My wife was driving the car the other day on the freeway in bumper to bumper traffic, when she saw smoke start coming out of the hood. She pulled off the freeway (thankfully there was an exit right there), parked in a driveway, and shut off the car. Thankfully, there just so happened to be a mechanic a block away who specialized in audi/vw's, and he drove the car the block to his shop, and was able to figure out what happened.

Apparently the thermostat that regulates coolant flow failed and stayed shut, so the coolant wouldn't flow anymore, causing the engine to overheat.

He did some emissions tests, and there were elevated hydrocarbon levels, which he said indicated the head gasket was damaged. (EST $2500 to replace). In the mean time, he replaced the thermostat (which was covered under warranty), and now the car runs fine again, and no fluctuation in the oil temperature now. (before it would go one notch past half sometimes when climbing hills).

However, there is now a faint syrup-like smell coming from the car. What could this possibly be? coolant fluid left that leaked during overheat just burning off??? something worse??

Also, Do I need to replace the headgasket now? If the car isn't overheating now does that mean the damage wasn't that serious? please help!

 

Your head gasket is blown and the syrup smell is your antifreeze. You need to replace the head and intake gaskets and check to see if anything got warped in the process. If it did it will need to be milled/resurfaced and then reassembled.

 

Oh and I would replace the seals, belts rollers, tensioner and waterpump while your at it. Chefro has a nice long thread going on that pretty much sums it up.

 

A faulty part that's under warranty caused a more expensive damage... isn't replacing the head gaskets covered as well since the thermostat was the culprit?

By the way, tks for the "plug", J!

 

Ouch. That's what I was afraid of. But since anti-freeze leaked when the thermostat failed, is there a chance that what I am smelling is just anti-freeze that sprayed into the engine compartment? Or is this a tell-tale sign of something worse (head gasket)

 

Waterpump was already replaced ~58k miles. Car as 62k miles or so on it now - do I still need to replace everything else?

 

The mechanic said he wasn't sure, and that audi may elect not to cover it because the car isn't running hot. He's calling them today, so we'll see

 

I want to point out that you are not talking about replacing a head gasket here but 2 head gaskets since your engine is a V6. if one is busted you should replace both.
While you are at it you could replace the timing belt.

 

Thats a good tip - part is only 60 bucks or so, right?
http://www2.partstrain.com/store/?Nt...3%204294964666

That work?

 

Time to apply a little logic here!

I am not a hydrocarbon expert so how does elevated Hydrocarbon levels point to a bad head gasket?

If the antifreeze level is dropping I'd agree that there is a leak and given what happened I'd say it probably is a bad head gasket etc. But if it not dropping I'd ask many questions before having the work done unless someone else is paying for it- and then I'd have them repalce everything - even the air in the tires. LOL