Hey folks,

2006 IS 250 AWD with about 75K on it. Lately, if i use the heat in the mornings, i've been noticing that when I'm stopped at a ready light, the heat (on max) will begin to blow colder air. As soon as the light turns green though, it'll start blowing hot air again.

Any clues/thoughts of what this might be? Fixable on own? Should i bring it into the shop?

thanks
ron

 

Have you checked your coolant level? Could be low.

 

Like Silver10 said, check your coolant cause you're probably low on it. Take off the radiator cap and check how to see if coolant is all the way to the top when the engine is cold.

 

thanks guys, i'll check tonight or in the morning since I just got in from driving it. If the coolant levels are normal, what else might it be? A leak in a hose(s)?

thanks,
ron

 

low coolant....... check for leaks. make sure you add the right coolant too

 

Any leak would give you an overheating issue, at least eventually. Low coolant is the likely suspect. The next time you stop at a light, try and rev the engine lightly and see if it blows hot again. This would be an indication that the coolant isn't flowing at low RPMs, but is being pushed normally at higher RPMs. Sounds like either the coolant is low or the impellers on the water pump are worn. Do realize that the latter would also likely give you an overheating symptom....

 

Actually its funny you should post this as your situation is exactly as mine was. The heat was great and hot (Sometimes sauna hot) when driving but when i would stop at a red light the heat would blow cold. Brought it to the dealership (CPO) and explained to them literally almost word for word exactly what you posted and they looked at me like i had 3 heads!!! 20 minutes after looking at it they found out it was the water pump

Sure enough since they replaced it no changes in my heat or cabin temp, heck i sat at a light the other day for like 10 minutes (accident in intersection) and heat worked perfect, before the pump was replaced after 30 sec it would have been blowin cold


hope this helps, good luck!!!

EDIT: PS my car is a 2007 IS350 with 50K