# Low Coolant level: topping off? underheating?



## Sputnikyuri (Jun 8, 2008)

Hello! First technical question.... (I already had an account here so that must have been a sign!)

tl;dr can G13 coolant be added to G12? (not G12plus, or plusplus, just G12). The coolant sure looks red to me. Coolant resevoir tank is labeled "G12."

My vehicle: 2008 Jetta Wolfsburg Edition 2.0T

We had our first freeze flash finally and, according to what I've read online , the coolant/antifreeze may have contracted and thus is below the minimum level line in the reservoir tank. For whatever reason the coolant may be low for, I'd like to add more to the tank. There is no readily visible evidence of any coolant leaking.

What prompted me to investigate was receiving the vague P2181 Cooling System Performance CEL code while driving around on a cool night, and also the acute symptom of underheating: Temperature will reach 190F at idle (too slowly) but driving lowers the temperature a couple marks; heat blows from the conditioner, but nowhere near as hot as it should be.

From what I've read, this is most likely the thermostat stuck open, which I'm willing to have a mechanic change out. I'd like to start simple and add coolant to rule that out. Would low coolant levels even produce this sort of symptom (not enough pressure)? My car has not performed like this in previous freeze flashes.

So, that led me to the famed G12 compatibility chart. Possibly the most German chart I've ever seen. Now I find ECS tuning has made their own rendition of the chart https://www.ecstuning.com/forum/audi/CoolantMixChart.jpg, but it leads me to some more questions. Not that it really matters as apparently G13 is the only stuff in stock at the dealers these days?

If I'm going to go to the dealer to get coolant, I might as well just have them top it off and not have to store a jug of half-used antifreeze in my apartment. But at this point, I just want to acquire current knowledge about the G-series of coolants and learn more about my cooling system.

Thanks for your knowledge and expertise in assisting with this!


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## rickjaguar (Apr 23, 2009)

From what i've read, yes G13 can be added to G12, but it's better to do a complete flush and replace with G13. Temporoary fix- but don't drive the next 4 seasons with this mixture. As for underheating P2181 code, I've been running with this for almost 2 years now. Thermostat is stuck open, and tbh i never really noticed any problems or lower cabin heater temps. No problem running a little cooler as long (as you're not in a subzero area).


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## Sputnikyuri (Jun 8, 2008)

Thanks for your response rickjaguar.

I stopped by local dealer and had them top off the coolant. The symptoms persist, so I'm going to have the thermostat replaced. The underheating isn't bad, but it does seem like my gas mileage has taken a hit. I should probably try to relax, but I don't want to ignore the problem either, especially if it all of a sudden presents itself as something higher priority (water pump, heater core).


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## Sputnikyuri (Jun 8, 2008)

Resolution report:

Vendor: 
TIRE KINGDOM

Fluids
Description | (QTY) :
- COOLANT FLUID EXCHANGE | (1)
. SOLTEC COOLING SYSTEM FLUSH
. MAXLIFE UNIVERSAL COOLANT DRUM*
. FILLED COOLANT TO FACTORY SPEC
. COOLANT EXCHANGE LABOR

Services 
Description | (QTY) :
- ENGINE DIAGNOSTIC | (1)
- New ENGINE COOLANT THERMOSTAT | (1)
- 48476 THERMOSTAT &/OR GASKET R&R IN-LINE | (2)
- New ENGINE COOLANT TEMPERATURE SENSOR | (1)
- New ENGINE COOLANT TEMPERATURE SENSOR O- (O-Ring) | (1)
- ENGINE COOLANT TEMPERATURE SENSOR LABOR (1)
- ALTERNATOR 200 AMP FUSE
- WWD ZL0-11254 ALTERNATOR 140 AMP



Results:
Detected coolant leak from radiator or radiator hose. Detected coolant sludge in reservoir tank. 

Prognosis: 
YOU GET WHAT YOU PAY FOR BUT YOU GET EVEN LESS IF YOU PAY THE WRONG PEOPLE TO DO IT.

* Yes the dreaded brown sludge. Universal highlighter fluid mixed with the VW spec fluid. I will post a reference photo tomorrow.


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## Sputnikyuri (Jun 8, 2008)

Here's the reference photo of what my coolant reservoir looks like:

Reference Photo

not good.


The suspect leak is apparently coming from a steel pipe. It seems like a lot of coolant but it's just a pinhole. Naturally this could be a coincidence or really have something to do with the mixed coolants. But just from my limited research so far, seeing what a thermostat looks like, and seeing what that coolant looks like, it doesn't look good at all.


:banghead::banghead::banghead:


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## stratclub (Feb 3, 2007)

The idea of a_"universal coolant"_ is pure nonsense. you have to get *ALL* of the old coolant out or you will many times get the brown sludge if you put in a different type.

When you drain a cooling system, you only get about 1/2 of the coolant out, so what you have to do to use a different coolant type is drain, refill and run the engine 5 or more times until what drains out is pure water.

I find it suspect that a 5 year car needed a new alternator. Unless the battery was connected backwards and blew the fuse and/or destoyed the OE alternator, the alternator should have been fine. Also, if they could not put the correct coolant in, the alternator they installed was most likely a garbage re-man from a local parts house.

Is your car a gasser or a TDI?


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## Sputnikyuri (Jun 8, 2008)

stratclub said:


> I find it suspect that a 5 year car needed a new alternator. Unless the battery was connected backwards and blew the fuse....


The fuse did blow. Honestly i think they messed up te alternator during service somehow. They did actually credit me the cost for it, but yes, I suspect it is inferior. Really the least of my worries right now.



stratclub said:


> Is your car a gasser or a TDI?


Gas / ethanol


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## Sputnikyuri (Jun 8, 2008)

OK. The shop replaced a seal somewhere up in the upper back of the cooling system. This time the invoice is vague. I saw some of the notes the mechanics took but didn't catch anything useful. The sale rep at the counter showed me on a diagram where the seal was replaced. These docs were ushered away as soon as I signed the invoice. Gulp.

The coolant is still frickin green! But at least not foamy and brown. :screwy:

Let's assume they actually flushed out all the old VW coolant, and the brown stuff, and there is just highlighter fluid in my cooling system now... how soon should I get this flushed? Can I get by a month or two like this? Or should it be asap?

Honestly afraid to take the car over 2k rpms right now.


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## rickjaguar (Apr 23, 2009)

If it isn't g12 or g13 there will be issues. I wouldnt drive it at all, personally. Yes ASAP!


Sent from my iPhone using Tapatalk


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## AlexNGAvw (Jul 6, 2013)

hogwash


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## Sputnikyuri (Jun 8, 2008)

Had a dealer flush the coolant today, half-off special this month. 

Hopefully they got ALL of the bad stuff out and JUST good pink stuff in. Fingers crossed.

Let this serve as a bulletin to anyone thinking about mixing coolants or saving money at the big-box shop.


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