Write-Up: Flushing Radiator Coolant

See Write-Up: https://rivperformance.editboard.com/t5920p15-write-up-flushing-radiator-coolant#82909

The wifes 99 Riviera has 78,000 miles on it and as far as I know the coolant has never been replaced, But the coolant looks like new.

Even the plastic reservoir looks new.
No muddy ,rusty looking crud on the radiator filler neck or on the bottom of the radiator cap, the coolant looks fine.
I used my suction gun to remove some from the radiator and examined it...

I was looking at the service manual and it says:

1.Open the radiator drain cock at the bottom of the radiator. (I have not spotted the drain "cock" yet... where should I be looking?)

2. Completely drain the system.

3. If the coolant is dirty, or if there are deposits in the radiator, flush the cooling system before refilling. Refer to Flushing.

Should I just drain as much as possible by opening the drain "cock" then drain the reservoir and refill the system with a mixture of 50% tap water and 50% GM Dexcool?



Bert

Haven't done the coolant change myself, on the Riv, but:

-If using Dex, you really need to be careful to get all the air out of the system.

-Don't use tap water.

1998 Riv wrote:

Haven't done the coolant change myself, on the Riv, but:

-If using Dex, you really need to be careful to get all the air out of the system.

-Don't use tap water.

Thanks Dave, I will be sure and bleed the system.

Bert

get distilled water (really cheap at the grocery store) or pay double price for the pre-mixed dexcool.

While inspecting the underhood area of the wifes 99 Riv I noticed something very odd.

I still have not drained/refilled the coolant so I was looking it over trying to get psyched up for the job.

The lower hose is "two piece" it has a short stub of a hose that is approx. three inches long that is joined to a normal lower radiator hose.

It looks impossible to get those clamps(pinch style factory clamps) off of the lower hose.

Is this normal on these cars or specific years only?

I looked in the service manual and it does not show or mention the two piece hose. Its factory for sure and not something that has been added.

Bert:tavis:

Here are some pics




Bert:tavis:

Drain cock is left front. Mine was a 55k car when I bought it, drained that GM crap and went with Distilled water and RMI. Put in a 180 and car runs great in 115* weather here in Phoenix. I started with tap water and ran the car for 10 minutes drained then filled repeated numerous times until that Dexcool was gone. Not sure if you freeze in Bama though?

So, does anybody have the two piece lower hose on their car?

Bert:tavis:

this what you do. disconnect the upper rad hose and remove the rad cap. cut the car on. take a water hose and force the water thru the hose. till you no longer see orange dex-shit coming out of the rad cap opening. continue to do this for about 30 min or so. make sure you check on the temp of the car while you are doing this. if you purchase a coolant cleaner solvent pour that stuff in first and follow those directions. then follow mine and it should remove all of the old coolant. at this point you can continue to add dex-shit in you car or put the good ol green stuff in. i sw=itched a long time ago after dex-shyt ate my upper intake up.

The only way to get at the draincock is to pull the front up on ramps and remove the front air dam. I drain and fill my radiator (not the whole system) once a year w/ dex/distilled and everything inside looks brand new. I have never flushed it.

My lower is a one piece.

My 98 had the two piece lower hose with reducer.
Manual doesn't mention it nor does the GM parts catalog.
I ordered the new lower hose from NAPA and it fit from the radiator to the engine (water pump) without the adapter. Just remove it and all will be O.K..
Also, the tablets GM sells for the cooling system are not a sealant. They are to help with corrosion of alum parts and supposed to help balance Ph levels.
If you are going to use these, install in lower radiator hose, then fill system with whatever coolant you are going to use.
I have a question for anybody in the know. I have read and been told by GM tech that Dex-cool is the likely culprit for chronic intake leaks. Has any one done any research on this subject and if so could you direct me to where I can find technical info on alternative coolants to use other than Dex-cool or straight water and additives. I need the freeze protection in this part of the country.
Plan on flushing the system soon, changing the T-stat to a 180* with new PCM and will change type of coolant if I can read about a good reason why.
Thanks for any info anybody can provide.

If you are not having coolingproblems, in my experience you cansafely ignore the coolant until after 100,000 miles. I now have ~190,000 miles on my Riv; just did the second coolant flush/fill (car was in shop already for water pump replacement so all I paid for was the coolant). Things to consider:

- always use de-mineralized or distilled water in the radiator, no exceptions, in the unlikely event you have to top it up.

- if you do flush-and-fill be sure to use those funky GM tablets. Otherwise, eventually you'll be whining about dex-cool leaks too.

- the first time the dealer flushed/filled my cooling system they installed one of those Prestone flush/fill kits - however all the parts were black plastic and it was not branded Prestone. I don't recall if it's a GM service part.

Albertj

ibmoses wrote:

The wifes 99 Riviera has 78,000 miles on it and as far as I know the coolant has never been replaced, But the coolant looks like new.

Even the plastic reservoir looks new.
No muddy ,rusty looking crud on the radiator filler neck or on the bottom of the radiator cap, the coolant looks fine.
I used my suction gun to remove some from the radiator and examined it...

I was looking at the service manual and it says:

1.Open the radiator drain cock at the bottom of the radiator. (I have not spotted the drain "cock" yet... where should I be looking?)

2. Completely drain the system.

3. If the coolant is dirty, or if there are deposits in the radiator, flush the cooling system before refilling. Refer to Flushing.

Should I just drain as much as possible by opening the drain "cock" then drain the reservoir and refill the system with a mixture of 50% tap water and 50% GM Dexcool?



Bert

Thanks Albert, I still have not done this. The coolant looks like new so perhaps I will wait for a while.

Bert

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

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?