Hi,

I have Audi A6 1998 C5 and it seems that my thermostat is stuck open. It wasn't bothering too much in the summer time, however ever since the temperatures are falling down in the Midwest it takes forever for my car to warm up. I know that replacing the thermostat is the only right thing to do, however I was considering other options to save few bucks. I got my timing belt and related things changes 3 years ago, and I'm not sure why the thermostat failed.

Anyway, I was thinking of installing the additional thermostat in the upper hose - just before it enters the radiator. I was thinking of using one of the Meziere thermostat housings - either WN0071 or WN0072 - however I'm not sure what is the inside diameter of the upper house. One of the housing is for 1 1/4" and the other one for 1 1/2" hose. Does anybody know what is the inside diameter of that hose? The outside is about 1 3/4", however I can't measure the inside one without disconnecting it first.

Did anybody do this kind of mod to the car? Should I drill a small hole in the thermostat to make sure there is a flow and prevent pressure buildup, or the small hose coming out of the coolant overflow tank takes care of it.

Thanks for any help and advise,
Jack