Coolant level - Andrew
Does coolant "find its own level" in an expansion bottle or should it be within recommended levels given by the manufacturer? And if it does find its own level how critical should this be?

The car is my Citroen BX TGD 1990 (written of before). Since the cylinder head has been replaced with a skimmed unit, the coolant level has been of this order:
last Saturday picked up car - noticed trickle of coolant thru filler hole after driving home.
Sunday still trickling out. Decided to check coolant level each am when engine cold
Monday; column of coolant measured 29 cm (manufacturer recommends 25 to 30 cm) coolant still trickling out during use.
Tuesday; column measured 34.5 cm.coolant still trickling out during use.
Wednesday; column 38.5cm (almost to base filler cap)coolant ceased trickling out
Thursday - today coolant level 17.5cm - brand new filler cap fitted

I've had conversations with the garage engineer who did the work. He claims the head was ok and the coolant system was pressure tested and kept its pressure - hence no leaks. Further that the coolant will find its own level - often quite a lot lower than the 25 - 30 cm mentioned in the Haynes manual. He suggested to try a new filler cap which I have just done.

Is there substance in what he says - or do I have to wait until the low level coolant warning light comes on?
Re: Coolant level - Matt
Sounds to me like you have too much pressure in the system-head or gasket must be faulty. Try squeezing the hoses after a run. They should not be too stif or rock hard


Re: Coolant level - John Davis
The coolant level, in the expansion tank, should be sufficiently high so that the main cooling system can be automatically"topped up" when the engine cools down. In use, and the engine hot, the water, in the radiator & engine block, expands and the excess water is pushed into the expansion tank. via a one way valve in the radiator filler cap. When the system is cooling down, water is drawn back into the cooling system via the one way valve, thereby maintaining the correct level in the cooling system ie, up to the radiator filler cap. If the level in the expansion tank is too low, air will be drawn into the system and it is important that the level in the expansion tank must cover the suction tube or aperture, through which the "top up" coolant syphons back into the radiator/cooling system. A slightly higher level, in the expansion tank, than that marked, is preferable to a slightly lower level. However, if the expansion tank is filling up, and water is overflowing from the tank filler, there is some excess pressure, within the cooling system, which is causing this. It could be gasket failure, and the cooling system is being pressurised by leaking cylinder pressure or, there could be a blockage somewhere in the system, ie, thermostat etc. Air trapped somewhere in the system, being pressurised and then expanding, can also force water back into the expansion tank. I would suggest a thorough check on the integrity of the hoses, especially the small hose through which the coolant is syphoned back to radiator, ie, around the filler neck.
As the head/gasket has been attended to and you have been told that the head is "OK", I would suspect that air, still trapped in the system is finding it's way out and, with the new radiator cap, bringing the level back to around 17 cm, small amounts of coolant, added to the expansion tank, over a couple of days, should bring the system back to normal. Yes, as you have been advised the expansion tank will find it's own level but, it cannot maintain a correct level if the level goes too low and air replaces liquid. I am, of course, talking of pressurised cooling systems generally. There may be features of the Citroen design which others could advise on
Re: Coolant level - Don Cox
I think this has been discussed before here recently. French cars particularly, and now quite a few others, have a cooling system that doesn't self bleed on refill. I'm not that familiar with your model of car but the situation you have now reached makes me think that you may have some trapped air in the system.
When everything is warmed up try opening the bleed screw(s), there will be one on the upper heater hose and possibly others. there will also be one on the top of the radiator probably near the filler cap. The screws on the hoses are usually plastic, with a big slotted knurled head, when you open them coolant should leak out under pressure, it wll be hot, keep the screw open until all bubbling stops, and then close.
Coolant does take a couple of heating/cooling cycles to settle down after a refill, but I think your problem has persisted for longer than I would expect.
When we refill this type of systems we apply pressure using our pressure tester and bleed the system whilst it is still cold this allows a check for leaks as well, with no possibility of burnt hands and of course engine damage.
Don Cox.
Re: Coolant level - John Davis
"water is drawn back into the cooling system via the one way valve"
Sorry, my mistake on the previous comment This should read " water is drawn back into the cooling via a seperate tube or waterway connecting the exapnsion tank to the radiator"
Where's DW, then? - Ian Cook
Several postings over the last couple of days should have attracted responses from DW.

You're not up to your armipts in that Land Rover engine rebuild, are you David?

He already knows that this thread - Matt Kelly
is here - the internet elves that keep an eye on things have told him but a considered, accurate and useful response takes time to compose.

There is someone on another forum that I frequent who has written a VBS application to check the forum for certain words so he knows when certain things come up 'cos his VBS app. tells him - cool.
Re: He already knows that this thread - Dave N
I agree. The usual cause of collant being pushed out is a busted head gasket. But all means try a new cap, but I forget the number of times I've bought caps only to find the innevitable head gasket gone.
BX oddities. - David W
Come on guys give a chap a break, I've had a very bad couple of days. Thanks to those who sensed this and mailed to see where I was.


I would have replied to your contact soon but here we go.

Don't worry too much about a day to day variation in a measured coolant level over a couple of inches...if you are sure it has been bled properly. You obviously have my fill and bleed article for BXs so is it worth trying this method yourself to check the garage has got all the air out.

Despite my first comment if there is air in the system this is potentially very damaging for the reasons explained in the article you have.

Note. My comments on coolant level variation assume you have the arangement with the supposed "header tank" on the side of the lower than the highest parts of the system!

I am sorry to say there are many stories in the BX world of engines never being right after a head change, hence my comment that one that has never had the head off (even at very high mileage) being best.

Re: BX oddities. - Andrew
Thanks to all who've come back on this - and David don't throw your "spare BX" away just yet. Awoke this am @3:45 (!!!) and pottered out with torch to remove filler cap and to measure coolant in expansion bottle - yes it is a "strapped to side of radiator version" and yes anxiety neurosis is setting in! Maybe too early yet, but the level was 18.5cm by the oil dipstick (yesterday was its lowest since the repair @17.5cm). If it remains stable over next week I shall assume the system has settled down and top up to the 30cm level. Fingers and much else of my anatomy crossed!

Value my car