dr bob

Fellow shark chums,

Zinc is used as a sacrificial metal anode in radiators and cooling systems, so that any electrical or ph-related potential is spent on extracting zinc ions before the precious steel and aluminum is given up. These work on metal radiators, where the anode is immersed in the coolant. Meanwhile, the reservoir cap on my car is inches from the normal coolant level, and is seated in the neck of the plastic coolant reservoir. So no regular coolant contact, and no ground path from that anode. So save your money.

dprantl

FYI, they sell special caps that have the sacrificial anode on an adjustable plastic rod that's almost a foot long.



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

dr bob

Nice! That takes care of issues around pH control. But doen't address any of the electrolysis concerns.

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Side Note: Boaters will appreciate the need for sacrificial anodes to protect metal parts exposed to the water. Several years ago now, I noticed that our "zincs" were being consumed at an incredible rate. It took a while to trace the 'problem' to a small neighboring boat, where the owner had decided to buy a standard automotive charger for his on-board batteries. The charger had a wicky ground, and the difference in potential 30 feet away in seawater was enough to eat through the zincs on all the surrounding boats. Better the zincs than props and shafts and bearings. Owner pleaded ignorance, despite pretty clear marina guidelines about using shore power.

victor25

I was just talking to Jeff, who gave up and went to a new Behr radiator. My question is this... what is causing the PH drop, acidity... from what I understand its the antifreeze aging and loosing it's properties, yes?? Surely most of us do not drive our cars in the winter, and most never see freezing temps. So why are we putting antifreeze in our cars? What other options do we have?

How about this for starters... http://www.ebay.com/itm/Evans-NPG-C-...p2054897.l4276

What about using distilled water and say 20% antifreeze with maybe some water wetter?

Bill Ball

Thank you, Dr. Bob! I had read long ago that radiator grounding is not a good idea, but I could not recall the reasoning, so I stayed out of this thread.

z driver 88t

I think there are at least a few of us with 928s as daily drivers, myself included. North FL gets about a dozen or so hard freezes a year, so while antifreeze isn't critical, its definilely needed and I did have an engine block crack one winter from not having antifreeze in it. Luckily is a $500 Z car engine that can be swapped in half a day.

But, a 25% mixture should protect you down to about 10 degrees F, which would cover a good part of the southeast. I've thought about that as well. However, I don't recall the ability of water to act as a buffer solution. In other words, just increasing the water concetration may not affect the final pH. It's not like adding pH 7 water to a pH 3 acid will give you a pH 5.5.

The waterless coolant is neat stuff and has been discussed here before, but I don't think anyone has discussed its long term pH stability. Worth looking into.

fraggle

I'm just going to get the cap with the sacrificial anode cap and wait until something leaks.

GregBBRD

Mark Thomas had huge problems with radiators and had a complete song and dance about checking the voltage in the cooling system and suggested grounding the radiator, as I recall. I've got a copy of what he suggested doing, around here, somewhere. Not really sure if there was "science" behind what he suggested doing or if it was just an excuse for leaking radiators.....he might know.

I've yet to see an aluminum radiator survive for 4 or 5 years.....much less 20-30 years, like the Behr units did. However, now that new Behr radiators are becoming scarce (I've still got a few, on the shelf) someone, who puts quality first, is going to have to come up with a viable alternative.

I've used the genuine Porsche Coolant, which they engineered to work in these cars and don't screw around with the cheap aftermarket stuff, which seems to turn acidic after a year or two. Consequently, I have had very few "radiator issues".

I know this:

The 996 and Boxsters that have always had the genuine Porsche coolant in them, seem to have no radiator issues. The vehicles that "got" aftermarket coolant (after a water pump or leak repair) seem to all have radiator problems. I've installed quite a few....and these cars are not my specialty, by a long shot. I end up flushing out all of this crap and filling them with the "real" stuff.

The "Porsche Coolant" is expensive, but not nearly as expensive as a radiator.

victor25

So Greg, where do we get the Porsche coolant? and at what cost? Is there a source other than the dealer?

z driver 88t

From what I've gathered in the other subforums of Rennlist and elsewhere on the web, the Porsche coolant seems to be relabeled Pentosin (same as for VW/Audi). It's still pricey, but can be found for less $$ when you remove the Porsche label. This is also used by several Porsche dealerships according to various posts by guys in the late model forums that are still using the dealerships for service and repairs.

http://www.pentosin.net/pressrelease...luid_Guide.pdf

GregBBRD

Dealer stuff.

Part number: 000 043 301 49

GregBBRD

These discussions on radiators and coolant always confuse my logic center.

There's a consistent point that I'm always trying to make. An original Behr radiator will last for more than 20 years.

I've yet to see an aluminum one make it 5 years.....

Where's the economy in replacing a $700 radiator every 2-5 years?

And as far as using cheap coolant that you replace every couple of years.....is that cheaper than using the factory coolant and leaving it in for 10+ years?

My logic center calls this: "False economy".

Carl Fausett

The electrolysis issue -

These pics are of a head from a 300 HP Euro 4.7 motor.

Using tap water (with high mineral/conductivity); not using anti-freeze (which contains anti-corrosion properties) and not having a good block ground causes this.

Sometimes we can grind out, weld up, and machine the head to save it.

Sometimes we can't.

(Note pictures below are from two different sets of heads. The first set was too corroded to save. The second set we were able to save).

Carl Fausett

Ridiculous comment. Aluminum radiators have been OEM for how long now? The 928 radiator core is aluminum, for chris'sake. And what fails on the 928 rad is more often the plastic end tanks - not the aluminum core.

False economics: buying an over-priced Behr radiator to get away from an aluminum radiator when it is itself an aluminum radiator.

FLYVMO

Some interesting info from Ron Davis Radiators, which I believe were the manufacturer of the Devek radiator. By the way, mine is 10 years old and I have had no problems. But it was always grounded, distilled water/anti-freeze mix only was used, and new rubber mounting pads were used.

1. Non-Racing Radiators
A. Custom radiators - Saddle type mounts absorb chassis flex, which can ruin your radiator. The lower mount should be under the tanks only; this is the strongest part of the radiator. The upper mounts should be at the ends of the core or where the tanks weld to the core.

B. Factory Fit Type Radiators - May have flanges that bolt the radiator in solid. Rubber grommets or vibration isolators should be incorporated into the mounting of the radiator to absorb chassis flex, which can ruin your radiator.

INSTALLATION INFORMATION
Completely flush the cooling system before installing your new radiator; this will help keep foreign matter out of your system at radiator installation. Cooling systems require a through flush of the radiator, engine, overflow tank, hoses and heater core. Failure to do so will lead to mixing coolants and contaminates and creates a corrosive cocktail for the radiator. Do not ruin your new radiator by improper filling! Aluminum radiators must not be subject to pressure surges that result from air pockets in the engine. When air surrounds a cylinder or area next to a combustion chamber, the metal becomes very hot. When water comes in contact with the hot metal, a volume of steam is produced that is larger in pressure than the cap can release. The resulting pressure bulges the tubes in the radiator and reduces the airflow and cooling capacity. It is very important that your engine be completely full. Use a quality coolant and follow the manufacturer’s instructions. If possible avoid brass parts in the cooling system. Brass and aluminum react to each other and cause electrolysis. Electrolysis strips away metal at the inside of your radiator and eventually creates leaks. Dissimilar metals, contaminates and improper maintenance of the cooling system lead to failure in the radiator. An electrical current can be generated by the rear-end transmission. This is particularly true with air bag suspensions, rubber pad suspensions and rubber-mounted transmissions. Any current generated will travel up to the drive shaft to ground through the engine coolant. Grounding rear-ends and transmissions are strongly recommended.

Just some interesting reading and perhaps clues to why some have higher failure rates than others?

Cheers!
Carl