Hi, I recently purchased an a4 1.8t auto. and its leaking coolant quite badly. I think its the upper hose on the back of the engine where it connects to the engine block. do you replace the entire hose? or is there I seal I can buy? and where could I buy something that would fix it one? thanks for your time and help.

 

If its leaking due to a hose check your clamps first and make sure its tightened down tight, if its leaking due to a bad hose don't waste your money on silly sealants or leak repairing glue they sell at stores, just buy a new hose.

 

its probably the coolant flange, which is plastic. but check before you buy. i highly doub its he actually hose.

 

Could also be the heater core hose that attaches to the coolant flange (if it's not the coolant flange itself). I replaced my coolant flange, and before driving anywhere developed a leak at that hose. Normally you're supposed to replace the whole hose, but it's only a little o-ring that leaks... I used an o-ring with the following dimensions:
7/8" x 1 1/8" x 1/8".

 

thanks, Ill look into those parts.