Burning coolant? Brown sludge in radiator

[GTPlzz]

Okay, so im not sure exactly whats going on here, i'll describe whats going on and i'de appriate your guys/gals opinions

97 GTP
Almost 240K miles, but still runs suprisingly well.

Recently replaced mt radiator and hose's (because i had a leak on one of the plastic sode tanks)

Okay so i replaced it, filled with cool ant and havnt had any issues for about a month, last night, the "low coolant" light comes on while sitting in a drive thru, and it starts getting a little hot (a tad over 1/2 way mark)
So i get home and check resevious tank, empty.

Pop the radiator cap and theres this thick brown sludge type stuff was Im on the cap and down the radiator neck, and radiator was pretty much empty of any coolant.

Why would this be happening?
Im pretty sure it has the plastic type LIM gaskets.

What im thinking is somehow it has developed a internal coolant leak somehow (does not leak on the ground or dont see any coolant pooled up.on LIM)

I also have replaced elbows with aluminum ones.

I am hoping i can replace my LIM and be done, since this cars my DD, untill i get my 2000GTP motor back in and running.

No coolant in the oil , dipstick.looks fine, no mixing. And from what i can see down into the valve.cover, no moxing in there either.

Possible head gasket?
or LIM?

Also not sure of this is worth mentioning, the car for some while , upon start up has a rough idle (sounds like it has a cam) but it runs and drives fine, and sometimes it idles fine, i only seem to notice when its idling or first started.



Any input is appricated!!
Thanks

[GTPlzz]

Sorry about all the spelling. I hate touch screen phones.

[Fivefingerdeathpunch]

I'd replace the Lower intake gaskets and do another coolant flush.

Not likely that its a headgasket. Also don't mix coolant colors or it will sludge up again.

[dsmuts]

I'd replace the lim gasket and put a new uim in it

[Scottydoggs]

i'd do a compression test. the coolant has to be going somewhere, bad lim gaskets on a supercharged engine wont eat coolant like the n/a engine will.

[GTPlzz]

It has had only green coolant in there since i've had it. when i refilled the radiator after i replaced it, it was with green.

Theres no way a bad lower intake gasket can cause the coolant somehow to burned off inside the engine? Mabey a small leak between a water jacket and intake port? Or something like that

Im just really hoping its not bad head gaskets. Im in the middle of dropping my engine back into my white 2000 GTP.

So if this 97 has a bad head gasket. Im SOL for a ride. Lol
If its lower intake, thats not a big deal. A day off and a 6-pack of corona can get that fixed pronto.

Note: last night i flushed the radiator and refilled, runs at its normal temp, but the coolant has to be getting leaked/burned somehow.

[FriboRage]

Just floatin this idea by...

Did you bleed the air properly when you put the new radiator and hoses on? It might have been slowly burping this whole time, finally evacuated a huge air bubble last night and that dropped the level to where the sensor picked it up.

And the color of new coolant mixing with old muddy stuff can really make an ugly brown color.

Have you tried filling it back up yet? Have you lost any more?

[dsmuts]

I didn't realize it was sc. Skip my suggestion for a uim lol

[GTPlzz]

Yeah i guess i didnt think of new coolant mixing with the old brown water, i was running only water in it for awhile, while the radiator had leak, after replaced radiator i refilled with proper mixture.

I thought i did a good job of getting all the ior bubbles out, because it never over heated or even got hot after replaced radiator.

I did flush radiator last night and refilled with water only (untill i figure out whats going on) i will check fluid level when my gf gets back from work with my car.

[hensleya1]

Dexcool, if it's been in there a while, likes to cake up in impossible-to-reach places, such as the insides of the block, the hoses, etc. Even after you flush it, it'll re-sludge before long as the caked up-sludge breaks down and begins floating around. You'll never get 100% of it, short of tearing the block down and power-washing everything.

I had some luck with using two bottles of Prestone flush with straight water - ran it for a week in a Monte Carlo and the sludge came right out - but it wasn't horrible to begin with, either.

As to the leak, apart from your checklist the only thing that leaves is the LIM gasket. Which I'd tackle at the same time I do the final flush.

[GTPlzz]

im pretty sure i figured my situation out, there was a leak one of the heater hose's that goes to alt bracket. The it noticed today as i was doing a final check-over before doing th LIM, only sprayed/leaked out when ubder throttle. Replaced and refilled with coolant & water.

Seems to be good now. Havnt driven it tho, i did bleed the cooling system, there was a ton of air in there.

Keepin my fingers crossed that its fixed.

Thank you everyone for your input, greatly appricated.

I am still going to do the LIM, but it will be put off until i finish my garage.