Easy way to change antifreeze concentration?

[Dennis Nicholls]

The dealer I bought my 986 from flushed/changed the coolant as part of prep for sale. However, I checked the concentration today with an ethylene glycol tester....reads -18 C/ 0 F. That corresponds to 1/3 AF and 2/3 water......IIUC Porsche wants 50%/50% mix. Coolant color is "red" so it should be genuine Porsche AF.

What's the easiest way to add some straight AF to bring up the concentration? How much mixing takes place in that "overflow tank" in the trunk? Could I just drain some coolant and put straight AF into the tank - would it quickly mix with the existing coolant? Or do I have to drain the whole shebang and mix it up in a bucket?

Algebra says my 2000 has 4.5 gallons capacity....existing mix has 1.5 gallons of AF....50%/50% mix would need 2.25 gallons....so I need to replace 1.136 gallons of existing mix with 1.136 gallons of straight AF.

[JFP in PA]

The dealer I bought my 986 from flushed/changed the coolant as part of prep for sale. However, I checked the concentration today with an ethylene glycol tester....reads -18 C/ 0 F. That corresponds to 1/3 AF and 2/3 water......IIUC Porsche wants 50%/50% mix. Coolant color is "red" so it should be genuine Porsche AF.

What's the easiest way to add some straight AF to bring up the concentration? How much mixing takes place in that "overflow tank" in the trunk? Could I just drain some coolant and put straight AF into the tank - would it quickly mix with the existing coolant? Or do I have to drain the whole shebang and mix it up in a bucket?

Algebra says my 2000 has 4.5 gallons capacity....existing mix has 1.5 gallons of AF....50%/50% mix would need 2.25 gallons....so I need to replace 1.136 gallons of existing mix with 1.136 gallons of straight AF.

"Shorting" the antifreeze is a common dealer prep trick to save some money. Problem you face is how to get a little over a gallon of new antifreeze introduced and then fully mixed into the balance. As the coolant tank holds nowhere near that amount by itself, you are going to need to drain some out of the system just to get it all in. Once you get to that juncture, you might as well dump the entire charge, correctly premix fresh with distilled water, and recharge the system, preferably under vacuum. While that may sound excessive, if they shorted the mix, they probably also did not use DI or distilled water either, so even if you did manage to get the glycol level up to where it needs to be, the charge would still end up being short lived if they did not use distilled water due to the salts now in the system.

Dump it and do it correctly, and you should not have any problems for many, many years.

[Dennis Nicholls]

OK it's my fault. Cockpit error. I needed to get the old Prestone AF tester completely full for it to read correctly. It reads now to -37*C / -34* F, which corresponds to the 50%/50% mix. Invoice from the dealer for the pre-sale work says qty. 2 of 000-043-301-49 AF (3.79 L), which the Pelican site says is the right part number for a gallon of Porsche AF.

Random web photo of Prestone tester.

Edited February 26, 2014 by Dennis Nicholls

[JFP in PA]

Amazing that a Mercedes/Porsche dealer would do this.....they also overfilled the engine oil by about a half quart. At least the salesman got them to suck out that half quart via the dipstick tube gratis. I am not impressed with their service department.

They gave me a copy of the invoice of the pre-sale service. Says quantity 2 of 000-043-301-49 antifreeze (3.79 L). The Pelican site says that's the right part # for a gallon of Porsche AF.

The Porsche AF is ethylene glycol based, right? My old Prestone AF tester should work correctly, right?

Your tester is fine and should work with any glycol based system.

Porsche antifreeze is glycol based, but employ's advanced OAT type technology to give it long life, which it has in abundance. Trick with OAT style antifreeze is that not all of them are compatible with each other, and mixing sometimes leads to gel particle formation which is a major pain to clean out of the system. As long as you stay with Porsche brand antifreeze and distilled water, you will have no problems as they have been very good in making any new and improved versions totally compatible with their earlier products.

[Dennis Nicholls]

Sorry my edit was late.

[JFP in PA]

OK it's my fault. Cockpit error. I needed to get the old Prestone AF tester completely full for it to read correctly. It reads now to -37*C / -34* F, which corresponds to the 50%/50% mix. Invoice from the dealer for the pre-sale work says qty. 2 of 000-043-301-49 AF (3.79 L), which the Pelican site says is the right part number for a gallon of Porsche AF.

Random web photo of Prestone tester.

Sounds like you are in good shape.