Using incompatable coolants

[haydn callow]

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"

[francophile1947]

Thanks Haydn - I particularly liked the black/grey finger test

[mikexgough]

Thanks Haydn - I particularly liked the black/grey finger test

I better try that next time I take my shirt off...... you should see the colour or my collars some days.....

Been done here....... http://www.igmaynard.co.uk/bongo/forum/ ... g+coolants Thanks to Scanner...

[djswain1]

We had a 'slime problem' at work on the heat exchangers on new marine diesel engines causing them to run too hot and in some cases overheat.
They have a salt water cooled heat exchanger (instead of a radiator) and the slime would coat the surface of the heat exchanger tubes bundle preventing the heat from transferring. The engine manufacturer did lots of testing with varying types of coolant and reckoned the problem was caused by silicates dropping out of suspension in some brands of coolant causing the slimey film.
The coolant they recommended to use to prevent the problem is a silicate free etheylene glycol OAT extended life coolant (Texaco Havoline XLC). The problematic engines needed the heat exchanger tube bundles removing and cleaning and the cooling system flushing thorugh fill with the XLC coolant and hey presto no more problems..

Might be the that the slime problem is the same and is due to coolant with silcate in..