately 1.15L will remain in the system after a complete system drain. The above quantities can be used for cooling replacement when cooling system service is performed.

7. Start the engine and check for leaks.

8. Enter diagnostics (See Section 8A) and monitor BCM parameter BD21 for coolant temperature. The temperature should not exceed 116C during an idle at 75-80 degrees Fahrenheit ambient.

9. With the system at operating temperature (approximately 108C), the heater core circuit and the upper left hand corner of the radiator core should be hot.

10. If the heater core and radiator left hand upper corner remain cold, raise engine rpm to approximately 2000 rpm to increase flow.

11. Shut off engine and allow system to cool.

12. After system has cooled sufficiently, add three (3) cooling system pellets P/N 3634621 and add sufficient coolant to the surge tank in order to bring the level slightly above the weld line visible inside the bottle.

13. Install the surge tank pressure cap.

The FSM for my '96 states to add the pellets to the lower radiator hose. I don't know why there would be different instructions for a '94.... I wouldn't worry about it unless the engine overheats - then I would check the surge tank hoses for plugged sealer.

There are no block drains on the Northstar - I discovered that when I changed the coolant on my '96 SLS the first time....

[MAC]

I also want to add that I made sure the pellets were broken up in the water before I added the mixture to the surge tank. I shook the bottle vigorously to make sure they were thoroughly dispersed. Since the system needed coolant, I figured the water/sealant wouldn't just sit in the surge tank and settle, but would go directly into the system. Also, I didn't pull the bottom hose off all the way--just enough to drain the coolant.

[Ranger]

Theoreticly, I suspect that would work as long as you are sure the pellets are completely broken down to small fibers and are held in suspension.