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I just bought this Jetta today and the temperature light is flashing. The manual says that its running hot or its low on fluid. Well the needle is right in the middle of the gauge and it raises up to there and doesn't go any further. So we (husband and myself) checked the level it was low and it seemed as if there was no coolant in the lines from the reservoir to the radiator.

We had already decided to do basic maintenance ie. oil change, system flushes, tires, breaks ect. So we bought some coolant from walmart and added it to the car. (at the time I didn't know that VW's took special coolant but we're just trying to flush the system) The light went off everything seemed to be working just fine. Went to the store and after a few miles (about 8 ) the light started flashing again. Pulled over and the reservoir had drained but now it seems like there was coolant in the lines.


Basically to sum it up the coolant was low... put more in and the coolants low again. What could it be? thanks
There are no obvious signs of a leak, but this is our first VW but he is a great mechanic we just don't know what the problem would be.
 

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If it was empty or close to it, it'll take around 2 gallons or a little more to fill the system. Add more when it's cooled down and try again. If it does it after a few times of this (no more than 2 or 3), then there's a major leak somewhere. Also make sure you run the heat at full blast for a while, too. Just start the car, turn the heat to full blast, and let it get up to temp. Then let it idle for 10-15 minutes. Let it cool, check coolant level, and add as needed. Like I said, if it still gets low, then there's a leak somewhere.

You could always fill it back up, park it on concrete, and put a big piece of cardboard underneath. Run the car and it'll show where, if any, leaks are happening. Good luck.
 

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I find going for a higher rpm drive up and down some steep hills really helps shake any air out of the system. Thankfully older VWs aren't too bad for air pockets.

A word of caution. You can run standard coolant in there it just wont last as long before it needs to be drained and the system flushed because of its reactivity to the various metals. The downside to standard coolant is the seals and plastics aren't speced to hold up to it too well.

If its just to get you by for a bit it will be fine but don't go too long on it. Standard coolant-green, and the G12 that comes in that car don't play well together. In mixing they start to make a pudding like substance that will start to gum up the coolant jacket. That leaves you with poorly cooled cylinders and since the heat core gets it coolant directly from the head you wont have much heat either. Somewear I have a pic of a VW 1.8 with the head off. You could see the result of the system not being flushed properly before. I had to use a pick and then an old bike spoke to clear them out. Block and head. It was bad. That was a long week in the garage.....

Drain the system by removing the lower rad hose and the re circ hose off the water pump for when the thermostat is shut. Flush out the rad via the upper rad hose and flush the block via the same and the resivoir. Don't forget to remove the hoses to the heat core and gently back flush it. Remember to blow the water out of it too after, and then pre fill it to help avoid air pockets and coolant drop.

Go to a dealer and by 2 gallons of pre mix G12 coolant. A lot of auto parts stores sell Pentosin G12 witch is the exact same stuff as factory fill. You can also upgrade to G12++ witch is what the new Audis use for the same price. It mixes with the G12 just fine. Pre fill the rad, pre fill the heat core, then fill the block via the upper rad hose, then fill the bottle up. Squeeze as many hose as you can to help burp it and then run it with the cap off for a few min at 2000rpm. I find if I over fill the bottle by about an inch it drops to the perfect level. Top it up if need be, slightly higher is fine and then go for a drive. Done for 5 years.

Your husband will absolutely love where the thermostat is on that car and how much work it is to get at........ Its one of those things you wanna make sure the coolant system is up to snuff and updated properly so that you don't have to get at the T stat again in the short future.

Edit: One really good tip I picked up along the way is a trucker trick. Drain the entire system the same way I wrote and then re fill it with water. Add a cup of cascade dish washer powder to it and drive around on it for a few days. It will mega clean the aluminum bits out nicely. The downside to that is you have to then drain it again, flush it. Run it on just water, flush it, then fill with proper coolant.
 
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