No Hot Air Through Blower - A FaultyThermostat?

[zakmuh]

Hi Everyone,

I have an issue with my 2003 Kia Sorento 2.5 CRDi climate control system, so wondering if anyone could advise me on this...

When driving around the locality, the heating system takes ages to blow warm air but it never gets to hot air level. When driving on the motorway it blows cold air.

Coolant level consistent, hot coolant in and out pipe temperature consistent (core not blocked) and heater blend door actuator working all okay.

Can I doubt that the thermostat is faulty and its stuck open - letting the coolant circulate through the radiator and this stopping the coolant getting to hot temperature to blow enough hot air through the heater core?

Thanks in advance

[TooMany2cvs]

What's the temp gauge telling you? Have you tried an IR thermometer to see what the temp REALLY is?

If the engine temp's good, then the problem's in the heater - either a blocked matrix or the flaps not opening. How's the hot-cold flap controlled?

[paintman]

Your symptoms are the same as I've had on a number of vehicles over the years - latest being my Sprinter at the start of this year - & on each occasion has been a failed thermostat.

If you haven't got an IR thermometer locate the thermostat.
Often on the engine end of the hose that goes to the top of the radiator - all ours have been but IIRC there are cars where it's located somewhere else.
Start the car from cold & keep checking the hose by hand as it runs up to temperature - might take a while.
If the stat is working correctly the hose should suddenly get hot as it opens. If it warms up slowly & in line with the rest of the engine then the stat is either missing or stuck open.

Edited by paintman on Tuesday 14th November 11:08

[GreenV8S]

If you leave the heater off for a while under cruise conditions do you get a brief burst of hot air when you turn it on again? That would suggest it's a coolant flow problem rather than a coolant temp problem. Blockage, a stuck valve, an air lock or low coolant level could cause that.

[zakmuh]

Thanks for your replies guys.

The gauge reads normal but no, I haven't tried with an IR thermometer. Hot/cold flap working all fine. I even bled the heater core and the water flow is all fine.

I know where the thermostat is and again no, the hose doesn't get hot suddenly - all the a coolant related hose warms up to the same temp and that why I'm pretty sure it's stuck open.

No again, under cruise conditions I don't get a brief burst of hot air when I turn it back on, I've tried this. When I pullover to a service station, then the hot air blows but not to its max. the engine has a fan at the front connected to the drive belt. So it keeps cooling down the coolant.

When I'm on motorway, I keep it fully off and shiver lolz.

I think I should start with replacing the thermostat, like Paintman did and see what happens . If the problem still there, then I'll have to take it to a garage?

[TooMany2cvs]

If the temp gauge is up to temp, it's getting up to temp in shortish order, and the rad is cool to the touch until the gauge rises, then gets hot to the touch - your stat is just fine.

[GreenV8S]

If it's a main coolant stat problem I'd expect the overall engine temperature to gradually creep up while the vehicle was stationary, bringing the heater output temperature up with it, eventually leveling out when the cooling fan kicked in to prevent overheating. Is that what you get?

[zakmuh]

The main issue here is the coolant will not get hot for a VERY long time, even if the engine is running for a long time on the drive way.

The engine is placed longitudinally with the fan running all the time (connected to the drive belt) - no secondary fan to kick in when the coolant is hot. So technically, the coolant running through the radiator gets cold down instantly before runs into the bottom bay of the engine...

[zakmuh]

zakmuh said:

The main issue here is the coolant will not get hot for a VERY long time, even if the engine is running for a long time on the drive way. Like after an hour or so only the coolant gradually starts to get warm.

The engine is placed longitudinally with the fan running all the time (connected to the drive belt) - no secondary fan to kick in when the coolant is hot. So technically, the coolant running through the radiator gets cold down instantly before runs into the bottom bay of the engine...

[TooMany2cvs]

zakmuh said:

The main issue here is the coolant will not get hot for a VERY long time

Ah... Stat is staying open, then. I presume the rad starts to get gently warm quite quickly after a cold start?

zakmuh said:

even if the engine is running for a long time on the drive way.

That's actually about the worst way to get warmth into an engine, especially if the bonnet's open.

zakmuh said:

The engine is placed longitudinally with the fan running all the time (connected to the drive belt) - no secondary fan to kick in when the coolant is hot. So technically, the coolant running through the radiator gets cold down instantly before runs into the bottom bay of the engine...

If the stat was closing, then the coolant in the rad can be as cool as it likes - it's not getting into the engine.

I'm very surprised that something as recent as 2003 has a direct-drive fan, though, albeit something as agricultural as a Korean sprogbus. I hope it is, at the very least, viscous...?

[zakmuh]

Thank you very much everyone. From what most of you're saying, its the stat I need to have a look at.

Stat is placed in an awkward place where I have to remove the alternator first to remove it. I'll get there

[zakmuh]

Hi guys,

Just a quick question....would a faulty water pump cause this kind of issues?

Thanks

[GreenV8S]

Don't see how. All it can do is pump, or not. I don't see any way for it to cause overcooling if the rest of the system is working correctly.

[TooMany2cvs]

zakmuh said:

Just a quick question....would a faulty water pump cause this kind of issues?

Very unlikely. If the impeller blades had eroded away to nothing, you'd be getting no flow and localised overheating. More likely would be bearing collapse or seal leakage.

[PositronicRay]

I had a problem on a Merc with only 1 side heating up, the other would kick in eventually but take ages. A new heater valve didn't cure it but a water pump did.

Odd

[Integroo]

I have this issue - only get hot air through the side vents, not the centre vents. No issues with engine temperature etc. and apparently it is the heater flap motor which commonly fails on my car. Sitting with a 9 quid replacement from eBay on my desk, and fitting it tonight! Will let you know if the fault is resolved.

[Kinkell]

Had similar symptoms on an Audi A3 and replacing the thermostat made no difference.
Replaced the water pump and all was well. The original pump's impellers had disintegrated.

[zakmuh]

Thanks.

My flap is working fine cos all the vents have same temp flowing through.

Say I'm driving down on a dual carriageway for 2 hours. During this time temp gauge reading correctly, staying at mid level but the air is very cold (changing to recycle mode makes no difference). Then I stop at lights, it blows warm air. Then again I start to move, cold air back again.

I'll try to look at the stat this weekend and update you all.

[GreenV8S]

I think you mentioned earlier about having hot coolant in and out but I wasn't sure where that was referring to. Can you confirm you're getting hot coolant at the inlet and outlet of the heater matrix?

If so, and if you get cold air when moving, I would suspect that ram air is entering the heating system. Presumably there is a path for the fresh air in hot weather (or chilled air, if you have a/c) and this may be staying open when you ask for heat.

[zakmuh]

Yes I'm getting warm (same warm temp on all cooling system hoses/pipes) coolant at inlet and outlet of the matrix - I checked it for blockage but all fine.

I almost dismantled the entire dashboard to check the matrix, hot/cold blender flap and fresh air inlet flap and all - everything functioning properly as it should be.

Let me explain my test drive with opened up dashboard:

When the engine reached to warm temp, I drove the car on the road and these are the results...
1. Car moving - heater core temp is too low. I barely felt the temp.
2. Car stationary - heater core got warm (not hot) gradually.

This tells anything?