Changing coolant

Here is a simple question: What is the best procedure for changing coolant?

I have seen the process done several different ways. The main question is how to make sure all the air bubbles are out of the system before putting the cap back on (including how long to let the car run without the cap on to get rid of the air).

Any useful tricks to this?

to drain take the bottom hose off the radiator, take the thermostat out and you can flush it all out with a garden hose. I think the best way to get the air out is to leave the thermostat out, put the housing back on and fill everthing up. leave the cap off the radiator and run the car, that way it will circulate the coolant. I would think when the car had been run for about 5 minutes all the air should be out, then put the thermostat back in, top off the radiator and run it up to temperature,

thats how I would do it

Hondo

Hondo,

Thank you very much. I've never seen the thermostat taken out, although it sounds like a good idea. How necessary do you think it is to remove the thermostat?

If you drill a small hole in the flange of the thermostat (say 1/8 or 3/16) it will allow coolant and air to pass thru and make it much easier to fill the system -- no need to R&R the thermostat just to fill.

Some thermostats come with this hole (and possibly a little bobble fitting as sort of a crude check valve).

I have never had a problem getting the system filled (as opposed to another vehicle I have where everybody has a theory on how to get the air out).

Geo Hahn said:

I have never had a problem getting the system filled (as opposed to another vehicle I have where everybody has a theory on how to get the air out).

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Aaah...you own a Jag too!!

All very interesting.... I have watched people change the coolant in my TR3 in the past, and they never did anything to the thermostat. Afterwards there were no problems...

I have a "tool" that I have seen used successfully on my car in the past.... A NAPA Professional 900 Series Spill-Free Funnel. It prevents most air from entering the system. The instructions do say, however: "If the cooling system has bleeder screws, open them to remove entrapped air. Air in most other systems can be removed by running the engine at idle and allowing air to purge through the Spill-Free Funnel."

I've drained the coolant from my TR3 many times and never had any problems with trapped air after refilling. I run the engine a bit, and then just top off.

A related question is: How often to change the coolant? With my daily driver American car and truck, I almost never change the coolant. Never had a problem. But with these LBCs, I read and am told that I need to change the coolant every two years (especially with an aluminum radiator). But modern American cars have aluminum radiators. Why the emphasis on changing coolant so often?

I've drained the coolant many times over the past 22 summers (109,000 miles) and re-used most of what I collected and filtered through a piece of paper towel. I would guess that it has been fully changed about 3 times. If you don't need to drain it for a specific reason, I would say you should be OK for 5 years.

Don,

My "advisors" tell me that an aluminum radiator should be drained and refilled with new antifreeze every two or three three years because I have a steel block and an alloy radiator. They have told me that the anti-corrosion chemicals in the antifreeze should be fine for years, but that most of the problems with dissimilar metals is electrolysis, and most of that is caused by my electrical system. Then they add, "Keep the battery terminals and grounds clean and it will be fine."

On one radiator website I read this: "The average service of an OEM copper/brass radiator is six to 10 years, and eight to 12 for aluminum."

Then, again, the shop people who installed my radiator have said, "This radiator if serviced properly (fluids changed every 2 years) will out-last you, me, and your heirs."

Some engines have real problems with trapped air. As Art said, it doesn't seem to be an issue with the TR3 at all. Fill it to the normal level (which is the extension only about 1/4 full), start the engine and let it idle until the thermostat opens, then top it up (again to the normal level).

How often to change depends on the coolant you are using. The old 'classic' green antifreeze is only good for about 2 years if your goal is zero corrosion. Some of the newer formulas are good for 5 years, but may have other issues. I've been trying Prestone's "any color" Extended Life but so far I've not gone long enough without some sort of problem forcing a change to say if it really works for 5 years. I've read that "Dexcool" is probably a bad idea, but have no experience with it myself.

Aluminum is way over to the left on the oxidation potential chart, meaning it is the metal that will corrode away if electrolysis is allowed to proceed. On a stock TR3 of course, the thermostat housing is aluminum, so that will be the primary corrosion site. Practically every Tstat housing I've ever seen has at least some damage; and some were so thin you could almost see through them.

One you probably could see light through, as the previous owner had "repaired" it with some sort of translucent epoxy that promptly failed when I tried to drive the car from TX to CA. Fortunately, the FLAPS we found had a housing that would fit and work, sort of, so we were able to complete our trip.

As a data point, the original copper/brass radiator in my 95 Buick wagon lasted until 2010. My radiator guy suggested sticking with copper, even though he would likely have made more money on the aluminum one; which was good enough to convince me.

I have never had an issue of trapped air in my Tr3. Been driving mine since 1982 and did many straight forward fills from the radiator top. If your having air in the coolant issues I'd check for leaks in the systems. Now for my other work vehicles "modern cars" it a bit different. There are many issues with modern cars with the heater core higher then the radiator. I purchased a spill free funnel years ago and that shortened my fill time and minimal air problems.

Then I purchased a Air E-Vac system that is one of the most awesome tools I've ever purchased. What it does is draw a vacuum on the cooling system to a point that the hoses collapse. You turn off a ball valve and replace the discharge hose with a filling hose where you have premixed the coolant in a bucket. Open the ball valve and watch the coolant get sucked into the all the engine coolant chambers and hoses on both sides of the thermostat. It swaps out 1:1 air for coolant. There's never been any cooling issues after the use of this tool.

You can check for leaks too when your switching hoses. Wait a few minutes because there is a vacuum gauge and the needle will move if there is a leak in the system and it can usually be pin point by hearing a hissing noise.

https://www.thetoolwarehouse.net/p-16855-mityvac-mv4535.aspx

There are 5 on ebay right now.

https://www.ebay.com/itm/mityvac-mv..._Automotive_Tools&hash=item4d0abff14c&vxp=mtr

At 80,000 miles in 1990 I changed my original radiator. In actual fact, I had them change the tubes and fins (the core) and since then my radiator has never caused a problem except for the joint where the fill box is soldered to the header. I don't call that a failed radiator. I just re-soldered the joints.

Got_All_4 said:

Then I purchased a Air E-Vac system that is one of the most awesome tools I've ever purchased. What it does is draw a vacuum on the cooling system to a point that the hoses collapse. You turn off a ball valve and replace the discharge hose with a filling hose where you have premixed the coolant in a bucket. Open the ball valve and watch the coolant get sucked into the all the engine coolant chambers and hoses on both sides of the thermostat. It swaps out 1:1 air for coolant. There's never been any cooling issues after the use of this tool.

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Interesting. I may try something like that when I get back to working on my Stags (which are notoriously hard to fill). Thanks!

The coolant in the car now is Prestone 50/50 - Extended Life (protection for 5 years). That's what I plan to use again, unless there is some reason to change. I won't keep it in for 5 years however, but only two or three.