Coolant alarm screw

[spud350]

A few times over the last couple of years I've had to change the screw that's screwed into the expansion tank. I know it's going as the alarm takes longer and longer to go off after start up. It's a pain in the a**e as I have to wrestle the leisure battery out which is flippin heavy and a tight fit.
It does surprise me however that in such a short time the screw is totally corroded away (and they're stainless). The ring connector also has to be changed as that's virtually gone as well.
Does anyone else get this problem or do I have particularly corrosive coolant?

[Gasy]

Are you replacing with stainless screws
Never heard of them being corroded away ( but I'm no expert )
They should get coated with a protective layer from the coolant and require a good clean once in a while
What alarm do you have

[Northern Bongolow]

what coolant have you in the bongo mate, ive never heard of this happening.
my wife and i have a bongo each both have coolant alarms, neither have been even cleaned in all that time, my mrs is on her second batch of 5 year coolant, so thats 2 lots of red coolant that lays down a dissimilar metal isolation layer on everything.

i use carplan premium red or comma 5 year red.

[Simon Jones]

Is this a Haydn alarm or one of the others on the market? They work by passing a very small current through the coolant which in itself should not cause a problem. Stainless steel screws will not rust away but they can build up a coating.

You may have a bigger problem with electrolysis within the system which could be significant if unattended to. Are you using a decent brand of coolant and has it been changed within the last two years?

[spud350]

Dunno what coolant is in it. It's either the same stuff that was in from Japan or something that the garage I bought it off put in.
The reason I haven't changed is the obvious I don't want issues with cooling system after unnecessary messing about. I just wondered if anyone else has this corrosion issue. The screws aren't attracted to magnets so I assume they're stainless.
Maybe the current going through mine is to much for some reason?

Edit: just bought some pH strips off ebay. This will hopefully prove the corrosive coolant theory or not.

[Simon Jones]

Conventional coolant should be replaced every two years as that is the typical life of the anti-corrosion properties. I understand the 'ain't broke don't fix' approach but with service items with a limited lifespan it's more of a case of 'prevention is better than cure'.

[haydn callow]

Measure the voltage between the screw head and earth with engine running.......
You have A problem not directly related to the alarm.
This. Is a new one!!

Also if you can get a reading you should be less than 50 micro amps at the screw

[haydn callow]

Been in touch with our research division in Oz......?Baffled......where did you get your replacement screws from ???? Are they A4 stainless???
If your eating quality screws I dred to think what else is getting scoffed......
Suggest you do a full coolant flush/ change and phone the webshop for a new screw.....measure the volts/amps and start again......

[haydn callow]

I notice you joined in Feb 2010.....so your coolant is more than 5 years old"......no a good idea....what colour is it??

[rita]

What was the cure the last time......


http://igmaynard.co.uk/bongo/forum/view ... rm#p556446

[Simon Jones]

So alarm appears to be running off the LB and the result sounds like electrolytic corrosion which might indicate a poor earth between LB & engine/chassis. If it were me, I'd put the LCA on to an ignition-switched supply inline with the previous guidance from Haydn.

[haydn callow]

Just read the previous topic of yours highlighted by Rita above.......in that you mention how clean the screw was but you had it wired wrong.....
Suggest you get back to basics and fit the alarm as pier instructions after sorting the coolant.

[spud350]

Right I'll try to answer the questions

Measure the voltage between the screw head and earth with engine running.......
You have A problem not directly related to the alarm.
This. Is a new one!!

Also if you can get a reading you should be less than 50 micro amps at the screw

Right I'll try that this weekend, but i'm not sure my meter is that accurate, will take a look.

Been in touch with our research division in Oz......?Baffled......where did you get your replacement screws from ???? Are they A4 stainless???
If your eating quality screws I dred to think what else is getting scoffed......
Suggest you do a full coolant flush/ change and phone the webshop for a new screw.....measure the volts/amps and start again......

The screws are off ebay, not sure of the material but I've never come across anything other than A4 in normal circulation. That doesn't mean they're not that though. Will get another.

I notice you joined in Feb 2010.....so your coolant is more than 5 years old"......no a good idea....what colour is it??

Erm, yes. Blue or green, definitely not red.

What was the cure the last time......


http://igmaynard.co.uk/bongo/forum/view ... rm#p556446

Good question I can't remember. I think I must have just changed the screw or cleaned the contact between it and the ring terminal or something. Nothing out of the ordinary springs to mind.

So alarm appears to be running off the LB and the result sounds like electrolytic corrosion which might indicate a poor earth between LB & engine/chassis. If it were me, I'd put the LCA on to an ignition-switched supply inline with the previous guidance from Haydn.

If I can brave the cold I'll check the wiring again. I don't recall how it all ended up being done. People say I have a short memory. I've no idea what they mean.

Just read the previous topic of yours highlighted by Rita above.......in that you mention how clean the screw was but you had it wired wrong.....
Suggest you get back to basics and fit the alarm as pier instructions after sorting the coolant.

Righto.

[haydn callow]

There are several grades of stainless...
A2. Is the lowest you might get away with.
A4 is what we supply and is good.

Buying a non standard screw is asking for trouble, the diameter,thread, pitch, length and quality are all important.

Get a replacement from us....( they are free )

Afraid it would seem your problems are self inflicted.

[spud350]

Measure the voltage between the screw head and earth with engine running.......
You have A problem not directly related to the alarm.
This. Is a new one!!

Also if you can get a reading you should be less than 50 micro amps at the screw

Edit: OK something odd here, I'm getting 14v at the ring terminal but also 1.4mA which is massive (relatively speaking) if that 50 microamps is correct. However am I measuring it correctly by putting my meter between the terminal and negative?