jeff spahn

That is exactly where the leaks were and the type of leaks.

jeff spahn

Let me update that. Came to $275 when I got there and haggled down to $250 (work for a Jewish guy so it rubs off). He used two complete epoxy kits instead of one. He's a 914 guy also. Likes my 928. Said there was something wrong with my 928 cause it had some kind of aluminum thing hooked up to it with this slippery green sweet tasting stuff leaking out.
Funny guy.

jeff spahn

Don't take this thread the wrong way Ron. You did a great job maintaining the car. I just don't have a coolant change schedule in the paperwork I got from you so I don't know the interval. Based on the other stuff you did, I would be safe to assume you did it at prescribed intervals. Now, the Doc that had it before you is probably another story. All of his paperwork doesn't show coolant changes and it seemed he had the dealer do everything.

Randy V

Your assumption may not be accurate - Ron was always too busy chasing poontang to work on the car.

Speedtoys

Yup. That's my problem.

One guy also told me its from from flex in the square shape...those are weak points as the shape of the rad changes in the chassis. Dunno.

j.kenzie@sbcglobal.net

Hi, I know this is an old thread, but why are all aluminum radiators prone to electrolysis, and part aluminum, part plastic radiators are not? They each have aluminum cores isolated from engine ground by plastic tanks and/or rubber hoses.
Just asking.
Dave

Barry Chan

My aluminum rad is 3 years young and it is leaking (very little, must be the fin) also.
I wonder how good of a repair job it is when epoxied instead of welding it?
I am also leaning towards getting a rad from Roger unlesss the epoxy last??

OTR18WHEELER

my radiator is 27 years old, no leaks. what gives?

Bill Ball

I think the tubes are too thin to weld. Epoxy works well unless the leak is inaccessible.

Bill Ball

Mine's only 24. Green stuff and tap water every few years.

OTR18WHEELER

I just use a little bit of bottled spring water to top off, alternate with the green stuff.

dr bob

So I'm trying to get my head around the electrolysis issue. Seems that if there's a voltage potential between the coolant and ground, the last thing I'd want to do is ground the metal part of the radiator. If I do ground it, I would have that full potential between the coolant and the aluminum, virtually guaranteeing corrosion. Perhaps the failures of the all-aluminum radiators is because they -are- grounded, rather than floating electrically and mechanically on the support donuts and the plastic tanks.

I'd similarly think that there'd be a problem at the block if there was such a potential, as the block is supposedly grounded. Check your engine ground straps and connections. Even a small resistance between the block and frame will generate a potential when the alternator is charging.

Thoughts?

z driver 88t

Somehow I missed this thread originally but just ordered one of those radiator caps with a sacrifical anode as a precaution. I've never checked the voltage from coolant to ground before. I'll have to do that this week. I think my 928MS radiator is a couple years old - no leaks yet.

I have been doing a little research on line and there is a pretty strong debate back and forth between whether or not grounding the aluminum radiator is a good idea. I need to do more reading from some sites with more of a chemistry / science background. Part of that decision may have to do with whether the coolant comes into contact with dissimilar metals. Most websites that discuss this topic have been geared towards aluminum radiators on cars with iron blocks and either iron or alumium heads. But our cars have aluminum blocks and heads, so there is no contact with a dissimilar metal, unless I am overlooking something (water pump??)

I have read a few things that give me some ideas. First pH seems to play a role. It seems that over time the acidity of the coolant mixture tends to drop into the acidic range. Some guys test the pH of their coolant using pH strips from a pool store and keeping it close to 7 is a general recomendation.

Also, distilled / deionized water does not conduct elecrticity so using DI water in you mixture (or if you buy the premix stuff that is generally made with a distilled water blend) that will also help reduce the current flow.

Since coolant (ethylene glycol) is not a conductor and DI water is not a conductor then I would think there should be pretty low potential for a galvanic reaction as long as coolant is changed regularly until impurities work their way into the system.

I really have a limited memory when it comes to digging up college chemistry from the gray matter - so this is just based on deduction and what I've been able to glean from a little on line research. It would be great to dig into this further.

dprantl

Some of the pipes in the coolant system are steel. For example, the hard line going down the passenger side of the engine bay terminating close to the coolant reservoir. After 10 years or so, that pipe is usually very rusty. But off-hand, my feeling is also that grounding the radiator is not a good idea. Always use only distilled water and good quality coolant, and if you are really worried, use a sacrificial anode in the radiator cap.

Dan
'91 928GT S/C 475hp/460lb.ft

dr bob

DI water is already starved for ions, and is corrosive to aluminum by nature. Distilled water is a good choice, but the conductivity is obviously affected by coolant and additives. Purified drinking water that's just gone through an RO unit but not "polished" through resin beds might be the best choice, but it's tough to find that casually. So distilled is the water of choice for most.

The voltage differential between coolant and radiator starts with the block, which at least ideally sits at the exact same potential as the radiator, steel coolant pipes and the heater core. When the engine is running, the alternator is generating current to charge the battery and run the accessories. The alternator 'pushes' this current through the block, the engine ground strap, the frame, and the battery ground strap, on the way to the battery. Many accessories run from the alternator end of the positive cable, through the CE panel circuits, the accessory itself, the frame, the engine ground strap and the block. The rest run from the battery end of the positive cable, through the accessory, the frame, the engine ground strap and the block. Common elements are the frame, the engine ground strap, and the block.

I spent loads of time over a period of lots of months casually trying to diagnose a charging anamoly that ultimately turned out to be cured with a new battery ground strap.

Detecting engine ground strap problems is easier, at least theoretically, by just putting the voltmeter between the running engine and a good chassis ground point. Got voltage? That's the potential that's available between the coolant and the rest of the external system components made of metal. Between the galvanic corrosion from that voltage potential and the ion transfer caused by low pH of the coolant, you can see how the block and radiator suffer such serious corrosion damage. The Good News is that the engine ground cable is not expensive at all, and it's relatively easy to replace. If yours is original, it's probably not the nice bright tinned-copper braid that it once was. If your hasn't been replaced in the last ten years or so, add it to your next parts order and replace it the next time the car is off the tires for any reason. It's a five-minute job that could easily save you $hundreds or even $thousands down the road. I'll speculate that many charging system "problems" will magically disappear with the return path from the alternator restored to full capacity.