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Water Temperature Gauge

Sage103

Sage103

Gordon
Messages
171
Location
Torphichen, Scotland
With a view to embarking on some long trips once we’re allowed out again I’ve been working on advice previously given on this forum to enhance the car’s dependability and fitted a water temperature gauge and a radiator thermostat bypass switch for when it gets really hot. All easily done despite not having a removable blank on the water pump to take the temperature sensor - so I used an inline adaptor on the top hose.

But a short test drive has resulted in the gauge hovering at the top end of the scale - not the reassurance I was expecting - and then dipping into the red as I let the engine idle to await the fan tripping on - which it didn’t before I chickened out and turned the engine off. I have witnessed it kicking in by itself previously. And all hoses under the bonnet were certainly hot - but the question is, how hot? Maybe it has always been this hot but without a temperature gauge to distract me it hasn’t appeared as a problem.

Should I believe the gauge (and maybe give the system a thorough flush) or are these gauges of variable quality? Or would it be worthwhile testing the sensor and gauge in a pot of water brought to the boil?
 
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That’s a possibility - I changed that section of top hose as it was looking fairly tired but with part of a Land Rover top hose which is a similar but slightly smaller diameter so the thermostat might be being constrained by the new hose. I did notice that it was slow to open during my test drive. So a bigger hose and I’ll get a new radiator switch too. Merci!
 
Sage of Torphichen said:
That’s a possibility - I changed that section of top hose as it was looking fairly tired but with part of a Land Rover top hose which is a similar but slightly smaller diameter so the thermostat might be being constrained by the new hose. I did notice that it was slow to open during my test drive. So a bigger hose and I’ll get a new radiator switch too. Merci!
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You should test the thermostat by placing it in a saucepan of water and bring it up to temperature with a thermometer next to it and see at what temperature it opens, sometimes their actual opening temp is vastly different from their advertised operating temperature range.
 
Very much in agreement with above points . I have a radiator mounted temp switch. I have also fitted a high temp warning light on the dash. I have the same or very similar temp gauge . Reading is similar but only a little lower. Keeps stable though and fab cuts in quickly
 
I would check the gauge accuracy through the whole range first and then try to troubleshoot cooling system Did the sensor come with the gauge as a kit?

Side note, fitting a temperature gauge after the thermostat is not a good idea, if the thermostat stays partially or fully closed it's not going to warn you.
 
Good point, Angel, on sensor placement. But possibly not a good idea to move the thermostat down the hose towards the radiator (to make room for the sensor adapter) which was my first thought?
And yes sensor and gauge came together as kit.
 
So after a couple of beers I’ve decided to stick with the current arrangement for now (given that this year probably won’t allow any serious R4 adventuring) and then in the depths of next winter I’ll drill into the water pump and thread a mounting for the sensor in the part of the pump casting where some GTLs have a removable threaded plug.
 
there is a direct replacement electric fan switch listed for Renault 5 gt turbo
normal one comes on at 85 c
at this time water at top hose will be 90 plus c
infra red hand held gun will confirm readings
 
An update on how my temperature saga is going - now replaced the thermostat and the radiator sensor and while the temperature sensor position isn't ideal (downstream from the thermostat) it does at least show me clearly that the thermostat is opening. But the gauge is still registering high in its range and actually goes well into the red before the radiator fan trips in. But the fan has an immediate effect and goes off again very quickly. And I can see when it comes on by itself as my manual bypass switch has an indicator light. I've also replaced the temperature sensor but without any difference. So that leaves the gauge - it has become a bit of a distraction to the driving experience as I find I'm constantly glancing at it - yes, ignorance can be bliss...........
 
Sage of Torphichen said:
An update on how my temperature saga is going - now replaced the thermostat and the radiator sensor and while the temperature sensor position isn't ideal (downstream from the thermostat) it does at least show me clearly that the thermostat is opening. But the gauge is still registering high in its range and actually goes well into the red before the radiator fan trips in. But the fan has an immediate effect and goes off again very quickly. And I can see when it comes on by itself as my manual bypass switch has an indicator light. I've also replaced the temperature sensor but without any difference. So that leaves the gauge - it has become a bit of a distraction to the driving experience as I find I'm constantly glancing at it - yes, ignorance can be bliss...........
Click to expand...
Surely the gauge is suspect?
 
Sage of Torphichen said:
An update on how my temperature saga is going - now replaced the thermostat and the radiator sensor and while the temperature sensor position isn't ideal (downstream from the thermostat) it does at least show me clearly that the thermostat is opening. But the gauge is still registering high in its range and actually goes well into the red before the radiator fan trips in. But the fan has an immediate effect and goes off again very quickly. And I can see when it comes on by itself as my manual bypass switch has an indicator light. I've also replaced the temperature sensor but without any difference. So that leaves the gauge - it has become a bit of a distraction to the driving experience as I find I'm constantly glancing at it - yes, ignorance can be bliss...........
Click to expand...

You say "the gauge is still registering high on its range and actually goes well into the red before the radiator fan trips in" (my italics) Do you know at precisely what temperature the fan does kick in? A gauge showing a "red" zone is only useful if one knows what this temperature is. The fact that the fan does cut in, thus confirming the sensor controlling its function is working suggests all is, in reality, well, but I appreciate your desire to see the movement of the gauge.
 
I agree that the gauge has to be suspect - the red zone is 100C plus so given that both thermostat and radiator sensor seem to be working as they should (at 88 and 85 respectively) I've bought another gauge to try once it stops raining........ if that doesn't make a difference then I'll invest in the external temperature reader.

Thanks for the comments.
 
One mod i do on most of my cars is to connect the fan to an internal switch so i can operate it manually and bypass the radiator sensor ( since all of them fail at some point ) . You can then preemptively control the fan when you think it might be needed, like a hot day at rush hour jam.
But now im thinking you might add the switch and also leave the fan connected to the sensor just in case.
 
Thanks - already done that and switch has green light which comes on when the fan is triggered by the radiator sensor or by the switch - good to have in an R4 when it can be difficult just hearing the fan coming on.
 
The gauge that you have fitted is, in my opinion, not correct as far as the reading on the face.
It shows 80deg, as being halfway which on a similar but OEM quality VDO gauge, half way is shown as being 92 deg.
On a VDO gauge your needle will sit nicely on the middle of the scale.
Also 100deg. on a pressurized cooling system is hardly considered "red".
Maybe you should invest on a VDO gauge, they freely available on e-bay and they not that expensive.
 
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