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Overheating and other issues

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cliffmills

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Jun 25, 2019
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2008 avalanche 5.3 New: radiator, cooling fans, temp sensor, water pump, fan fuses and relays, thermostat, plugs, wires, all o2 sensors, both cats. Fans dont always turn on high when a/c is on. Normal temp of 210 when driving, 225 when idle even if fans on high. When at highway speeds, and punching the pedal, will get sel and random misfire code. Shop found o2 wiring loop to keep ses light off. They wired new sensors corectly, now I get reoccurring p0420 and p0430. Also, rough idle, poor gas milage and slight loss of power. No coolant loss. A shop found no signs of head gasket leaks and suggested cats, so I replaced them.
 
Holy moly that is a lot of parts without success, I'm feeling for ya cliffmills! Did the shop investigate the overheat issue too, if so they should make it right. Are the parts that were replaced OEM, quality aftermarket or cheapest ebay had to offer?

What procedure was used to get the air out of the system after replacing the radiator and the other parts? Have you checked for soft hoses, perhaps a hose collapsed internally? Wondering if there is a solid or air blockage somewhere.

The misfires should be a completely separate issue. Do you have access to a scan tool with Mode $06 data? You can view the misfire counts by cylinder, although if there were enough misfires on any one cylinder it would log a P030X code.

With that same scan tool, log/graph o2 sensor readings for B1S1, B1S2, B2S1, and B2S2. These are the o2 sensors before and after the catalytic converter, post results here if you want feedback on the results. However, with new cats installed the P0420 and P0430 codes are likely due to the misfire alone. Don't let that misfire go too long or it will kill your new cats.

For my own curiosity, how many miles on your avy?

Edit: came back to ask if you flushed the coolant system and if you got good flow or if it was restricted. If flow is good when flushing, and pump is doing its job it makes me suspect of the new thermostat.
 
Another thought, remove the thermostat and test if it still overheats. This will at least eliminate one possibility.
 
Why do you assume your truck is overheating?

Sounds normal to me... When your AC is on you should only be running one fan... Likely the secondary fan.. (Not sure with these trucks but I know my Caprice ran secondary fan when AC was on, would run Primary fan if engine got a little hot and both fans run if the engine got hotter regardless of AC setting.)

With a 180F stat it would be reasonable to get 210F in the summer and if you are not moving 225F Doesn't sound unreasonable.  With the pressure cap on your overflow working properly even if you were running straight water, at 225 the water would not be boiling and with a proper mix of 50/50 even with the cap off you wouldn't be boiling.

The most I would do is check if your fan relays and fuses are working... If they are working then maybe lightly flush the radiator fins from the back side with a garden hose to flush out any dirt, bugs or debris...  Also, if you have ever used tap water in your system you will want to use radiator flush, lots of distilled water and flush your system out a couple times then refill with proper 50/50 mixture.

Doesn't sound like your coolant system has anything wrong but you can make it perform better by flushing the radiator both in and out.

Again NEVER use tap water to fill your radiator or to flush it unless your water is run through a reverse osmosis filtration system...
Well Water generally has lots of minerals in it that will coat your radiator. If softened it will still have the salt in it you softened with and will coat the inside of the radiator.
City water will have Chlorine or Limestone in it. It will also likely have phosphates in it to coat old lead pipes. (See Flint Michigan Water issues for those areas that don't to see what will happen... So chances are, your water has it in it.(Fluoride may also coat stuff. )

Using tap water that isn't filtered with a reverse osmosis system will coat the inside of your engine and radiator making transfer of heat more difficult. (Whole house filtration is likely reverse osmosis. But check to make sure whatever system you have is removing everything from the water...)  And just because Johnny says he always used tap water and never had problems doesn't mean you wont. Don't push the issue, only use distilled or otherwise purified water. (Carbon filtration is NOT enough.)

Good luck... But still not sure your temps are bad at all.. Water boils at sea level at 212F... When the pressure is raised on the water it boils at a higher temp. When you add antifreeze, the combination of antifreeze and water will not only not freeze until lower but also won't boil until higher temp than normal. The actual boil rate depends on the characteristics of the antifreeze and pressure on the system.
 
cliffmills said:
2008 avalanche 5.3 New: radiator, cooling fans, temp sensor, water pump, fan fuses and relays, thermostat, plugs, wires, all o2 sensors, both cats. Fans dont always turn on high when a/c is on. Normal temp of 210 when driving, 225 when idle even if fans on high. When at highway speeds, and punching the pedal, will get sel and random misfire code. Shop found o2 wiring loop to keep ses light off. They wired new sensors corectly, now I get reoccurring p0420 and p0430. Also, rough idle, poor gas milage and slight loss of power. No coolant loss. A shop found no signs of head gasket leaks and suggested cats, so I replaced them.
Click to expand...
Hey cliff, did you ever figure out your situation?? I know it’s been about three years…
 
RayFinkle3 said:
Hey cliff, did you ever figure out your situation?? I know it’s been about three years…
Click to expand...
You may not get a reply since last time he logged in was: Sep 21, 2020.
(FYI if you hover over a member's avatar name you can see when they last logged in to this site...)
 
OK; av started requiring fluid about once a moth. Now I am adding every day. also after driving for half an hour the temp will go up. pull over let idle temp will bounce down into normal range. drive a bit and will go up again in few mints goes back to normal. T-stat, water pump, Head gaskett????? just installed new e-fans and can manually turn on and off.
 
Coolant is going somewhere.

Buy or borrow from a parts store a radiator pressure test kit.

Install the kit and pump the pressure up to 15 PSI.

If the leak is external, it will make itself known in short order.

If it is internal to the engine, it will make itself known in other ways.

How is your oil level staying?

Here is a link to my adventure in finally determining where my missing coolant was going.

New oil catch can may be finally showing what is wrong with my engine.

Now, I never did have any issues with the engine overheating, but I was loosing coolant.

Using the pressure tester, I was able for find and repair several small external coolant leaks before I finally found the cracked head.

The coolant from my cracked head all ended up in the crankcase and mixed with the engine oil.

I never had any coolant in the exhaust.

I never had any exhaust gases in the cooling system.

The clues I had to work with was a slow loss of coolant, a slow rise in oil level and jet black oil on the dipstick a few hundred miles after an oil change.
 
SRFNSNO said:
No oil looked fine, a little dark. Set to take in to shop this weekend.
Click to expand...

Just a reminder, the oil on my dipstick was jet black after only a few hundred miles after an oil change.

The only place I saw anything milky was under the valve covers or in the oil catch can.

At first, I just found it odd that the oil level on the dipstick looked really full, but not so much you would say "Holy cow!"

Only after discovering the coolant leak did I figure out the oil level was slowly rising.
 
how much coolant do you add?

Places coolant can go:
- Engine crank case - from head gasket leak, cracked block or head
- On the Ground - From a bad leaking hose, radiator, heater core, water pump, thermostat housing, &/or freeze plug leak
- On the Ground - From optional Block heater if you have it.
- Into Tranny via leaking tranny cooler inside radiator tank but you also get tranny fluid into radiator.
- SKY via evaporation - OVERheat or bad radiator (Overflow Tank) cap.
 
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