Dexcool Maintenance

bdeboer · April 22, 2005

How many miles before replacing the Dexcool? I was looking at my 2001 impala 3.4L with 91000 miles last night and the coolant was low and a brown color. i bought the car with 54000 a year ago from a dealer who supposedly did the full checkout. This made me take the radiator cap off, and there was brown muddy stuff on the bottom of the cap. I am also curious why the chevy dealer who did an oil change and transmission flush at 89000 did not mention this. Obviously the Impala needs flushed, but this made me check the 2002 Suburban with 55000 miles, and this looked fresh. The Suburban may have been serviced by the dealer before I bought it at 51000.

Butters · April 22, 2005

Sounds like it has stopleak in it.

snoman · April 22, 2005

Sounds like it has stopleak in it.

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I do not think do because I have seen that "mud" in vehicals that have never had stop leak in them.

tryn2lrn · April 22, 2005

Both of our previous blazers had mud/crud issues, we ended up selling hers after the intake gasket was fixed and all components were replaced even the filler tank by GM and the thing crudded and gurgled again in 2 months. Both of those had the coolant system flushed many times, heater cores replaced, radiators replaced etc under extended warranty. Those late 90s & early y2k systems with dexcool really had some major issues.

Oh yea, neither one of them had more than 75k on them when they got traded

asepgrad98 · April 22, 2005

IMO the Dexcool systems should have a pressurized overflow jug. Those appear to have a lot less sludge.

snoman · April 23, 2005

Both of our previous blazers had mud/crud issues, we ended up selling hers after the intake gasket was fixed and all components were replaced even the filler tank by GM and the thing crudded and gurgled again in 2 months. Both of those had the coolant system flushed many times, heater cores replaced, radiators replaced etc under extended warranty. Those late 90s & early y2k systems with dexcool really had some major issues.

Oh yea, neither one of them had more than 75k on them when they got traded

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I have never had those issues at all but I always run 60 to 70% antifreeze/Dexicool to instead of 50/50.

elgineddie · April 23, 2005

The crud is from '"degraded" Dexcool. I was starting to see a brown ring around the overflow bottle and I knew it was time for a flush. That was at something like 60,000 miles. I drained everything out, flushed it real good, bought a new screw-on overflow bottle cap at Napa Autoparts and filled it with the Dexcool-like fluid from Prestone. All is well now and I'm over 100,000 miles.

From what I've read, the brown crud is from Dexcool that's been exposed to air and thus degraded. If you've got the time and resources, have the system pressure checked for piece of mind but I bet it's OK. Our Dexcool systems are supposed to be 100% sealed systems, but the only air in the system is in the open space in the overflow bottle. Coincidentally, that's where the crud is usually found.

Lots and lots of anti-Dexcool people out there but if you keep on top of this "100,000 mile coolant" and change it at 50,000 intervals, it's been pretty much agreed upon that you are gonna be OK.

Later man!

tryn2lrn · April 24, 2005

Here is an interesting blip from gm about the cooling system, everyones system is exposed to air:

Pressure Cap

The pressure cap is a cap that seals and pressurizes the cooling system. It contains a blow off or pressure valve and a vacuum or atmospheric valve. The pressure valve is held against its seat by a spring and protects the radiator by relieving pressure if it exceeds 18 psi. The vacuum valve is held against its seat by a spring, which permits opening of the valve to relieve vacuum created in the cooling system as it cools off. The vacuum, if not relieved, could cause the radiator hoses to collapse.

The pressure cap allows pressure in the cooling system to build up. As the pressure builds, the boiling point of the coolant goes up as well. Therefore, the coolant can be safely run at a temperature higher than the boiling point of the coolant at atmospheric pressure. The hotter the coolant is, the faster the heat moves from the radiator to the cooler passing air. However, if the pressure exceeds the strength of the spring, the pressure valve rises so that the excess pressure can escape. When the engine cools down, the temperature of the coolant drops and a vacuum is created in the cooling system. This vacuum causes the vacuum valve to open, allowing outside air into the cooling system. This equalizes the pressure in the cooling system with atmospheric pressure, thus preventing the radiator hoses from collapsing.

jhm · April 25, 2005

IMO the Dexcool systems should have a pressurized overflow jug. Those appear to have a lot less sludge.

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I don't know about your's, but my '01 has a pressurized overflow jug. It has a 15# rated cap, there is no cap on the radiator.

MS3DALE · April 25, 2005

IMO the Dexcool systems should have a pressurized overflow jug. Those appear to have a lot less sludge.

I don't know about your's, but my '01 has a pressurized overflow jug. It has a 15# rated cap, there is no cap on the radiator.

Both my '99 I had and my '04 have pressurized caps on the overflow bottles.

I would change the Dex-Cool around 50-60,000 miles (I changed it at 62,000 in my '99)

I would never leave it in for 100,000 miles.

April 25, 2005

Here is an interesting blip from gm about the cooling system, everyones system is exposed to air:

Pressure Cap

The pressure cap is a cap that seals and pressurizes the cooling system. It contains a blow off or pressure valve and a vacuum or atmospheric valve. The pressure valve is held against its seat by a spring and protects the radiator by relieving pressure if it exceeds 18 psi. The vacuum valve is held against its seat by a spring, which permits opening of the valve to relieve vacuum created in the cooling system as it cools off. The vacuum, if not relieved, could cause the radiator hoses to collapse.

The pressure cap allows pressure in the cooling system to build up. As the pressure builds, the boiling point of the coolant goes up as well. Therefore, the coolant can be safely run at a temperature higher than the boiling point of the coolant at atmospheric pressure. The hotter the coolant is, the faster the heat moves from the radiator to the cooler passing air. However, if the pressure exceeds the strength of the spring, the pressure valve rises so that the excess pressure can escape. When the engine cools down, the temperature of the coolant drops and a vacuum is created in the cooling system. This vacuum causes the vacuum valve to open, allowing outside air into the cooling system. This equalizes the pressure in the cooling system with atmospheric pressure, thus preventing the radiator hoses from collapsing.

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I don't have time to go out and look at my system but a properly designed system would have the overflow hose attached to the pressure valve thus saving coolant whne it opened. The vacuum valve should be attached to a hose at the bottom of the overlow tank so it sucks coolant back into the system when needed. As long as the overflow tank were never empty there would be no air introduced into the system even with a non-pressurized tank.