Corvette Builder

I kept getting a 16500 code so thanks to the many posts here, I was able to figure out it needed a new coolant sensor. Bought one at the dealership for $28, installed and light stayed off for about 30 miles then came on again tonight!!
What can it be now?
thanks in advance for your thoughts.
Colt

Nate (ETKA+Scumbag)

You need to actually clear the codes out. Have you tried that?

Corvette Builder

Yes, I cleared the code. But was fool enough to put in prestone coolant after I flushed. Could that be whats tripping the code again?
I guess I need to change to G-12 ASAP.
Also what if it's the thermostat?
Where is a tech article to change that?
thanks

Nate (ETKA+Scumbag)

Mixing is bad.

As far as the thermostat location, you've said nothing of what engine you have or what year. Look in the tech section or the FAQ. The timing belt change for the 1.8T article will cover the t-stat I'm sure.

GPJ

16500 is set as soon as the coolant temperature lies under 55C (131F) after engine start, but 18 minutes later the temperature has not risen to 70C (158F).

Corvette Builder

It's a 97 A4 quatro. I flushed out the old coolant before adding the prestone.
Now the water temp has never gotten clost to the mid-way point (pointing straight up).

It sounds like changing a simple thermostat change is not simple at all....

I guess I'll have to take it to the dealer to look at. Was just trying to avoid that.

Nate (ETKA+Scumbag)

I'm not sure about the 2.8l.

Corvette Builder

It's a 2.8 engine. I'm thinking maybe the thermostat is stuck open. The water temp barely gets warm. The oil temp hardly registers either. Of course, it's benn about 30 degrees hear the past week...

AudiMick

If its due do the water pump and timing belt at the same time. You are 90% of the way there.