I recently had an overheating issue on my 4.3 2000 blazer. I noticed the coolant looked terrible (ashamed to say) and it was the horrible dex-cool ( IMO). I flushed then entire system via a water hose attachment and was surprised at the gunk that came out. I looked at the discharged coolant for traces of oil but found none. System took several hour long flushes to rid it of gunk and the water ran clear. I installed a new thermostat and 50/50 green. It ran great until now. It overheated again! I opened the hood and low and behold... brown rusty looking coolant again! I was about to remove the thermostat to see if I could get it home when I had an idea. I opened the radiator cap to vent and it didn't overheat on my 70 mile trip ( bad cap?). Anyways, why does the coo,ant keep turning brown? It runs great, heats good in winter, but seems like when the coolant goes brown it overheats. Its not sludge-like and seems to have the same viscosity as it did fresh out of the bottle. Any ideas?
Thanks.

 

Do another flush and this time fill it with water and a bottle of CLR. I ran mine for short trips to get up to temp and keep it there for 15-20 min then let it sit and soak each day for about a week then reflushed it again and holy crap the crap that came out of there!! When I flushed mine I took the time to pull the rad inlet tube and back flush the system and also (I have a flush port on the heater core hose) blocked off the "away" side of the port to force water thru the heater core if that makes sense. The CLR will break down all the crap that's still stuck in your system so it can be flushed out. I went through the same issue with mine flushing it several times and filling with 50/50 and the brown kept coming back. I think what's happening is the crap that is stuck is being loosened by the 50/50 then its reclogging in different areas. I haven't had any more issues with mine since doing this Another tip is to make sure you remove the tstat while you are doing your flush or it will just stay closed and crap will pile up at it but I'm sure you knew that already. I would also replace the tstat again just to be safe.

 

when i had to replace my rad when she cracked i took it apart to see what 200k + miles did to it. needless to say the bottom channels where clogged badly almost 2" up from the bottom of the rad...so i think its safe to say it wasnt running at its best.

rex is on to something with his fix, sound like your having a flow issue in the rad.

 

Ok. I tried the CLR and gobs of junk came out, but it seems as though little circulation is going on in the reservoir. I force flushed the system and allowed it to flow over the fill neck on the overflow reservoir. Again, a good bit of gunk came out. Filled it with water ran it a day or 2 with no t-stat. Drained it. Filled it again with water and CLR. Ran it a day 2-3 days. A whole lot less gunk came out. Out of curiosity, I refilled with water and let it sit. Obviously clean. Ran it for an hour and opened the reservoir cap... tiny globs of OIL!!! Oil level has never had a sudden noticed drop, ATF seems good, exhaust doesn't smell funny or smoke, truck runs great (minus the overheating randomly part), always cranks on first try. What's the deal? Was the gunk blocking a leak or was there so much junk in the system the leak was undetectable? The CLR was in the system at most 3.5 days so I doubt it directly caused it. Does this model have a oil cooler that is routed through the coolant system (that is supposed to be sealed, obviously) and is possibly leaking or should I pretty much assume its a failing head gasket that has got to the point as to show obvious signs (power loss, milkshake fluids, etc.)?

Thanks guys.

P.S. Out of the entire reservoir of water I'd say it's probably at a tablespoon of oil after 3 drives over a week. So it appears to be slow, but still shouldn't be there.

 

I work with a guy that put a can of Irontite sealer in his neglected mustang
Irontite claims to seal cracks etc etc

he then started overheating , his rad drained felt 10X the weight of the new rad
Guess the sludge firmed up in his rad

 

I just ran into this same exact issue with my sisters 98 blazer. Hers was leaking tranny fluid into the coolant internally from the radiator. Bet you need a new radiator.

 

In reference to:
https://blazerforum.com/forum/2nd-ge...t-again-79814/

Let me start by stating the now obvious... the brown coolant is in fact being caused by a blown head gasket. In reference to the above thread I began, I got fed up with hopeful possibilities () and did a leak down on it and it fail. Just to be sure I checked the oil cooling system and ATF cooling system (which it does have... I guess I never noticed it although it IS a 4WD ) using a compressor and decided my shot in the dark was wishful thinking. Anyways... boohoo and all that other nonsense. My question:

Should I mess with a repair? Engine swap? Suggestions?

Let me start by saying I am completely capable of the rebuild as far as most tools and technical skills go. This is not my first rebuild either. Like I've said before: I know a good bit and for everything else there's google (and the forum here lol). I don't have a good way to test the block at a shop and I'm not a big stickler on specs and tolerances as far as the head goes (mating surfaces) unless they are way out. - Don't mean to start an argument on following spec tolerances, just my opinion is all. If I were working on your car, I'd follow spec. (and the gut).

The vehicle is a:
2000 Chevrolet Blazer LT
4.3 Vortec w/ 4WD and all the bells and whistles of its time with a sun roof.
112,000 miles
I use it for hauling mostly so its a backup vehicle and not a commuter.

History: I bought the truck used from a car lot in 2002 at ~50,000 miles. It is paid off now. I've taken decent care of it with regular oil changes, bearings repacked, greased front end regularly. I've changed the fuel pump twice and the transmission when out in 2004 and I had it rebuilt.

What's wrong with it: Head gasket, may need new water pump from gunk, driver side door panel broken (must shut door with window down... I hate plastic!), driver side ball joints showing wear, 6 disc cd changer (built into console between seats-aftermarket addition) won't eject cartridge.

Honestly, it still runs great. A/C is good, always cranks, battery's 2 yrs old, gonna need new tires (~1 yr). I'm unsure how it was treated before me, but it appeared good at the time and seems to have been a decent truck. The head gasket has just now began to show signs of failure. I don't have the money for a new 4WD vehicle right now and I do need a vehicle capable of hauling as I live on a farm and out in the county where there is no trash pick up, dirt to be hauled, the occasional break down on small vehicles to be hauled, etc. I don't pull tractors or a million tons of rubble, but I do pull a 4x8 and a 6.5x18 ft trailer from time to time.

Suggestions are welcome. What would you do?

Thanks guys,
The 6lb Sledge.

 

Like you said "its paid for "
For a couple months payments on a B/N truck you can get yourself a "long block" rebuilt motor for your Blazer
If the antifreeze has got to the bearings you could be opening up another can of worms
Most factory rebuilt motors come with the required gaskets to complete the swap
Water pump is fairly cheap

If the body is still decent and you can run it a couple more years , your money in the bank

 

whatever you do don't run DEX-Cool in the new radiator. super crappy antifreeze and it eats away at all of your seals n such...

 

actually dex-cool is a great anti-freeze. the reason GM uses it is because the green stuff does not have corrosion inhibitors that are compatible with aluminum. dex cools issue is when it comes in contact with air. like a LIM leak, a bad rad cap, hoses seeping..... that why the overflow reservoir looks like crap. The standard green coolant will attack aluminium. sooo if you want to get away from dexcool, use GO5.