My temp gauge normally stay right in the middle when I drive, but when I get stuck in about 30 min traffic(bumper to bumper). It starts moving to the right. The other night, (45 min traffic) it was really nearing 3/4(seemed close to over heating) and i could smell some boiling. So I changed roads and got out of traffic, sped up abit then the temp when back to the middle.

Does anyone have experience with this problem?

Researched and it seems it might be either cts, thermostat or water pump. can anyone confirm?

 

It could be any of those. CTS is the easiest and least expensive to change, not to mention it's a known pain in the *** on these cars, so I'd do that first and see if the problem goes away.

 

Pass on the CTS, for now - it seems to be accurately reflecting what's happening with your coolant temp changes. Have you verified that your viscous clutch for your fan is working correctly? If it's OK, then I'd check your lower cooling hose to see if it's hot to determine if your T-stat is opening properly.

 

Good points, and actually take a good look at that lower hose. I'm not sure if the A4 is known for this, but on my 300ZX, I replaced the lower hose with an aluminum coolant pipe with silicone connectors because under hard driving, I was seeing the lower hose collapsing and choking off coolant flow. Just something to keep in mind, although I haven't heard of it happening on an A4 yet.

 

yeah i'm going with tstat or water pump. same thing happened to me...