Water alarm or voltage problem?

[miker]

Some more info to help diagnose issues with the water alarm....

My problem in the end was down to a corroded screw and unscrewing it from the expansion tank and screwing back in cleaned it sufficiently for the alarm to work again, however, when I replaced the screw with the new one that Haydn kindly sent me gratis , I found the time that the alarm sounded when the ignition was first switched on (the self test) was significantly shorter with the new screw than with the corroded screw. Hope that helps someone else......

[haydn callow]

The fact that your sensor screw became coated/corroded implies to me that your coolant mix could well be a bit acid........have you had a fairly recent coolant change and was the system "flushed" after draining the old??
This has happened a few times now and in every case so far the coolant had been changed within the past 12 months....If it is coating/corroding the SS sensor it could be doing the same to the RAD and HEAD.....I would suggest the system is flushed with the correct fluid in the near future.
It's all about mixing coolants and silicates coming out of suspension.


I have now had 3 bits of feedback from peeps (and there have been a few in Oz)..the problem has been that the Low Coolant Alarm has developed into a almost continual "twittering/blinking" condition.
This is often caused by a bad connection.. In a few cases it has been caused by the "probe" screw in the front of the expansion tank (immersed in coolant) becoming coated in a slimy grey substance...This causes poor conductivity and the above symptoms....Some have put this down to a condition known as electrolysis...our investigations suggest this is not the case as the voltage at the probe is only -2volts and the currant less than 40 micro amps (this is tiny)...further investigation has shown that in every case reported the symptoms have only emerged soon after a coolant change. The info below confirms what I had already suspected.
Anyone thinking of changing their coolant and are not 100% sure of whats already in there should give the system a thorough flush and I would suggest a good flushing fluid. Getting it wrong can turn your coolant acidic.

What happened to that probe screw has happened occasionally here too.

In every case it has been found to be the result of incompatible coolants being mixed
and causing them to become acidic.
This acidity them eats away at radiators and cylinder heads, water pumps etc.
The oxide is then carried away around the cooling system and deposited everywhere
including on the probe.
Taking the probe screw out and wire brushing or replacing it will make the alarm work again but will not fix the possible underlying problem


I had a customer tell me he had constant problems with false alarms after fitting an LCA
I didn't realise he had changed his radiator and coolant at the same time.
2 years later his radiator failed.
He blamed the LCA.
Further investigation revealed he had used an incompatible coolant without flushing.
After a new radiator, a complete flush and the correct coolant, his alarm functioned perfectly.
The coolant mix had eaten his new radiator away in 2 years!

A quick check is to wipe a finger around the inside of the radiator cap neck.
If is comes out black/grey, there is a problem.
This is fairly common these days with all the different types of coolants out there
and many of them claiming to be "Universal"

[miker]

I have replaced the coolant twice in the last 18 months, once due to a pin hole leak in a main pipe (which the LCA warned me about ) and once when I replaced the thermostat after seeing too high a running temp' after changing the temp' gauge to read something useful. Neither time did I run any system flush through though! I just ran a hose pipe through and then filled with coolant until I had the 50/50 mix flowing out. I think I'll flush it and replace the coolant again just in case. The small amount of coolant that flowed out when I replaced the screw was the same colour as I had filled and no grey/black gunk on the cap. The old screw was 'rusty' for the last 4 threads and the point of the screw had corroded off. I wouldn't be surprised if the original coolant was at fault but I'll flush and check the rad just in case. I'd hate all this effort to be wasted and the head go anyway, the wife would string me up if I killed her beloved bongo!!!

[haydn callow]

I would suggest you put a flushing solution through it.

[miker]

Will do, thanks for the timely advice.

[haydn callow]

Don't forget to bleed it properly....good luck.