Iron block, aluminum heater/head, brass radiator

[fjasper]

in a 1988 Audi. Cold climate.

Is there any way to figure out which coolant to use, or if it even matters?

The brass radiator is aftermarket, since the car came with an aluminum radiator. The OEM plastic/aluminum ones had a lot of problems with cracks and leaks.

It had good ol' green in it when I got it last summer, so that's what I put in after I flushed the system with citric acid, but when I took it to the dealer to get the block heater replaced, it came back with VW G11 blue.

I've heard there may be an issue with G11 and lead solder, but I can't find anything authoritative.

I'm leaning toward grounding the radiator, heater core, head and block, replacing coolant every year, and hoping the various metals can get along with each other.

 

[Kestas]

From what I remember, if you have lead solder in the system you should use a silicated conventional formula.

I'm not sure you need to ground the radiator and heater core. The rubber hoses and rubber mounts for the radiator should be enough to electrically isolate these components. Transmission cooling lines may change this thinking.

 

[mechanicx]

I agree. Since you probably have lead solder in the radiator, best is a conventional Green IAT. I don't think grounding the radiator will help much.

 

[Dan55]

IIRC VW/AUDI specified a phosphate free antifreeze at that time I would go with G-05.

 

[mechanicx]

Actually he is nto using the stock aluminum radiator and I think what you need for lead solder protection is phophates. this is probably what made traditional green work well with old soldiered radiators. Molybdate is also really good for this, but who knows what coolant has it or not.

Here's a good link,
coolants
Quote:
Different inhibitors protect different metals. From Vukasovich and Sullivan (also "Engine Coolant Testing, 2nd Symposium"):


"The data show aluminum heat-transfer corrosion was best inhibited by silicate and most poorly by phosphate and borate... copper was best inhibited by molybdate and most poorly by benzoate; high-lead solder best by molybdate and phosphate and most poorly by nitrate, silicate and benzoate ; low-lead solder best by tolytriazole and molybdate and most poorly by nitrate and silicate; mild steel best by molybdate, phosphate and nitrite and most poorly by tolytriazole and benzoate; gray cast iron best by nitrate and most poorly by benzoate, tolyriazole, and borate; and cast aluminum best by silicate and most poorly by phosphate and molybdate."

 

[qship1996]

Prestone all makes will work fine, so would any other like Peak global, or other off the shelf choice.....just change it every 3-5 years.

 

[mechanicx]

Originally Posted By: qship1996
Prestone all makes will work fine, so would any other like Peak global, or other off the shelf choice.....just change it every 3-5 years.


Do you even know what you are talking about? This guy's radiator is a lead soldiered copper/brass unit. No manufacture recommends an OAT for copper radiators, let alone the other problems a dexclone in the wrong application can create. These type of radiators can and do corrode and leak within a few years with the wrong anti-freeze. I think you are doing a disservice recommended dexclone for everything.

To protect this radiator the Euoropean coolant that is in it now is probably one of the worst. American green would be good, and best would probably be Fleetcool. NAPA has it and HD dealers. It has phosphate/molybdate which is idea.

Fleetcool

 

[qship1996]

Prestone protects all metals......you have some strange paranoia regarding coolants.......I think prestone/peak/etc engineers know a little more about the uitability of their products than you.....ALL MAKES, ALL MODELS


There is nothing about lead solder, copper, or brass that prohibits a dexcool or organic based coolant. You are in the dark ages

 

[mechanicx]

You are just talking out of your back side. Dexcool was never intended for use in copper/brass soldiered radiators. Dexcool protects aluminum and iron well but does very poorly on copper, brass and soldier. I'm going to post Zerex datasheet showing that Dexcool is very poor on these materials. Where is your proof that it protects these materials?

http://www.valvoline.com/pdf/zerexdexcool.pdf

Let me interpret that since I wouldn't be surprised if you are unable to understand the significance. This test results show very poor protection of solder, copper and brass. It's a lot worse than provided by Green or G05. and don't even try to claim the unlicensed Prestone Dexcool could somehow be better. It's mst likely even worse than Zerex.