Agreed.. seems like a bad fan, fan temp sensor, or thermostat not quite opening all the way.

 

I just went to NAPA and bought the only coolatn temp sensor they offer, which is exactly the one pictured here: https://www.audiforums.com/forum/alb...pictureid=1159 and its the wrong one. The one on my car is blue with 4 pins in the clip. Ill think Ill just get the sensor replaced along with the waterpump.

Oh, and I have verified the electric fan does come on, it was one of the first things I checked.

 

actually, that suggests the opposite. a bad water pump would either a) stop pumping coolant entirely (unlikely) or b) drain your coolant out of the weep hole (more likely for water pump failures). if it stopped pumping entirely, you would overheat regardless. if it was draining coolant (i'm assuming you've checked the coolant levels) it wouldn't overheat until it started running low on coolant, and then it would overheat when it was running at any speed. you would also notice a strong coolant smell. same thing with a stuck thermostat to a much lesser degree and without the coolant smell. however a stuck thermostat would have the opposite symptoms (overheating under load, but will cool when idling). for whatever reason, your car is not moving enough air to cool the coolant (which is why it will cool down at highway speeds), or your radiator is bad. i'm leaning towards air flow.

 

My radiator isnt bad, the mechanic tested it before replacing the clutch fan. So now there is a new clutch fan and the electric fan is definitely working. The guy who checked it out for me said if the waterpump is on its way out it may be working better on the highway because im revving higher and spinning it more. Is it possible for the waterpump to lose efficiency without failing entirely?

 

what car/drive train do you have?

for the pump to "lose efficiency", you would have had to have damaged the impeller.

we can sit here all day long and bounce ideas back and forth. nothing will be for certain until the repair has been effected and your car is operating normally. only then will you know the root cause. for the purposes of informing those of us who have been following, helping those who search for an issue like this in the future, and your own peace of mind, ask them to perform the originally requested repairs without replacing the CTS and see if that fixes the problem. if is does not, then replace the CTS. if the problem still has not been resolved (highly unlikely) maybe we can offer some more suggestions.

 

I have a 1999 2.8l Quattro

Thats what Ill do, now I have the dilema of finding the right temp sensor. I guess Ill have to go to the dealership tomorrow, do they stock this?

 

just out of curiosity, how do you know the electric fan is working when it's supposed to? not that i'm doubting your diagnosis, i'm just making sure we're on the same page here. turning the A/C on while it's idling will show the fan is operable, but if you're not constantly running with A/C, the ECU might be shutting the fans down, thinking the temps are low enough due to the CTS readings. have you idled the car with the environmental controls off and let it start to overheat?

 

the dealership should definately stock it, but a place like advance auto should stock it as well. the advance auto website shows it as Part No. WT5129 @ $8.99

 

Advanced auto doesnt stock it they order it, atleast near me anyway. NAPA stocks it, I bought it and that sensor is not the sensor that is in my car. I used this pic https://www.audiforums.com/forum/alb...pictureid=1160 and info on the forums to locate the CTS and the one in my car is blue with 4 pins.

Its the only sensor in that area(pass side, rear of engine, under TB intake tube) so i dont think I am looking at the wrong thing.

 

aftermarket replacements might not be the same color. the WT5129 is round 4-pin plug judging from the images on the advance website.