Scott

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.

Justin

Sajeev,

I have a 2001 Buick Regal LS. I bought it in 2007 with 14,000 miles on (yes, from a grandmother). It has 72,000 miles on it as of this morning. It’s not a great car and has required plenty of maintenance (for example, I’ve had to replace the brakes completely 3 times already). However, I have a few questions about long term items:

1. Spark plugs. Should I change them? The owner’s manual specifies 100,000 miles; does time play a factor in that at all? I’ve read that sometimes the back 3 never get changed anyway (apparently it’s a PITA).

2. Coolant. I had it changed once in 2008 (it’s Dexcool) because I had been reading the horror stories. How often should I be changing this?

I’m unsure how long this car is going to last, but I’ll keep limping it along until the cost gets too high. So cost is a factor here too.

Thanks!

Sajeev answers:

As you learned, buying a low mile original car isn’t necessarily a great idea. Unless you buy it for an occasional, collector type of vehicle. (*cough* H-town swanga *cough*) Though a 6-year-old car with low miles doesn’t exactly fit this definition: you replaced the brakes three times in the past 58,000 miles?  Whaaaa?

Either you got screwed by a mechanic or you are a seriously aggressive driver that needs elbows and vogues to slow yourself down.  Perhaps you should take a page from the Houston playbook, and keep that GM sedan Slow Loud And Bangin’.  But I digress…

• Spark plugs: the 100,000 mile tune-up interval has been proven valid for every car I’ve seen, mostly because platinum plugs are that great. There’s a chance that age hasn’t been kind to the ceramic part of the plugs, but if the car idles smooth when cold, gets good mileage, decent power, no check engine light, etc…don’t worry about it.
• Previously discussed here, here and here, Dex-Cool is a bizarre case where you can either flush it out (entirely, no margin for error) and switch to another type of coolant, or continue topping off with a Dex-cool compatible coolant, or you can continue to use Dex-Cool and service it as per the owner’s manual.  If you choose the latter, I’d service a little more regularly than suggested…out of fear of the Dex-Cool devil that comes from neglect.

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry.

Nate writes:

Ok, you asked for input and I’ve got a question about my 2003 Cadillac CTS. I figure I’m more likely to get a reliable answer from you and the best & brightest of TTAC than the goof balls at Car Talk (this letter is from February-SM), so I’ll ask.

I bought this CTS back in November. It had 135,000 miles on the odo, came from a private owner and apparently had significant engine work accomplished a year or so ago apparently as a result of a timing belt failure after it wasn’t replaced on schedule. Before being able to get the car licensed, I paid to have the thermostat and temp sensor replaced as I had a CEL and a P0128 code and the car wouldn’t pass inspection with a CEL code. The code came back after just about 1 week.

The CEL will clear if the ambient temps move up above 45-50 degrees but returns when the temps get back down to Utah normals for winter. I’ve been unable to find an online solution. I’ve considered installing a temporary partial radiator block, (cardboard & duct tape) to see if that old school fix brings the temp up. The car doesn’t have a temp gauge- thanks for nothing GM; but seems to warm up the cabin appropriately if not exceptionally fast.

Am I going to have to reset the codes each December before taking this in for emissions inspection or is there a real fix?

Sajeev answers:

Much like LSX swaps for people wanting to make a slow car fast, much like Panther Love for someone wanting a cheap and durable ride, I pretty much always think Dex-Cool is the problem when certain vintage GM products have temperature control problems.  As this paragraph shows, Dex-Cool is not my friend…and I am somewhat less goofy than the Car Talk peeps.

On the plus side, others are in your situation and they agree with me. Let’s face it: the timing belt proves that this car was neglected.  It’s a safe bet that Dex-Cool was never changed either, possibly topped off with non Dex-Cool compatible fluid too.  So there is a TON of the stuff you see in the photo below. And above. So I suspect that the 1 week grace period you mentioned was the time necessary to re-clog that temperature sensor and cause the P0128 to trip yet again.

I’d recommend a closer look at your cooling system, probably replacing the radiator too.   Just be careful how aggressively you remove Dex-Cool from the cooling system, you could flush it all out and get a ton of Dex-Cool “snot” stuck in the heater core. Which means you no longer have a heater. Which means…well, have fun removing the interior to get the heater core out. In a Utah winter. Damn, Son…

Sorry, I wish I saw another way out.  Maybe the B&B can help.

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry.