Yukon 2004 collant leak repair help

[ittrainer]

You are correct that the a/c can be affected by the hot water flowing through the heater core, but only a very small amount if the system is working properly. There are devices called blend doors that seal off the heater core when in the cooling mode. It is common for these blend doors to start hanging open due to component wear and failure.
The door actuators (motorized gear assemblies) are not made of high quality components-they have plastic gears like cheap battery drills and motors and temperature and location sensors made with inexpensive parts. So, besides the common bad o-rings that cause the leak you have, the whole system eventually needs to be rebuilt under the dash over time.

Larry

Good inforation.

How to test the state of door actuators and blend doors?

Thank you.

 

[sefiro]

Normally, with the heater and ac working correctly, run the controls through the settings. Mode door controls direction, blend door controls his much the heater door opens or closes.

The gm systems are designed to assume some heat cleared though the"door" but with no air flow through the heater coil (door closed) the amount of heat transfer is minimal and is easily overcome with the ac and should not require a bypass.

With all that said, I've had the heater hose connection on the firewall leak or break a couple of times. Ended up bypassing the heater with loop back fashioning clamps etc from various parts. Worked great for getting home.

As for fluid change, normal change/fill while running cold will get 98% fill. The engine leans back a bit so air would be towards the front. There is often a purge line from this part running under/ around the throttle. Small hose running back to the surge tank. That will allow the final air to escape.

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[ittrainer]

Normally, with the heater and ac working correctly, run the controls through the settings. Mode door controls direction, blend door controls his much the heater door opens or closes.

The gm systems are designed to assume some heat cleared though the"door" but with no air flow through the heater coil (door closed) the amount of heat transfer is minimal and is easily overcome with the ac and should not require a bypass.

With all that said, I've had the heater hose connection on the firewall leak or break a couple of times. Ended up bypassing the heater with loop back fashioning clamps etc from various parts. Worked great for getting home.

As for fluid change, normal change/fill while running cold will get 98% fill. The engine leans back a bit so air would be towards the front. There is often a purge line from this part running under/ around the throttle. Small hose running back to the surge tank. That will allow the final air to escape.

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Thank you for the detailed information.

What quantity and which antifreeze or water wetter to be mixed with distilled water do you recommend after flushing the old coolant knowing that our climate is extremely hot about 50C in summer and fair in winter around 10C temperature ?

 

[sefiro]

If never freezing, then 100% water would be ideal as it is a better coolant agent (absorbs more heat). Anti freeze is needed for freezing weather and in some systems, lubrication of water pump seals. So run 50-65% water.

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[sefiro]

And on a related fyi, many racing associations do not allow anti freeze in radiator systems , only 100% water. Accident that spills anti freeze leaves the race track slick and is harder to remove.

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[ittrainer]

If never freezing, then 100% water would be ideal as it is a better coolant agent (absorbs more heat). Anti freeze is needed for freezing weather and in some systems, lubrication of water pump seals. So run 50-65% water.

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Good.
What about boiling water and corrosion with 100% distilled water without antifreeze due to the very high summer climate temperature of 50C in my area and around 10C in winter?
Thank you.

 

[sefiro]

Key component of auto coolant systems is the stalled pressurized system. Under pressure, water won't convert to gas and as s liquid, better capture heat. Under pressure, the boiling point is raised above that of normal auto operating temperatures. (Basic high school physics). The added glycol does change the molecular makeup, lowering the freeze point and raising the boiling point. However, without a pressurized system moving the liquid around, the heated liquid will expand and find a way out. With expand molecular space, less heat is captured, engine temp rises and eventually the liquid boils. So, the pressurized system provides a better method of raising the boiling point.

As for corrosion, the original problem with water was the rust and rust formation with iron blocks, heads etc. The green antifreeze of the time helped with rust formation,,, but not as much as the pressurized system with little oxygen and the slow conversion to aluminum and various other metals.

The problem with green is that it would break down with time turning to acid which ate water pump seals and the aluminum. (thus the 24 change cycle). Many greens had buffer agents added to minimize the acid growth. Ultimately, this is what gave rise to the corrosion stories. The modern antifreezes don't break down into acids thus the longer lifecycle.

Yet we still use antifreeze in hot weather, only because we don't change coolant every 6 months, so we might as well mix for the freezing temps.

So, that's the technical reason. Here's the legal scoop: if you don't use the correct antifreeze mix, you'll void your warranty. The warranty void question should only be applied to those cases where freezing coolant damages occurred , not for overheated engine problems. The argument that the mfg will make is that water must of froze one night and damaged the item, leading to a leak, and over heating.



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[ittrainer]

Yet we still use antifreeze in hot weather, only because we don't change coolant every 6 months, so we might as well mix for the freezing temps.

Thank you for the detailed information.

I will NOT change coolant every 6 months,
So what is your advice whether
;
1.To use 100% distilled water ?
2.Or mix 70% water with 30% antifreeze?
3.What are the best brands of antifreezes ?
4.Which type of glycol or water wetters i use that is compatible with Yukon 2004 ?
5.Or just i use any universal antifreeze?

 

[sefiro]

Gm specifies Dexcool (orange) for the vortec engines at that time. However, if someone put in a different antifreeze (non dexcool), then problems like corrosion, sludge etc could result.

In theory, anything labeled as dexcool should work but I highly recommend that different brands of dexcool are not mixed as three is no telling what additives might not play together nicely. Flush well, a couple of times, then fill with reputable brand that you can get elsewhere if needed. I've been running prestone for years in my 01 and 04 in Texas without any problems. Typically running about 40%. Temp ranges from -15 to 40.

As for wetters, they are designed to attract water to metal surfaces better by eliminating the small air bubbles or vacuum bubbles that are created when fluids move against a fixed surface. By better contact, more heat is transferred. But once again, chemicals are mixing and there is no telling what the result will be. Flush well twice and fill. Note that 40m dexcool cars on the road represent well tested technology for the engine parts whereas the wetters are not as well tested and it's unclear what happens when the chemicals break down (so they become acids?)

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