Piston Slap: Cooling to the MAXX?

Hello –

Saw a Dex-cool question you posted previously, and figured I would try my own. We have a ’06 Malibu Maxx SS. Basically the car runs hot, but not all the time. I have been religious about flushing the cooling system and using only the correct fluids.

It has 91k, and I’ve read online that they tend to run a little above avg temp. Like your CTS questioner, this car was clearly driven hard before we bought it, but nothing horrible. It doesn’t throw any codes and doesn’t get into the red, but its definitely high according the gauge. On the highway it tends to sit right in the middle. If it sits in traffic it will rise a little, if I drive it hard it will shoot up but eventually come back down.

The water pump was recently replaced, but otherwise we have had no real problems with the car (aside from the usual crappy GM build quality, ISS, and lots of brake pads). I just ordered a new t-stat, figuring that was a cheap fix to try.

The car is paid off and I would like to keep it for a while, but I am worried putting my wife and daughter in this thing in the heat of summer, or going on a road trip, etc.

Sajeev answers:

So this Malibu was driven hard before you got it, but you’ve been good about respecting The Dex-Cool Monster…not letting the system get contaminated. This means, depending on when you bought it, the previous owner coulda mixed fluids. And mildly gunked up the system.

See how being an Internet Automotive Mechanical Detective works?

More to the point,“if I drive it hard it will shoot up but eventually come back down” points to a partially clogged radiator. Partially clogged because of mild gunk accumulation.

When we’re talkin’ about a two-owner vehicle running Dex-Cool…well, I’m just being my typical snarky, untrustworthy self. No detective work there. Radiators do go bad over time, failing more epically when sporting partially plastic construction too. The water pump? Not super-likely, unless the vehicle has plastic impellers (cough, VAG products) and they are crumbling to bits. The electric cooling fans? Probably not: they are merely less effective when pushing/pulling on a cloggy radiator…so the recovery time from hard driving is longer.

You can flush the radiator, or have a local shop do it for you. Or for added piece of mind: eliminate a known wear item on aging vehicles by spending all of $100-150 on a new one from an on-line parts vendor. I’d just order a new one and be done with it.

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.