Hey All,

I am having problem with my Engine Temp Reading Cold when I turn on the heat.
When I dont have any heat running my engine temp is reading normal most times but when I put on the heat it gradually goes all the way down to Cold only coming up a bit sometimes. What could be the cause of this and what are possible solutions.

I don't think its really harmful to the engine but what are your thoughts?

Thanks Guys.

 

my guesses are:
1) air in your cooling system. this can cause all sorts of weird problems with heater core/valve operation and coolant temperature reading.

2) thermostat stuck open or partly open. your heater core is like a second radiator. when you turn on the heat, coolant flows through it and cools down. if the thermostat doesn't close to get the coolant back up to temp, then the temp will drop.

question - does your car take a long time to warm up? the VQ30 cooling system is a very efficient design. the engine should come up to temp quickly even in very cold conditions. if it takes more than a couple minutes or a couple miles then you have issues (air, thermostat, etc).

 

Hey Sky,

It does seem like my car takes a bit more time to heat up and when it does I dont think the heat is coming out as strong as it used to. I think as my first step I should probably get the coolant flushed, this would remove any air in the system right? If that doesnt solve it maybe its the thermostat like you said. Your comments.

By the way, Thanks a lot for helping me with my coil problem a week ago, I put it in myself and it was a snap. My car is running great now.

 

your first step should be to purge the air yourself (don't flush just yet). don't go to a shop they will rip you off.

there a quick write-up on purging air in this thread...
http://forums.maxima.org/showthread.php?t=502765

I would add a few things:
1) make sure your heat is on full blast
2) you may have to purge the air a few times. and do rev the engine to 2-3krpm when it starts to warm up to get that coolant flowing.
3) after the car warms up and you cap it, feel the upper and lower heater core hoses. they should both be hot. if they are not you either have air trapped in there that can't be purged the normal way, or it could be clogged. another orger recently had his heater core replaced and the shop didn't purge the air out of it before installing it. he finally fixed it by removing the lower heater core hose while the car was running and letting coolant flush out.
4) always make sure there is coolant in the reservoir after you cap the radiator. if it runs dry you will suck in air.

so do this stuff first. if it fixes the problem, great. you may still need to flush your coolant - but let's deal with that when the time comes. for now just make a note of the coolant's condition (dirty, brown, "floaties", etc.)

 

I'll give it a try.

 

Hey Sky,
Just reading the other thread you posted for me. When you rev up the engine and the coolant gets sucked by the water pump, should I be adding more coolant or should i just wait till it gets and hot and gets pushed into the radiator, thats when I should cap it.

 

you want to add coolant as the water pump sucks it down (too keep air out of the radiator core). since you're not draining it first the level may not drop much (if at all) until the thermostat opens - at which point the upper hose will spew hot coolant in anyway. when it begins to overflow, cap it, then heat cycle (drive it around for a couple miles keeping any eye on the temp gauge).