Overheating Again

Overheating Again [Resolved]

So... my Jetta's overheating again. I thought I fixed this a month ago, but apparently not.

Here's what happened today:

• Drove 2.5 hours with no problems, 190 degrees, AC on.
• Stopped for 45 min
• 30 min in to drive home, AC got warm and temp shot up
• No heat from vents
• Lots of pressure in coolant tank
• Lower radiator hose not hot
• Only small fan comes on when AC is on (never saw the driver's side on even with temps above 230)

I'm confused because I read the Overheating Diagnosis thread in TDI 101. It points me towards a bad Water Pump.

However:

• Installed metal Graf Water Pump (DieselGeek Deluxe TB kit) less than 20k miles ago.
• Installed OEM thermostat 2 weeks ago.
• Installed new thermostat housing 5k miles ago.
• Installed radiator fan assembly this summer.

I got a tow home.

I'm confused as to what I should start replacing first.

Would it be possible for a Metal Graf WP to fail this soon? How do you inspect it without removal?

As a side note: I've had a heater core leak since I bought the car (4 years of pancake smell) but it's never caused any major problems. Could it have played a roll in this? I just read the VWVortex thread on replacement and I'm praying it's not to blame.

PS: I have Sam Adams Octoberfest for any Richmond TDIers out there who might be able to show me a thing or two.

UPDATE:
I ended up replacing

• the fan assembly
• thermostat housing (and bolts)
• thermostat gasket
• temp senso
• and the coolant expansion tank.

Note: I had a gradual coolant leak for about 1-2 months prior to the cooling system crapping on itself. It never dripped coolant on the ground, so I could never pinpoint the leak. In all my prodding and poking over the last few days however I think I found it.

The metal coolant pipe that connects to the top of the coolant expansion tank has both of its nipples broken off. The nipple closest to the driver side began spraying coolant everywhere after all the replacement parts were in. I ended up cutting the leak off the pipe and shortening the pipes overall length as a quick fix. I'm assuming that the nipple broke or bent itself and creaked a pinhole leak, which was not visible because of it's location.

Also: No heat was coming out of the dash. After the parts were in and the car was at operating temp, I turned the heat on and got nothing. I drove it 2 miles to test everything and turned the heat on again and got this:



After the steamy coolant cleared, I had great heat coming from my vents. Any ideas what could've caused that?

do you know why the driver's side fan is not coming on? Seems like that would be the place to start. sensor or the control module for the fan(s).... or a bad fan even though it is new.

riebs said:

PS: I have Sam Adams Octoberfest for any Richmond TDIers out there who might be able to show me a thing or two.

Click to expand...

In the case where you get stuck and don't know what else to do, you are very fortunate to have an excellent TDI guru only 1 hour away:

http://forums.tdiclub.com/showthread.php?t=204790

if the heater core is leaking , it needs to be fixed. the system is not under ideal pressure. you can bypass it by connecting the two hoses in the engine compartment.
But , from what you describe it sounds like there is air trapped in the system. Both fans are supposed to come IF activated by the thermoswitch. when running the AC , that would be the FCM.

I would bypass the heater core and pressure check the system for starters.

@mk3: I don't know why the fan isn't coming on. Regardless, I'm taking your advice and replacing it since it's still under warranty. I'll let you know if that worked later tonight.

@dadsdiesel: I read that entire thread last night after I posted this. I'm going to PM him once I get my car running. It needs to be "once-overed" by someone who knows what they're doing. Unfortunately, I used all of my insurance towing miles just getting the jetta home last night.

@Dimitri16V: I didn't know about the bypass. I'll try that today after I replace the fans. As far as air in the system, how do I go about purging it?

riebs said:

@mk3: I don't know why the fan isn't coming on. Regardless, I'm taking your advice and replacing it since it's still under warranty.

Click to expand...

oh! sorry I meant to say that investigating the reason for the fan not coming on would be 'the place to start'.. not to just go ahead and replace the fan. The fan may not be at fault at all. To test it you would either need to remove the fan and put 12V to it to see if it runs or else put a meter on the wires in the car and see if you get 12V-14V but a non-running fan at the same time.
It might be a little more complicated than that.. the fan might have multiple power leads for different speeds. the wiring diagram would tell you that.

@mk3: You were right.

The large fan wouldn't turn on yesterday. I assumed it was bad. I pulled it out and gave it 12V from the battery: Nothing.

... or a bad fan even though it is new

Click to expand...

Grabbed a replacement assembly from Advance. Got home, plugged it in, and turned the AC on. Small fan: On. Large fan: Nothing.

I figure it's the Fan Control Module, but take a closer look at my "new" assembly and see melted wires leading to the Large fan motor.

I give the "new" Large fan 12V from the battery: Nothing.

I multimeter the fan harness coming from the car: 12V on both small AND large fans.

... or a bad fan even though it is new

Click to expand...

So it turns out you were right mk3. Turns out it was two bad fans.


Also: My thermostat is leaking like crazy since the overheat. Please tell me I didn't do something stupid and put the gasket on the wrong way. It does go between the thermostat and the plastic housing right?

I'm guessing the high heat deformed the gasket and now the seal is bad?

I finally got a good set of fans. I got a new gasket for the thermostat. I put the new gasket in, filled with coolant, started the car and symptoms are:

• No heat from dash
• Leaking like a sieve from the thermostat area.

I'm ordering a new coolant tank, temp sensor, thermostat housing, and another gasket from IDparts today.

I'll update once they arrive and are installed. Hopefully then I'll be able to get this to my local guru Tom.

Head Gasket bad?

Updating this thread instead of starting a new one because I think my new problem is related.

The overheating has been fixed. After 300 miles, no high temps.

However, the new issue is coolant loss while idling.

When the car is cool, the coolant is b/w the min and max lines. After about an hour of driving, when I come to a stop, the coolant light comes on. When I start driving again, the light goes off.

I pull over and checked out the reservoir. It looks like coolant has leaked from the cap, and the coolant level is below the min line. When I unscrew the cap, a TON of pressure is released.

Also, the coolant is starting to look black.

I've read the forums and found that this all points towards a bad head gasket, but I'm confused. I thought a bad head gasket would pressurize the coolant under load, not while idling.

Any care to point me in the right direction?

I emailed my local guru Tom to see if he can't take a look at it sometime soon.

Head gaskets can fail in different ways... between the cylinder and an oil gallery, between the cylinder and a coolant gallery, or between the oil gallery and the coolant gallery.

When the latter occurs the 80 psi oil sneaks into the 15 psi coolant gallery and your coolant becomes contaminated with oil.

The other common oil->coolant gallery breach is at the oil/water heat exchanger bolted beneath the oil filter flange... probably worth checking it for leaks before tearing the head off the engine.

Good info vince. I hadn't read that yet. I'll check and get back to you.

it looks like the headgasket , get a new head from frank06