need help replaced t-stat on 12v b5 2.8

[cookies2shoes]

first off my heater core is by passed i replaced the t-stat but car is overheating i've searced everywhere on the search thread.h20 pump is new as well as t-belt roller/tensioners.before my temp gauge would go to almost 3/4 so i figured the t-stat was'nt opening all the way. no oil in water or vice versa.any ideas.some jackass ran regular coolant in for a while i flushed now it just climbs till temp light comes on then i shut it off. could i have an air bubble? is it because my heater core is bypassed radiator is new too.heater core hoses are not getting hot.help!!! thanks noob

[djwimbo]

an air pocket is a possibility.

question, why is your heater core bypassed?

Do you have VAG-Com? I had to work on a customer's car (97 2.8) a couple weeks back that had a similar issue. The gauge would move at normal speeds, but would rise to 3/4 or so and sometimes come down to 1/2. We did just about everything to this car. Waterpump, T-Stat, Coolant temp sensor, chemically flushed the radiator and heater core, and it still did it.
I got to messing around with VAG-Com on the car. The Instrument cluster was reading coolant temps of ~245*F, whereas the ECM was seeing a nice, normal 195*F. After looking through all the info on the instrument cluster, I think I found the issue. The cluster (in park) kept putting out weird readings, like the vehicle speed was doing 177MPH at idle.

I'm not saying it's the same issue, but it's something I've seen.

[generik777]

Their is a way to check if the cluster is putting out the wrong info. You can use your climate control to do a limited amount of diagnostics. It will tell you what your coolant temp is without using the cluster gauge. I had to use it for a while when my coolant temp sensor went bad. Here is a LINK to directions on how to do it. You'll need code 51 to see the coolant temperature, And It will display in celcius.

[v8b5]

Do yourself a favor and drain the coolant. Lift the rear of the car about a foot. open the bleeder screw by the firewall to the left of the resevior on the coolant pipe. Fill the resevior till coolant comes out the bleeder. Close bleeder, start engine and let run untill temp gets to about half way. shut car off and slowly open bleeder. Let air out untill coolant comes. refil and do this until it doesnt over heat. The first A4 2.8 I owned did the same thing about 10 years ago. Just start over and bleed properly. You will be pleased!!!

[cookies2shoes]

thanks guys ive been still working on the coolant temp thing i tried bleeding it a few times still does it im gonna try the code thing on the climate control.this is my 3rd b5 but ive gotton into the maintenence way more.when i had major probs w/ my other ones 1.8t and another 2.8 i just got rid of em.well ive done alot ot mods on this one and turned alot of wrenches so im determined to see this one thru.thanks for all the helpful suggestions.heres a pic of her 97 fwd 01 facelift 19's shaved mldgs/shaved markers/fender badges always thought they were too busy on the fenders/black roof. i just moved to southern ca. from oregon if anyone is close by and would like to trade ideas sometime let me know thanks adam,my g-friend set up my sig so disregard the cookies2shoes ill be changing it soon. <a href="http://s11.photobucket.com/albums/a172/mysticalchickens/?action=view&current=001.jpg" target="_blank"><img src="http://i11.photobucket.com/albums/a172/mysticalchickens/001.jpg" border="0" alt="Photobucket"></a>