Coolant change/flush

[markqc]

What is the proper procedure to drain/flush/change the coolant and how often? I hear the dexcool will not last the 5 year/160000KM as stated. Any help would be appreciated.

Thanks,

Mark

[rubberman]

on the drivers side of the radiator at the bottom corner there is a twist drain plug. That will drain the coolant from the radiator. To get the rest i think you need to get the Prestone radiator flush kit. It allows you to hook a garden hose so you can flush out the rest thru out the block. Bad thing is that its messy.

[1999montana]

Originally Posted by markqc

What is the proper procedure to drain/flush/change the coolant and how often? I hear the dexcool will not last the 5 year/160000KM as stated. Any help would be appreciated.

Thanks,

Mark

Interesting link on the GM lawsuit concerning DEX-Cool not going the distance:

http://www.imcool.com/articles/antif...le-Excerpt.pdf

Mine has been in 6 years minus the top up done in 2002 for the intake gaskets.

Guess it might be time to flush and fill for sure!

[cdru]

Originally Posted by markqc

What is the proper procedure to drain/flush/change the coolant and how often? I hear the dexcool will not last the 5 year/160000KM as stated. Any help would be appreciated.

Despite what GM says, I wouldnt' trust Dexcool to last 5 years in a vehicle. Maybe 3...longer then the green stuff, but not 5 years. If the system is properly maintained, it will last a long time. However, it seems that air is a killer for the life of Dexcool. If a system runs low or a significant amount of air is allowed to remain in the system, Dexcool has a tendency to form a brownish gunk that sticks to the internals of the cooling system. In high flow rates areas (e.g. water pump, upper/lower radiator hoses, its not as much of a problem. But in slower areas or smaller areas, it has a tendency to accumulate. Take a look in your resevoir. If it's dirty looking or has a film over things, air's likely the culprit.

To flush the system fully, you should drain as much coolant out of the system, remove the thermostat, then back flush everything. Leaving the thermostat out, hook up the hoses again and fill with water, this time run a chemical flushing agent through (follow directions), then open up the system again and back flush.

Removing the thermostat is a PITA though becase you either need to remove the TB or exhaust crossover pipe to get to the bolts for the themostat housing. So it's really your option as to if you want to completely flush the system. Running several cycles of a chemical flush and/or water, allowing the thermostat to open each cycle, will do a decent job.

At a bare minimum, open up both bleeder valves, drain the radiator using the drain cock, as well as the two block drains. There is one near the oil filter, and one on the back side of the engine. These three plugs will get a lot of the coolant out. Unfortunately, a lot of coolant will still remain in the heater core and coolant lines, especially if you have rear heat.

Now getting the coolant back in and removing ALL the airbubbles is the tricky part...

[1999montana]

Originally Posted by cdru

Despite what GM says, I wouldnt' trust Dexcool to last 5 years in a vehicle. Maybe 3...longer then the green stuff, but not 5 years. If the system is properly maintained, it will last a long time. However, it seems that air is a killer for the life of Dexcool.

Thanks for the detailed reply.

I've done many flushes exactly as you describe. Sounds like I'll have a blue cloud of profanity floating over Lake Ontario before I get the thermostat out, but this is the best way (to flush the system I mean, not the profanity!) no question.

Yes, a rear heater too. Sounded like a good thing when we bought it, but not now!

[cdru]

Originally Posted by 1999montana

Thanks for the detailed reply.

I've done many flsuhes exactly as you describe. Sounds like I'll have a blue cloud of profanity floating over Lake Ontario before I get the thermostat out, but this is the best way (to flush the system I mean, not the profanity!) no question.

Yes, a rear heater too. Sounded like a good thing when we bought it, but not now!

The TB isn't too hard to pop off. Drain the coolant using the resevoir, remove the two clamps for the coolant lines goint to the TB. Unplug the sensor plugs as well as the accelerator cable and cruise control cable. Unbolt the couple of bolts and a nut holding on the TB and it should pop off. That should clear up enough room to get an open end box wrench down to the two bolts on the housing. You'll have to wrestle a little to get it to pop off but shouldnt' be too much problem. If you are going to replace it, replace it with a GM part. Don't get an aftermarket one as they protrude slightly more and it's nearly impossible to get the cover back on without taking the crossover pipe off.

Sometimes a complete engine flush may expose more problems that it fixed. After 6 years, crud can build up in places acting like a seal, helping to prevent leaks or plugging pin hole leaks. When you flush/backflush, a lot of that crud will get distrubed. It may expose new leaks, or it could also lodge itself elsewhere, plugging a water passages. Many water passages are not very big...I'm in the midst of a head gasket change and the holes in the gasket for the coolant are smaller the the diameter of a pencil. If a big chunch of something semi-solid comes loose, you could be in trouble.