I gotta' do a coolant/antifreeze flush, after checkin' why the heat isn't.

The gravy in the reservoir was a little brown, just needed salt.

Any precautions? Like no chemical flush agents, anything???

Thanks...

 

You probably already know this but someone said to never mix the older style green coolant with the new red coolant. Supposedly it turns to gravy!

 

Yeah - I've seen the red coolant form deposits in 4 GM's, including in an '02 1 ton that I bought new, and which stayed running...

Did GM red get used in '94?

No LT1 flush precautions???

 

it's orange... Dexcool.

No, not 1994... at least not to the best of my knowledge. I think it started in 95...

However, the coolant is brown and milky? Check your oil.

 

Not sure if you need them, but here are some notes about the flush procedure in general:

The engine cylinder cooling jacket sits lower than the radiator, so in order to get any more than half the coolant out you will need to raise the car and unscrew the knock sensors, which are screwed directly into the cooling jacket. Drain the radiator as well.

With the knock sensors still out, I recommend using a hose to force water through the system to dilute any of the old that's left.

Run the engine almost up to temp with the fill cap off. This should get most of the air out of the system. Refill as necessary.

Lastly, I believe there are two bleed screws on the LT1 to open and close once liquid flows out (as opposed to air). One is on top of the thermostat, and the other, not present on the LT4, is on the throttle body. This will get any remaining air out of the most stubborn places.

 

Just a little humor about campbells, bogus... No oil; pretty dark, but clear. And just light flow through the heater core, judgin' by the weak heat.

Would the shop vac and the vacuum pump get some residual juice from in the block without damagin' the thermostat???

 

Good question. I know others have tried a shop vac but I am unaware of how their thermostats fared.

 

A little brown is usually just the gunk from the GM sealing pellets.

 

I would splice in a radiator flushing kit and flush all that stuff out of there. Then I would get a good radiator cleaner agent and follow the instructions. Last time I did mine, I let it flush for 15 minutes before all the crud and foam disappeared. Then add coolent and burp several times.

 

If you want to get most of the coolant out of the block make sure you pull the knock sensors with the car level. Use distilled water since the radiator is aluminum.


Dave

 

A word of caution. If you do repeated flushes with plain water to try and get every last bit out of the system, pay attention to the gauges. If you leave the radiator cap off and are successful in purging the coolant, the remaining water will boil at 212 and because it is circulating, all of it will be ready to boil at the same instant. Pretty darn exciting when that happens.

 

If you're flushing then you're constantly adding cold water so no such thing happens.

If you just filled it with pure water and left the cap off then OK I can see that happening, but why would anybody do that? And 50/50 coolant will also boil if you leave the cap off.

 

when I flush my block, I pull the thermostat, and re install the water neck, and stick the garden hose in it, take off the lower radiator hose and crank the garden hose full blast and try and seal it off around the water neck so its amost preassurized. every thing thats yucky in the engine block should come out this way after about 15 min.

 

It does happen. It just depends on the rate at which you are draining. You can easily fill coolant/water at a faster rate than it drains. In my case, after a couple fill, drain, refill, cycles, I was draining the radiator at the bottom while filling from a hose in the top.

Why do some people insist that what you experienced could not occur?

BTW, when I finally got all the gunk out of the car's system, a heater core leak appeared.

 

I also agree with finding the leak once all the old fluid is out. my leak was the little valve that operates the heater core flow. mine was "taking a pee" right out the shaft. had to by pass the heater core for a little bit while I found a new one.

 

I think you just answered my next question there brian (ya need to get yerself yer own psychic hotline there )...

So chime in with other info/comments too...

All summer, no cooling problem - A/C on, stop 'n' go, 235* max temp on the guage.

Good flow, right?

But the heat wasn't - maybe 85*. The fluid was dark, but clear, so I got the GM red 'plug'???

Nope. I opened the radiator drain, and it drained pretty light yellow (bogus probably right on GM red '95+). Then I uncapped a line to the heater core - the one where there's a 'T', with one line goin' to the TB (or the intake manifold below it) and plugged in the garden hose, and pulled the trigger.

I could hear the hose water flow, then slow, then break free with the Campbell's chunks in the heater core. Comin' out from the 'T' and the radiator drain was good stuff, then it got darker, and I could feel the chunky jam hittin the back of my hand in the coolant comin' out of the 'T'.

So the heat that I had was not much more than 'interface' with the main system flow. The plug was not the pinkish-white slime plug that you get from GM stuff.

So the question was, is there a flow controller to the heater core in a '94? Since there is then, when is it open? Always when the heat is on? Only when the heat is on max?

If there's a heater control valve in the coolant line, that is closed all summer, isn't every car gonna' get jam accumulatin' in the heater core?

If ya' put in a by-pass to allow 'always' flow, ain't ya gonna' get better coolin' in the summertime? Will the heater core heat increase the interior temps, when the heat is NOT on?

EDIT:
Next question: have you ever seen the heater valve controller? If you feed the garden hose into the heater core line, can you break the valve door with water pressure in the line?

OR, maybe the door doesn't completely shut off the flow, so you can't break it, AND it allows a little flow ALWAYS, which [supposedly] prevents plugs formin' in the core???

And, where does the thermostat control flow for? The heater core? So there's redundant heater core flow control?

 

I think it was already there chat...

That gunk was lodged in the heater core, and stopped the hole from leakin' before you did the flush.

The winter before, that stuff froze in your core (even tho' your coolant in the main part of the system was good), and when it froze it ruptured the line.

The gunk just stopped the free-flow leak.