My c4 is playing games I don't like

[admiral51]

I am guessing your C4 is a left hand drive but i have a C4 2005 and during the winter months i have noticed my coolant level drops a little.
If you put your hand up under the centre console on the passenger side on a RHD so drivers side on a LHD is it damp, not wet but damp if that makes sense?
Somewhere in my hazy memory i read a post about a joint leaking under colder temps, it drips onto the carpet just below the centre console but is easier to spot on RHD models as it is on the passenger side, LHD models will mean extra footfall on that side and in wet weather the drivers footwell would be wetter than on a RHD model

[Cutac]

I'm not sure if the level would've stayed as it was as I've topped it up and won't be letting it get that low again.

Admiral, nope, carpets are dry as a bone. I did run it on temperature set to high to see if pipes in the interior would leak but they didn't.

[white exec]

It's important to find out whether you have a leak, or whether the drop in level in the tank is down to expansion/throw-out.

So long as there is coolant visible in the tank, and covering the connection snout near the bottom when engine is cold, there is no risk to the engine: the level will rise as it heats up.

What we do need to know, though, is whether the coolant remains at the low level (when cold), or whether it carries on dropping. If the latter, you have an on-going leak.

[admiral51]

Hard for me to explain, but you need to put your hand up between the carpet and the centre console, i only have experience of a RHD version but the carpet does not cover the whole of the transmission tunnel,any leak will not show as a wet carpet, it will drip and run underneath and be soaked up by the foam underlay.
Sometimes i have found a small drip on the carpet but only when the temp is very low, touch wood it is heat expansion/retraction related.
You can lift the edges of the centre console up just enough to get your fingers in if that helps.

[Cutac]

It's important to find out whether you have a leak, or whether the drop in level in the tank is down to expansion/throw-out.

So long as there is coolant visible in the tank, and covering the connection snout near the bottom when engine is cold, there is no risk to the engine: the level will rise as it heats up.

What we do need to know, though, is whether the coolant remains at the low level (when cold), or whether it carries on dropping. If the latter, you have an on-going leak.

I know there's no theoretical risk to the engine, but what if I lose, let say 100ml while driving? If the tank is filled to the maximum, it would be alright, but if those 100ml's are on the bottom, it might be interesting. It's just that I don't want to risk it.

Also, why would it be a case of a throw out? It's been fine for 6 and a half years, why would it start to happen now?

Hard for me to explain, but you need to put your hand up between the carpet and the centre console, i only have experience of a RHD version but the carpet does not cover the whole of the transmission tunnel,any leak will not show as a wet carpet, it will drip and run underneath and be soaked up by the foam underlay.
Sometimes i have found a small drip on the carpet but only when the temp is very low, touch wood it is heat expansion/retraction related.
You can lift the edges of the centre console up just enough to get your fingers in if that helps.

I get you, but I think heater pipes are alright. But I'll check under the carpet but I hope I won't find anything except a clean frame

[white exec]

I know there's no theoretical risk to the engine, but what if I lose, let say 100ml while driving? If the tank is filled to the maximum, it would be alright, but if those 100ml's are on the bottom, it might be interesting. It's just that I don't want to risk it.

Also, why would it be a case of a throw out? It's been fine for 6 and a half years, why would it start to happen now?

One cause of throw-out is as follows: A small air-pocket (usually in the head or engine block) overheats (because of lack of direct coolant contact) and then causes what is termed 'local boiling'. The boiling creates steam, which forces coolant up to and out of the header tank. (See also final paragraph, concerning the pressure cap.)

Air pockets can be difficult to dislodge unless the cooling system is filled and bled thoroughly via all the bleed screws, and sometimes requiring the use of a temporary header bottle to push coolant down into the system via the bleed screws, and allow air out. This is one on an XM, where proper bleeding is essential; it may or may not help on the C4:

Header bottle makes a snug fit in the expansion tank neck, using a short bit of hose, and blocking off any overflow pipe.
Coolant level is brought up to about ¼ way up the bottle, and engine allowed to idle its way up to temperature.
Coolant level in the bottle will rise, and air trapped in the system can bubble out.
Level in the bottle maintained at at least ½ full.
Engine brought up to full temp, indicated by the fans(s) cutting in a couple of times.
Every one of the bleed screws (hoses, radiator, engine) opened in turn to allow trapped air out.
Large hoses can be squeezed to also encourage air out.
Engine left to cool; coolant level in the bottle will drop, as coolant returns to the expansion tank.
When cool, empty any excess coolant from the bottle, remove bottle.
Remove any excess coolant from the expansion tank, down to the normal Level marker.

There should be no real risk in driving for a reasonable distance with the expansion tank coolant level allowed to be low (when cold). It will rise as it heats up, and likely more than compensate for any loss which occurs from the tank. What is of interest (as said) is whether it falls to an even lower level after it has completely cooled - as this would suggest a leak from the system, if it isn't being thrown out at the pressure cap/overflow.

One very basic thing I forgot, and apologies for that: Is the pressure cap working ok? When the system is up at full temperature (eg after a drive), if you squeeze one of the large rad hoses, can you feel considerable pressure there? If not, the system isn't operating under pressure, and will therefore be prone to boiling, and coolant loss (normally from the expansion tank overflow . . . which can be checked with a small catch-bottle).

[Fake Concern]

How about trying a kit to find the loss? Like this.......https://www.ebay.co.uk/itm/UV-Dye-Torch ... :rk:1:pf:0

[Cutac]

I've bled it and it's still losing coolant. Lost 100ml today on a 150 km drive(highway and city).
Still no visible leaks!! Especially since I can't monitor it while driving. In the time it takes me to get under the car, leakage evaporates...
Pressure cap is OK.

Fake Concert, I might try something like that or I will take the car to my mechanic. I'll have to think about both solutions.
Problem is that my mechanic is 60 miles to and from and it's not practical for me to go there "blindly".

[GiveMeABreak]

Head gasket or a coolant hose with a small nick in it?

[white exec]

Some coolant mixes/antifreezes do leave a very visible trace (often bluey-white) at a leak - others don't, which isn't helpful. Others produce a very distinctive (anti-corrosion additive) smell.
Here, I use PSA's own PRO coolant, which does both. Has helped pinpoint both heater matrix and engine bay weeps.
As said, a leak-revealing dye might be a good idea.

[Cutac]

Don't think it's a head gasket since both oil and coolant are completely free of contaminants.
Nick in a hose could be.

I can smell a small hint of coolant around the radiator when car is switched off, but radiator is close to the engine so I can't really distinct where it's coming from, exactly. I've found one leak, a small leak from gearbox selector rod O-ring, nothing else. Not even something that looked like there was a leak there at some point.

[white exec]

Try parking up, and leaving a sheet of cardboard/paper under the car, to see whether any drips show up.
If nothing shows up, run the engine and allow it to get fully up to temp, to see whether heat expels anything. (Cooling engines can actually suck in through leaks .)

[moizeau]

Rad on the condenser/front side, like you say the engine is hot and will evaporate. On a 307, similar, you can just get you hand in. Use toilet roll to check, it finds the smallest of weeps. Just done the rad and condenser on my 407 and there was half a hedge stuck between them, and some feathers. The fitting of AC stops you seeing the front of the rad..If the rad could be the problem, you could remove top and bottom hoses, block them up then use the header tank breather to pressure test in situ, not sure what pressure, but a bike pump with an old tyre valve should do the trick

[xantia_v6]

You can't easily pressurise the breather on these tanks. My weapon of choice is a pressure tester. This one is ex-military stores, probably surplus after they got rid of the land-rovers. by coincidence the rubber bung exactly fits the PSA header tank.

[white exec]

Normal working pressure of cooling systems is around 1.3bar. I wouldn't go anything much beyond that for test purposes.