Rust in coolant.

[supertrucker1978]

How exactly are you flushing your system? Just putting a hose in the top of the radiator and opening the petcock at the bottom? Or are you using a "flush and fill" kit like the one in the link I posted?

http://www.oreillyauto.com/site/c/d...ap?ck=Search_N0185_-1_1531&pt=N0185&ppt=C0075

 

[94Sierra4x4]

Head gasket. Cracked heads are common in TBI trucks too but normally show signs of water in the oil.

What color is the antifreeze that you put in it and that was in it before? Dexcool is orange/yellow.

Haven't seen any sign of water in oil whatsoever, will be doing oil change in a few hundred KM so I'll have another good look then.

The antifreeze I used was green. Don't recall a time using orange/yellow af

How exactly are you flushing your system? Just putting a hose in the top of the radiator and opening the petcock at the bottom? Or are you using a "flush and fill" kit like the one in the link I posted?

http://www.oreillyauto.com/site/c/d...ap?ck=Search_N0185_-1_1531&pt=N0185&ppt=C0075

Just a hose in top of rad with petcock open. Not with a kit like that.

 

[JollyGreen]

Haven't seen any sign of water in oil whatsoever, will be doing oil change in a few hundred KM so I'll have another good look then.

The antifreeze I used was green. Don't recall a time using orange/yellow af

You're good as far as the coolant goes.

 

[supertrucker1978]

Just a hose in top of rad with petcock open. Not with a kit like that.

I suggest getting the kit, it will flush the entire system. Engine, radiator and heater core. When you put a hose at the top of the radiator and open the petcock most of the water being introduced to the system is either coming back out the top pf the radiator or coming out of the petcock and not being circulated through the system.

 

[DonYukon]

You're not using dex cool are you?

If dexcool is exposed to air it will turn a rustic orange color and rust parts just a FYI heres what I found out , wish I knew this sooner
http://www.gmc4x4.com/topic/128-dexcool-important/

 

[sewlow]

When you flush the cooling system, along side the hose, run an airline with about 10psi flowing out of that, into the top of the rad, too. The air percolating with the water inside everything helps to break up any deposits in there.

 

[95Escahoe]

When I first got my 95 Tahoe I had the same issue, the previous owner neglected the cooling system flushed and refilled it 3 times and it would turn rusty after awhile, it wasn't until I replaced the radiator that it went away, now after all new hoses, radiator, heater core and water pump it is perfectly green and stays that way

 

[frito-bandito]

Sound like a solution. I actually just got a new fitting because when I tried taking the old one out during the rebuild it broke right off.

My fitting leaked forever (didn't know that was the problem till it finally broke) and it broke on me one night, I shoved a shaved down piece of broomstick wrapped with electrical tape in the hole and vise gripped the hose so I could make it to the parts house, then I had to buy an Easyout to get the old fitting out, if I recall right, the new fitting is stainless instead of aluminum.

As for the rust, I suspect the waterpump.

 

[Enginebuilder]

Step 1: Drain all fluid from cooling system. (best done when cold)
Step 2: Fill system with DISTILLED water + a cooling system flush kit or CLR (CLR tends to be cheaper)
Step 3: Set heater controls to max heat
Step 4: Start truck and allow to reach operating temperature. Let run for an additional 15 minutes.
Step 5: Allow engine to cool down, usually takes 3-4 hours.
Step 6: Drain cooling system by pulling lower radiator hose. (this allows large particulate matter to be evacuated from the system, whereas the petcock may get plugged)
Step 7: Back-flush the heater core by disconnecting the heater hoses and hooking them up to your garden hose- alternate direction of flow until you get clear water coming from both directions.
Step 8: Now is a good time to inspect/replace your thermostat
Step 9: Reconnect all hoses
Step 10: Fill cooling system to required levels, using either the 50/50 pre-mix, or by using straight coolant and distilled water.


Following the above procedure should take about half a day, mainly because you need to wait for the engine to cool back down once you've put the cooling system flush (or CLR) into the system. Shouldn't have any further problems with discolored coolant.

FYI: This may not be rust at all, but "Radiator Stop Leak". If you aren't familiar with this vehicle's previous service history, this stuff may have been used. I personally HATE the crap, as all it does (IMO) is to hide (temporarily) a real problem, and tends to clog the tiny cooling passages of the engine, heater core and radiator, leading to poor cooling system circulation & poor heater performance. All around bad stuff, and it is notoriously difficult to remove from the system. Can usually tell by the rust-colored buildup at the radiator fill neck; looks like rust, but when rubbed between two fingers, crushes to super-fine particles, with almost a grease-like feel.

FYI2: Aside from flushing the heater core, avoid using tap water for your cooling system. The minerals in it tends to create a galvanic reaction, leading to premature failure of aluminum components. To be sure, in an emergency situation, I'd use tap water, but only then- distilled water has had all the minerals removed, and thereby reduces the corrosion caused by galvanic reaction.

 

[8716valver]

I made the mistake of using stop leak in my 96 a few years backs and it actually collected in the overflow hose so much that I would no longer get any coolant flow t/from the bottle. Dont use stop leak!