testing cooling system health

[nfn]

It's easy to get paranoid about the bongo's cooling system given that cooling-related problems are common in bongos -- as they are in other older cars too (Haydn's coolant alarms offer great peace of mind for this). I was over at a forum for volvo owners, as I just bought a 1988 Volvo 240GL and have been going through it looking for problems. Somebody on the forum suggested testing the voltage of the coolant to look for signs of electrolysis, which will quickly destroy metal parts of the cooling system (rad and heater core) leading to blockages and leaks. The voltage of the coolant should not exceed 0.3 volts, or there is significant electrolysis occurring, along with big cooling system repair bills in your future. Along with checking the clarity of the coolant, it seems like this would be a sensible test to carry out when buying a bongo, and every year or so afterwards. This might be old hat to some of the more technically minded on Bongo Fury, but it seems like a good test for heading off at least some overheating and coolant leaks before they happen. My bongo's coolant (engine and key off) was 0.09 volts. The volvo edged in ahead at 0.08 volts. I wonder how many bongo cooling system failures are preceeded by significant electrolysis?

There's a web page on cooling system electrolysis here, including how to test the voltage:
http://www.myradshop.com/information/el ... is.htm#how

[mikeonb4c]

Crikey

Might this be one for Haydn as he seems to have picked up some knowledge on issues concerning coolant electrolysis?

Ignorance is bliss as far as I'm concerned

[haydn callow]

It's the current rather than the voltage that causes the problems.. more than 100 micro amps can cause problems...
Our alarms run at 2 volts and 25 micro amps......some vehicles have had them fitted for over 10 years (50 micro amps in those days) with no problems at all.
One of the problems of rigging up your own system is being unaware of this.
One guy put 12 volt stright in and no current limitations.....(reinvented the electric kettle)

[nfn]

The low coolant alarm does appear to produce additional voltage in the coolant when the key is in the on position: the voltage (in the expansion tank) with the key off was 0.09 volts, key on 0.32 volts. Turning the key on in my volvo or running the engine made no difference to the voltage measured at the expansion tank. When the key is turned off in the bongo the voltage in the coolant returns to low levels very quickly.

So I guess there could be a trade-off involved in the low coolant alarm: you get information that coolant has been lost, but increase the level of electrolysis somewhat when driving, which is damaging to the cooling system in the long-term. It seems like a worthwhile trade-off -- the increase in voltage is not extreme.

Or I have a minor electrical problem elsewhere... I guess next I should see whether disconnecting the alarm results in a drop in coolant volts with the key on.

[haydn callow]

As I said above...the voltage is not a problem....It's the current that needs to be controlled.

[nfn]

How would one measure the current? -- set the multimeter on amps and stick both probes into the expansion tank to measure current between the two probes through the coolant?

[mikeonb4c]

The low coolant alarm does appear to produce additional voltage in the coolant when the key is in the on position: the voltage (in the expansion tank) with the key off was 0.09 volts, key on 0.32 volts. Turning the key on in my volvo or running the engine made no difference to the voltage measured at the expansion tank. When the key is turned off in the bongo the voltage in the coolant returns to low levels very quickly.

So I guess there could be a trade-off involved in the low coolant alarm: you get information that coolant has been lost, but increase the level of electrolysis somewhat when driving, which is damaging to the cooling system in the long-term. It seems like a worthwhile trade-off -- the increase in voltage is not extreme.

Or I have a minor electrical problem elsewhere... I guess next I should see whether disconnecting the alarm results in a drop in coolant volts with the key on.

Not that this is very scientific, but I have an LCA fitted and didn't change my coolant for 3 yrs and it all came out clear as a mountain stream and looking the same colour as when it went in three years previously. As you say, IF there is a downside then it appears inconsequential compared to the upside.

I have to say (and I don't do product endorsements!) that my LCA has behaved perfectly in the 3+ yrs I've had it fitted.

[mikexgough]

(and I don't do product endorsements!) that my LCA has behaved perfectly in the 3+ yrs I've had it fitted.

You just did......

[mikeonb4c]

(and I don't do product endorsements!) that my LCA has behaved perfectly in the 3+ yrs I've had it fitted.

You just did......

But really I just gave a factual report. I've never had any commercial interest in the products success (as professional 'product endorsers' do), but I've always been happy to see enterprise succeed where it brings real benefit (only wish I had the time, opportunity and entrepreneurial skills to pursue such avenues myself ) .

[g8dhe]

Umm.. I read the start of that article and had to go and rest my brain for a few minutes. I'm not quite sure whether that article is trying to do but it contains an awful lot of nonsense mixed up with some factual statements.
I'll reserve my main comment to its test for electrolysis and how to test for it. First Electrolysis will happen between any and all differing conductive surfaces, it cannot be tested for in such a simple way as explained in the article because your going to use a conductive, metallic, probe which is almost certainly going to be some form of plated brass this WILL be different from the other materials used in the cooling system and hence all you are going to measure is the potential difference between the probe and all the other materials in the cooling system. Perhaps some pictures of a typical classroom experiment will assist - here is my kitchen experiment a plastic pot of water, a multi-meter, probes and two other materials a piece of aluminium and a piece of copper;
First identical probes alone;

A very small reading +0.032 Volts this shows that if you have identical metals then electrolysis doesn't occour.

Next Probe to Aluminimum;

Ah -0.466 Volts greater than his safe level of 0.3 volts.

Finally Probe to Copper;

+0.103 volts

This only shows that if you try to measure a the effects of electrolysis in this way, all you end up doing is measuring the the potential differences between the two metal probes (Here is a table of some of the most common metals).
If all the metal parts in the cooling system were the same material, nothing would happen to the cooling system, but if you used a normal meter probe then you would measure a difference.
Cooling systems aren't all the same material, and until they build up various oxides and other coating then corrosion will occour, and even after they have built up different coatings in some cases corrosion will still occour.

But its not all nonsense, additional currents flowing through the cooling system perhaps caused by other electrical apparatus will cause problems, especially if any of the pipes are not metallic and hence insulate different parts of the system from each other - e.g. rubber / silicone hoses etc.

[haydn callow]

There goes a man (above) who knows what he is talking about......


During the electrolysis process the anode is deposited on the cathode with D/C
The probe is the anode, the rest of the system is the cathode.
The S/S anode doesn't deplete much if at all at that current/voltage

[mikeonb4c]

Its 20+ years since I did my HNC in biochemistry and dealt to a small extent with electrolysis, electrophoresis etc. so I'm rather rusty (no pun intended - ha ha!), but I was prodded into reading the article after Geoffs evaluation. Although perhaps not the best written piece I've ever read, it seemed to more or less describe electrolysis as I remember it.

You've said in the past Haydn, when warning those about to attempt a DIY kit, that the real risk was one caused by thinking you could put an unadulterated 12v through the coolant as port of making the circuit using the coolant as a conductive medium. This seemed to fit with what the article was saying.

Presumably then, the key issue is not so much one of dissimilar metals as in the potential for potential (as it were - ha ha!) to promote electrolytic processes that might have an adverse effect over time. However, as I understand it, the designers of the LCA set about their task recognising this. They therefore designed the LCA to run on the minimum voltage that would allow an alarm mechanism to exploit the difference between the lower resistance of the coolant (when it is present between the upper and lower contact screws in the header tank), and the higher resistance of the air between the screws when coolant isn't present (as when level is too low). Have I got that right?

[nfn]

My understanding of circuits is pretty limited. My understanding is that you can think about voltage as potential energy stored in a battery (or coolant, it appears). To discharge it would require a completed circuit to draw the electrical current (create a flow of electrons?). I figured that if you measure the voltage of the coolant, then you have measured a potential for flow (measured in amps), and hence you also have the potential for electrolysis (which is undesirable in a cooling system). So, I guess I'm confused by Haydn's statement that current matters but voltage in the coolant doesn't, since the two things are related.

[haydn callow]

Voltage is indeed important (but is easy to control).......But current more so (difficult to control)

[g8dhe]

Electrolysis can be confusing because it can arise from two sources.
The corrosion occurs because a current is flowing between two differing conductors it doesn't matter why or the cause of the current.
The first source is due to the use of dissimilar metals, in there own right they will generate a voltage difference, which will cause a current, as you can see in my experiment above, no external source of power is required. In the second case applying a voltage across different parts of the system will cause a current to flow, and hence corrosion, this is the case with the LCA and why Haydn went to such lengths to reduce the current flow down into the region of μA. Normally both situations apply, you have different materials present (first source) and car electrics use the chassis as the earth return for electrical circuits (second source). To do serious damage takes either a lot of current or a lot of time, or the combination of both time and current!

The other thing that causes scratched heads is that the voltage and current don't always obey Ohms Law, because there are chemical reactions going on between the metals and the liquid (electrolyte) these vary with time and temperature and cause all sorts of unexpected results just to catch the unwary!