03 Jetta TDI coolant loss

Ive been losing coolant in my 03 jetta steadily. I've been doing the research trying to track it down. The thermostat was replaced in the last year, the flange doesn't appear to be the spot either. it started leaking only on the passenger side but it recently started dropping on the driver side as well. Any suggestions on where to maybe start? Also is it normal for the coolant to have an oily feel to it after its been through the system? It is lighter in color and not darker like engine oil. Any help is appreciated!

Head gasket failure

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That was something I saw and was considering but I was really hoping it wouldn't be the issue. I wasn't interested in spending that kind of $ lol.

Maybe pressure test your cooling system to confirm. Under pressure you should be able to actually see where the coolant is coming out. Source of leaks can sometimes be deceptive.

I'm going to attempt that tomorrow at a shop. I didn't assume a head gasket leak cause the head was replaced and whatnot a few years ago. So with that gasket being only a few years old I was hoping it wouldn't be the source.

Fingers crossed that it won't be a head gasket. Repairs, however, can be iffy, something not done quite correctly or a marginal replacement part. It's possible that that head job is failing prematurely. This is why it's always best to do what you can to keep from getting into the situation where you have a major repair (with proper maintenance the probability of needing a major repair is significantly reduced).

Coolant is "slippery", yes. It may be the head gasket but there are other places it can leak as well; get out an inspection mirror and see if you can find the "it's wet below" points. Hope it's not "at the point between the head and block"....

In many (but not all) cases of the head gasket being bad, or the head cracked, you'll get some form of cross-contamination -- either coolant into the oil, oil into the coolant (or both) or combustion gases into the coolant. If you are getting combustion gas into the coolant it can be tested easily (NAPA sells a little kit to do it) and sometimes you can see the gas in the stream coming into the hose that goes into the bottle on the top. when the engine is running (that should have coolant, and no bubbles coming through in it.)

check the quick connects on the fire wall for the heater core . it leaks down behind the sound deadeaner applied to the fire wall until it soaks the material then drips off the subframe everywhere

If you see it leaking externally, I doubt it is the headgasket.

Pressure test the system and see where it leaks. Not a very complex cooling system and everything is easily seen.

The above poster is correct about the quick couplers at the heater core.

Didn't see this suggested yet but what about the water-pump? I had a water pump failure a few years back. Prior to the failure I was noticing coolant loss and a faint smell of it but I wasn't 100% sure. I was on the highway and heard a pop under the hood, then steam. Immediately shut it down and let it coast to the side of the highway. Sooo lucky that the TB didn't blow or skip a tooth for that matter.

After that incident I immediately parked her in the garage and did a TB and replaced all of the applicable components from a reputable vendor (the PO had the receipt for a 100k TB kit from their mechanic which was at about 60k of it's 100) but there was still failure.

I haven't been able to narrow it down yet. There was some coolant pooled up almost directly under the coolant sensor so that made me suspicious. I checked the sensor and noticed that I could spin it back and forth in the spot where its seated? Is that normal or should it be pretty firm and have no movement? I did replace the sensor a little while ago and I also replaced the clip. Thoughts?

There should be no movement; when you replaced the sensor did you replace the O-ring?

I bet it's leaking, especially if you see coolant under there. It's a very common problem and the O-ring is easily replaced -- but you do need to drain down the system first or you'll make a HUGE mess (some coolant will wind up coming out in any event, but you can reduce it a LOT by pulling the oil cooler coolant hose, draining at that point and the radiator before you remove the sensor.)

Ya the sensor has a lot of movement in it right now which seemed weird. I did replace the O-ring when I replaced the sensor but maybe something got loosened up somehow. I'm going to take it for a pressure test here in a little bit so hopefully that'll pin point the issue.

Bad O-ring perhaps.... it should be REAL obvious if it's leaking there if you put a few psi of pressure in the system and wiggle the sensor...

EGR cooler could be suspect. I'll second the heater core connections. The only way you'd get oil in the coolant is if the oil cooler (under the oil filter housing) was leaking. That's the only place on these motors where the two can mix.

As Shoveltrev stated:"check the quick connects on the fire wall for the heater core . it leaks down behind the sound deadeaner applied to the fire wall until it soaks the material then drips off the subframe everywhere"
I had the same loss of coolant problem. Spent hundred$ replacing parts. Finally found the problem was a 50 cent o-ring on one of the fire wall heater core quick disconnects!

The temp sensor should move. Maybe it was a cheap O-ring. The leak on the front could be the water pump as mentioned. That's one that needs a good, careful look at.

Why was the head gasket replaced and what all was done? Just because it was done, doesn't mean it was done right or that there isn't another problem with the head.

My MkIV was recently leaking heavily at the upper connection point to the coolant overflow bottle. Replaced the bottle, replaced the two hoses that connect to the bottle. When warmed up to operating temp, with the hood up and the engine running, it was obvious where the coolant was escaping.