Last August i got a 98 Lesabre that had in the green antifreeze in it . i am a person who goes by putting in what the car came with and that is Dex Cool . Up until last month when i replaced the coolant reservoir i was losing coolant . Once i put the new reservoir in never really lost coolant but i already see like a brown build up in the container could this be air? How do i go about bleeding the cooling system in a 98 buick leaser thanks guys

When you put the Dex back in, did you remove *ALL* of the green? They can't be mixed.

well when i did it last summer i flushed it all out using the directions on the bottle of the prestone super flush so pretty sure it didnt all flush out. Ive changed the water pump and belt tensioner and i see dexcool come out of manifolds so im assuming maybe all the green is out

Dex makes a brown sludge if air gets in it. Perhaps wash out the bottle and it should be fine. As long as your not seeing sludge in the cooling system.

Oh ok, maybe thats it, Where would be a good spot to check for sludge? Are you a fan of dexcool?

Take off the radiator cap and look on the bottom of the cap.

I have no problems with Dex, it'* a good coolant. I use green because I like the high visibility you get with the green. Dex is a bit harder to identify on the ground. But if your asking if I'm one of the people that thinks Dex eats gaskets, no, I'm not.

Great , thanks for the advice, do you think im ok if i just flushed the radiator but when did work on the cooling system never saw green?

When Dex and green get together you get a thick black sludge. If it'* looking clean then your OK.

Dex is fine as long as you change it if you don't it will eat gaskets as it gets acitic after time.
Is there a bleeder on the T-stat housing?

No it won't eat gaskets. When you've seen as many as say Dan and I have, you start to get a clearer picture and ask more questions. The plastic gaskets have relief notches and it'* those areas that collapse. Then the seal is compromised. The issues are more heat related than coolant related. Dex will sludge/turn back to OAT with air and it does turn brown when mixed with the old green coolant.

OP: it sounds like you may want to perform another flush and ensure you flush the motor well. You may have gotten some mixing.