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Discussion Starter #1
Morning all, I have a 2010 Grand Scenic 3 1.5dci. The heater has started to temperamentally not blow out hot air even when the dial is right round to max. Doesn't make any difference if the engine temp gauge is up to the middle or if the AC is turned on or off?

The engine temp gauge appears to be a bit up and down too although she's not over heating.

I'm guessing thermostat but could be wrong, anyone got any ideas? If it is the thermostat where is it??

Thanks as ever.
 

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First check the coolant level. Is it correct? Then, from a cold engine next time you go out watch the temp gauge whilst driving. It should stay on cold for about no more than a mile (give or take) then move to normal reasonably quickly. If it does this, then the thermostat is probably OK. Next check would be the radiator and heater supply and return hoses. Are they hot where they should be? If we can rule out the thermostat and cooling system then we can focus on the heater.
 

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Discussion Starter #3
Thanks, coolant level is fine and the pipes all look ok.

I've just been out, the gauge rises and the heater starts to work then the gauge starts to go down again and the heater starts blowing cold again??
 

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Super Moderator Technical Supremo Platinum Member
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Is this something just come on or has it always been like that ?
And how long are your journeys ?
It can take more then a few miles for a diesel to build enough heat in system to keep the heater nice and toasty.
 

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My 2012 Clio 1.5dci is the same - Low heat output from the interior heater. The engine temperature gauge reaches the 1/3 mark on the gauge and stays there rock solid - the thermostat keeps the engine pretty cool. I have thought about swapping for a higher temperature item but not sure if it is by design. It has been like that for all of its 150,000 miles......I have only ever heard the rad cooling fan cut in a hand full of times and then only in exceptional temperatures such as stuck in uphill crawling traffic on hot summer days and the likes.

My previous post on the subject https://www.renaultforums.co.uk/44-heating-cooling/508050-cold-weather-issues-clio-iii-interior-heater.html
 

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Discussion Starter #7
Thanks, I'll try that.

This is a very new thing for the car. I had the windscreen replaced on Monday last week then this heater issue started!! Pretty sure the 2 are not connected!

Basically the temp gauge rises normally and the heater kicks in, then the temp gauge starts to drop again and the heater blows cold, then slowly the gauge rises to the middle again, stays then and the heater begins blowing hot again! Very odd...…..
 

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Discussion Starter #9
I've just been out in the car but only 5 minutes or so. When I got back I opened the bonnet to look at the coolant and the expansion tank was full to bursting. With the engine off and barely warm I released the cap and coolant came shooting out. Sound like the thermostat is opening too slowly??
 

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With a cold engine and coolant eruption I would suggest head gasket failure allowing combustion gas to enter the coolant system.
With a hot engine, it is normal to have massive (and dangerous) coolant expansion if you open the expansion bottle.
Let the engine cool, remove the expansion bottle cap and let it run. If you get air (gas) continually bubbling from the expansion tank then the head gasket has failed.
 

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Super fantastic Mod Technical Supremo Nice Guy
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Unless Thermostat is sticking, and it does not have a jiggle pin inside it..
Then the water is only going so far, getting too hot for the rad fan to control .. ( No water circulating, fan switch wont know engine is hot, water boils and makes steam ,
First thing, get the thermostat out/checked..
All the classic signs of a thermostat stuck shut,, ..
 

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Discussion Starter #12
Thanks for the info.

Would I not have other symptoms if the HG had gone, coolant loss, oil in the coolant and vice versa? I have none of those and the engine is running well?
 

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Thanks for the info.

Would I not have other symptoms if the HG had gone, coolant loss, oil in the coolant and vice versa? I have none of those and the engine is running well?
Not if the gasket has failed between a waterway and the cylinder bore.
I would suggest you check out the thermostat per ours2012's advice first and if a new thermostat does not solve your problem then go on to further investigation such as the head gasket (cylinder bore compression test or pressure test the cooling system).
 

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watching this thread with intrest, as I have a very similar issue on my clio 1.2 (2002).


Heater blowing cold air, no coolant loss, Engine temp gauge stays rock solid in the middle. Can hear radiator fan coming on every now and then and sometimes even after I turn off the engine. Engine feels a bit lumpy when starting cold but runs normal after few minutes.


The garage suggest it will need replacing water-pump(and should do cambelt too since while at it), but I want to make sure its not the thermostat. How can i check that?


Thanks all
 

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Your 1.2 sounds like the engine temperature is fine hence I would not suspect thermostat or faulty pump however, it sounds like the coolant is not getting to the internal heating matrix or far more likely the flaps which direct air through the matrix into the car are stuck closed. Is the car fitted with a basic hot / cold control knob rather than climate control? If so does the knob feel and sound like it is operating anything? It could be the cable has become detached?
 

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Your 1.2 sounds like the engine temperature is fine hence I would not suspect thermostat or faulty pump however, it sounds like the coolant is not getting to the internal heating matrix or far more likely the flaps which direct air through the matrix into the car are stuck closed. Is the car fitted with a basic hot / cold control knob rather than climate control? If so does the knob feel and sound like it is operating anything? It could be the cable has become detached?

Thank you for reply!

Feels good to hear that you don't suspect the water-pump as I am not too keen on spending ~£300 on changing belt and pump. The heating is manual, so a basic hot/cold control knob; will check later today if its operating anything.



-If the coolant is not getting to the internal heating matrix, how do I access and fix it? or is it a case just replacing with new one.
-Another question, where is the sensor for engine temp gauge located? does the radiator fan use same sensor or has another one on radiator body?
 

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Flushed the coolant from heating system. Hosed it few times until rusty colour changed to clear. Refilled with new coolant and now the temp gauge does not fluctuate and looks steady good.


But the heater matrix looks blocked. One of the pipe going in becomes hot but the one coming out stays cold even when heater is set to full. Thinking of trying any descaler in heater matrix to see if it unclogs it.


Any other suggestions? am not keen on removing the whole dash to replace the matrix.
 

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Super fantastic Mod Technical Supremo Nice Guy
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Sure someone mentioned dishwasher tablets on here..
Wait for some more replies to this, if no joy,. then
Start a new thread asking for recommendations .
 

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Sure someone mentioned dishwasher tablets on here..
Wait for some more replies to this, if no joy,. then
Start a new thread asking for recommendations .
IIRC Dishy Tablets, BUT NOT the ones with the Green Ball. Remove that first. Just the plain white ones.
 
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