2008 Chevy Tahoe Overheated

[Dustin Jackson]

Need some help here. Wife said the transmission overheated to 250 on the way home and wouldn’t go into 4th gear. She drove it about 4 miles home after seeing the trans temp. She didn’t know where the coolant gauge was at so didn’t know if the motor overheated. Upon inspection the radiator is busted leaking coolant and The coolant jug is about half full. This morning I test drove it and the transmission is missing 3rd gear now. No coolant in the trans fluid, smells burnt. Can’t tell if the motor overheated or not, no stores codes for overheating.

Engine still runs good from the sound of it but not sure if there is a problem there to look for but can’t test for head gaskets with a bad radiator.

So far I need a radiator and transmission and to teach my wife where the engine temp gauge is at, suprised she knew enough to check the transmission temp.

Any idea what happened here? Did the crack in the radiator cause the overheating or did it overheat and blow the rad?

 

[Marky Dissod]

The ATF coolant & motor oil should all be consider overheated; change all 3 at once. OK, now I'll read what you wrote ...

Wife said the transmission hit 250F on the way home and wouldn’t go into 4th. She drove it about 4 miles home after seeing the ATF temp.
She didn’t know where the coolant gauge was at so didn’t know if the motor overheated.
Upon inspection the radiator is busted leaking coolant and the coolant jug is about half full.
This morning I test drove it and the transmission is missing 3rd now. No coolant in the trans fluid, smells burnt.
Can’t tell if the motor overheated or not, no stores codes for overheating.
Engine still runs good from the sound of it but not sure if there is a problem there to look for but can’t test for head gaskets with a bad radiator.
So far I need a radiator and transmission and to teach my wife where the engine temp gauge is at, suprised she knew enough to check the transmission temp.

Any idea what happened here? Did the crack in the radiator cause the overheating or did it overheat and blow the rad?

Again, ATF, coolant, & motor oil have all overheated, and should be replaced immediately. Sequence no longer matters.
This'll also give you a chance to check ATF coolant & motor oil for cross contaminations of any kind.
Very likely it'll need a trans rebuild SOON. If any coolant in ATF, SOONER.
Oil in coolant, possible engine's ok. Coolant in oil, new head gaskets at a minimum.
Obviously new radiator, also coolant reservoir, cap, & if you don't remember when last you changed 'em, heatercore and rear coolant T & Y as well.

 

[Dustin Jackson]

@Marky Dissod Transmission doesn’t have 3rd or 4th and I don’t think I’m getting them back so I think I’ll need a transmission and a radiator.

Curious how this occurred because there’s still coolant in the system so not sure why it overheated so soon.

Can’t see any signs of cross fluid contamination but the fluids smell burnt for sure

 

[Marky Dissod]

Even if the gauge is accurate (if often isn't), the gauge usually measures temps where it was easiest to install a sender, not where the fluid is actually hottest.
(This goes in your mouth. This one goes in your ear, and, this one goes in your but.
'Error dings' Schidt, hang on a second. This one ... no ... uuhhh ... this one, this one goes in your mouth.) Sorry to digress.

Anyway, my point was
If ATF gauge hits 230F, somewhere else in the transmission, ATF is already hotter than 248F.
If coolant gauge hits 230F, somewhere else in the engine, coolant is already hotter than 248F.
Since the radiator also has integral heat exchangers for motor oil and coolant, if one has overheated the others are very close to overheating soon.

 

[Joseph Garcia]

My recommendation to you is to drain the motor oil and send a sample to the lab (Blackstone?) for analysis. Your motor is probably OK. Get a replacement radiator, torque converter and transmission on order.

As an aside, WAY back, my wife drove her car with the hot idiot light on after a radiator hose burst, until the motor seized. I had to rebuild the motor myself, and I gave her the job of scraping out the carbon inside the piston ring grooves with a piece of broken ring, as her 'contribution' to her caused fiasco. She NEVER ran the car again when an idiot light turned on.

 

[strutaeng]

Well,

1. it sounds like unfortunately "at least" your transmission is fried if you are missing gears and the atf fluid smells burnt. Does this vehicle have the transmission thermostat? I believe those can cause issues where they get stuck and no fluid is circulated to the cooler, causing overheat. I would drop the pan and look for any evidence of clutch material next.

2. How is your radiator busted and your reservoir still has coolant? Where is your radiator leaking from exactly? Small drip of massive gush out? It doesn't sound like your engine blew a head gasket from any overheating, based on what you described. You can do a few tests to further conclude no engine damage.

3. Without further information, it's just a guessing game on what happened. Perhaps only the transmission overheated, and you happened to also had a radiator leak, that you were not aware of until now? I'm just guessing here.

4. No codes at all? Not even for the transmission? Seems strange if you are missing gears and you wouldn't have some gears?

@NickTransmissions may provide some input, or correct me anything i adviced.

I hope things work well for you and keep us posted.

 

[Dustin Jackson]

@strutaeng

1.) I believe there is no thermostat on this 4l60e like there is on the 6 speeds

2.) Rad seems to be leaking from a crack in the driver side radiator plastic tank. It appears it was spraying coolant all over the power steering pump area so not big enough crack to pour but enough to spray coolant.

3.) Not sure. I had the Tahoe dialed in when I gave it to my wife a month ago.

4.) No codes, I use an OBD2 Bluetooth dongle with torque pro on an Samsung phone

 

[Marky Dissod]

Perhaps only the transmission overheated, and you happened to also had a radiator leak, that you were not aware of until now?

Perhaps the 'radiator' leak is actually the radiator's ATF heat exchanger leaking, might explain why the ATF overheated.
It's possible - unlikely but possible - that there was no coolant compromise.

That in no way changes my advice about changing the motor oil & coolant, as well as changing the ATF.

 

[strutaeng]

@strutaeng

1.) I believe there is no thermostat on this 4l60e like there is on the 6 speeds

2.) Rad seems to be leaking from a crack in the driver side radiator plastic tank. It appears it was spraying coolant all over the power steering pump area so not big enough crack to pour but enough to spray coolant.

3.) Not sure. I had the Tahoe dialed in when I gave it to my wife a month ago.

4.) No codes, I use an OBD2 Bluetooth dongle with torque pro on an Samsung phone

1. Oh, ok. 4Lxx...yes, no thermostat.

2. So that sounds like an external leak.

3. Understand. Sometimes stuff just happens. Also, what was the history with the transmission. Did you ever service it such as fluid/filter replacement?

4. Umm...

Perhaps the 'radiator' leak is actually the radiator's ATF heat exchanger leaking, might explain why the ATF overheated.
It's possible - unlikely but possible - that there was no coolant compromise.

That in no way changes my advice about changing the motor oil & coolant, as well as changing the ATF.

Yes, that's possible. Internal radiator leaks causing cross contamination are not a common thing on these GM full size trucks AFAIK (doesn't mean that's not likely of course), but external leaks are more common.

On vehicles where that's very common such as early 2000s Tacomas/4Runner, when radiator leaks internally and cross contamination occurs the vehicle will start slipping and the transmission dipstick (or coolant, can't remember) will show a definite "pink milkshake," I think that's what they call it?

Also, there's no rule or law that says you can't have 2 unrelated problems at the same time...? IDK?

 

[Dustin Jackson]

@strutaeng I serviced it last at 160,000 miles. Never had any problems with the transmission other than it’s old, fluid always looked good. It has 210,000 miles now so got my money worth I suppose.

Going to redo the cooling systems and get it running. I’d like to determine if the motor is fine before I put another transmission in it.

 

[swathdiver]

The radiator probably sprung a leak first and took some time to empty and cause the transmission and engine to overheat. Too bad that we don't have a low coolant pressure alert!

 

[Marky Dissod]

I’d like to determine if the motor is fine before I put another transmission in it.

With coolant reservoir and hood already OPEN, start engine as COLD as possible. Immediately go and check coolant reservoir for bubbling.
If you see consistent or very chronic bubbling, put coolant cap back on, drive straight to mech, and tell them to check for coolant leaking into oil AND vice versa.
Goes without saying that, if you haven't changed the oil and checked it for coolant, go change oil and check it for coolant already.

If you're gonna do a formal oil analysis,
speediagnostix.com

 

[Dustin Jackson]

I already have the thing torn apart. I have a new radiator, water pump, thermostat, and radiator hoses ordered. I’m going to get the engine put back together with fresh oil and cooling and dig in some more there.

Already have 1 transmission quote for $3,800. Gonna get a couple more.

Here is where the radiator was leaking from, seems the plastic tank and the metal were separating. Talking to my wife more it sounds like the transmission was having trouble and overheating and I suppose that caused the radiator damage so given the amount of coolant left in the system I hope my poor 5.3 is fine.

Still runs fine. Looks like I didn’t get the front seal right when I did my AFM delete because it’s been misting oil all over the place making it sludgy. Might button that up before I get the new water pump on.

 

[Dustin Jackson]

Got the cooling system back together. Ran the motor for about an hour and did as much driving as I could with 2 gears to test the cooling system and I can’t detect any problems so far.

Exhaust looks clear when hot.

The coolant jug has some steam coming out of it when the cap is off but nothing crazy, might be normal?

The heater smells pretty toasty, I don’t remember it smelling like that.

Oil looked fine.

Anything else that I should check on before I throw a bunch of money at another transmission?

 

[Marky Dissod]

... coolant jug has some steam coming out of it when the cap is off but nothing crazy, might be normal?

Coldest start possible - give the engine enough time to cool down to ambient temp.
Start engine cold, quickly pop open hood, run outside and unscrew coolant cap, be ready to screw it back on.
If coolant is emitting a steady stream of bubbles, go get checked for head gasket leak after you crew the cap back on BEFORE shutting down.

 

[Dustin Jackson]

@Marky Dissod I’ll Check that in the morning. Today it was just a little steam coming off like a cup of coffee

 

[Dustin Jackson]

@Marky Dissod Here is a video I took of the test, nothing out of the ordinary here.

 

[Marky Dissod]

I'd've left the camera focused on checking for bubbles a bit longer because I'm paranoid,
but if there are no bubbles being made in there, and the exhaust doesn't smell like something you'd use to get chicks drunk, you're probably ok.

 

[Dustin Jackson]

@Marky Dissod I left it running for a couple more minutes after I turned the camera off and nothing came from it.

Looks like I'm the proud owner of a 210,000 mile 5.3 still!

Now time to pick where to get a transmission from. One place had a good warranty but this other place outlined all the upgrades they do on the 4l60e.

 

[alvocado]

You can always pick up a block test kit which will detect exhaust fumes in your coolant. It's a surefire way to know if you have a compromised head gasket/warped head.

Amazon.com: Block Tester BT-500 Head Gasket Combustion Leak Test Kit - Made in USA : Automotive

Amazon.com: Block Tester BT-500 Head Gasket Combustion Leak Test Kit - Made in USA : Automotive

www.amazon.com

It's still puzzling to me that you had coolant in your reservoir with an overheat. That would point to coolant flow vs. coolant loss as the reason for overheating. Perhaps you had a radiator leak simultaneously with a separate trans issue?