I had a mechanic tell me that partial coolant changes were easier & safer to do for the average Joe . The thinking I suppose is to change coolant at a 40% to 60% rate on a regular basis and not having to open heater settings (thermostat) , burp coolant hoses , etc. risking air bubbles or other issues doing a full coolant change improperly . The above said - who does partial coolant changes and what is your approach ?
Partial Coolant Changes ?
- Thread starter ChrisD46
- Start date
It's all I do, as in I never remove engine drain plugs. Nor do I pull thermostats to "flush." But just draining the radiator gets quite a bit out. I only do water flushes if I want to change coolant chemistry, for example if I get a car with "green" but don't know if it's classic silicate or new AM/AM.
I have a refractometer to get an accurate coolant concentration when I'm done, and recommend it as the gold standard.
I have a refractometer to get an accurate coolant concentration when I'm done, and recommend it as the gold standard.
Define partial?
I always do spill and fill - no flush. In my Nissans I get about 2 gallons of the 2.75 gallons, so like 70%?
I never have had any issues getting the air out - but I have heard it is a thing?
I always do spill and fill - no flush. In my Nissans I get about 2 gallons of the 2.75 gallons, so like 70%?
I never have had any issues getting the air out - but I have heard it is a thing?
I only drain and fill from the radiator as well
Easiest way to do it. I drain radiator and refill every other year.
I do drain and fills about every third year, got one of those funnels that help with refill and burping.
The procedure is very simple, drain, fill with premix, make sure there are no air locks and coolant level is right.
The procedure is very simple, drain, fill with premix, make sure there are no air locks and coolant level is right.
That is pretty much all I ever do. Mostly it is driven by a cooling system component replacement eg. water pump, hose, radiator etc.
Approach - nothing special, all my cars have radiator petcocks, I open that until it stops draining, then replace the component. If the coolant is old (say greater than 2 years roughly), I put fresh coolant in, if it is new(ish) I reuse. To purge, it depends on the cooling system in question, but purging the air is very important. I find it easiest to loosen or remove a heater hose nearest to the thermostat. If I am replacing a thermostat and it doesn't have a "jiggle" valve, I drill a small hole in the thermostat base plate to serve as a purge / bleed.
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I did that with my Ford Edge. Extracted the contents of the degas tank several times over a couple of hundred miles. Refilled with proper coolant. Draining the engine from the petcock is a Ford horror story. Plus this engine has an internal wp which may destroy the engine if it leaks.
The Lazy Boy technique is to buy a gallon or two of pre-mix, pull the rad plug and drain it out. Put the plug back in and fill with premix. A lot dealerships do exactly that. Do that every 5 years with 10 year coolant and you won’t see any problems. If you want to be extra careful do it every 3 years with 10 year coolant.
Bittogers like myself like to drain, add water, run, drain, add water, run, drain add 100% coolant. In the 2nd last fill you can even add some sacrificial 50% coolant. Using this technique my Burb has 280,000 miles with the original rad, water pump and heater core using Prestone Dexcool.
Bittogers like myself like to drain, add water, run, drain, add water, run, drain add 100% coolant. In the 2nd last fill you can even add some sacrificial 50% coolant. Using this technique my Burb has 280,000 miles with the original rad, water pump and heater core using Prestone Dexcool.
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Unless your coolant is really dirty, or you bought the vehicle and it came with the wrong coolant, all I would do is a radiator drain and fill. Or if I am doing a thermostat, water pump etc, I do that too of course. But I don’t remove engine block plugs at all.
Some vehicles that are stubborn to burp, you can remove the top radiator hose at the rad and hold its end in the air. Pour coolant in that hose (stuff a funnel in if necessary) and it will work its way through the engine with the added head pressure of another couple feet of altitude. When it starts dribbling out the open rad nipple, you know you're good.
Dump and refills annually works for me
I just did a partial flush on my Buick. Drained the radiator, filled with 100% distilled water... ran some errands. From there, let it cool. Next day I drained again and refilled with 50/50 mix to radiator. Not too worried about 50/50 ratio since I live in AZ. (No freezing). I think doing it this was was easier than "flushing" the entire system and disconnecting everything.
JHZR2
Staff member
Nothing wrong with a partial fills and tons of benefit. Including more of often than the standard interval, IMO.
In a well designed engine with easy access to a block drain, and clean way to drain it, I’d call that the gold standard. But it isn’t always easy or practical.
A radiator draincock drain and fill is pretty ideal and you really can’t go wrong.
In a well designed engine with easy access to a block drain, and clean way to drain it, I’d call that the gold standard. But it isn’t always easy or practical.
A radiator draincock drain and fill is pretty ideal and you really can’t go wrong.