Porsche Enthusiasts Club Forum

Hi I am planning to do a coolant change soon. Which is the best choice of coolant to use? I'm not 100% sure what is currently in the car, it could be blue but it could also be green I can't tell for sure.

For convenience I had thought about using Halfords Advanced OAT coolant

http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_219452_langId_-1_categoryId_255224

Any thoughts?

Also I suspect that if I am changing coolant type then I should do a full flush first. I am thinking that I would drain the current coolant, fill it with hose water and a coolant flush of some sort perhaps Forte. Run the car for 30 mins then drain it again. Then fill back up with new coolant and distilled water. Any opinions?


Cheers,
Mike

Having looked through the products on the Halfords site I have noticed this

Comma XStream G48 Antifreeze
http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_759381_langId_-1_categoryId_255224#tab1

Which claims to be suitable for Porsches up to 1995 except 911. VW/Audi/Seat/Skoda/Porsche (TL774-6)

http://www.halfords.com/wcsstore/libraries/document/comma-xstream.pdf

A better option perhaps?

Hi Mike
Thats what i have put in mine ,but Halfords did,nt have a clue and said any antifreeze would do My local motor factor looked up the right spec, you will need two cans of the stuff as i think its about 16 lts of coolant in the system
Cheers Grahame

This is a very timely thread!

Have been spending today installing new rad in my S4 after old one sprang a leak (I still don't know if leak was from core or the more common failure of side tank weld). Almost done - just the fan shroud to put back now.

When I last changed coolant couple of years ago I used Halfords Advanced which is an OAT (organic acid) which somehow I'd got into my head that that was correct for aluminium heads. In fact it's a no-no for 928s! The Advanced in fact says on label for post-1998 cars.

That Comma Porsche-approved coolant was not there when I looked last week when I bought new coolant preparatory to changing rad, so it must be new stock. It looks ideal and I'm pretty sure heard people refer to the VW G11 coolant which it is on Rennlist. I bought the regular Halfords which should be fine and friendlier to silicone seals than the OAT pink stuff.

After draining block today I flushed it repeatedly with water till it ran perfectly clear, so I'm pretty sure all the OAT coolant is out the system. No need to flush rad with a new one of course, and I'm taking opportunity to replace the top and bottom hoses while I'm at it.

Thanks for pointing out the Comma product. Usually I keep all 928-related receipts but somehow don't have the one for the coolant I bought in Halfords, or I would be tempted to exchange as I'm probably refilling the system tomorrow.

G-05 seems popular on Rennlist but it may be to do with availability as I think it may be designed for American cars. G48 (aka G11) seems like it might be a good choice as it specifically states Porsche. I think they are both phosphate free which I have seen several posts mentioning is important. I suspect that my car may have had G48 (aka G11) in it as I think it is blue, in which case it should be safer to stick with the same kind. Either way I'll be doing a flush as I am not 100% sure what was in it.

If you are going to change the coolant type (for example blue/green to red/orange) I would recommend waiting till the weather is a bit warmer, draining it, filling it with just water and going to a 20 mile blast before draining it again and refilling with the new type.

Any trace of the old blue coolant tends to turn into a weird crystallised jelly when they have mixed and typically causes obstructions to flow in the heater matrix, radiator, around the thermostat and cylinder head. Anywhere that there is a constriction in the flow.

Going for a blast, ideally with the heater on, will ensure anything left in there is extremely diluted.

I personally would either stick with blue or switch to red longlife, as getting hold of blue to top up in years to come may become tricky.

I mention doing it in better weather because driving around in a car with just water in the cooling system even on a 2 degree day (or less) at this time of year can result in a frozen rad when you account for wind chill.

Dont use tap water!!

OAT will work with most (if not all) aluminium engines (I'd use it in the Stag (an engine known for having alloy heads of a dubious material quality) if I was more sure of certain facts (read on...)). The post-98 label is more to do possibly with the construction of the radiators (which is another can of worms in itself). There has been quite a bit of debate over the years over whether OAT can deteriorate the solder on copper cored radiators, something which many a manufacturer continued using until the end of the last millennia (Rovers for example (MGFs/TFs depending on year will have different coolant specifications on many a manual!). Some reckon it does attack the solder joins, yet others believe it is only the older type of solder that it attacks (closer to pre-war stuff) since the type of solder itself changed).

My current 944 has OAT in it (and has done for many years) and AFAIK it has been fine. My previous 944 did not, and had a failed heater matrix: the only copper cored item in a 944's cooling system (it was leaking surely enough at the tank to core join, and it had been leaking for quite a bit of time over the years. The receipts did say that the car had OAT coolant in it but the coolant was fairly black in colour when I acquired the car (probably from several doses of K Seal etc...). An old MGB of mine however ran fine for a year on OAT which is a cooling system based on copper cored bits! No rusty coolant was present either.

OAT seems to last almost a lifetime though and offer superior corrosion properties (I believe OAT is more inert, whereas IAT (blue) coolants tend to react more). Either way, old Peugeot 306s I have owned with mixed metal engines have produced zero silt with OAT coolants, but there was the presence of silt with the blue coolants (especially when changed infrequently (hence probably why many a 306 owner recommends coolant changes every 2 years.). Even my Mondeo on 200k has spotless hoses inside (although that runs on Ford's own OAT coolant).

Anyway, that's my take on it. As for recommending a coolant, it's horses for courses. If you do have blue coolant though, ensure that it is changed on a regular basis. FWIW Porsche now only sell red OAT coolant for the 944 if you go to an OPC...

Hi Chas that's very interesting about OPC supplying pink OAT for 944s!

OAT is aluminium-friendly, but I thought the issue was with OAT attacking silicone in seals/gaskets. Happy to be corrected!

I understood about longer life of OAT so plan to change the blue I've just filled with in a lot less than 2 years.

Anyway my 928 now fully restored to coolant health with new rad.

Cheers

Adrian

Porsche's coolant may be a Hybrid (HOAT), but somehow I doubt it. When I asked years ago they told me it was red OAT coolant with the usual long life properties.

There are rumours that it attacks seals etc, but I reckon this is only the case for older stuff which had a poor cooling system anyway (read plenty of radweld present).

You still have the S4 then I see? A friend of mine bought an S the other week .