Coolant change intervals? Is it based on time or mileage?

[SeafoodSC]

I know you're supposed to change coolant regularly to preserve headgaskets among other things, but are you supposed to do it at certain mileage intervals, or over a period of time? Reason I ask is because my SC only gets driven ~1,500 miles a year and sits in the garage all the time. I drive it only a few times a year, but take it out for a 30 min ride every month to keep it fresh. I haven't changed the coolant in 3-4 years, but it looks like its new still.

[935spd]

Its definitly time to change the coolant. All that sitting around can't be very good. I would change every 2-3 years. Better to be safe than sorry.

Nick

[Robert Kohlman]

I would change it every two years. Just because it looks good doesn't mean that it is working properly. It is more what happens to it chemically as it ages than anything. As the coolant ages its chemical composition changes and starts breaking down the head gaskets. Also the antifreeze looses its ability to perform its functions of lubricating and protection from freezing and overheating.

Bob

[Phil Kuhn]

I change mine every year regardless of mileage and I drive mine less than you do.

Same with the oil.

I still have the original gaskets after nearly (10) years.

[onequiksc]

The main ingredient in anti-freeze, ethylene glycol, does not wear out over time. However the corrosion inhibitors in coolant DO wear out from the effects of heat and minerals, so changing it often is cheap insurance.
And when you consider the sediments and rust as well as the electrolysis that occurs from dissimilar metals (aluminum and iron which we have in our cars) it's not something you want to push the envelope with.

I've done it every year for almost 12 years now, and I still have the original HG's and radiator.

[Mike8675309]

For such a use, I would consider talking to your local oil company (there is always a local distributor) who often also handles anti-freeze in bulk for local trucking companies.

They can provide you with access to testing strips/kits to actually test for the presence of the corosion inhibitors and let you know if the coolant should be changed.

They may also be available from other places, but I've only seen them come from oil companies at heavy truck shops.

In addition there are additive packs that can be added to good coolant to recharge it with the anti-corosion chemicals. Can't find any right now. NalCool 2000 was one. I believe they are called SCA additives.

[Jimmy 2Coupes]

Be safe and change it once a year. I change the coolant in my SC's every spring when they come out of winter storage.

[SeafoodSC]

o.k., I guess I'll change it soon then. What is the proper procedure besides draining the radiator?

[Phil Kuhn]

The best method I've found for flushing a cooling system (short of having a flush machine, like the ones from BM systems) is:

1) Drain small amount of coolant from vehicle.

2) Add cleaner agent, run vehicle for 10-15 minutes, make sure heater is on.

3) Let car cool off a bit.

4) Locate heater core hoses.

5) Remove the heater core hose that "evacuates water" from the heater core - you might have to start the car to figure out which one it is, but basically, you want to see water coming from the core, not the hose. Be careful - water will be warm.

6) Attach an adapter to the heater core, so that you can pump water through the core first, then have it drain out of the hose that you just removed (it needs to make a full circuit through the cooling system to do this, and it will run "backwards").

7) Remove the thermostat (otherwise, when you pump cold water in, you won't get any water circulating as the t-stat will close due to cold water).

8) Position drain under the dangling heater core hose.

9) Start garden hose with a steady stream of water; don't over-do it, you don't want to damage anything (heater core).

10) Flush the car for a good 15-20 minutes. Turn off the hose and let as much fluid drain out (should be clear water) as possible.

11) Mix-up 50/50 mix of antifreeze and distilled water.

12) Remove the adapters, but leave the heater core hose off; prop up the hose so it's higher than the heater core, if possible.

13) Start adding the coolant mix until you see coolant mix coming out of the heater core.

14) Install T-Stat (you'll loose some coolant) and re-attach heater hose to heater core.

15) Top off coolant.

16) Jack-up the front of the car, so that the radiator opening is higher than the heater core. Block the wheels with blocks.

17) Let car run until it reaches operating temperature, add coolant as necessary. Let it idle and burp for a few minutes, then rev engine to about 2500 - 3000 rpm and hold. Coolant level will drop significantly - add coolant to make up the difference, and install the radiator cap.

18) Drive vehicle for about 10-15 minutes.

19) Let cool completely, check fluid levels, top off as necessary.

20) All done, repeat in 24,000 miles or 2 years, which ever comes first (if using normal antifreeze).

[SeafoodSC]

Thanks Phil