I know this has been talked about quite a bit but I cant really find the answer im lookin for. I have a 2002 blazer 4dr 4wd I noticed like a brown sludge in my radiator so I flushed it and got some of the crap out of it. I filled it back up withthe good old fashion green antifreeze. Then it got to where the engine wouldnt warm up unless you put it in nuetral and wound it up a little bit and got the pressure in the cooling system built up and blew the crap out of where ever it was stuck. Then I flushed it again and replaced the thermostat. Now the engine is warming up fine and the heat works for awhile then goes away if I put it in nuetral and wind it up again the heat starts workin again, I have a 40 mile drive and I probly have to put it in nuetral and wind it up a dozen times or so in that 40 miles. Also if I get a little carried away on winding it up it jumps forward a little and the speedo jumps not exactly sure it should do that in nuetral.I know its the heater core getting plugged up,is there anythingI could do or somethingI couldput in it tohelp get the sludge out? I have been using the prestone flush and radiator cleaner, I also put a back flush kit onsoIcould flush it myself with the garden hose. If anybody has any ideas that would be great because I kinda miss drivin the blazer back and forth to work it gets way better gas mileage than my truck and the weather is to crappy to drive the camaro.

 

Did you check both hoses into the firewall to the heater core? Both should be too hot to touch when the engines up to temp if youre heater core is functioning properly. But to me it sound's like you have an air bubble in the system.

1) did you replace the radiator cap when you flushed the system? The GM black plastic ones are pretty bad for keeping pressure in and air out. (air also is coincidentally what causes the sludging of the DexCool)

2) If you have replaced the cap and are using a nice Stant metal one, then try parking the blazer with the front end elevated (on blocks/ramps/ an incline) and leave the cap off overnight to allow the air to fully escape.

Good luck and hopefully you're heater core is actually fine!

 

Yeah, the heat problem sounds like you have air in the system still.

 

I have to agree with there being air still in the system!!!

 

I found a stant cap out at the farm because you cant buy one around here without ordering it online and put it on and and drove it about 60 miles and didnt notice the heat didnt fade out so Im guessin that fixed it.So there is 1 problem down and 2 to go, an exhaust leak thats murdering my gas mileage and the blend door doesnt work right yet.... Thanks for the help guys.

 

No problem we like to hear about things getting fixed!!

 

sludge in the radiator is from air in the system breaking down the del-cool. with the heater core it would probably be easier just replace plus it sounds like there is still air in the core. one other thing is to do another flush and make sure to put dex-cool back in the system, not the typlical green stuff. when you do a flush it does not always get 100% of the old coolant out and you will always have a little coolant caked on the walls of the water passages inside the motor, and mixing the two coolants is always a very bad idea, they break each other down and will cause more problems. gm has design its vehicles to use dex (even though it can be a pain sometimes). as for the thermostat, betting when you replaced it that it was stuck open, causing overcooling. hope this helps