Temperature gauge always reads low

B

BubbyBoyUK

Joined
Sep 10, 2021
Posts
23
Likes collected
17
Location
North Devon, UK
Funster No
84,092
MH
Renault Master 2.5 T
Hello - my new (to me) 1998 Renault Master Mk 2 cooling system temperature gauge, never reads higher than half way between cold and the mid point - once warm, the needle stays within a tiny fraction of that 'quarter' mark. The engine is a 2.5 Diesel with retro fitted Turbo (fitted circa 2008) - mileage 70k. Everything else works as exactly as it should and drives 100% , never showing signs of unacceptable performance, overheating or any other issue and always 'starts on the button'. The engine is based on the 8140 model, also fitted to earlier Citroen and Peugeot vans.
My highly experienced and local mechanic has changed the thermostat and temperature sensor, but to no avail. We then thought the problem may be a defective gauge, so bought a complete replacement instrument cluster (used) and changed the whole cluster over, but the problem remains - this of course tells us that the temperature gauge is presumably not the problem. Incidentally, I've asked the mechanic to measure the actual temperature, once the engine has warmed up after a good run, in order to establish if it's running at the optimum temperature for that model engine. He'll do that next week.
My concern is that if the gauge is not displaying the correct temperature, any over heating issue may not register, with the obvious consequences.
Has any other member had a similar experience or have any ideas on the subject? Secondly, I'd thought of fitting a separate, dedicated temperature gauge mounted on the dash away from the cluster. Has any other member had one fitted to a similar engine, and if so, which make and model gauge?
I'd really appreciate any assistance/advice/views - thanks very much.
 
Your mechanics OBD plug in tester should be able to tell you the temperature that the engine thinks the coolant is running at - it should be around 80 deg C.
 
What sort of cooling fans does it have?

Is it mechanical or electrical thermostatically controlled?

What happens to the temp guage if once up to temp you run it stationary.
 
NicM said:
Have you tested the engine thermostat? Maybe
Click to expand...

BubbyBoy said:
Hello - my new (to me) 1998 Renault Master Mk 2 cooling system temperature gauge, never reads higher than half way between cold and the mid point - once warm, the needle stays within a tiny fraction of that 'quarter' mark. The engine is a 2.5 Diesel with retro fitted Turbo (fitted circa 2008) - mileage 70k. Everything else works as exactly as it should and drives 100% , never showing signs of unacceptable performance, overheating or any other issue and always 'starts on the button'. The engine is based on the 8140 model, also fitted to earlier Citroen and Peugeot vans.
My highly experienced and local mechanic has changed the thermostat and temperature sensor, but to no avail. We then thought the problem may be a defective gauge, so bought a complete replacement instrument cluster (used) and changed the whole cluster over, but the problem remains - this of course tells us that the temperature gauge is presumably not the problem. Incidentally, I've asked the mechanic to measure the actual temperature, once the engine has warmed up after a good run, in order to establish if it's running at the optimum temperature for that model engine. He'll do that next week.
My concern is that if the gauge is not displaying the correct temperature, any over heating issue may not register, with the obvious consequences.
Has any other member had a similar experience or have any ideas on the subject? Secondly, I'd thought of fitting a separate, dedicated temperature gauge mounted on the dash away from the cluster. Has any other member had one fitted to a similar engine, and if so, which make and model gauge?
I'd really appreciate any assistance/advice/views - thanks very much.
Click to expand...
 
Hello B - I hope I've used the right 'button' to reply to your question, but I'm new at this. But, thanks for your comment.
I know little about engines. Are you saying there's a thermostat on the engine and in the cooling system?
 
Most factory fitted temperature gauges are almost useless, when I had a Bongo with an aluminium head,I fitted an i-alert which gave ba digital temperature reading as well as a preset alarm. I don't know if they're still available but I'm sure something is available.
 
BubbyBoy said:
Hello B - I hope I've used the right 'button' to reply to your question, but I'm new at this. But, thanks for your comment.
I know little about engines. Are you saying there's a thermostat on the engine and in the cooling system?
Click to expand...
Yes the first question is: does the vehicle heater blow out very hot air?

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Phill D said:
What sort of cooling fans does it have?

Is it mechanical or electrical thermostatically controlled?

What happens to the temp guage if once up to temp you run it stationary.
Click to expand...

Just noticed on my last post, that I've said Hi to myself - sorry about the Phil.

I'll find out from the mechanic about the controls and get back to you.
 
The Ex-Gasman said:
Most factory fitted temperature gauges are almost useless, when I had a Bongo with an aluminium head,I fitted an i-alert which gave ba digital temperature reading as well as a preset alarm. I don't know if they're still available but I'm sure something is available.
Click to expand...
Thanks I'll look into that.
 
Years ago the only true way to test if the thermostat was working, was to place it in a pan of water with a cheap thermometer heat it up then you will see the thermostat open and you can note at what temperature it happens.
 
Diesels never seem to run that hot, are you in the UK or somewhere warmer? So far only in the Uk, my 2001 Peugeot Boxer 2.8Hdi based vehicle never indicates more than one third even after a long run. Otherwise no problem.
I suppose it is possible that if the engine never gets up to temperature your fuel consumption could be worse.
One test would be to put a piece of cardboard down in front of the radiator and do a test run - while of course keeping an eye on things - you may even hear the fan cutting in.

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68c said:
Diesels never seem to run that hot, are you in the UK or somewhere warmer? So far only in the Uk, my 2001 Peugeot Boxer 2.8Hdi based vehicle never indicates more than one third even after a long run. Otherwise no problem.
I suppose it is possible that if the engine never gets up to temperature your fuel consumption could be worse.
One test would be to put a piece of cardboard down in front of the radiator and do a test run - while of course keeping an eye on things - you may even hear the fan cutting in.
Click to expand...
which is why i asked what type of fan, it may be cutting in too soon or permanently.
a lot of vehicle rely on ram air to assist with cooling and it was not unheard of years back to put grill restrictions in place in winter to get the vehicle upto temp.
 
Diesel engines do take longer not get to temperature on local roads, they need to work hard but most temperature gauges are "damped down" so much they are almost useless
 
my 2006 2.8Utd runs a tad under half way and after it’s been working hard, and I do mean hard it goes up to half but soon goes back to “normal” afterwards.
As has been mentioned is the heater warm, hot, or extremely hot?
 
My 1999 2.5 Ducato engine temperature gauge didn't work until I did .....
1) Replaced temperature sender (front right side of engine as you open bonnet).
2) Added an extra earth strap from engine to body (probably not related but a wise thing to do).
3) Pulled connector off rear of dash gauges and pushed back on (remove static).
My hardly moving gauge then sprang to life but in normal running always sat below half way
 
My 2000 Homer / Ducatto with an iTDTI 2.8 diesel is pretty similar it runs at 3/8 ie below the mid N position most of the time. It rarely gets to half way. Stated Running temp is 80 degrees so that would male sense if 100 is Normal. Perhaps it’s just a feature.

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80 ish degrees is good for a Diesel engine. 100 is too high for continued temp, an is only expect to see that whilst working very hard, and would then want to see the temp soon drop below 100.
As an indication, the 2.3 Fiat engine with electric fan, runs at 80-85 c normal running. The primary cooling fan comes on at 95c and then goes off at 90. That shows that Fiat on this engine would like the temp below 95, ideally below 90.
 
Years ago, I had a pop-top that overheated when the radiator sprung a leak. Temperature senders back then tended to "give up" after reaching half-way (normal) on the gauge no matter how hot the engine got. As least that was what mine was reading as steam issued from the bonnet!.
 
The heater output temperature will give you a good idea, also a lot of digital multimeters do have a temperature range using a separate probe -handy for ovens etc. if you taped the sensor to the top hose by the exit from the engine it might explain what, if anything , is wrong.
Mike
Ps most of the cheapie ebay thermometers only go up to +70 degrees
 
BubbyBoyUK said:
Everything else works as exactly as it should and drives 100% , never showing signs of unacceptable performance, overheating or any other issue and always 'starts on the button'.
Click to expand...
Erm, sorry but what’s your problem then? Just leave it alone! I had exactly the same set of circumstances on my first m/h, a 1984 Joseph Arnold (forerunner to RMB) with a 3L mercedes 5 speed box, supposed to run at 90° 3/4 on the gauge, never got past half way apart from a couple of occasions when I did really long runs. New thermostat, water pump etc, no change, it did have a Kenlow fan which seemed to run most of the time though, it ran like clockwork but was a bit heavy on fuel (19 mpg) I had it for years, sold it 20 years ago and as far as I’m aware, it’s now owned by a Funster after three or four other owners and still going strong. Don’t fret about it till something goes wrong (y)

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The Ex-Gasman said:
Most factory fitted temperature gauges are almost useless, when I had a Bongo with an aluminium head,I fitted an i-alert which gave ba digital temperature reading as well as a preset alarm. I don't know if they're still available but I'm sure something is available.
Click to expand...
Absolutely agree most are useless and only a guide , if you get trouble it will probably in my experience the needle will zoom over to the red or right then that's the time to stop and switch off, obviously if needle keeps to left or zero that's when you start eliminating faults , for example with ignition on earth out connection on sender. If gauge goes to red,/ right you know gauge works , then it's probably sender or thermostat stuck open , if it's one of these I would replace sender, by releasing system pressure ie. Undo header tank cap, undo sender and quickly fit new sender without draining system , changing / checking thermostats means draining system or part draining then bleeding the system
 
You say it had a turbo retrofitted. Does the temperature indication fluctuate? The original thermostat (non turbo) was set to open at 79°. On the later engine, with turbo, the thermostat is set to open at either 83° or 89°. The coolant temperature sender should have 2 outputs, one will feed the engine management ECU and the other should go to the gauge. Generally these days the temp gauge reading is "electronically weighted" to display a steady reading if the temperature is within the correct range (+/- 5°?). As suggested, it could be the thermostat opening at a lower coolant temperature (pre turbo thermostat fitted) and therefore not getting into the temp gauge managed range. If the temperature does fluctuate then this could be a possible cause. Hope this helps 😎.
 
I suggest which I already above , there's probably nothing wrong, go to a Renault Dealer with the vehicle in normal working temperature and ask them could they have a quick look at your gauge or be cheeky and see if you see a Technician walking about and ask him .
 
i have a Renault master 1998 turbo diesel only done 35,000 ex film set ambulance i will check tomorrow but the temperature gauge is always low . heater does blow nice and hot.
 
The only time my 2000 , idtd 2.8 has shown anything above half , is when i discovered the cooling fans were not working properly , shortly after i brought it , and that was on a hot day . Like a few others , fans now working , mine shows just under half . Should it move higher , normally only on a steep ascent and slightly at that , it soon slips back once over the brow . A good indication of how warm the engine is , is the heater on 1st speed , it will only heat as much as the engine . Mine is perfectly acceptable , blows hot when i need it . I've just completely rebuilt my cooling system . Pretty much the only original bits left are the cooling fans , and the engine itself . So i expect it to run even cooler now .
In complete contrast my 05 Suzuki carry van , 16v 1.3 , is a cool running engine . During the summer the engine will rise to just under half on a hot day , but this time of year , it barely gets off the peg . As one person has already mentioned , i do blank half the radiator off , to enable the heater to get little bit warmer .
Newer vehicles , be it car , van , or whatever have undersize radiators , and rely on electric fans to keep the temperature in order , where older vehicles had larger rads . I'm not quite sure why this is the case , but i've been lead to believe , this is to save weight . Personally i think this is a load of old crock . However no better witness to size , is the fact my previous 1990 series 1 Super carry radiator , is twice the the size of my now 2005 series 2 Carry , which in itself , is little bigger than the radiator on my 500cc motorbike .
I doubt you have a problem my friend , but the temperature check your garage is arranging should give the evidence .

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