Coolant changes & additives

piddlerdad3August 21, 2005

I have a 2000 Honda odyssey, and it has ~90K on it. i'm reading thru the owner's manual and i'm thinking about changing the coolant based on their recommendation of every 30K miles under normal conditions. Except for living in a hot climate (Dallas), normal is mine. i bought it used, and have no idea if/when it was ever changed before. I checked it and it is Green - like the Prestone ethylene glycol i've used for decades.

Do i need to change it? If so, i'm planning on using Prestone coolant. Is my plan ok? would additives help prevent some of the MILD corrosion i've seen over the years in aging vehicles? without causing problems? do modern cooling systems really benefit from additives?

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Changing the coolant is a good idea because even though it looks fine, it becomes corrosive with age. That's why you see the rust in older cars that have had poor (or often nonexistent) cooling system maintenance. I've never used any type of additives. To me, if there were any additives that had any proven value, the manufacturers would use them when the car was new.

    Bookmark   August 21, 2005 at 10:15PM
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IMO, they do! Additives have helped in the Saab, VW, Mercedes,Honda, Chevrolet,etc...
I have been using an anti-rust for now decades;I never regularily change the coolant in any of the cars.
This changing of the coolant, I feel, is a waste of money.

But the green anti-freeze is becoming passe..

Be very careful with these newer cars.
Best to use exactly what the car-maker states to use..

    Bookmark   August 21, 2005 at 10:20PM
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**Do i need to change it? If so, i'm planning on using Prestone coolant. Is my plan ok?**

Sounds good to me. Change it every couple of years or 30k miles and your cooling system should always be happy. Additives are not required. To me it's kind of like the synthetic oil discussion. I'm sure there are fine products out there but to me there's not much to gain by spending the money on them when following the recommended schedule. They say oil is cheeper than engines. Same goes for coolant. Coolant is cheeper than heater cores and radiators. jmo.

    Bookmark   August 22, 2005 at 12:20AM
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By using this anti-rust, I have yet to lose a radiator or a core, but water pumps still go at 80 plus K miles.
Anti-rust costs one dollar annually...

Regular oil is fine for low to middle performance cars and those who consider the motor vehicle an appliance.

I probably do waste money by using a synthetic (Mobil 1) in the Saab 900S (na), but then I do not change until 6 months go by...

    Bookmark   August 22, 2005 at 12:57PM
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Check your service manual before you change coolant/antifreeze. Your Honda may require a non-silicate antifreeze.

Antifreezes with silicate additives were blamed for water pump seal failures in relatively new Honda Gold Wing motorcycles. The water pumps failed soon after the first change to coolants having silicate additives in the antifreeze.

    Bookmark   August 26, 2005 at 7:50PM
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Guys, thanks for the good info. I just checked my Honda manual and JemDandy is right. I need a non-silicate coolant/antifreeze made for aluminum engines. Of course, Honda says use Honda coolant only. I looked on Prestone's website and found this:
"Prestone Extended Life 5/150 Antifreeze/Coolant is recommended and formulated for use in all GM vehicles that require a GM DEX-COOL® approved formula coolant, as well as all other cars and light-duty trucks with aluminum radiators. This patented formula has a concentrated blend of premium, long-lasting inhibitors for extended performance, protecting against temperature extremes and the ravages of rust and corrosion for 5 years or 150,000 miles. ... Prestone® Extended Life 5/150 Antifreeze/Coolant is phosphate, silicate, and borate free. ... Prestone® Extended Life has been proven in the laboratory to be compatible with all new extended life formulas at concentrations typically used in all newer vehicles coming off the production line today. These automobile manufacturers include:

Audi General Motors Suzuki
BMW Honda Toyota
Daewoo Mercedes Volvo
DaimlerChrysler Mitsubishi VW

Along with all these praises from Prestone comes instructions to completely drain & flush my cooling system prior to filling with this reddish concoction. oh boy, here we go with lots of work. can i remove the radiator hoses & just use the water hose on high to put into all the available openings? then pressure spray all the stuff out? or do i need to remove more hoses from the heater core as well? I'm looking for effective draining, so i can benefit & leave this new stuff in for 5 years. but i'm also wanting a simple way to do this as i don't understand how all the plumbing works.

Thanks for all the help,

    Bookmark   August 27, 2005 at 6:18PM
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If you are refilling with a coolant that is comaptible with the old stuff, you don't have to get every last drop of the old stuff out, just most of it.

First, leave the radiator cap in place. Loosen the drain cock at the bottom of the raditor (with a drain pan in place of course). It won't drain very fast, but it should suck coolant out of the overflow bottle. After most of the coolant has been removed from the overflow bottle, proceed to a quicker method of draining.

Remove the radiator cap. The outflow should increase. if that isn't fast enough, remove the bottom radiator hose at the raditor and the coolant should gush out.

Very likely you will be changing the thermostat as well. That is recommended. Loosen the housing containing the thermostat and more coolant should flush from the engine. Clean off the gasket surfaces and put in the new thermostat paying attention to the correct orientation. Some thermostats can be intalled backwards. In general, the temperature sensing slug (wax motor) should face toward the engine (toward the hot water side) - check your manual for this or pay attention to the old thermostat before removing it.


Rather than to try to guess the proper amount of water and antifreeze to pour in, pre-mix the solution in a covenient container, say an old antifreeze jug. Usually, this is a 50/50 mix by volume. In very cold climes, you may wish to increase the amount of antifreeze. Pour a can of corrosion inhibtor and water pump lubricant into the raditor, then finish filling with the premix. If one jug of premix isn't enough, mix up another jug. The leftover can be stored on the shelf and used for makeup fill later on. Just cap it tight.

By the way, I forgot to mention: Put the hoses back on before refilling.

Sadly, the system will not completly refill. Some manuals instructs to relieve the air somewhere around the thermostat housing. This aids in filling the heads. In any event, put as much in as you can, then start the engine (with the radiator cap off). Put the heater control on max heat. Go back to your post at the raditor. You'll want to shut off if the coolant starts to gush out, but I don't think it will. Nothing much happens until the theromstat opens, then the fluid ahould drop as the engine heads and heater core fills. Add more remix as necessary. Also, fill the overflow bottle to its recommended level. When you have put in all the premix that you can, put on the raditor cap and tighten it. From now own, you will dealing with a sealed system.

It takes about three thermal cycles of heating and cooling to flush out the air and bring the system to its desired level of fluid fill. After the initial engine warm up. Stop it and allow it to cool. You should see coolant being sucked out of the overlow bottle into the engine. When the level of the overflow bottle slows in change, restart the engine to flush more air out of the system. when the engine nears operating temperature, refill the overflow bottle and shut off the engine. This is thermal cycle no. 2 and the system should be nearly filled. Allow the engine to cool until it nearly stops taking fluid our of the overflow bottle, then refill the bottle. At no time should the port at the bottom of the bottle be uncovered, else it will admit air into the coolant system.

From now own, always add makeup coolant to the overlow bottle and keep raditor cap sealed. Drive the car normally keeping watch on the overflow bottle. Add coolant as necessry. The system should stablize after the about the third thermal cycle.

None of these shenanigans are necessary if one could get the system completely filled in the first place, but in my experience, I've always needed to put on some thermal cycles to completely flush out the air.

Some auto models have instruction to aid filling the system. Study the recommended procedure and apply it for best results.

    Bookmark   August 28, 2005 at 4:55AM
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JemDandy, If you had entered these instructions in a contest for your average car owner who (like me) forgets how to do these simple maintenance tasks - i'd have voted you a winner. These are clear to me and makes good sense. i'm used to reading really informative directives such as 1) locate draincock 2)Drain radiator 3)Flush cooling system 4)Refill cooling system 5)Drive car and recheck fluid level.

These familiar instructions leave a lot to be figured out. i still remember nearly frying my engine in an old Toyota truck when i tried doing this the first time. i figured since the system was full after i emptied a 50/50 mix and topped off the radiator that i was done. The thermal cycle hit, and i was driving down the freeway going to work when the engine temp gage went into the red in a matter of a minute or two. Bad experience. I'm not the brightest apple in the bushel, but i could have educated myself better and avoided this mishap. I'll check into replacing the thermostat during the coolant change as well. hadn't thot of it.

Thanks for taking the time to put this info on the thread.

    Bookmark   August 29, 2005 at 12:11AM
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I know it's two years later, but I just replaced the coolant in my '03 Odyssey last night.

Never use tap water for flushing or topping off your coolant. You have no idea what metals and compounds are in the water and what they might do to your car.

If you need to flush, use distilled water.

Honda OEM Type 2 coolant is dark blue, premixed, and expensive ($13 a gallon in San Jose, CA).

The manual specs 7.9 gallons for vans with the rear heater.

These are the instructions out of the OEM manual from memory:
1. Set the front cabin temp dial to maximum.
2. Remove the radiator cap.
3. Open the radiator drain. In my van, it's a white wingnut-looking draincock accessible in the center bottom of the radiator through a hole under the bumper/air dam.
4. Put a length of hose on the engine block drain located on the passenger side above the axle and open the drain. Mine had a blue plastic nipple. I used 2 feet of 1/4" ID clear vinyl tubing and a short 12mm flare nut wrench. I also lifted the front of the van on jackstands and removed the passenger front wheel for better access. It took a while to drain.
5. Close the engine block drain and remove hose.
6. Close the radiator drain.
7. Remove the coolant reservoir and dump it and reinstall. On my van, the reservoir just lifts up and out. No fasteners.
8. Fill the radiator to the neck. It took a little over a gallon.
9. Start the car and run it at 1500 rpm until it reaches operating temp (until the radiator fan turns on twice). You'll probably hear gurgling from the heater.
10. Shut the car off.
11. Check the radiator and top off with coolant.
12. Set the front cabin temp dial to minimum.
13. Start the car and run it at 1500 rpm for 5 minutes.
14. Check the radiator and top off.
15. Set the front cabin temp dial to maximum.
16. Start the car and run it at 1500 rpm for 5 minutes.
17. Check the radiator and top off.
18. Set the front cabin temp dial to minimum.
19. Start the car and run it at 1500 rpm for 3 minutes.
20. Check the radiator and top off.
21. Set the front cabin temp dial to maximum.
22. Start the car and run it at 1500 rpm for 3 minutes.
23. Repeat the min/max/3 minutes/1500 rpm cycles until you don't have to top off the radiator and you don't hear gurgling in the heater. It helps to set the fans to low to be able to hear the gurgling. You might get some boil-over out of the radiator as well.
Then the manual has a procedure for testing the performance of the rear heater. It includes a graph of interior air temp to rear heater vent temp. Too involved for me. Instead, I just followed their continuing steps.
24. Replace the radiator cap loosely. Turn it enough that it engages the locking tabs but not so much that it is completely tight.
25. Set rear heater control to heat.
26. Start car and run at 2500 rpm for 5 minutes.
27. Check rear heater for gurgling noises. If you get gurgling, repeat the min/max/3 minutes/1500 rpm cycles until you don't have to top off and you don't hear gurgling in the rear heater.
28. When your heaters are quiet, replace the radiator cap fully tight.
29. Fill the reservoir to the max line.
30. Add .4 quart more coolant to the reservoir.
I'd keep a close eye on the coolant level through several thermal cycles just as JemDandy suggests.

    Bookmark   April 18, 2007 at 2:29PM
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"The manual specs 7.9 gallons for vans with the rear heater".

rekiwi your post regarding coolant change for your Odyssey gave me the boost I needed for trying to do the same for my '02 van. However my local Honda parts manager quoted $19/gallon as the current cost of the type 2 coolant but also said that "our mechanics use only one gallon for the job". Should I buy 8 gallons or just expect to use one gallon ($152 vs $19 for the job)?

    Bookmark   December 19, 2008 at 8:44PM
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First off you need to know the quantity your cooling system holds. You also need to know if the coolant you're buying is premixed or needs to be diluted with water. Straight antifreeze is not a good thing. After you know those two things, you'll know how many to buy. Bet it's more than one no matter what.

    Bookmark   December 19, 2008 at 10:40PM
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