Coolant temperature drop at idle - problem? - Honda Prelude Forum

Ferrari · 12-29-2003, 08:39 AM

Ever since I changed my coolant 2 months ago, the coolant heats up fine and temperature stabilizes at a bit below mid-point on the stock temperature gauge. Yet when I stop and let my car idle for about 2 minutes, the coolant temperature needle drops about 2mm down. After I start driving again, the temp needle goes back to normal.

Would that mean that I have some air bubbles in the coolant, or is there something wrong with the thermostat?

reyke · 12-29-2003, 10:31 AM

if you had air bubbles in your car then it would cause your needle to go up not down, and it would be an intermittent issue not a constant one, it sounds like the mixture you're running has more water than coolant, you might want to drain just a hair of it out maybe a cup or two and add straight coolant. But before we go through all this work and effort, does your car run fine, do you have any reliability issues, becuase if not then maybe you should calm down and relax about that 2mm drop when your idling, just a thought.

Ferrari · 12-29-2003, 11:24 AM

The car runs very well, the engine seems smoother than when new. There's no coolant leak as I'm not losing any, and there's no coolant contamination in the oil. The coolant is premixed Honda coolant that I bought from the dealership, and I did the fluid change myself so I know what I put in.

The weird thing is that this started happening after I changed the coolant, it didn't use to do that before. Could it be something else, like the thermostat?

reyke · 12-29-2003, 09:55 PM

I know this is going to sound odd but in all honesty thermostats going bad is actually quite rare, we have maybe one or two come through our shop in a months time, and it's usually becuase the owner never changed thier coolant and the unit became clogged shut, or whatever, or they had some sort of buidl-up and was lodged causing the thermostat to stay open. I really think your car is just being a little odd since it got some new coolant, there's really no need for alarm on your part.

Ferrari · 12-30-2003, 11:32 AM

Cool, thanks!