Gunked up radiator

Hey im searching for a way to solve my gunked up radiator problem. I have replaced the old gunked up radiator and thermostate back in may/ april. I am having the same issue with the new one. I have taken it to be flushed by the shop and he said he had to do it twice to get it all out. Now i am having the same issue again. My question is; what is causing this and how can i prevent it from happening again?

Welcome, I don't know which of the two engines you have, either 3400 or 3.8 V6. Each of these is known to have issues with the lower intake manifold gaskets failing which is most likely the cause of your gunked up radiator. There is a "sticky" posted at the top of this forum that will explain the details of the repair. Unfortunately it's a costly repair in the range of 500-700 at most shops. The gasket set is not the major cost, it's the labor/time at about 3 to 4 hrs. Post back with your engine size and mileage which will help as others here will reply as well.

If you are still running DexCool, get rid of it. It loves to gunk up when any air is introduced to the system. I flushed the DexCrap out of my Grand Prix a few years back and put good ole green in there and won't look back.

Hey and thanks for the reply. Its a 3400. It has 72,556 miles. I bought it in march of this year. I took it to a radiator shop they said it looks like it might have stop leak in there. Its thick gunk and hard to scrape; but it does come off. How do i find the "sticky"?

Stop leak could very well be the answer. That stuff does more harm than good. You're probably going to have to do several flushes to get it all clean.

Thats what i have heard. Thanks i appreciate it y'all.

Hey and thanks for the reply. Its a 3400. It has 72,556 miles. I bought it in march of this year. I took it to a radiator shop they said it looks like it might have stop leak in there. Its thick gunk and hard to scrape; but it does come off. How do i find the "sticky"?
On the page your post is listed there are posts in red :Important (intake gaskets)
On the stop leak, just about every garage guy I talk to uses some when they do radiator flush, even the dealer does this, Or I should say MY Chevy dealer does. If the gunk is oily brown sludge, that is from the oil migrating through the lower intake gasket. On the 3400 and (by the way thanks for reposting that info) you may also see an oily area down in the lower intake valley behind the power steering reservoir towards the back. you will need a good light to see this. This sludge is not really hurting anything and if your not overheating you could just maintain with a flush and fill once a year or two years. Just use the coolant type that you have in it now the green and the orange do not mix (don't play well together)...
That is pretty low mileage for a 2003 you may just be looking at stop leak residue the problem with the intake gaskets was the original gasket failed and were as I understand it redesigned in 2003 but I am not certain when that year. Mine is a 2002 3400 and gaskets went bad at 105K I now have 129K Just more info for you

Thats what i have heard. Thanks i appreciate it y'all.

your coolant problem maybe the result of oil getting into the coolant. could also be from using drinking water with the coolant [antifreeze].. you need 50% min of antifreeze to protect from corrosion not just freeze protection. mixing coolants with drinking water is not good in todays engines. what is needed is an acid flush product to clean out all the crap. then the coolant system gets flushed out to remove and neutralize the acid. before new antifreeze and distilled water is installed. to determine if oil gets into the coolant system you use a dye that will reveal its self when exposed to UV light .. this is the tool to determine if you have a oil leak in the coolant.. could also be the transmission fluid is leaking into the coolant if an oil contamination issue.. MOST TIMES THIS IS FROM [GOOP]MIXING DIFFERENT TYPES OF COOLANTS !! DEXCOOL DOES NOT MIX WITH OTHER COOLANTS ... IF ITS NOT GM APPROVED DEXCOOL IT IS NOT COMPATIBLE !!!!!