# Can I use Prestone DEX-COOL coolant on my 1990 8v jetta?



## rick90210 (Mar 22, 2004)

Hi. 

Had to change one plastic water outlet because it bursted a small crack and started leaking fluids... I was using Prestone green coolant... but Now there is this Prestone DEX-COOL orange coolant that , at least, looks like the proverbial G-12 coolant... 

can I use it safely in my old bucket?


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## ps2375 (Aug 13, 2003)

If you flush the system very good. I, myself, would stay with the green or go with the "All Makes, All Brands" yellow stuff and stay away from anything labeled as Dex-cool.


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## rick90210 (Mar 22, 2004)

ps2375 said:


> If you flush the system very good. I, myself, would stay with the green or go with the "All Makes, All Brands" yellow stuff and stay away from anything labeled as Dex-cool.


 thanks... i've read a bunch of infos and unhappy people on the net about dex-cool... 

one question, do you happen to know what is the required coolant type for this car?


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## ps2375 (Aug 13, 2003)

That was VW"green" coolant, which is prolly the same as any green coolant. So, really you are open to use what ever you wish, I would be sure to flush and use some thing that is readily available.


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## Glegor (Mar 31, 2008)

ps2375 said:


> That was VW"green" coolant, which is prolly the same as any green coolant. So, really you are open to use what ever you wish, I would be sure to flush and use some thing that is readily available.


 i use the GM red coolant in all my VWs (gas and diesel) without issue.. 

it IS IMPORTANT to flush the entire cooling system very good before switching from green to red tho.. they do not mix.. 

i think the newer red coolant is not so picky tho.. i think it actually mixes with anything.. 

there is nothing wrong with running dex-cool in the jetta.. 

Dexcool is made to work with any type of metal it may come in contact with, and not corrode the metal.. IE: safe for aluminum heads and that sorta thing..


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## Seax_Smith (Jun 1, 2007)

Don't know exactly what DEX-cool is, but if it is the oragne, pet friendly, tooth paste ingredient, low pressure stuff designed for reverse flow systems that will actully move heat faster than the coolant is being pumped, DO NOT MIX IT WITH GREEN or you will have a very ugly mess to clean up and risk burning yourself when the low presure stuff purges teh water (50/50 mix) from the system.

Did a quick google search.... dex-cool seems to be the same low pressure, pet friendly orange stuff that used to go for $60/gallon. Really cool stuff but you need a reverse flow system to actually make use of the expasion/contraction thing that sucks heat out of the head when the hott coolant in the radiator cools and causes a vacuum to form behind it, pulling the hot coolant in the head forward.

Not worth the pice unless you are concerned about the dog lapping up the coolant you slosh or leak.


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## rick90210 (Mar 22, 2004)

So the G12 coolant doesn't really helps to mantain the car engine cooler than the green stuff? does it transfer heat better than the green stuff?


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## Glegor (Mar 31, 2008)

Seax_Smith said:


> Don't know exactly what DEX-cool is, but if it is the oragne, pet friendly, tooth paste ingredient, low pressure stuff designed for reverse flow systems that will actully move heat faster than the coolant is being pumped, DO NOT MIX IT WITH GREEN or you will have a very ugly mess to clean up and risk burning yourself when the low presure stuff purges teh water (50/50 mix) from the system.
> 
> Did a quick google search.... dex-cool seems to be the same low pressure, pet friendly orange stuff that used to go for $60/gallon. Really cool stuff but you need a reverse flow system to actually make use of the expasion/contraction thing that sucks heat out of the head when the hott coolant in the radiator cools and causes a vacuum to form behind it, pulling the hot coolant in the head forward.
> 
> Not worth the pice unless you are concerned about the dog lapping up the coolant you slosh or leak.


what is this reverse flow system you speak of? is it just like it sounds? the coolant flow is backwards of normal? instead of leaving the head, and going to the radiator, it leaves the top of the radiator and goes into the head?

the dex-cool im running seems like it maintains temperature better than the green stuff i usually run. seems to be less fluctuation on the needle when going up hills at low speeds, or under high engine load situations.. my cars never get any hotter than half way on the temp gauge..


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## Seax_Smith (Jun 1, 2007)

Glegor said:


> what is this reverse flow system you speak of? is it just like it sounds? the coolant flow is backwards of normal? instead of leaving the head, and going to the radiator, it leaves the top of the radiator and goes into the head?


That's exactly it, sort of; you want the H2O pump forcing coolant into the head, through the head and then toward the radiator. With th low pressure orange stuff and reverse flow, when the coolant is cooled in the radiator is contracts significantly causing a vacumm to form behind it. Conversly when it is heated in the head it expands significantly and is sucked into the radiator by the vacuum since there is positive flow preventing it form expanding in any other direction. So what actually happens is the heat is moved faster than the coolant is actually being pumped by the water pump.

Stuff used to be $60 a gallon, and it takes 3 gallons to purge and fill the system. With the orange low pressure stuff water is a contaminate and will actully be forced to boil out which makes for a glorious eruption out of the coolant reservoir and one hell of a mess to clean up. Down side to it is that when the system is full and cold, you cant see anything in the recovery bottle. Work better with a 'rocco radiator with a cap and internal expanion tank, and even better if you completely shroiud the radiator.

(always wondered if the system was big enough and with a oneway check valve, if the H20 pump could be delted altogeather.... sort of running like some geothermic systems or the solar hot water stuff. sort of ->head -> heater core -> radiator -> check vavle -> thermostat-> head....)


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## rick90210 (Mar 22, 2004)

so dex-cool would be ok if I remove the green stuff from the system?


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## Glegor (Mar 31, 2008)

rick90210 said:


> so dex-cool would be ok if I remove the green stuff from the system?


absolutely..

im gonna venture a guess, and say you have a gallon just laying around at home, and you are broke, and dont wanna go buy a gallon of green coolant? and figured, well hell, if this red stuff works, ill use it.. right?

make sure you flush the radiator, engine, heater core, and hoses. take the thermostat out of the engine to flush it.. otherwise the engine will fill up to a certain point, and not drain.

taking the thermostat out is prolly gonna be hard. your car probably has a/c and power steering.. good luck getting to that thermostat.. i think i would just buy a bottle of green, rather than go thru all that extra work..


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## rick90210 (Mar 22, 2004)

Glegor said:


> absolutely..
> 
> ... i think i would just buy a bottle of green, rather than go thru all that extra work..


thats what I will probably do... the thing is that I fear the scenario where I didn't flushed the system properly and end up with a bunch of gunk inside the engine and with a bigger problem... and if there aren't real cooling benefits in using the G12 coolant, and it performs the same as the green stuff in real life... the work involved in properly and completely flushing the system is probably not worth it

one other thing, right now the car is running with very low coolant mixture (probably 70 or 80% water and 20% coolant) and the needle stays just a tad below the middle with the AC on, (it stayed above the middle when I had 50/50 of water/coolant mix) how could this be? it isn't supposed to cool better with a 50/50 mix?


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## Seax_Smith (Jun 1, 2007)

rick90210 said:


> one other thing, right now the car is running with very low coolant mixture (probably 70 or 80% water and 20% coolant) and the needle stays just a tad below the middle with the AC on, (it stayed above the middle when I had 50/50 of water/coolant mix) how could this be? it isn't supposed to cool better with a 50/50 mix?


A 25% coolant mixture will cool the car better than a 50% mixture. THing is the 50% has a higher boiling point and a lower freeze point.

Coolant is added to the water to do 2, maybe 3 things.... Prevents teh water from rusting everything, raises the boiling point/ lowers the freeze point and arguable lubicatess the water pump.

If you aren't getting internal corrosion, stay with the mix you have and add a bottle of water-wetter if you want more effective heat transfer from the coolant. Distilled water and water-wetter is a comon mix in many racers.

The standard is 50% becasue it won't mess up anything and will work well just about everywhere , year round. It's not the standard becasue it is the most effective.


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