Piston Slap: Pushing the Hot Button to Slime GM's Dex-Cool?

Sajeev Mehta
by Sajeev Mehta
piston slap pushing the hot button to slime gm s dex cool

TTAC commentator jpcavanaugh writes:

My mother is in her mid 70s. Of course, she drives a 2006 Buick LaCrosse with about 10k miles. It is the first GM car in our family since the 1970s. She planned to remain a loyal Ford customer for life after 20 happy years with a pair of Crown Vics, but she won the Buick in GM’s last Hot Button contest.

I recently learned of this stuff called DexCool that is the factory-fill radiator coolant. From what I have read, I do not much care for this stuff. If it were my car, I would drive quickly to my independent mechanic and flush the system with the old-fashioned green stuff. So what do I tell mom to do? The choices, as I see them, are (in order from my least to most favorite ideas):

1. The car only has 10K miles, coolant is probably fine, leave it alone.

2. Even though the car only has 10K miles, try to get the Buick Dealer to flush it and refill it with the green stuff, which they probably don’t stock and which they will probably refuse to do.

3. Even though the car only has 10K miles, have the Buick dealer flush and fill with fresh DexCool, and to do this every 2 or 3 years, even though the mileage intervals will be really low.

4. Her Ford dealer offered to service the Buick to keep her as a customer, and she might be willing to do this, as she had always been quite happy there. Take the car to the Ford dealer now, get it flushed and refilled with green stuff then make sure the Buick dealer never ever touches the cooling system.

5. Leave it alone till the warranty is up in October, take it to the Ford dealer, have it flushed and refilled with whatever they use and have the car serviced there from then on.

Sajeev replies:

No matter where I look, there are far too many valid concerns about Dex-Cool. So, yes, flush it out and never look back.

But I think time and low mileage are on your side, so wait for the warranty to expire and go to town on that cooling system. Make sure the Ford dealer knows the repercussions of not flushing out all the old stuff: aside from goo-ing up the cooling system, Mom can lose her heater when D-Cool mixes with green stuff and slimes the heater core, Ghostbusters style.

[Send your technical queries to mehta@ttac.com]

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2 of 24 comments
  • Wibblywobbly Wibblywobbly on May 29, 2009

    I thought that DexCool got the blame for GM's crappy assembly and crappy gaskets. I use to own an Alero with the 3400 in it that had the lower intake manifold gasket go like every other one. A lot of people blamed DexCool for eating away at the gaskets, but apparently as a cost saving measure GM slightly changed the assembly method. Along with a cheaper gasket, they used fewer bolts. In addition to not securing the gasket as tightly they were often over tightened and often not properly aligned... leading to shorter gasket life. Gaskets go, coolant leaks.... very slowly and often in to the engine so there is no tell tale stain on the floor and very little, if any, white smoke. Nobody checks their coolant level and when the idiot light comes on the dash the damage is done..... Since most people expect that the gaskets on their engine will start leaking a bit later in life than 42k miles, they blame it on the coolant. My first and only experience with GM quality.

  • Phillip Phillip on May 31, 2009

    From my personal experiences, the "gunk" was actually pellets that are put into the cooling system at the factory that are designed to seal leaks in the system. I've had several cars this dexcool and never had a problem with any.

  • David S. For a single quarter, only ninth best-selling (estimated?) of 2022. Maybe ICE vehicles would sell at a similar rate if the government paid people to buy them too?!
  • Dukeisduke I don't like how they've changed their nameplates and font from the Star Trek-ish LEXUS, to L E X U S, kinda like VW's lettering on the back of the T A O S, or those stick-on letters you can buy at the parts store that people use to their own names on the back of their cars.
  • Dukeisduke So, the screen goes blank for two-tenths of a second, every once in a while - what could go wrong?
  • Dukeisduke "Hello, IT. Have you tried turning it off and on again?"(Roy in The IT Crowd)
  • Dukeisduke Just Say No To Bugs!