Dexcool goop problem, question on flushing coolant
 

Hi, looks like summer is over. Monday we had weather in the 40's here and when I put my heater on it blew cold air inside the window and fogged up the window on the way to work. Also the temp gauge raised almost to the top of the temp gauge before it kicked down a little when driving. Long story short, when I got home and removed the radiator cap I found all the brown Dexcool mud in the radiator filler neck. I tested my radiator cap and it held no pressure so that was the cause of my leak. So now I have to flush the old coolant and goop out of the system. I got a Prestone flush 'n fill kit and a jug of the super radiator flush along with a couple of jugs of Prestone. My question is for the 2003 Monte Carlo 3.8 there are 2 heater hoses coming from the firewall going to the top of the belt tensioner it looks like. Which hose is the inlet hose? According to the Prestone, the one running to the top of the engine is the inlet hose, but both of these run to the same area so i can't figure out which is inlet and which is outlet. I would guess that the lower hose going into the heater core would be the inlet but not sure on this car. anyone know for sure? Here is what I want to use to flush the system. Attachment 22032

Also looking through the shop manual I cannot locate the heater hose replacement for 3.8 but under the flushing instructions it shows to remove the 2 knock sensors from the bottom to drain all of the coolant inside the block. Has anyone tried doing that? How hard is it to get to the knock sensors? What tool is needed to take them out?
Thanks for the help
Dave

Doesn't really matter which hose you use. I have one on each, in my Vette, so I can back flush the heater core. (They are not fun to replace) I also would not use dexcool, mainly because of what you're dealing with. Go with green, or if you really want something awesome, go with waterless. It lasts forever basically, and its boiling point is about 100 degrees hotter, so no blown head gaskets. h

You would need to follow the heater hoses through that bracket to where the coolant elbows (which go into parts of the engine) are to determine the true top one. As mentioned, not sure it will be a big deal.

As for draining the block and removing the knock sensors, I don't believe that is necessary with what you are doing (I've never done that on any flush I have done).

And as for dex vs green, it really does not matter with today's formula of dex. Dex has a bad rep but those days have been behind us for almost 15 years. Dex does sludge up if you don't flush it on a regular basis and I believe if you expose it to air within the cooling system (such as having a cooling leak). I and many people I know run dex in car that GM called for it and it's been that way for years. Remember if you decide to switch to ol' green, you want to get 100% of the dex out (unless you don't care about discoloration) and even with old green, you are still supposed to flush the cooling system on a regular basis. So no matter which coolant you are going to use, flushing the system is still a requirement.

Thanks for the tips. I'm going with the green this time, also will be replacing the thermostat and coolant elbows with the Dorman metal ones while I have everything apart and the coolant drained. Just wanted to be sure it did not matter which one I attached the flush and fill inlet to, looks like from your comments that it does not matter much.
Dave

If you have a leak that's causing coolant contamination, you might have a more serious issue than a flush will solve.

Not a problem, I believe a bad radiator cap caused my air leak, as I tested it and it would not hold any pressure. I flushed it today without the thermostat in until I got clear water out, kept it flushing for another ten minutes then drained it out, put the new Thermostat in, and new green Prestone. With a new cap on the radiator it seems to be ok now, heater is blowing hot air and the temp is staying where it should.
I ended up skipping the heater bypass elbows, as there was no leak near these so figure I will save these until needed. Too much work to change these if they are not bad to start with.
Both the original radiator cap and thermostat were coated with what looked like chocolate pudding, that is what happens to the Dexcool when it gets air in the system.

Sounds like you got a good flush. Should be good to go now! h

If I were u I would of changed those elbows, they can go at the most inconvient time, also if you still aren't holding pressure look around the throttle body, and everywhere, ifbu put enough air in you just might hear hissing and can find your leak

Should have taken your advice, last couple of weeks I've been leaking coolant, seemed easier to just put some more in every couple of days but friday I sprang a major leak, under pressure I saw it was the elbow from the tensioner to the manifold. So with a nice day yesterday I was able to install the new ones, hopefully that solves the problem. Does not appear to be a LIM leak as my oil is clean.
Dave

Read into the green antifreeze coolant vs dexcool before as I noticed the breakdown and sludging as well. Notice of caution what I found was the green is used on different rad systems that are made out of different materials. Everything that came up when I searched said the green used instead of dexcool in an aluminum radiator the green Is way more reactive to the metal and will eat away the radiator. Id use the yellow universal type. I stay with the dexcool. Has it faults, but who does the rad flush at the required 5 year or mileage equivalent like gm recommends. hope you upgraded the elbows to the aluminum ones.