Fitting a cheap temperature gauge

[malcolm]

Worth some notes about how to fit a cheap temperature gauge as there have been questions recently. I've got an overheating issue to diagnose and I'll need a temperature gauge for that. I thought about throwing a thermocouple into one of the hoses but gauges are cheap so decided to go that way. I did no planning or research before I bought the temperature gauge and there may be more suitable ones available.

I went really cheap and bought this one:



The sensor on the 747cc engine (and I think all Renault 4 engines including 845cc and 1108cc) has a M18x1.5 thread but all the cheap temperature gauges have a 1/8 NPT thread so an adaptor is needed. On the early engines the temperature sensor was placed in the waterpump and for the GTL there will likely be a threaded blank in the waterpump that can be removed to fit a sensor. I bought this adaptor:



The thread in the adaptor looked about right but the sensor was too big to pass through the hole in the adaptor. I drilled out the part after the thread to about 10mm leaving a gap around the sensor. The sensor doesn't stick out past the adaptor which isn't good. Normally you would want the sensor to stick out into the cooling water. Hopefully some water will get around the sensor. The sensor part didn't screw in fully to the adaptor possibly because there is a taper to make a seal. I smeared a bit of sealant around the sensor thread and screwed it in to the adaptor as far as it would go. The adaptor itself screwed in perfectly and it came with it's own copper washer.



I'll follow this up with a part 2 post when I actually fit it, then a part 3 where I find out if it works or not.

 

[Homegrown]

"The sensor doesn't stick out past the adaptor which isn't good. Normally you would want the sensor to stick out into the cooling water. Hopefully some water will get around the sensor" Dont think you will ha any problems, mayby a tiny delay in theory but nothing you see on your guage.
Looking forward to updates.

 

[malcolm]

The sensor installed in the water pump. The theads don't screw in all the way. I think it's some sort of plumbing thread that seals by itself with a taper.



The temperature gauge needs power, ground and a wire to the sensor. The two thin wires are for lighting and I've left them disconnected. There aren't many easily accessible ignition feeds on the Rodeo so I've used a piggyback spade terminal on the interior fan feed. The ground wire goes to the interior fan ground.



The mounting is secured to the underside of the dash with a couple of self tapping screws. Seems to work. The thermostat seems to be opening but the engine is running a bit hot at idle.



After some full throttle runs setting up the distributor the temperature was sitting at 100C. The cooling system wasn't venting so I guess it is pressurising OK. I think the gauge is probably accurate - it doesn't matter if the feed is 12V engine off or 13.5V engine running. It'll be useful having the gauge to see what effect changes make to try to fix the overheating.

Hopefully a nice new radiator will make the gauge sit at 80. Otherwise I'll know it's something else. Answer to that will be on https://www.renault4.co.uk/forum/threads/rodeo-recommissioning.11517/page-4

 

[Sage103]

I have the same temperature gauge and it generally sits at just under 100 once the engine has warmed up. Initially I thought that this was too high and something must be wrong but the engine feels fine and the radiator fan cuts in when the gauge goes over 100. And no signs of overheating. So I have just got used to it and accept it as being ‘normal’ but maybe not truly accurate.

 

[malcolm]

That's a good call. The gauge over-reads by 20 degrees!

 

[malcolm]

Turns out you have to calibrate them. The bezel comes off with a lot of prying and force, then the needle pulls off with more force than you want to use. Just pop the needle back at the 100C mark while the sensor is boiling away in a kettle. Reassembly is possible by prying the bezel back around the plastic case but isn't easy and the glass is fragile.

 

[jjad]

It will be interesting to see if it's correct across the range though: can you check it at other values too?

 

[malcolm]

Could check it if I owned a thermometer. Figured the important thing to know is when the water starts to boil.

 

[jjad]

 

[malcolm]

I was hoping I fixed an overheating problem by fiddling with the gauge. But still got to 95C this afternoon.

 

[jjad]

Given that the system is pressurised (so water won't boil at 100C) what temperature range were you expecting?

 

[malcolm]

In the MG the needle sits in the middle of the gauge all the time so maybe 80C. I've never fitted a temperature gauge to a Renault 4 before so don't know how they normally behave but I think the Rodeo doesn't have quite enough cooling. I've been running with the heater on full to supplement the radiator.

The early cars don't make sense to me. On the GTL the radiator is just behind the hole in the grille so air is going to go through the radiator On the early cars the radiator is back near the engine and air might have gone somewhere else by then. Maybe they still rely a lot on the fan at speed, and Angel mentioned the fan shroud.

 

[Homegrown]

What temp range is your termostat?

Cooling Pack for Billancourt engine for Renault R4 4L.

This cooling kit for Renault R4 4L sedan or F4 van with Billancourt engine will be mounted in place of your old parts damaged or destroyed.Allows a complete and rapid restoration of your cooling system.

vehicules-anciens.fr

Cooling Pack for Billancourt engine for Renault R4 4L. has a 86°C temostat

• 1.00 x Calorstat, Thermostat for Renault R4 4L and Estafette. Value 86°C. (VA11031-19)

If you got an 86°C engine temp will be like 86-95 normally maybe 100°C under load.
Your thermostat is the piece that determines wanted engine coolant temp, and the radiator and fan should give thermostat "cold water" to work with to be able control engine temp.
So first choose thermostat of right temperature for given engine temp.
If radiator cant handle to cool down the water enough for thermostat to control temperature then you start fault diagnos that area.

 

[malcolm]

Not sure what the thermostat is. It's a new one. Car idles at 80C so probably about that. EDIT> It's a Gates part opening at 83C.

I think it's a lack of cooling capacity as the radiator is 50 years old and maybe a bit blocked. I think the water pump is OK as the interior heater runs hot. I've ordered one of those aluminium radiators that they sell to RAID people for driving in Africa.

 

[angel]

My "hot weather" cooling pack on my 1975 845cc:

-74 deg.C thermostat - low temperature but not completely removed, having a slight restriction to coolant flow at this point is said to be beneficial because it eliminates vapor locks in the head / block.
-Recored Billancourt radiator with a 3 row core.
-6 blade plastic fan.
-50/50 mix of Valeo Protectiv 100 green coolant and tap water. More important, I think, is the fact that when I overhauled the engine in 2002, I wire brushed the inside of the block and have always used a good quality coolant. Absolutely no sediment or rust in coolant or radiator since then.

Operating temperature measured at the back of the head is 80-105 deg.C in summer (30-40 deg.C ambient temperature), mostly depending on engine load.