Thread: Aluminium Radiators - are they good or prone to failure?

The copper/brass radiator (the original) in my ’96 SI Disco is at end of life. The radiator repairer has done a pressure test on it and declared its condition terminal. So I’m now looking at options to replace it.
Options 1 and 2 are to re-core it (quoted $1300) or replace it (quoted $1000). Option 3 is to get a good second-hand replacement (cleaned and pressure tested) from my local parts recycler ($400).

Option 4 has my attention right now. What about replacing it with an aluminium radiator?

Pro’s:

• It’s significantly cheaper than any of the other options (around $300 to $350)
• The engine has an aluminium block and heads and it makes sense to use one metal throughout
• Many modern cars are fitted with ali radiators nowadays – it’s proven technology
• The good ones are robot welded which produces reliably good finish and secure joints
• I can get a 4-core radiator (slightly thicker) which has even more capacity than the original 3-core which will improve cooling efficiency on hot days

Con’s

• It can’t be repaired if it starts leaking
• It’s reported to be prone to fracturing due to vibration
• It’s reported to be prone to corrosion due to electrolysis (more on this shortly)
• Many people are wary of them based on their reputation for failing

Dealing with the cons first

Can’t be Repaired
Actually there are plenty of people who have repaired them and that includes some on this forum. Repair requires special skills and it’s tricky which leads to unreliable repairs. But then if it’s installed and treated appropriately (avoiding problems leading to electrolysis and using the correct coolant with de-ionised water) there is no reason to expect it to fail any more than a copper/brass one would.

Fracturing due to vibration
Clearly it needs to be mounted so that it is buffered on rubber mounts (which is how the disco works anyway). The mounting rubbers need to be in good condition and the radiator needs to be mounted so that there is no torsional stress on it. That shouldn’t be hard to achieve in reality.

Corrosion due to electrolysis
This is where people really seem to get their knickers in a twist with ali radiators. That, I think, is because few people discussing this on the motoring forums understand the mechanism from an electrical point of view and they certainly don’t understand the difference between earthing and bonding.
For electrolysis to occur there has to be a flow of current through the metal and this can happen when the engine is not well bonded to the chassis (the “earth” connection) and the radiator is also bonded (perhaps poorly)to the chassis. This allows current flowing from the battery's positive terminal to flow back to the “earth” terminal of the battery partly via the earth strap on the engine, and partly via the coolant (which has to contain free ions to allow this) and then via the "earth" connection between the radiator and the chassis.

(A complete aside lest someone wants to shoot me down because I referred to current flowing in the positive to negative direction. I’m a broadcast tech and I understand very well that current flows (as physics tells us) due to the transit of electrons from negative terminal to positive terminal. However this concept was not understood in the early days of electrical experimentation and it was assumed that current flowed in the opposite direction. This mis-guided assumption still useful in some explanations, and the use of “conventional current” persists because it can be helpful to explain some things. I’m using "conventional current" here because, here, it is useful, and I choose to do so. But thankyou, I do know all about electrons.)

So while it is true that the radiator should be electrically isolated from the chassis to eliminate the possibility of electrolysis, it is very important that the radiator be electrically bonded to the engine (bonded … not earthed!). This concept is in accord with my knowledge of liquid cooled digital TV transmitters and with lightning protection on high ground transmitter sites. The French company, Thompson made a high power DTV transmitter which was bought by the commercial stations here in Aus for some of their sites and it was, not to put too fine a point on it, a POS when it came to its cooling system. The cooling system had, in its path, copper, brass and aluminium; three dissimilar metals. The coolant was de-ionised water, and yet it suffered horrendous electrolysis issues because of the three dissimilar metals that the coolant came into contact with, to the extent that one of the techs referred to it not by its commercial appellative of “Thomcast” transmitter, but the more fitting, “Dripcast” transmitter; that is, it needed drip trays throughout to catch the leaks. We believe that the de-ionised water did not stay de-ionised due to the construction methodology used in the transmitter. On the other hand, the equivalent NEC transmitters with almost entirely aluminium construction (apart from the heat exchangers) running de-ionised water with anti-frogen, have been fine (the only issues have been erosion of U-bends in the heat exchangers due to cavitation).

So I would contend, based on my experience, that there is a greater risk that the disco will develop electrolysis issues in its standard configuration of aluminium engine with copper/brass radiator and using an aluminium radiator actually reduces the risk by reducing the number of dissimilar metals (note that there is still the brass thermostat and the steel impeller in the water pump).
In addition, I believe that bonding the radiator, electrically, to the engine (not done in the standard Land Rover configuration), eliminates the possibility of the flow of current (electron or conventional) and thus the possibility of electrolysis.

Reputation
I really can’t offer any rebuttal to the reputation argument other than to suggest that maybe it’s a case of “give a dog a bad name and it sticks”. Are aluminium radiators as bad as chatter on the Net suggests? Are Ford Lion 3.0Lt TDV6 engines as prone to breaking crankshafts as chatter on the Net suggests? (In my case referring to the latter, I’d answer yes, but only because mine seized just short of breaking!) If they’re so bad, why do car manufacturers persist in using them? (Because they don’t care as long as the car makes it past the warranty period?)

So I’m hoping to provoke some considered debate here. Please be objective and give me some evidence-based opinions back. I’m interested to see where this goes ….

Thanks everyone for your thoughts.

Interesting because, based on my research so far, I thought that the controversy would be around electrolysis, which is why I went to some lengths to outline my thoughts.

However it seems based on your experiences that any issues I might have if I go down this path are more likely to be around build quality and possible cracking.

To answer one of the posts, I would be looking at a full aluminium radiator rather than one with plastic tanks.

It was this one (yes, yes, on fleaBay) that took my attention initially:

ASI Ali Radiator.jpg

If I do go with this, and I'm still undecided, I'd be inclined to buy it from ASI themselves rather than one of the resellers because I would expect it would be easier to handle any warranty issues. I'd be pressure testing it before I put it in even though the description says they're all pressure tested after manufacture.

Again thanks everyone, and if I do go down this path I'll keep you posted on how it goes.