Car heat gauge going over midline where it's never gone

[Dennis S]

2002 Buick Park Avenue. The heat gauge has always been a little below the big midline, even when the temperature is in the high 90's. I noticed today, with a temperature of 67, that it's creeping over the line, which it has never done. It's too ho to look at the radiator right now. It's always right up to the lip when I check it. However, the overfill reservoir is dry. Can I add some distilled water to the reservoir? It rarely gets in the 20's here and will be awhile before it does. Of course, stuff like this always happens of Friday afternoon.

[JoeH]

If the reservoir is empty with a hot engine, then you have a leak in the coolant system somewhere. Adding the water is a stopgap at best, better would be a 50/50 antifreeze mix. Depending on where the leak is, you might get by with adding a leak stop compound. The coolant system should be pressure tested if an obvious leak doesn't show up.

[Acer]

Look for leaks on the garage floor of course. But barring that, might just be low from use. Just get some antifreeze and top it off as indicated in the reservoir. Antifreeze cools, too. Distilled water in a pinch, but antifreeze is not expensive. See if the problem returns.

[Dennis S]

About how long does it need to cool before I can take the radiator cap off?

[Carm]

Probably a leak, that’s what usually leads to an empty reservoir. Replace thermostat if you never have and drain/replace fluid. Check hoses for leaks before fluid replacement.

[Speedy]

Never use water except in an emergency. Antifreeze is useful both in hot and cold climates.

[Carm]

Dennis S wrote:
About how long does it need to cool before I can take the radiator cap off?

Squeeze one of the hoses, if the pressure is high it won’t have any give. If it cooled down enough you can squeeze without much pressure on the hose.

[Dennis S]

My mechanic is closed for the day and there are no others I know in this small town. He drained to GM Dexcool and put in green antifreeze. Everything at Walmart seems to be All Purpose. Is that OK? As far as water, it will be many weeks before it gets below freezing. I need to make a 45 mile trip and back tomorrow.

[OWC Jamie]

Hi -

That's a 3800 V6 series 2 with a plastic radiator I bet. They fail interally and will sludge up inside causing that. My old Grand Prix(es?) I had two.... both did that after 100,000. Just part of that wonderful (NOT) Dex-Cool they use.

I'd figure on replacing it. Or you can try letting it cool and hosing it out, but in my experience it didn't work Replace and keep on driving, 3800 is a great engine.

[Dennis S]

It's at 106,000.