On my particular car I did check the coolant voltage. Mine had a voltage of 50 mV. The coolant was just over 2 years old when the radiator developed a small leak. To me, that voltage seemed pretty safe. Most info I've read indicates electrolysis starts becoming an issue from 100 to 300 mV. So I would presume that my case was a manufacturing issue.

Uneven thermal stress was the biggest eater of all-aluminum radiators back when I cared about them. Most folks mounted the radiator rigidly in what they thought was a rigid radiator support. Temps in the radiator change, car goes around a curve, and that boxed aluminum support structure with coolant inside would torque/flex until it failed. Moral-- Mount the radiator so it can move around, and don't twist it with the frame/body. The factory radiator has a baffle/diverter on the hot side to help keep temperature loading more consistent top to bottom. It considers that there's more airflow at the borrom of the radiator so goes only part way down inside the tank. Downside is that there's an isolated/orphaned vapor space at the top of the hot-side tank, which can lead to early end tank failure if the radiator end of the system doesn't purge well during warm-up, through the purge line from the top of the cold-side tank.

I just installed a 928MS aluminum rad and new AC condenser. I also put new mounting rubber top and bottom but left the tops a little loose so the rad can flex and twist just a bit.

The quality of the build of the new 928MS rad looks to be as good or better than a new Behr. Since my insurance was paying the bill, we found the last 928 rad available through NAPA and had it available to compare to the aluminum rad for quality of workmanship and fit.

I had zero problems with the installation but remember to put sealant tape on the overflow tank fitting or you may have a small seep. After wrapping the fitting with tape, all is dry.

For those who don't want to spend crazy money on a Behr, if you can find one, Carl's rad is a good solution.

Type of Coolant
 

I just completed reading the entire thread and didn't see this topic addressed in it previously....

Polecat, I'm having Carl install a new 928MS radiator and expansion tank into my '79 928 and his recommendation is that we refill the system with a 50/50 mix of ethylene glycol (old green coolant) and distilled water, as that's what the engine was designed to use when it was manufactured. I'm not sure if Porsche used a different coolant in the newer cars like your '87 or '89, but staying with the original spec may be the safest bet. Other here may have some additional opinions and insight on what type of coolant should be used, but I'll be sticking with Carl's recommendation.

The only consideration I have when choosing coolant is to make sure its the type suitable for alloy engines. i.e. phosphate/silicate free.

I've seen both green (ethlyene glycol) and orange (OAT) coolants which say this, and also seen both types which do not.

Thanks for the info.

Please see the thread with the name "Ground Radiator"

https://rennlist.com/forums/928-foru...l#post10806744

I posted pics of suspected electrolytic damage in post #43

I have a "DEVEK" radiator for 12 years when I put it in m car I left the top rubber loose so it can flex and twist also. I also put in a 50/50 mix of ethylene glycol an and distilled water It has not run hot all this time an with 165,000 miles it runs great every day. If you keep up an change things that are getting old on the car the 928 will last a very long time. Vernon

Seeing as how this thread is staying updated, I want to mention that I have an BEHR radiator that I replaced with a 928MS radiator. It's in great shape, save for the leaking passenger side end cap, which is what prompted the replacement.

I'm willing to sell it to anyone who wants to take it to a repair shop for new end tanks, and have minimal downtime on their own car.

Our first batch of CSF radiators arrives tomorrow :)