Coolant warning light on with ignition - off when started

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MikeT
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Coolant warning light on with ignition - off when started

Post by MikeT »

Is it normal for the light to come with the ignition and extinguish on engine start? The Citroen handbook doesn't mention it though it tells me how all other lights should act/react so I find it a little puzzling.

It hasn't bothered me before but today I got the warning light while driving and found I needed to top up the coolant with about 400ml - indicating a small leak somewhere.

What's the best DIY method to detect coolant leaks? I can see/smell no clues other than a slight green furring along the top fins of the radiator but no indication of water or steam coming from it.
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Post by Peter.N. »

This will happen if the water level is low as the water contracts as it cools and then expands again when heated, hence the level rises and puts the light out, a rise in water level can also be caused by a leaking head gasket as the pressure build up tends to push the water out of the block, check around the header tank cap and overflow for signs of coolant being blown out, this would show up as white streaks. Green furring would indicate a leak of coolant, but again it may only be happening when its cold, the expansion when hot closing the gap.
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Post by MikeT »

Hi Peter, sorry if I didn't make myself clear.
Whether the coolant is stone cold, warm or hot, the warning light will illuminate on ignition and immediately go out on engine start, in fact I think it goes out when cranking.

Even so, this is a temperature warning (top part of the coolant temp gauge), not a level indicator isn't it? I don't understand how a low level can cause a (too) high temperature reading.

I'll look for white streaks around the expansion bottle - you've given me an idea :idea: I'll install a catch bottle to the overflow as well.

Can you please clarify your point about green furring and coolant leaking only happening when cold and the gap closing? I understand water expands when hot but what gap are you referring to that gets closed when hot?

Thanks
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Post by jeremy »

I expect the light is wired in with the oil pressure warning light - and separated from it by a diode. The idea is that the bulbs are tested when the ignition is turned on but as soon as the engine is running its extinguished - at the same time as the oil pressure light goes out.

There may be others similarly wired (can't think of any at the moment)
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Post by MikeT »

Ah right, thanks for that Jermey, the Haynes wiring diagrams confuse the hell out of me. I wanted to know what circuits were linked to what as I have so many electrical faults.

All I know is the guages are fed from a voltage stabiliser in the dashboard circuitry and the sensors provide a variable resistance to earth. While both my temp and fuel gauges appear to be working I'm not sure about their accuracy as the fuel gauge seems to be indecisive and overly pessimistic.

What I did notice was that the temp gauge remained in the normal zone (above 70 below 90) when the warning light came on during driving.
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Post by Peter.N. »

Hi Mike

OK sorry about the confusion. Regarding the leak I was only suggesting that a leak from a metal construction i.e. the radiator, can leak when cold but natural expansion could cause the gap to close when hot. The best time to look for leaks is soon after starting, while the water temperature is rising and the pressure building but the system still cold.
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Post by MikeT »

Peter.N. wrote:Hi Mike

OK sorry about the confusion.
No, no apology needed, I'm sorry for being thick! :oops: I get like this sometimes - other times I'm fully asleep :-$
Peter.N. wrote:Regarding the leak I was only suggesting that a leak from a metal construction i.e. the radiator, can leak when cold but natural expansion could cause the gap to close when hot. The best time to look for leaks is soon after starting, while the water temperature is rising and the pressure building but the system still cold.
Thanks for spelling it out for me Peter and that's a good tip I'll try tomorrow.
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Post by jeremy »

Hint - if you apparently have many electrical faults in one area look at what affects them all - ie the earth point.
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Post by xantia_v6 »

hints:

1. I think that on a Xantia with A/C, the coolant warning light is driven from the bitron unit, which has a separate temperature sensor from the guage, and this sensor (or the connection to it) can become intermitent.

2. It seems that a common "invisible" water leak is the water pump seal, a reason for changing the water pump every time the cambelt is changed.

3. By far the best way to detect a coolant leak is to presurise the system while it is cold. You may be able to do this with a bicycle pump connected to a bleed valve. (have not tried it on a Citroen), but NEVER presurise above the rated system pressure or you will blow a seam on the radiator.
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Post by Clogzz »

The overheat lamp in the gauge comes on when going to ‘ignition’ before starting, and stays on, together with the 4 bottom lights in the display, until the engine is cranked.
The lamp often comes on for no reason while driving, together with the STOP lamp.
It’s usually caused by the brown temperature sensor plug needing a clean or tightening.
Intermittencies in the brown sensor wiring also cause the cooling fans to go to high speed for no reason.
The brown sensor is item 8008 on the map, going to pins 7 & 14 of the Bitron. :mrgreen:

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Post by MikeT »

Clogzz wrote:The overheat lamp in the gauge comes on when going to ‘ignition’ before starting, and stays on, together with the 4 bottom lights in the display, until the engine is cranked.
I guessed it was normal but as the handbook doesn't mention it I thought I'd better ask.
Clogzz wrote:The lamp often comes on for no reason while driving, together with the STOP lamp.
This did happen to me yesterday though the reason was low coolant level cured by a top up.

Thank you
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Post by MikeT »

Clogzz wrote:The lamp often comes on for no reason while driving, together with the STOP lamp.
It’s usually caused by the brown temperature sensor plug needing a clean or tightening.
Intermittencies in the brown sensor wiring also cause the cooling fans to go to high speed for no reason.
The brown sensor is item 8008 on the map, going to pins 7 & 14 of the Bitron
The problem is getting worse. The stop light and the coolant temperature warning light is illuminating more often - usually after acceleration though it also comes and goes at will. As you say, the fans kick in full speed.

Where can I find the brown sensor, is it on the fuel filter housing? Is that also where the thermostat is? Can the wiring be traced easily enough?
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Post by MikeT »

Clogzz wrote:The brown sensor is item 8008 on the map, going to pins 7 & 14 of the Bitron. :mrgreen:

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I think that may be the wrong part - 8008 (according to Haynes :!: ) is the refrigerant temperature sensor.
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Post by RichardW »

Mike,

I'm sure that's the right part - what ever the BOL says 8)

If you look at the fuel filter, the termostat housing is under it. There will be 2 or 3 temp sensors screwed into it (depending on whether your engine is ECU controlled or not - I suspect it will be). One of the sensors will be brown and have 2 wires going to it (usually front right as you look at the housing) - this is the one that feeds the Bitron. If you unplug it then both fans should roar into life at high speed - note you might need to turn the ignition on to stop the fans again (been there, done that!). I would disconnect it to see the fans come on to know you've got the right one, then clean up the pins and reconnect, then waggle to wire to see if you can generate a fault (is fans come on).
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Post by Clogzz »

Thanks for that endorsement, Richard. :D
The BoL probably got its translation from French wrong, as réfrigérant means coolant in French … the engine cooling fluid.
The Bitron casing says ‘Bitron Video’, and the input is too sensitive, picking up interference.
There’s been a free modification with a screened cable in France:

http://xu10j4r.free.fr/xantia/notexantia.pdf
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