after my h/c swap it looks like there is mud in my radiator. any idea what this brown **** is?

 

Im not sure witch one it is the orange or the green coolant but eventually a brownish sludge will build up in your radiator.

 

It's probably oil unless you have dexcool, which could very well cause a muddy condition in the radiator.

 

when using dexcool or plain antifreeze you must remove all traces of air. if all air isnt removed or purged from the system then this brownish sludge will form. once it forms enought for you to see it throught the radiator cap then your radiator is full of the suff and it is inhibiting the performance of the radiator. flush it good and flush it untill nomore brown comes out. i use bleach to flush it when mine looks like that. and it usualy takes 30 min to a hour to throughtly clean. i recomend cleaning it your self becuse a shop is just going to pump out the old coolent and pour in new and not remove any of the sludge thats stuck in. pull your radiator out and use something to plug the bottom hole and fill it up with bleach and let it sit for a hour or so then drain it and fill it up with water and draint it continue dooing this till you dont smell bleach any more. then reinstall it and fill it up with water and run it till the thermostat opens up and let it run for about 5 min more then drain out all of the water and replace it with what ever colent your car calls for. i would also pull the thermostat and check to see if any of this sludge has formed on it if it has clean it and reinstall it with new gaskets. once u fill it up with coolent let it run till the thermostat opens up (have the cap off ) and add coolent untill it stops "burping". now put the cap on run it till it pressureises and let it cool off and add coolent as needed.

 

Dexcool = DexDEATH

 

The hundreds of thousands of vehicles using Dexcool would seem to be the exception to that statement.

 

Using distilled water in my Z and changing often (twice/yr - run different mixed for spring/summer/fall and winter) it looks brand new inside rad, with green anti-freeze. The Dexcool in my 2000 ZR2 has plugged up the heater core 3 times and it's been flushed 3 times, in 2 yrs. I have to flush the heater core again so I can have some heat this winter

Dexcool + tap water = lotsa sludge.