Really annoyed here, my 2003 buick lesabre runs great, but my heater core keeps getting blocked with sludge. I've had it flushed twice this year, why does it keep coming back? I also think I have a leak somewhere but its not a big enough leak to cause a problem, hopefully its not the head gasket leak . I have a moderate amount of white smoke coming out of the exhaust, but I can only see it on cold mornings. I have regular green antifreeze in it and not the infamous " Dex Cool" ,, is there anyway to stop all the sludge from building up in my radiator and heater core?

 

Sounds as water/antifreeze is getting into the oil. Usually a head gasket, especially if oil is whitish-brown milky looking. Check coolant level also? Haven't installed engine heater lately with crossed lines?

 

Here comes the 64 $ question .
Was any type stop leak put into the cooling system ?
If so, that could be part of the problem.

When we examine some points , explanations sometimes present themselves.
Cooling system pressure is generally 15 psi
Oil pressure is usually between 20-30 psi
Cyl compression pressure is generally over 125 psi.

Usually if compression is getting into the cooling system , we get an overheat problem
If oil pressure is higher than cooling system pressure, and there is a path , I guess we know what to expect.

What is sometimes done is to put some dye (that shows up under UV light) into the oil and see if that is also present in the coolant. If so , well here again we know what needs to be done.