Write-Up: Flushing Radiator Coolant

albertj wrote:

OK Bert - yep - in my experience if no other problems, DexCool once properly filled really does run 100,000+ miles.

I suspect the issues other have come from using tap water in a fill or change - the minerals and the pH are problematic.

Albertj

I read a bunch about the problems with the Dexcool. GM pretty much decided the problem was caused by the coolant level in the radiator not being full.

Although the overflow tank was filled properly in most cases- the radiator was not full.
Not sure how this is possible unless like on my 95 PA the very bottom of the overflow tank in the corner where the coolant would exit the drain pipe was clogged with sludge.
So although the oveflow tank was full it would be possible for the radiator to be low...

After all most people probably never removed the caps to look into the radiator.
They just look at the overflow tank and make sure it looks like it is filled properly.

My personal hunch is that the problem is worse in the colder climates.

Bert

Yep - if one uses tap water there's a higher risk of sludging up depending on pH and mineral content.

Albertj

My '94 Regal's Dex-Cool looked like sludge after nobody touched it for 100K miles. I had to flush the system twice to get the inside of the radiator looking somewhat clean. I never got the overflow res. clean. It was always brown and sludgy. After I cleaned and refilled (with Dex-Cool) I never had any problems with the cooling system again. The car is still running well to my knowledge. I might even take it back into my possesion soon! (My mother has it in Florida right now...)

I need to revise my statement above regarding using the GM Sealant tabs.
I did a complete flush last year of the cooling system even though everything looked very clean. (coolant and inside radiator). Spent a lot of effort to flush properly. Removed thermostat, added cleaner ran engine per instructions drained and repeated flush with clean water. Never saw anything but clean coolant on first flush and clean water on second one.
Installed new thermostat and added GM sealant tabs to lower radiator hose with all new hoses and Dexcool. (That was 1 year ago)
A couple of days ago I drained radiator to install 180* tstat and noticed nasty brown crap on inside of radiator and under side of cap. Appears to be the remnants of those GM coolant tabs (sealant). Flushed system again before finishing job.
Later I researched my Service Bulletin list for another topic and came across one from GM engineering saying "Not to use the coolant tabs as a regular maintenance item after servicing coolant system" as I had been told to do by a GM Tech. "Only use if diagnostics fail to repair a small leak" TSB #00-06-006C Dated May, 2006.
So, I would not use these tablets as they will leave thick residue in the cooling system as any other Stop Leak additive will. I was initially given bad info from my GM tech friend.

hello everyone, I have 96 sc. I'm looking for a write up on the site on how to flush my coolant. i'm not overheating or anything but I the coolant just looks nasty. Also theres a lot of muck getting built up on the inside of my coolant resevior. I could take it to get done, but I enjoy learning how to work on my car so if anyone could direct me to a link or a write up I would be greatfull. thanks

How to flush a rad:
1. Climb under car and remove the little plastic faseners that holds the bottom plastic guard on. A rough guess wuld be that there are 9-10 of them. You pull the plastic center, and the rest of the clip comes out of the hole.

2. Remove plastic guard from the bottom.

3. Facing the front of the car, on the right, under where you removed the plastic, is a hole for the rad drain bung. Remove the bung and let the coolant run into a shallow bucket.

4. Dump in a container of something like Prestone Rad flush.

5. Top up with water.

6. Run the engine, for around 15 min with the heater on full plast.

7. Let car cool.

8. Drain rad again. Replace bung.

9. Remove the coolant canister and rinse out with a hose if desired.

10. Fill with new coolant following the reccomened mix on the bottle. I use prestone "mixes with anything" stuff.

11. Top up the coolant canister to the cold mark.

12. Open the little valve on the LIM where the large coolant hose enters it. It will be on your right, by the boost bypass actuator. Near the EGR on the 95. There is a little screw for bleeding out air, slot screwdriver opens it.

13. Run the engine, wait for spitting on the little valve. Close valve.

14. Let engine run for a bit. Cool. Open Valve again, repeat engine run till water comes out valve.

Thats about it, off the top of my head. I do have a folder full of pics from my rad change that documents the same procedure, that will eventually end up in a write-up when I find time.

good writeup on flushing, but here's what I'd do if I were you:

drain the radiator.
Add RMI25 according to instructions on bottle (a good cleaning solution and lubricant)
Refill with proper 50/50 mix (use distilled water for that 50)
repeat next year.

I've never been a fan of flushing the system.

Here are a few pics I took while draining/refilling the coolant on the 99 Riv today.
Hopefully they will help someone.

The radiator drain bung is kind of hard to spot so here are a couple of pics of what the little bugger looks like after it is removed from the radiator.


Here is a pic of the bleeder screw:

And a pic of the chin spoiler/belly pan that must be removed to gain access to the radiator drain bung:

The chin spoiler/belly pan is a lot easier to remove/reinstall than it looks. It only takes a couple of minutes to remove or to reinstall.

Bert

Looks like the weather was nice there today for working on the car.
It's been snowing and raining and snowing here all day. And it's only the middle of October !!!!!!

How much radiator fluid does the Riv take?

Just about 2 gallons in my experience. One gallon of anti-freeze and one gallon of water.
I pre-mix the two or you can buy the Anti-Freeze already pre-mixed at the auto parts store. Just look for 50/50 on the bottle.
Then you just have to put it in and not be concerned with mixing it.

Rickw wrote:

Looks like the weather was nice there today for working on the car.
It's been snowing and raining and snowing here all day. And it's only the middle of October !!!!!!

Things are weird out here on the left coast, too... Last week we got 6 inches of rain in 1 day, and this morning the "few showers" that were forecast dropped 1.5 inches in 2 HOURS! In SF, water was gushing out of manhole covers.

Rickw wrote:

I pre-mix the two or you can buy the Anti-Freeze already pre-mixed at the auto parts store. Just look for 50/50 on the bottle.
Then you just have to put it in and not be concerned with mixing it.

Rick makes a good point. If you don't buy pre-mixed, or pre-mix it yourself, you'll inevitably find yourself with either too much or not enough anti-freeze in, when the system stops accepting any more...

When I flushed the hell out of my car to convert it back to trustworthy green coolant, I'm pretty sure it took more than two gallons (it's rated for 3.) However, being a cheapskate, I figured the cheap and fairly easy thing to do is this:

Buy 2 gallons of the regular full-strength anti-freeze and 2 gallons of distilled water;
Start the engine and pour one gallon of anti-freeze and one gallon of water into the empty radiator;
If the car won't accept any more when the thermostat opens, you can return the second anti-freeze - otherwise,
Pour half of the 2nd water bottle into the empty coolant jug and then top it off from the 2nd anti-freeze bottle;
Pour the rest of the water into the 2nd anti-freeze bottle, and now you've got 2 gallons of pre-mixed, 1 more for the radiator and one for topping up later.

I know it sounds a little Die Hard 3/Simon Sez, but you'll have spent (at the minimum prices) only $20 for 4 gallons of mix, instead of $30 for 3 gallons of pre-mix... Who doesn't like half price?

[quote="95 super3800"]theres a lot of muck getting built up on the inside of my coolant resevior.[/quotewhen you have the cooltaint out of the system then take the resevior(remove the litle tube what goes to the radiator and some nuts)

when you have it off but a bit of SAND in it and somekind cleaning fluid like dich waching fluid (i'm not kiding...) and add some water in it till its 1/3 full.
then but the cap on the resevior and hold one finger on the place where the tube connects the resevior and SHAKE IT!...the sand will start to rube and hit the dirt off the walls and the cleaning fluid dos not let it get stuck again...do it so long till its clean...fluch it whit water....

I cleaned mine this way

Actually, that does sound like a good way to clean the inside of those tanks

What's wrong with running straight anti-freeze? A 50/50 mix doesn't sound like it would be good for below zero temps.

I've heard straight antifreeze actually freezes sooner than a 50/50 mix! And without water I doubt it cools as well. Costs more than water, too.

Jack the R wrote:

What's wrong with running straight anti-freeze? A 50/50 mix doesn't sound like it would be good for below zero temps.

Jack,
Anti Freeze is good for corrosion protection, and to prevent freeze up. A/F actually does not transfers heat as well as water. The more A/F you use, the less heat transfer there is. That is why they tell you on the back of the container not to use more than 70% A/F to water. My neighbor actually had a chronic overheating problem that he could not figure out until he said to me "I don't understand it, I'm using 100% A/F". We drained half out, and added water. That did it. If you live in a warmer climate where there is no danger of freeze up, you are actually better off with 100% distilled water, and a bottle of Red Line water wetter or similar additive for corrosion protection. The water wetter lowers the surface tension of the water. It enhances heat transfer even more. That is what the Racers use. The engine runs cooler.

AA wrote:

I've heard straight antifreeze actually freezes sooner than a 50/50 mix!

I don't think so. I'm pretty sure I've got straight anti-freeze in the Charger (not currently running, so no overheating worries), and it floats all the balls on the temperature tester (shows what temp your mix is good for).

When using a mix I've always found it difficult to get enough of the balls to float as is sometimes necessary. Drain a little, add antifreeze, drain a little, add antifreeze, drain a little, add antifreeze. . .

Forget the floating balls.
Read the manufactures recommendations on proper mixture of anti-freeze and H2O.
50/50 provides the highest boiling point and the lowest freezing temp.

A 50/50 mix protects down to -34* How much more do you need?

http://www.justanswer.com/questions/gxu3-undiluted-antifreeze-freeze

If you dig around, some sources show that using straight antifreeze (or less than 30% water) lets the coolant freeze (or gel) easier than using a mix.



Both the green stuff and orange Dexron III coolant are ethylene glycol type antifreeze.

From Larry's link:

"As the name implies the third main function of antifreeze is to protect the cooling system from freezing. The way to achieve maximum freeze protection differs between ethylene and propylene glycol. For ethylene glycol the maximum protection is at 67% ethylene glycol in water. A ethylene glycol solution of this concentration will freeze at -84° F (pure ethylene glycol freezes at 8° F)."

There are numerous opinions about what anti freeze should be used to replace the antifreeze in your 95-99 Riviera.
Below is a link to a thread that contains many of those opinions and a great amount of information regarding Dex cool and the traditional "green" antifreeze as well as the "mixes with anything" antifreeze that is also available:

https://rivperformance.editboard.com/care-maintenance-f8/gm-dexcool-coolant-antifreeze-t1364.htm?highlight=dexcool

Personally I buy the Dex cool concentrate and mix 50/50 with distilled water and use this mixture in our 99 Riviera.

Bert

When I have used a chemical cleaner when flushing, after I drain it out of the car I like to do another run with just water in the system to be sure I have it sufficiently rinsed out and neutralized.
I always get more gunk with that second run.

Then after I drain that, I add my fresh new coolant.

I also mix the coolant closer to maybe 60 or 70% since there will still be a certain amount of plain water in the block yet.
I figure once it all gets mixed together in the engine I am then closer to a 50% mix.

AA wrote:

Both the green stuff and orange Dexron III coolant are ethylene glycol type antifreeze.

I was under the impression that DexCool (Orange) was Propylene Glycol, which is the supposed culprit in the LIM gasket failure.
Or am I incorrect on this.???? I guess I need to do some research as I can't remember anymore.
I used to know.....Duh.....Getting old SUCKS.
Can't remember shit.