continuos stream of small bubbles in exp. tank

maxgreenwood · Post by **maxgreenwood** » Mon Jan 19, 2009 7:40 pm

no coolant being lost at the moment.

maxgreenwood · Post by **maxgreenwood** » Wed Jan 21, 2009 11:01 am

quick question:

if the plastic reservoir things on the edges of the radiator are heating up but not the rad is it blocked? After driving the car for a while and the engine heated up, heater matrix chucking out hot air, the rad was cold. The rad only warms up if the car has been idlling stood still for 40 mins.

Geoffrey Gould · Post by **Geoffrey Gould** » Wed Jan 21, 2009 11:48 am

Hi I dont want to muddy the water and make things more complicated than they are but check the water pump, I know its a pain but quite some time ago I had symtoms of air getting into a cooling system but no one could find anything wrong. When the water pump was reving and there was pressure in the system it was sealing, when it was not reving, on tick over, it was drawing in air past the gland. It was one of those things where there was no logical easy explanation, the pump did not leak either. Replacing it cured the problem.
Something to think on perhaps although it does in all honesty point towards a porous/cracked head. K-seal does work. BUT get the rad sorted and change the thermostat it could save you a whole load of heart ache.
Doc had a (new) rad block up in 9 months and he is always spot on with the 'anti freeze'.
All the best.
Geoff.

BX Bandit · Post by **BX Bandit** » Wed Jan 21, 2009 12:01 pm

That's a nugget of golden information from Mr Gould Snr! I never would of guessed that in a million years!

On the rad, if it's cold after a run but gets hot on stand still then the rad is doing it's job and giving it's heat up to the passing air. Leave it to idle 10 mins and it'll get hot again all being well.

maxgreenwood · Post by **maxgreenwood** » Wed Jan 21, 2009 1:23 pm

thanks, i'll put the water pump on the list to check. the service record shows no signs of it being changed, even at the last cambelt change.

do i need to get a new seal for the thermo housing for when changing?

toddao · Post by **toddao** » Wed Jan 21, 2009 7:40 pm

Max wrote

do i need to get a new seal for the thermo housing for when changing?

There's a gasket involved yes or two depending on whether the bolts want to come out or not. You'll just need the big one that goes between the two halves if the housing opens easily but sometimes the bolts are rusted in there - perhaps apply some penetrating oil if you can. Also the thermostat can be very hard to remove - the action of water again. You need some good circlip pliers and a vice - and a new seal for when you put the thermostat back.

mountainmanUK · Post by **mountainmanUK** » Thu Jan 22, 2009 4:30 pm

It's also worth remembering that ANY tinkering about with the coolant system on a TD BX leaves a good chance of getting a dreaded airlock somewhere in the system. It's a well-known fact that Tds are notoriously difficult to bleed properly!! (I know that from my own experiences!).

Last time I had my rad out for flushing, all seemed OK when refilled, bled, etc., etc. . An hour and a half, and 95 miles down the M6 later, the red coolant warning light came on!!! Pulled off the M6 and into the first layby, and re-bled the system again. About 15 minutes later I was able to resume my journey, and have had no further coolant problems since (about 4k miles ago). I really thought that I'd blown the HG or similar, and I was extremely relieved to get it sorted so easily!

Moral of the story......bleed the system properly in the first place....and don't always assume the worst! BX's are a pretty eccentric old Froggy bird, and like to wind us up from time to time!

Dave

maxgreenwood · Post by **maxgreenwood** » Thu Jan 22, 2009 4:39 pm

ah a ray of hope cuts through!

thats interesting. This bubbles thing only began after i'd replaced the short fat thermo housing hose, and i thought i'd bled it properly. The car was in the garage shortly before this for the bradied back hoses and they drained and refilled with coolant and bled properly.. the problem wasn't there then.

i re-tried to bleed last week but kept getting these bubbles and fizzing from thermo bleed screw and top rad bleed.

a small amount of air collects at the top of the rad too, i can bleed this out.

I must check the temperature sensors work - what do i do, bridge the wires on the sensors on the back of thermo housing? I've never seen my lights come on, so i need to know they work. they don't come on apparently in the 1st key position when the others come on.. the BX manual confirms they don't too.

BX Bandit · Post by **BX Bandit** » Thu Jan 22, 2009 6:38 pm

I think just removing the wire to the two sensors on top of the thermostat housing should cause the amber and red warning lights to come up!

If the bubbles are due to air trapped within the system (and so not 100% bled) then as the bubbles escape, the water level should go down by displacement.

Way2go · Post by **Way2go** » Thu Jan 22, 2009 9:11 pm

BX Bandit wrote:I think just removing the wire to the two sensors on top of the thermostat housing should cause the amber and red warning lights to come up!

I believe the light's are switched on by the sensor grounding the minus side of the lamp supply to chassis. Soooo.... that will not work.

BX Bandit · Post by **BX Bandit** » Thu Jan 22, 2009 10:00 pm

/\ ner na ner na ner na ner...clever cloggs!

I am but thinking of the two pin connector on top of the thermostat housing (on a/c models) so I have it seems..........wait for it............got my wires crossed!

RichardW · Post by **RichardW** » Fri Jan 23, 2009 9:17 am

If the cooling system is still under pressure in the morning* then the gasket or head is FUBAR

My BX TD was like this for 4 years / 70k miles when I was less initiated, and always used a bit of coolant. Eventually it started loosing coolant more rapidly, and it had to be decapitated.

Normally there is no system pressure when cold. As the the system warms up the coolant expands and compresses the air in the header tank, causing pressure, once cooled again the pressure is reduced - so there should be no pressure in a cold system. If the HG is leaking then pressure is built up in the system by the combustion gases - up to the point where the cap beings to simmer and relieve the pressure, however, because this is higher than the normal temperature related pressure, once the system cools down there will still be pressure there.

*try this: remove cap cold, take for a run, leave to go cold overnight, check pressure.

maxgreenwood · Post by **maxgreenwood** » Fri Jan 23, 2009 1:30 pm

Hi Richard,
It has a small residual kind of pressure in the morning if i've run the car the night before.
I'm going to have to wait til next week now to properly run through the whole system, flushing rad, new thermo, checking hoses, bleed til i can bleed no more and see if the problem persists. If so, i think i'm going down the K-seal route for the time being as i can't really afford the cost/time/learning curve of replacing the HG or head at the moment. A couple of hydraulic things to sort out, if they go well i might consider the head again then.

DLM · Post by **DLM** » Fri Jan 23, 2009 6:09 pm

Best tips I ever picked up about coolant-bleeding a diesel BX were:

(1) Finding an appropriate slope to work on, and parking the car diagonally nose-up with the filler at the highest point.

(2) Not so applicable to a TD as it has a header tank, but the use of an o-ringed 2litre plastic drinks bottle as a makeshift header tank.

(3) Topping up after the first decent post-fill run, repeating the bleeding process. A fair amount of top-up can be needed.

DavidRutherford · Post by **DavidRutherford** » Fri Jan 23, 2009 6:59 pm

RichardW wrote:If the cooling system is still under pressure in the morning* then the gasket or head is FUBAR

Not necessarily.

If the head gasket has failed, then I would expect no pressure at all in the morning, as all the pressure would weep away though the fail.

Cooling systems always generate a bit of steam, and hence usually run at the rated pressure of the pressure cap. I would expect some of this pressure to still be there in the morning.