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Discussion Starter #1
Bought a 2005 Beetle w/ 100k miles for a first car about a year ago and lately I've been having a few problems with it here and there. My main problem is that once I get on the highway and start going 60+ and have the A/C on, the overheating warning light comes on and beeps, even if I have full coolant. Even if I don't have the A/C on, just driving it for about 30 minutes makes the light come on. When it gets like this and I keep driving it, it eats up a lot of coolant. Any reason it could be doing this? IIRC the dealership said it had a new hoses and a new water pump. Just needed an oil change and for the radiator to be flushed.
 

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You might try scanning for trouble codes and see if there are any for the coolant system. Codes, can be specific to "performance" problems pointing to bad water pumps, thermostats and bad coolant temp sensors or coolant tank level sensor failures. Using a scan tool and reading live data; is a good way to minitor the coolant temps and confirm, if the engine is overheating when the temp light is blinking. It maybe possible you are losing enough coolant; you are getting low enough, the light starts blinking and/or the
engine is getting hot.

Here are the coolant temp light modes:

Blue coolant light = engine cold
Flashing blue coolant light = fault in the coolant monitoring system
Flashing red coolant light = low on coolant
Steady red coolant light = engine overheating, pull over and stop engine IMMEDIATELY and do not run until the problem has been identified.

Here is a video, tht goes over checking the waterpump performance and confirm it is working well by checking the coolant return line:

https://www.google.com/search?client=safari&hl=en-us&q=youtube+exovcds+a4+quick+check+water+pump&spell=1&sa=X&ved=0ahUKEwjLq9C6_ZLXAhVEw4MKHfC9AoIQvwUIIigA&biw=375&bih=559

Coolant loss and leaks can be hard to find; i find a coolant system pressure testing kit, a excellent way to pinpoint leaks in the systems. For possible head gasket failure; you might try a combustion leak tester and a leak down tester, can confirm the integrity of the head gasket.

Just because the wayerpump has been replaced; do not assume, it has failed ir isn't leaking out of the weep hole.

Coolant system pressure testing kit

(i use the harbor freight version;!that comes with a adapter that fits our vw's):

https://www.google.com/search?q=coolant+system+test+kit&ie=UTF-8&oe=UTF-8&hl=en-us&client=safari

Combustion leak tester:

https://www.google.com/search?client=safari&hl=en-us&ei=BUv0WdjlNaz-jwTH5rjQCg&sjs=3&q=combustion+leak+tester&oq=combustion+leak+tester&gs_l=mobile-gws-serp.3..35i39j0i20i263j0l3.210505.222694..225310.......142.2712.0j22............mobile-gws-wiz-serp.....3..0i67j0i131.MKe0F3wWsJ8=

Leak down tester:

https://www.google.com/search?client=safari&hl=en-us&ei=6Uv0Wdy1Csrf0gKcjZ7YCQ&sjs=3&q=leak+down+tester&oq=leak+down+tester&gs_l=mobile-gws-serp.3..35i39j0l3j0i67.7844.16316..16966.......241.2175.0j14j2............mobile-gws-wiz-serp.....3..0i20i264j0i20i263.NJVVXQYfRkA=
 

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Discussion Starter #3
Cool! Thanks for all this information, I'll definitely have to look into all this and check everything out. This is especially handy since I don't have the owner's manual for it. Also, I noticed that everyone says that G12 is the coolant you should be using but a guy that works at my local O'Reilly's said that it used G40. Would that make a difference or cause any issues?
 

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I'm not familiar with that coolant he is referring to but i use the coolant brand Pentosin; which you can find at most auto parts stores: Pentafrost SF (G12+)

http://www.pentosin.net/f_antifreeze.asp

You can get the correct coolant at your vw dealer as well but it may cost a bit more than the aftermarket Pentosin brand.
 

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Discussion Starter #5
G40 is made by Zerex. It's 50/50 pre-diluted. It says it's used for Beetles but no one on here has mentioned it. Also, is there any reason my A/C might start to get hot after driving awhile? Seems like it starts to get warm before my over heating light starts to flash. Can't really have it on when I'm on the highway because of that.
 

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From what I can tell; Zerex G40 is Valvoline's G12+ compatible coolant, which meets VW's coolant spec.

Valvoline™ ZEREX™ G-40® antifreeze coolant is premium automotive engine coolant developed by BASF AG and Valvoline. The patent-pending hybrid carboxylate formulation has an extended service life. It incorporates state-of-the-art organic acid technology in an ethylene glycol base for protection of all cooling system metals including aluminum.

ZEREX G-40 contains no phosphates, imidazol, borates, nitrates, amines or nitrites. ZEREX G-40 is approved by Mercedes-Benz & DDC for trucks. It is approved for the latest VW group requirements for service and factory fill. Valvoline recommends ZEREX G-40 for late model VW (G12++) vehicles. It is dyed pink to distinguish its unique chemistry from traditional green and yellow coolants.


ZEREX G40 is an approved formula for the following specifications:

VW TL 774 G

ZEREX G40 is formulated to meet or exceed the following antifreeze specifications and/or is recommended:

VW TL-774G
VW TL-774J


Zerex? G-40® | Valvoline Heavy Duty

download their "PI" sheet; for the technical details.

I don't think ZEREX G40 is mentioned, as much around here; as Pentosin Pentofrost SF, is more commonly available from most auto parts stores or can be ordered from their warehouses, same or next day. In my area, Pentofrost SF is in stock on the shelf at my local O'Reilly's and Pep Boys, I think Autozone can get it same day and I may have seen it in stock at Advanced Auto.

https://www.google.com/search?q=Pentofrost+SF&spell=1&sa=X&ved=0ahUKEwiApPSVxpnXAhXIqVQKHSClCaIQvwUIJSgA&biw=1250&bih=609

As for your A/C problems; you need to get that problem diagnosed, the blinking cooling issues may not be directly related to the cooling of the a/c not working as it should. I would get your cooling issues worked out first and then go from there.
 
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