How hot is too hot? [DW10ATED MK1 C5]

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How hot is too hot? [DW10ATED MK1 C5]

Post by Spurious »

Hello all,

Started a new job which requires me to drive to Liverpool for a month or so. I've to negotiate the motorway network at peak hours now; lots of stop start driving, 1st-2nd gear stuff.
The temp coolant guage seems to rise to about 3/4rs of the way up (maybe a little more), not very far off the red zone when sitting in traffic. It's never overheated or never gave me an overheating warning on the display. The Oil temp gauge never seems to be above 1/2 or so.

Now the C5 I had before this, didn't seem to get as toasty, but I wasn't doing this sort of urban driving and it was a few years ago so I could be mistaken.

I've pulled the connector from the temp sender and it's immediately triggered the overheat warning and tripped the fan, whirred away happily. I had a very brief look at the wiring and it seems like it's okay. The relay is happy too, gave it a quick test. So I think it's okay?

Am I just overreacting? Will the fan eventually trip on? I don't want to overheat it on the M60 in the morning, it's not the most ideal spot.
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Re: How hot is too hot? [DW10ATED MK1 C5]

Post by GiveMeABreak »

The fan on your C5 is a single fan and either dual or triple speed.

On the dual fan assembly, the fan comes on at single speed at 97 °C, and the second speed at 105 °C.

The three speed fan system kicks in at 97 °C for first speed, 101 °C (or 17 bar in the cooling circuit) and third speed at 105 °C (or 30 bar in the cooling circuit). The warning kicks in at 118 °C.

So I wouldn't worry too much about it as these are quite high values before the fans kick in.

I would just add a Chop Suey alert here - be warned that on this system the fans can kick in without the ignition being on so just be aware.
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Re: How hot is too hot? [DW10ATED MK1 C5]

Post by white exec »

Is that really 17 and 30bar in that cooling system, Marc?
That's way above normal lift-off cap pressure of 1.5 to 2bar.
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Re: How hot is too hot? [DW10ATED MK1 C5]

Post by EDC5 »

I recently bought a new official Citroen reservoir cap and it had a blow-off pressure of 20psi.

How is the pressure measured in the cooling system?
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Re: How hot is too hot? [DW10ATED MK1 C5]

Post by GiveMeABreak »

Hi Chris - yes, those are the stated values - but I think they are relating to the overall 'cooling' system and are including the air conditioning circuit for this - probably factoring in the high pressure of the A/C gas in hot conditions were the compressor would cut out if the system wasn't getting enough cooling.

We know already that the slowest speed of the fan kicks in straight away when the car is at standstill and the A/C in in operation.
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Re: How hot is too hot? [DW10ATED MK1 C5]

Post by moizeau »

Possibly PSI? 30 bar is 3 times the level of guarantee for house plumbing?
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Re: How hot is too hot? [DW10ATED MK1 C5]

Post by GiveMeABreak »

No definitely BAR Pete. - But as I said this may include the A/C as part of the 'cooling' system, as I mentioned above.
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Re: How hot is too hot? [DW10ATED MK1 C5]

Post by GiveMeABreak »

As I thought - this explains the influence of the A/C system on the Fan speed:

For cooling of the condenser, the B.R.A.C. function (Air Conditioning Need For Cooling) supplies the F.R.I.C. function (Cooling Function Integrated into the Engine ECU) with a reference speed in accordance with the pressure of the air conditioning circuit.
The linear pressure sensor of the refrigerant fluid fitted on the condenser supplies a voltage proportional to the pressure in the air conditioning circuit and transmits this information to the BSI on the CAN IS network.

The built-in systems interface sends a speed setting to the engine management ECU to control the variable speed of the fan assembly.
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Re: How hot is too hot? [DW10ATED MK1 C5]

Post by Hell Razor5543 »

Marc, is it possible you missed a decimal point? 30Bar is about 450PSI!
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Re: How hot is too hot? [DW10ATED MK1 C5]

Post by moizeau »

The rubber hoses can't take that, otherwise everyone would plumb there house with hosepipe!
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Re: How hot is too hot? [DW10ATED MK1 C5]

Post by GiveMeABreak »

Guys - I don't think you are understanding this is NOT the pressure in the engine water coolant system!
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Re: How hot is too hot? [DW10ATED MK1 C5]

Post by moizeau »

Marc, I had the OP's question in my mind, you went in to too much detail (for my brain) saying why and when the fans cut in
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Re: How hot is too hot? [DW10ATED MK1 C5]

Post by Hell Razor5543 »

GiveMeABreak wrote: 21 Oct 2018, 17:28 The three speed fan system kicks in at 97 °C for first speed, 101 °C (or 17 bar in the cooling circuit) and third speed at 105 °C (or 30 bar in the cooling circuit). The warning kicks in at 118 °C.

That looks like you ARE talking about pressure in the engine water coolant system, Marc.
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Re: How hot is too hot? [DW10ATED MK1 C5]

Post by GiveMeABreak »

:rofl2: it’s late in the day Pete 😀

But as you can see the temperature in the high pressure circuit can indeed reach such high pressures depending on ambient temp which can impact the cooling efficiency:
532919CE-A136-4D7A-A647-BEEFB7ACC30A.jpeg
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Re: How hot is too hot? [DW10ATED MK1 C5]

Post by GiveMeABreak »

Hell Razor5543 wrote: 21 Oct 2018, 18:50
GiveMeABreak wrote: 21 Oct 2018, 17:28 The three speed fan system kicks in at 97 °C for first speed, 101 °C (or 17 bar in the cooling circuit) and third speed at 105 °C (or 30 bar in the cooling circuit). The warning kicks in at 118 °C.

That looks like you ARE talking about pressure in the engine water coolant system, Marc.
yes but I did qualify the definition in a later post James. That was PSA terminology, don’t shoot the messenger. 🔫
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