Yeah if your not sure if your car has had the coolant changed then take the time to do it before your road trip. Its very easy to do so you dont have to waste your money having the dealership do it for you. Less than $20 is all you'll need.
What is the simplest way to do that coolant change? I have a '96 Eldo. I was thinking remove lower radiator hose, drain coolant, then replace with same amount of 50/50 Dexcool/distilled Water through surge tank? Should I add the stop leak powder too?
Check your radiator cowl for the recommendation on using the Barr's Leak Tabs (HDK). I'd suspect it says to add three tabs to the lower radiator hose. I'd drain the coolant through the drain, remove the lower hose and add the Barr's tabs. Put three tabs in a plastic bag and smash 'em with a hammer and pour the powder in. Refill through the surge tank 50/50 distilled water and Dexcool. I do not recommend using the pre-mix - do it yourself. Mark the fluid level on the distilled water jug. Use a marked pitcher and pour off a measured 2 quarts of distilled water out of the gallon jug. Mark the 2 quart line on the jug. Add 2 quarts Dexcool to the full mark and presto - 50/50 mix and the wife shouldn't get mad because you only put distilled water in her pitcher. For the OP: sealant tab recommendation may have been discontued by 02.
Thanks. Cowl label is not present. But I did get a GM Service Manual and it does say to add 3 tabs of the GM Sealant to the lower radiator hose during a coolant change. I understand that the Barrs Leak tabs are an acceptable replacement.
The GM and Bar's are one and the same. Bar's G12BP (powder in a tube) is also the same article. My '02 STS manual also calls for the product.
GM recommends changing the DEXCOOL every 5 years. I would fudge that and do it every 4 years religiously. If the DEXCOOL was changed to green coolant, or is pre-'96, use a new low-silicate green coolant, 50/50, and change it every 2 - 3 years.
Use a 50/50 mix of coolant to distilled water (supermarket) and fill the system to halfway up the surge tank, COLD. Leave the surge tank cap off and start the car. Observe the purge line discharge. It should spit some coolant and bubbles and settle down to a steady coolant stream. BEFORE the engine heats too much, shut down and check the coolant level again. Fill to the halfway mark, install the cap tightly and go for a 15 mile drive, suburban. Come home and let the car cool way down. Check the coolant COLD and fill to halfway again. Check it again next week. Good for 4 years for DEXCOOL and 2 - 3 years for green..
(If you live in an extremely hot or cold climate, GM allows a maximum 70/30 ratio of coolant to distilled water. This lowers the freeze point from -34 to -85 and raises the boil point from 265 to 276 at 16 psi.)
Bottom line for the OP is that if he can't document a coolant change in the cars history it needs to be done. Change, don't flush, listen to sub and go distilled and Dexcool, follow the instructions and do it yourself, save 100 bucks and use it for gas on the road trip.
GM no longer recommends the sealant tablets during a routine coolant change. The reason, however, is that customers were complaining about the particles in the coolant and thought is was rust or something (from aluminum?) So, they stopped adding it to a routing change...only if there is a minor leak. Since you are on this forum, you would know the stuff in the coolant is normal...it is your choice. My car has crystal clear Dex-Cool, so obviously the last change done at the dealer in 2004 did not include the sealant. And since I just replaced my cracked and leaking surge tank, my coolant is mostly new again.
I would use the drain rather than the hose to drain it. You will not get all the coolant out even if you use the drain. If you look at the lower radiator hose you'll see that it is rather high on the radiator so you will get even less out.