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heater is nice and warm when moving but colder when stopped

TonyJZX

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i have a V8 commode and guys would know how hot the heater is

but when i'm stopped at the lights its not as cold? but the fan is still ok

is there a blockage somewhere?
 

Pollushon

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I'm confused, title reads it's hot under steam and cooler at idle, thread reads not as cold (warmer) when idle......

If it's as per title, I'd suggest you have air in the system possibly or as you've stated a blockage, any temp issues? So when you're driving and the pump is pumping hard there's plenty of hot stuff getting into the core, idle not so much. Or your pump fins have rounded away, same effect based on revs. Or maybe the heater tap is stuffed (actuator) and under pressure it opens, less pressure it closes. Missing thermostat? Does the blower fan come on too early? Just some thoughts.

How many kms on her?
 

TonyJZX

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its BOILING hot when the car is moving as per usual but it tends to be only warm-ish when stopped

its had a new tap maybe 10,000km ago? and a new water pump otherwise no temp issues

i got 150,000km on it which is low on an LS1 i guess
 

st3r3otyp3

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flush your heater core it prolly gunked up.
 

BlackVXGTS

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1. Check that the vacuum hose running from the inlet manifold to the heater tap isn't leaking.
2. Check that your thermostat isn't partially blocked.
 

Cashman_309

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Check also if you're low on coolant.

If your heater is giving these sort of symptoms and you haven't had your cooling system serviced in over 12 months then have it flushed ASAP.
 

inSight

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Have an odd problem with my cooling system too.

The temperature gauge doesn't budge. It stays on cold most of the time. When using the heater it blows cold with a small bit of warmth. However, when the gauge finally does decide to work or show a reading (usually very low but sometimes normal operating range) the heater actually starts blowing warm air.

I also noticed the engine doesn't get hot (although I did wait a few minutes). It's like it's not heating up. What could cause this?

I already have a new water pump, cooling hoses and thermostat ready to be installed using quality radiator flush and 6L Nulon 100% concentrate (the red, and expensive, stuff) with 6L demineralised water. But the weather hasn't been kind.

Might be a few more days before I can do the job. Have a bunch of other parts I want to do at the same time as well.
 

st3r3otyp3

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This sounds like a thermostat that is set to cold for your engine so it opens up to early, if I am correct remove it ASAP.
 
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