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Old 16th March 2019, 16:18   #1
Steve2016
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Default Cool heater on diesel with new stat

Hello, I have a R75 diesel auto with the usual lack of heat from the heater. A couple of years ago I fitted the recommended in-line 89 degree thermostat in the top hose and although it has improved, in winter it is still not what you would call warm.

Today I set the dash display to show temperature and took it on a run including a motorway. The highest reading was 84 degrees. Should it be higher? Is it worth trying a different 'stat or is that as hot as it should get?

I've done all I can to eek out as much heat as possible, with a new matrix, ensuring no kinks in the hoses and shrouding the hose that passes in front of the engine. Is there anything more I can do?

Many Thanks
Steve
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Old 16th March 2019, 16:26   #2
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Well. I dunno, mine gets to 84 after around 3-4 miles, doesn't get any higher until the car climbs a hill. A steady uphill climb will see 87-88 degrees and then stat opens and it drops back to 84. I think this is normal, heater is hot enough but hotting up times are dependent on outside temperature.

Last edited by Heddy; 16th March 2019 at 16:27.. Reason: Spelling
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Old 16th March 2019, 20:10   #3
slovcan
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There is an inline thermostat housing available that uses a "standard" size thermostat as opposed to the inline Renault type. This can give you more options of manufacturers and temperatures - like a 92 degree one WITHOUT the little bypass hole in the frame. That could be better for fuel mileage AND heat.

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Glenn
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Old 16th March 2019, 20:12   #4
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Motorway driving isn't a good way to test it. Better drive it under more load or a lower gear. Notwithstanding the 84C reading, the heater's output will be poor if coolant isn't flowing through the matrix properly, so it would be worth checking that it's not silted up. Maybe backflush the matrix by connecting a hosepipe to the underbonnet heater hoses (disconnected obviously) and putting the hose onto the heater outlet side.


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Old 18th March 2019, 12:54   #5
Steve2016
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Thanks for all your replies. I have already fitted a new matrix, so don't think that's the problem.

I can't identify any other flow restrictions and suspect the only way I'll get more heat out is if the coolant temperature was higher. Is it a practical option to use a higher-rated 'stat or will that just risk damage to the engine?

I can live with it as it is, it's just in the middle of winter that I get complaints from my passengers.

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