Coolant issue in the cold...

[filipin0_vr6]

Hey ya'll. I've been a lurker here for quite some time and last year finally had a good opportunity to pick up one of my dream cars growing up, a B5S4. Not my first tango with a VAG product, and have been bringing the car along slowly to make it up to snuff as a reliable DD. But i digress...

Wanted to pick everyone's brains, since I'm stuck at behind a desk for the time being. Last night had the coldest temps in NJ by far this year (+9F) and this morning it wasn't much better at +12F. Being in a rush for my commute, I hopped in the car and drove off without warming up and was going to drive it gingerly until it got up to temp. The 1st half of the commute consisted of a 25 mph steep downhill coast with no throttle for 5 minutes; 25-35mph steady flow for 15 minutes on a local highway. At this time, the coolant temp gauge just started coming to life. 2nd half of the commute is steady drive on the interstates for 15 minutes without too much congestion. After driving for 5 more minutes, I notice that my coolant temp wasn't tapering off and was still rising. I pull over and shut it down to check. notice that coolant was spitting out through the pressure relief cap/overflow hose. No leaks around the block, coolant pipes or turbos that I can see back there and under the car. Coolant level was just under min line at this point.

Let the car cool down back until the coolant needle is back in the middle. Drive it again for 5 miles, coolant temp gauge creeps up and the oil temp does as well. Pull over, shut it down, and let it cool down since I'm close to work. Start it up and the coolant temp alarm starts beeping at me, but the temp gauge was within normal parameters at this point? After driving for a minute, it goes away. Pull into my office parking lot 5 minutes later, without the coolant and oil needles deviating from their typical temps the whole time. Check the coolant level and all the coolant in the fill tank is 90% gone, and was blown out. No other leaks. Started again for kicks after 5 minutes, and the coolant temp alarm beeped at me but it was within normal parameters again?

[filipin0_vr6]

Last summer, the original coolant cap crapped out. The the plastic around the pressure relief spring broke, so the system was stuck closed. I was lucky to be idling in a parking lot at the time, and the lower radiator hose popped off and dumped coolant everywhere. Replaced the cap and replaced the 2 coolant sensors since I was in there.

[jaychen]

Are you sure you're not mistaking the 'coolant temp alarm' for the coolant level warning?

[filipin0_vr6]

You are correct sir. I have alot of missing pixels, but after a quick lookup there is no 'coolant temp alarm symbol' lol. I'm surprised my coolant sensor still works. When I just recently did the ICM delete kit since I had 1 bad coil and another one on the way with a cracked seal, I unbolted the coolant bubble to get access. The wires to the sensor was brittle and one of them broke at the connector. Resoldering that was on my spring list of things to do when it gets warm again and working on the car in the driveway is bearable again.

[bps4]

There was air in the system. Either it wasn't bled properly, or you've got a leak somewhere (if there system can't hold pressure your coolant mix will boil). Pressure test and report back.

[filipin0_vr6]

sorry just got home and saw this.

update: gf to the rescue after work with a bottle of coolant, topped off with straight g13, bleed at the heater core hose, warmed up, no leaks, temp needle stayed at it's happy spot. drove it home with no issues.

Sent with no regard for grammar

[filipin0_vr6]

during the day, with the help of some coffee, I was thinking of causes... thinking out loud...

when I replaced the cap and sensors, I filled it with straight distilled water. when it was fall and temps were starting to drop, I got lazy and decided to pour in straight g13 into the coolant tank and top off. the excess mixture would be pushed out during normal driving, and I would add more straight g13 the next day and kept adding it throughout the week until I eyeballed a 50/50ish mixture.

could having a not so optimal mixture+colder than usual temps cause the thermostat to stick closed? or create turbulence enough for an air pocket? etc? I just think I'm lucky for nothing worse to happen other than a being late to work

Sent with no regard for grammar