Cooling system: flush agent + sump w/ crud...?


I have a 1992 citroen ZX 1.4 carb. Prob. foreign to you Americans, but I’m an american living in the UK at the moment so this is the car that i’ve ended up with.

My heater isn’t working and so I’ve embarked on the coolant system diagnosis… I need to at the very least drain, flush, and refil w/ good antifreeze…

I need to know: I have an aluminum engine, thus need to be careful about chemical flushers right? So, would you recommend using a chemical flush agent on my car? Or just water to flush out…

I will refill w/ at least 50% antifreeze mix, though I might use the advise of the person above for 2:1 mix… make sense.

Do I need to worry about the sump of the system that collects corrosion/bits/etc? I have never actually heard of this small detail. Where is this sump depostory of old crud? Is there any way i can actually access it and clean it out? If so (without buying a new water pump) i would be interested in doing it.

I am not sure how corroded the system is, but it hasn’t been flushed out in 6 years and w/ my heater not working (OK not sure on cause yet, I do hope it’s not the matrix) I need to make sure crud is OUT!!).

Thanks V much


what are the symptoms of the heat not working?

have you checked the level of antifreeze in the radiator AND the expansion tank? are they full in the radiator, and between the marks on the expansion tank?

in all likely hood it is NOT quality of the antifreeze that is the problem.

how has the temperature of the car been? does the car have a temp gauge or an idiot light?

when you run the car, shut it off, and feel the radiator hoses. are they warm? is the radiator warm? (BUT DONT GET YOUR HAND/FINGERS IN THE COOLING FAN… IT CAN START AT ANY TIME EVEN WITH THE CAR OFF)
if you can find the smaller hoses which go off into the firewall, (under the bonnet) whoa i just learned british huh? near the center of the car, should be about 1" or so in diameter. feel if they are warm too.

i suspect the thermostat may be broken. after ensuring that the fluids are at the correct level, this is the first thing to ascertain as being functional.

if your car is operating at normal temps, and the inside fan is working, more info is needed.

does the fan blower (inside the car) work, at all different speeds? (is it blowing air, just not hot?)

this summer did the AC work?

BTW, my cars/van and truck are all this age and have NEVER been flushed. (but i have had to put two thermostats in)

Putting in a higher concentration of antifreeze gains nothing. This is why it’s recommended a 50/50 mixture be used. Any higher concentration can cause the coolant to gel.

I don’t suppose they sell a Prestone flush kit over there? If so, that would be what to use. If not, why not order one off line?


Putting in a higher concentration of antifreeze gains nothing.

Not only does it not gain anything, it can increase the freezing point and reduce cooling capacity. It is always best to follow the recommended mixture. It is also generally a good idea to use de-mineralized or distilled water.

It may be a good idea to just flush once or twice with plain water from a garden hose, fill with plain water, then follow the above advice from cappy to check for heat. There is no sense in putting in your antifreeze immediately (unless frost is predicted) since you may have to replace components to get the heat going again.

Once the heat works, use the normal 50/50 mixture. Don’t fuss over a sump; cars don’t have one. Well, Citroen likes to do things its own way; one never knows, does one?

Agree! The best protection is obtained with 50% glycol. That is good enough for Alaska, so it should be OK for most of Europe! Too high a % of glycol will gell it and not circulate properly, and could wreck you engine. To get heat in your car, your engine has to heat up, then the coolant has to circulate properly, then the coolant has to flow freely through your heater core, then the air has to flow freely OVER your heater core, etc. If the car heats up (feel the rad hoses), and the heater hoses stay cool, your heater core is plugged or,if there is coolanrt inlet valve, it is not functioning properly. Also, your heater air inlet door could be defective. None of this is rocket science, and a reasonably good mechanic can fid the problem quickly.