911tracker85

sorry to resurect this thread, but out of curiosity I called one of the local porsche dealerships and asked what they suggest for coolant in 928s. "just go to autozone and get the green stuff...." I did quiz the guy, suspected it would have been a waste of both our time....

I checked with a local audi dealership on the price for the blue coolant suggested by Malcolm. $26 a jug. I checked and the red audi coolant I got for the A8 is a different part number.

getting a couple jugs of the Zertex G-05 from roger.

move along .... nothing more to see here ... move along

dr bob

My local mainstream retail places no longer carry the Zerex. The local K-mart used to carry it too, but no longer. Found it at a CarQuest warehouse store in the City of Industry, conveniently on the way home from our monthly PCA gathering. Otherwise I have to drive over to North Hollywood near Ryan's neighborhood to get it. Point is, you can find it but it's not always at the local Autozone/Advanced/Pep Boys/Checker/whatever. Plus it gets changed only once a year, so it's worthwhile just keeping a casual eye out for it as you do your normal shopping.

tv

PEAK Global™ LifeTime™ Antifreeze & Coolant - Antigel/Réfrigerant features a patented, advanced organic acid technology (OAT) that provides guaranteed LifeTime protection -

Provides guaranteed LifeTime protection - for as long as you own your vehicle - Formulated for use in all American, Asian and European automobiles

Features a patented non 2-EH formula that is phosphate-free and silicate-free





Aluminum and ferrous metals form a surface-layer of corrosion in the presence of moisture, even the little bit of moisture in the air. OAT coolants anneal this metal-oxide layer into a thin surface coating that protects against further corrosion. With either type of inhibitor, there must be enough in the coolant solution to occasionally re-establish the barrier as needed.

Silicates plate out quickly on metal engine parts; thus, the silicates in a coolant solution can drop to less than 20 percent of the starting level in less than 10,000 miles. Another problem with silicates is that, under certain conditions, they can drop out of the solution and form minute deposits.

If this occurs between a shaft and seal, the resulting abrasion will eventually cause a leak. In a cooling system that turns off coolant flow to the heater core when the heater is not in use, silicates can form a gummy deposit that, over the course of a summer season, might clog the core tubes.

dprantl

Any coolant that is advertised as lasting a "lifetime" is a LIE. Unless of course by lifetime they mean 100k miles, after which the car falls apart. This is just like the "lifetime" transmission fluid, what a crock.

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

tv

It is not the lifetime part that is important here, it is the chemical make-up, mainly whether the coolant has any silicates or not.

I won't use one that has it.

AO

Very informative. Thank you.

I've seen a number of 928 engines pulled apart now. The block is generally in excellent condition. There is usually some scale, but no pitting or active corrosion. I attribute this to the alusil material.

The heads on the other hand seem to be prone to corrosion and pitting. My '91 GT had green coolant in it when I bought it. I changed it out to the Zerex G-05 and that is my coolant of choice for the 928's.

I had a head gasket failure... well not exactly. The head had corroded around the fire ring of the HG allowing the coolant to seap past it and get into the combustion chamber. Whan I pulled the head, the HG fire ring looked fine. It was the head that ad failed.

Luckily I was able to get it welded and decked. All is well now.

dprantl

Ok I see.

Dexcool (OAT) is phosphate and silicate free. It is subject to numerous lawsuits for severely damaging engines. I'm pretty sure the Peak stuff you link above is the same as Dexcool. I have seen with my own eyes the gelling and crusting that happens with it.

Zerex G-05 (HOAT) is phosphate free and "low silicates". It is used by Mercedes in their cars from the factory. Note that Mercedes has many all-aluminum engines, some even have Alusil-similar engines made by Mahle like the 928 does. I have never heard of any complaints with G-05.

So you are saying you still want to use an OAT coolant in a car that was not filled with it from the factory? It's your engine...

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

tv

I will redo my research and will post what I find. I did the original research a few years ago. I believe the Dexcool problem was a certain ingredient unique to Dexcool that caused the issue and not the whole category of OAT tech.


http://sancarlosradiator.com/images/...-%20Z-1217.pdf


http://www.search-autoparts.com/sear.../detail/159744

dprantl

Reading that chart... is it really true that Audi/VW/Porsche have been using only OAT coolant in all new cars since the late '90s?

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

tv

The Dex-cool problem (or what I found)- It would be hard to believe that a different company would still be selling anything that could possibly result in the same mess. From my reading the dexcool was incompatible with a plastic intake manifold gasket used in gm engines. ( Just as Glen said on page 3 of this thread. )

Also some of you have posted that Dexcool specifically could not be mixed with any other coolant. Whereas PEAK say that Global Lifetime can be used to top off any color coolant.


dexcool mess

http://www.bobistheoilguy.com/forums...Number=1527004

http://www.imcool.com/articles/antif...l2007Part3.php

http://www.sancarlosradiator.com/dex-cool.htm

tv

Looks that way to me



I am still searching but I would point out that my 928 came with dino juice and I now only use full synthetic. Technology improves.
Still looking at the coolant though.

tv

OK- just got off the phone with the tech guy at Peak (Old world industries) and read more. I am confident that Peak Global is the stuff for me to use in my 928. The tech guy agreed and said their stuff is different than dexcool.

Dex-cool uses 2-EHA which among other things is a plasticizer which has the effect of softening plastic


PEAK GLOBAL LIFETIME Features a patented non 2-EH formula


I am staying with Peak Global with no silicates or phosphates

SILICATES deplete in conventional coolants and are linked to water pump gasket failure and are most prone to dropout problems.

Leon Speed

According to Dr. David Turcotte of Valvoline Co., cooling systems are mechanically designed to work with specific types of coolant. Filling a system with the wrong coolant could cause problems. In a 300-hour test of OAT coolant in a Ford engine designed for HOAT coolant, the water pump impellor and backing plate were seriously damaged by cavitation corrosion. Turcotte and Fritz both told us that it’s not possible to have one product that meets the coolant requirements of all the different automakers. Because some OEMs require silicatefree coolant and others mandate the presence of silicate, “one size does not fit all.”

http://www.search-autoparts.com/sear...27/article.pdf

tv

yeah I read that, but OAT coolant is a category not a brand, many differing types of OAT. I am happy with the choice I made. Last time I checked Ford did NOT build my 928.

dprantl

Interesting, maybe the Peak coolant does not have the Dexcool drawbacks. However, I will stick with what Mercedes recommends for the Alusil-sleeved AMG engine that puts out 109hp/liter in my 928 engine: HOAT G-05. YMMV.

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