misterhu

Heat only works when I step on the accelerator and keep it above 3k rpm for some time. If I let off, it stays hot for a duration and then it starts getting cold. Its the winter here in New York so I'm talking about ice cold. On top of that, my driver side heat is slightly, but noticeably, weaker than the passenger side while its working after stepping on it for a bit (not using the dual climate feature.) Air conditioning worked fine during the summer.

I had my mechanic flush out the heater core and its still displaying the same symptoms. My baby is getting up there in mileage, just past 100k miles (2007 IS350).

Servos going bad? Water pump going bad? What do you guys think it might be?

alexs350

iTrader: (1)

My brother has a similar issue but his ac didnt blow cold only after stepping on it it starts to blow colder and then goes back to blowing less colder. And he still didnt figure out whats the problem.

Gville350

iTrader: (10)

I would start at looking at the water pump.

valeoray

how bout a thermostat stuck partially open?

jgr7

iTrader: (1)

Sounds like the water pump. You said that it is full of antifreeze of the right mix correct?

1fastcobra

water pump for sure

quick123

iTrader: (2)

Guys, could be as easy as air bubbles in the coolant lines...I would start by burping the coolant and checking for a coolant leak. If you can't find a coolant leak, you will need to check the cap itself and the thermostat.

FYI...I just fixed this concern on Friday on a 250 with the same concern, and all it took was burping the coolant. That does not mean that this will fix everyone's situation, but it is the proper starting point.

misterhu

I recently took the car in to the dealership for the VVTI recall. They didn't say anything about coolant leaks and I haven't noticed any leaks either. Could the water pump be going bad without showing signs of leakage?

The coolant temperature gauge is the dash hasn't been spiking or doing anything weird. It stays pretty much a little cooler than the mid line. That leads me to believe the thermostat is working properly.

My mechanic had it running with the coolant cap off and topped it off from there and said there it seems to be full and there doesn't seem to be any air in the system before he flushed the heater core. Should I try it again myself and burp it on a slope or something?

quick123

iTrader: (2)

If the water pump fails without leaking, that would mean the bearing would be bad and you would hear the roaring noise...or the impellar inside would be damamged and you could hear the knocking noise...if it didn't work at all, your coolant gauge would read hot.

You know if your thermostat is working if the lower hose to the thermostat gets hot after the fan turns on...

I still think you need to properly burp the coolant...don't just take the cap off, use the proper funnel attachment and make sure you run the car from a cold start all the way until the thermostat comes on...it take a while, and maybe your mechanic didn't know how long to do this...no slope is needed, needs to be on a flat surface.