What did you do to your NNBS GMT900 Tahoe/Yukon Today?

[George B]

Added more coolant. Seems to be a much more frequent thing when it's cold. Since there is no visible leak in the front, could there be any other way to lose coolant while driving other than a head gasket?

I'm kind of dumb to the rear-heater system, so is it possible that coolant is escaping from that? How would I check?

Would I be able to fire up the truck, engage "REAR" on the HVAC controls, and then waddle my ass under the truck to look for drips?

Do you ever smell hot coolant but can’t find it? Some leaks evaporate before they drip. More in winter makes sense because the range of temperature change from cold to operating increases. I would toss some leak tabs in it and see what happens.
Genuine GM (12378255) Fluid 3634621 Cooling System Seal Tablet - 4 Grams, (Pack of 5) https://a.co/d/6Qx6R8C

 

[Sparksalot]

Added more coolant. Seems to be a much more frequent thing when it's cold. Since there is no visible leak in the front, could there be any other way to lose coolant while driving other than a head gasket?

I'm kind of dumb to the rear-heater system, so is it possible that coolant is escaping from that? How would I check?

Would I be able to fire up the truck, engage "REAR" on the HVAC controls, and then waddle my ass under the truck to look for drips?

The Tee’s in the coolant lines. Radiator tanks. Look at the upper end of the driver side tank.

 

[Doubeleive]

Sitting in a Canadian mom and pop shop waiting for alignment on yukon after replacing front strut/coils.

Someone brings in a F-250 that hasn't been on the road for a year asking what it minimum needs to get back on the road.
Owner calls them after taking a look and saying it will need at Minimum:
- New battery
- 4 rotors ( said they "think" calipers and pads can be reused )
- 1h further inspection for error codes etc

I'm sitting here thinking "makes sense, sounds like 600$ CAD?".
Owner goes "we've priced the estimate here, you are looking at 1465$ CAD ( ~1100$ Freedom Dollars ) as a minimum here, excluding anything else we will find"

What the fudge?

that's about what the gm dealer here would charge
battery $200 +
brakes $399 (per axle)
1hr labor $189 (inspection time)
+tax (10%)
you can find independent shops offering deals on brakes but you would be getting the cheapest of the cheap for parts

 

[Doubeleive]

Added more coolant. Seems to be a much more frequent thing when it's cold. Since there is no visible leak in the front, could there be any other way to lose coolant while driving other than a head gasket?

I'm kind of dumb to the rear-heater system, so is it possible that coolant is escaping from that? How would I check?

Would I be able to fire up the truck, engage "REAR" on the HVAC controls, and then waddle my ass under the truck to look for drips?

all the rear controls do is make the air blow slow/fast, hot/cold or up/down
if the engine is up to normal operating temp then the coolant is flowing thru the entire system each time the thermostat opens. regardless of anything.
if you have ramps or jack stands get the front end up off the ground high enough to get under it with a flashlight and look up, rear leaks are extremely rare but not impossible.
look all over under it but concentrate on the passenger side and under radiator, use a small mirror and look under water pump.
if you can't find anything visual, then place some cardboard under the engine area after a good drive and check for a wet spot the next morning and look directly up from there.
if you really suspect the rear then look it under at the rear passenger corner, you can place cardboard there as well.
if you still can't find anything then you can do a block test but these engines don't seem to have that issue, the gmt800's sometimes did
you could also send a oil sample out to blackstone labs for a more detailed analysis if the block test is not showing anything.
usually it's the radiator or heater hose t's, water pump, cracked coolant reservoir tank.

 

[Charlie207]

The Tee’s in the coolant lines. Radiator tanks. Look at the upper end of the driver side tank.

I should have mentioned that I have (this summer) replaced the radiator, coolant overflow tank, most* of the hoses. (Along with EOC lines).

I'm just not seeing any leaks, when I look down from the front bumper with the hood open. I guess I'll have to get more perceptive.

 

[Charlie207]

Do you ever smell hot coolant but can’t find it? Some leaks evaporate before they drip. More in winter makes sense because the range of temperature change from cold to operating increases. I would toss some leak tabs in it and see what happens.
Genuine GM (12378255) Fluid 3634621 Cooling System Seal Tablet - 4 Grams, (Pack of 5) https://a.co/d/6Qx6R8C

Yes to the smell, I sort of assume right now that it's coming from the exhaust.

 

[Doubeleive]

Yes to the smell, I sort of assume right now that it's coming from the exhaust.

nah, there would probably have to be a lot in the oil to smell it from the exhaust and the oil filler cap would be all nasty looking under it, like bad nose snot and oil filler tube would be all yucky too.

 

[Charlie207]

all the rear controls do is make the air blow slow/fast, hot/cold or up/down
if the engine is up to normal operating temp then the coolant is flowing thru the entire system each time the thermostat opens. regardless of anything.
if you have ramps or jack stands get the front end up off the ground high enough to get under it with a flashlight and look up, rear leaks are extremely rare but not impossible.
look all over under it but concentrate on the passenger side and under radiator, use a small mirror and look under water pump.
if you can't find anything visual, then place some cardboard under the engine area after a good drive and check for a wet spot the next morning and look directly up from there.
if you really suspect the rear then look it under at the rear passenger corner, you can place cardboard there as well.
if you still can't find anything then you can do a block test but these engines don't seem to have that issue, the gmt800's sometimes did
you could also send a oil sample out to blackstone labs for a more detailed analysis if the block test is not showing anything.
usually it's the radiator or heater hose t's, water pump, cracked coolant reservoir tank.

I apologize for any lack of clarity: I don't mean the rear controls that the kids hit with their feet from the backseat. I mean the button on the dashboard that I hit, named "REAR", which turns on the rear vents. I'm sure i'm dense, but does turning that button on cause coolant to flow to the rear of the vehicle for a rear heater?

I asked for a diagram of the system in a differnt thread.

It just snowed here, so I'm a big scaredy cat of getting wet/cold by laying on the ground. Buuuuut, I'll see if I have any big chunks of cardboard to lay on.

 

[Charlie207]

nah, there would probably have to be a lot in the oil to smell it from the exhaust and the oil filler cap would be all nasty looking under it, like bad nose snot and oil filler tube would be all yucky too.

Oil on dipstick just looks like oil, and there's no gunk under the filler cap.

So you're saying that coolant can't make it's way into a cylinder and be burned away without evidence in the oil?

 

[89Suburban]

Added more coolant. Seems to be a much more frequent thing when it's cold. Since there is no visible leak in the front, could there be any other way to lose coolant while driving other than a head gasket?

I'm kind of dumb to the rear-heater system, so is it possible that coolant is escaping from that? How would I check?

Would I be able to fire up the truck, engage "REAR" on the HVAC controls, and then waddle my ass under the truck to look for drips?

I have a weeping tank on my radiator but not enough to drip onto the ground.