When to change coolant
Tolero Apto Victum
Joined: Jul 2007
Posts: 9,669
Likes: 37
From: Woodlands TX
Tolero Apto Victum
Joined: Jul 2007
Posts: 9,669
Likes: 37
From: Woodlands TX
I think most of us know that anti-freeze (be it Dex Cool or the earlier Green Ethylene Glycol version) has a lot of stuff in it other than the Ethylene Glycol that keeps the coolant from freezing. One of the other things is a corrosion inhibitor package. I'm not a chemist, but that corrosion inhibitor package does not last forever, and when it looses it's effectiveness, you will definitely see dissimilar metals in the cooling system corrode. Will your entre cooling system turn to a corroded mess one day after the five year service interval - of course not !!! But, it certainly seems like false economy to try to save $25 and a couple hours of your time by not buying two gallons of Dex Cool, and to have a head gasket or a radiator fail because the coolant failed to protect these components from corroding...
I've had the "pleasure" of working on a C4 that had eon's old coolant in it (this is prior to the "extended life coolants, and the Dex-Cool days). When I finally did a coolant drain - the stuff that came out of the block drains was dark brown... When the heads came off the engine a while later, there was a "green slime" in the cooling passages of the cylinder heads that was nearly impossible to get off (a 2,000 psi pressure washer didn't even make a dent in the stuff). Think that cooling system was operating anywhere near as efficiently as it should ???
Fundamentally - the fluids in our cars - be it Engine Oil, Coolant, Brake Fluid, Gear Oil etc. are cheap compared to the damage that can be done if they're overlooked for too long. Enough Said ???
I've had the "pleasure" of working on a C4 that had eon's old coolant in it (this is prior to the "extended life coolants, and the Dex-Cool days). When I finally did a coolant drain - the stuff that came out of the block drains was dark brown... When the heads came off the engine a while later, there was a "green slime" in the cooling passages of the cylinder heads that was nearly impossible to get off (a 2,000 psi pressure washer didn't even make a dent in the stuff). Think that cooling system was operating anywhere near as efficiently as it should ???
Fundamentally - the fluids in our cars - be it Engine Oil, Coolant, Brake Fluid, Gear Oil etc. are cheap compared to the damage that can be done if they're overlooked for too long. Enough Said ???
Le Mans Master
Joined: Jan 2009
Posts: 5,656
Likes: 112
From: ocean springs mississippi
where do you drain from radiator to get the max mount of coolant out? lower hose or is there a plug? should I flush with distilled water before refilling with coolant? 05 z51
Team Owner
Joined: Sep 2000
Posts: 24,964
Likes: 2,676
From: Far NW 'burbs of Chicago
St. Jude Donor '13
There is a drain at the bottom of the radiator, passenger side IIRC. Gets about half of the coolant out, OCD people like me will refill with distilled and run the engine long/warm enough to get the thermostat open and mix the old and new, then drain again. Can even do it once more if you really want. Fill with 50-50 Dexcool/distilled water.
The filling instructions are in the Service Manual and are not complicated, but lots of people seem to have problems with air locks in the system when using some other methods, I'd get the right info.
GM says you can use clean tap water, and that seems to work ok. But I sent a sample of my factory coolant to a lab and they flagged it for excessive hardness and recommended always using distilled.
The filling instructions are in the Service Manual and are not complicated, but lots of people seem to have problems with air locks in the system when using some other methods, I'd get the right info.
GM says you can use clean tap water, and that seems to work ok. But I sent a sample of my factory coolant to a lab and they flagged it for excessive hardness and recommended always using distilled.
Le Mans Master
Joined: Jan 2009
Posts: 5,656
Likes: 112
From: ocean springs mississippi
There is a drain at the bottom of the radiator, passenger side IIRC. Gets about half of the coolant out, OCD people like me will refill with distilled and run the engine long/warm enough to get the thermostat open and mix the old and new, then drain again. Can even do it once more if you really want. Fill with 50-50 Dexcool/distilled water.
The filling instructions are in the Service Manual and are not complicated, but lots of people seem to have problems with air locks in the system when using some other methods, I'd get the right info.
GM says you can use clean tap water, and that seems to work ok. But I sent a sample of my factory coolant to a lab and they flagged it for excessive hardness and recommended always using distilled.
The filling instructions are in the Service Manual and are not complicated, but lots of people seem to have problems with air locks in the system when using some other methods, I'd get the right info.
GM says you can use clean tap water, and that seems to work ok. But I sent a sample of my factory coolant to a lab and they flagged it for excessive hardness and recommended always using distilled.
Burning Brakes
Joined: Oct 2005
Posts: 1,205
Likes: 66
From: Orlando Florida
There is a drain at the bottom of the radiator, passenger side IIRC. Gets about half of the coolant out, OCD people like me will refill with distilled and run the engine long/warm enough to get the thermostat open and mix the old and new, then drain again. Can even do it once more if you really want. Fill with 50-50 Dexcool/distilled water.
The filling instructions are in the Service Manual and are not complicated, but lots of people seem to have problems with air locks in the system when using some other methods, I'd get the right info.
GM says you can use clean tap water, and that seems to work ok. But I sent a sample of my factory coolant to a lab and they flagged it for excessive hardness and recommended always using distilled.
The filling instructions are in the Service Manual and are not complicated, but lots of people seem to have problems with air locks in the system when using some other methods, I'd get the right info.
GM says you can use clean tap water, and that seems to work ok. But I sent a sample of my factory coolant to a lab and they flagged it for excessive hardness and recommended always using distilled.
Team Owner
Joined: Sep 2000
Posts: 24,964
Likes: 2,676
From: Far NW 'burbs of Chicago
St. Jude Donor '13
If you are draining it multiple times then it is safe to say there is no more Dexcool left in the system, just distilled water. So, in that case I would fill with straight Dexcool to half of the cooling system capacity. Then top off with just distilled water only. This way you should have the proper mix.
Tech Contributor
Joined: Oct 1999
Posts: 40,998
Likes: 9,764
From: Charlotte, NC (formerly Endicott, NY)
I change mine every 5 years. Currently my 03 Tahoe with 98K miles on it is on the third fill. My 08 Malibu is on its 2nd fill and the 08 Z06 is on its first fill since the engine was replaced two years ago due to a dropped valve head. Have been doing that since I purchased my 97 the first car I had with Dex in it. Every one I changed the coolant looked just like it did when it was first put in.
When I change the fluid I use regular drinking water just like the FSM recommends. No need to use distilled or deionized water. I drain the system, refill using the garden hose and drain again. I repeat until the drained fluid runs clear. Then I add half the capacity of Dex and top off with water. Has worked fine on 7 different cars.
Bill
When I change the fluid I use regular drinking water just like the FSM recommends. No need to use distilled or deionized water. I drain the system, refill using the garden hose and drain again. I repeat until the drained fluid runs clear. Then I add half the capacity of Dex and top off with water. Has worked fine on 7 different cars.
Bill
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Race Director
Joined: Mar 2005
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From: Austin Texas
Le Mans Master
Joined: Jan 2009
Posts: 5,656
Likes: 112
From: ocean springs mississippi
How do you get the sludge in the overflow tank clean
* residue on the sides*
* if there is brownish looking residue in the overflow tank....would it be in the engine as well? I flushed it three times...*
* residue on the sides*
* if there is brownish looking residue in the overflow tank....would it be in the engine as well? I flushed it three times...*
Last edited by C U IN REARVEIW; Jun 7, 2014 at 02:35 PM.
Le Mans Master
Joined: Jan 2008
Posts: 6,457
Likes: 297
From: corpus christi Texas
Le Mans Master
Joined: Jan 2008
Posts: 6,457
Likes: 297
From: corpus christi Texas
There is a drain at the bottom of the radiator, passenger side IIRC. Gets about half of the coolant out, OCD people like me will refill with distilled and run the engine long/warm enough to get the thermostat open and mix the old and new, then drain again. Can even do it once more if you really want. Fill with 50-50 Dexcool/distilled water.
The filling instructions are in the Service Manual and are not complicated, but lots of people seem to have problems with air locks in the system when using some other methods, I'd get the right info.
GM says you can use clean tap water, and that seems to work ok. But I sent a sample of my factory coolant to a lab and they flagged it for excessive hardness and recommended always using distilled.
The filling instructions are in the Service Manual and are not complicated, but lots of people seem to have problems with air locks in the system when using some other methods, I'd get the right info.
GM says you can use clean tap water, and that seems to work ok. But I sent a sample of my factory coolant to a lab and they flagged it for excessive hardness and recommended always using distilled.
I want even drink tap water....
