Engine overheating, coolant stuck?

[Rocket Man]

Following

 

[Sam Harris]

Really seems to me that there’s likely an air pocket in the system. Can you park it on an incline while it warms to operating temperature, and top it off..?

 

[BG1988]

New guy here, have read a lot, but never joined cause I didn't want to be the odd man out seeing as I don't have a Tahoe or Yukon, but anytjme I'd search for.. well.. anything really, this site was always first page, and has definitely helped me out a lot. Then I saw you had an 'Other' section.

I have an 05 Avalanche LT Z71, 5.3. 210k, that overheated on me one day after a very short drive.. maybe a mile or two. The temp gauge didn't max out but I got the message on the DIC. Was on a 3 lane rd no shoulder so had to keep driving another 30 seconds or so before I could pull over. The cooling fans were working (electric), the hoses were hot.

I figured it was the tstat not opening as there weren't any leaks that I could see and no coolant loss. Oil looks good. Changed tsat. Used the procedure shown in attached pics to refill. It's for an 02 but figured it would apply just the same. Maybe not?

Coolant level never dropped in the surge tank even though I had plenty left to add. Instead, it started smoking and a good quart at least boiled over and out onto the ground.

Never had an issue before, temp gauge had never been above ~190. I'm thinking water pump but they usually leak out the weephole, at least a little bit, right? Could the impeller have separated somehow? I did see on the tensioner pully what was either oil and dirt buildup, or possibly belt material. Belt is probably due for replacement, but alternator and PS pump are fine so would a bad belt really only not drive one component? I hate throwing parts at an issue and praying for the best, especially after I went against my better judgement on getting the thermostat but for <$10 I said f' it. Well it f'd me back ha. I read that the tstat is not supposed to be replaced by itself but a new inlet should be installed with it, which I did not do. Is that important?

Could it be a restriction in the cooling system? I've only had the truck a few months and was unable to procure any meaningful service history. I have discovered, however, that the coolant level sensor has vanished, and I can't find the connector that went to it..

just turn on the front/rear heater full blast and windows down if it happens again... this will get the temp down in a pinch

 

[exp500]

Since no-one else mentioned it , I will.
How about a radiator tank hose plugged from stop leak? Just another of the I found its!

 

[03catburban]

Your issues don't line up with the early 706 head issue, The complaint with those was a coolant loss and couldn't be found.

Yours sounds like an air pocket, pull upper hose off at radiator and pour in coolant through the hose to fill the engine and that'll push most of the air out so now the engine running can burp out the rest.

I've done many ls swaps and that's one of the easiest ways to purge air

 

[noodlesandsam2]

Ok - so you changed the Themostat - how is the fan clutch. I went 270K on my 01 XL 5.3 - overheating is not a problem in general. Bleeding is also not difficult on that setup. If you can, park it nose up, heat on full, and turn it on. see where the coolant settles to. You should have a low coolant sensor, has that triggered? If you don't see mixing of coolant and oil ( that milky stuff ) on the dipstick, or in the tank, the heads might be ok. I will warn you, that if you overheat, the exhaust studs do break....

 

[Rocket Man]

I will warn you, that if you overheat, the exhaust studs do break....

I hate to break it to you but exhaust studs have been breaking on LS engines for over 20 years, no overheating required. Probably 80% of these engines have at least a couple broken, it’s a well known issue. So much so that several companies have designed clamps to hold the exhaust manifolds tight when removing the broken bolts isn’t easily accomplished.

 

[noodlesandsam2]

Yeah, I know that the studs can be an issue. in the 21 years, and 270K that I had the 5.3, that was the only broken stud issue I had. I now have a 6.0, and I will likely upgrade the studs before the winter.

 

[Rocket Man]

Yeah, I know that the studs can be an issue. in the 21 years, and 270K that I had the 5.3, that was the only broken stud issue I had. I now have a 6.0, and I will likely upgrade the studs before the winter.

I highly recommend ARP. I’ve never heard of one of these breaking. This kit fits any LS based engine.

 

[Meathead16]

Your issues don't line up with the early 706 head issue, The complaint with those was a coolant loss and couldn't be found.

Yours sounds like an air pocket, pull upper hose off at radiator and pour in coolant through the hose to fill the engine and that'll push most of the air out so now the engine running can burp out the rest.

I've done many ls swaps and that's one of the easiest ways to purge air

I tried this and it worked great! I drained the surge tank and poured it in through the upper hose and could hear al the air gurgling out. It took everything that was in the surge tank and an additional quart or so of coolant before it was level with the upper radiator hose fitting, and then however much it took to fill the surge tank. Engine temps built up normally, and didn't move too much after reaching 210.

I pressure tested the system to make sure there were no leaks anywhere and I couldn't get the system to build any pressure. It was kind of weird, the gauge never registered any pressure, but when I'd remove the gauge from the cap adapter there was a whoosh of air like pressure was being held. I tested the gauge by itself and was able to easily pump it up to 15lbs and it held until released. I found some coolant near one of the bleeder pipe bolts and on the front of the engine and the thermostat housing was wet along the underside. I'm thinking maybe while the engine is running, the coolant is managing to seep out of the thermostat housing and make it's way down the engine back to the exhaust manifold and that's what's causing the smoking. I really don't think the smoke is anything that is being burned off at this point simply because it hasn't stopped at all. It takes a few minutes to start, but once it starts it's very consistent in how much there is, how thick it is, etc. It acts more like a steady stream rather than a puddle being burned off, and it will not stop until the engine is shut off, and continues for a minute or two after shut down. I've cleaned the area multiple times with brake cleaner and towels but it keeps coming.

Besides the smoking the only other thing is that it's developed a noticeable misfire. It's reminds me of a four legged animal trying to run with a broken foot. The battery is relatively shot and I just had the alternator tested and it failed. The amp gauge on the dash floats between 12 and 14 and the dash lights have a very slight "led light when viewed through a camera" type flicker to them. I can jump start it and it will stay running on it's own but shut it down and try to start it immediately is a no go. Could a failing alternator and/or bad battery cause a misfire like that?