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Overheating

superman072000

By superman072000
in Ask A GM Technician

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superman072000 Enthusiast

superman072000

Posted
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I have a 2004 Chevy Silverado 2500HD wtih 77k. It is overheating periodically. I changed the thermostat about 5k and 6 months ago. It was fine for 6 months now it started doing it again. replaced the belt last week still not fixed. the top radiator hose is hot when running so I think think the system is flowing, no leakes anywhere. Could i have not filled the system right with the pressurized system isntructions? If the mix isn't exaclty 50% coolant 50% water could that be it? Water Pump? Do I have to bleed the system, and if so where? please help

bill190 Enthusiast

bill190

Posted
Posted

In addition to the fan needing to work to cool the radiator...

 

Is there hot air blowing out of the radiator?

 

And is there hot air blowing out on all areas of the radiator?

 

Radiators can get blocked and the coolant may not be able to flow through all areas of the radiator.

 

Have you used a leak seal product? I've seen these "glue" a thermostat shut and also block radiators if not used per the instructions.

 

Sometimes you can "reverse flush" a radiator. Do this by removing it from the vehicle, turn it so when water from a hose is inserted into the bottom radiator hose connection, the water will be flowing "backwards" in the radiator in a "downward" flow through the radiator.

 

So sometimes the "regular" flow of a radiator is from the top hose into the top of the radiator and then "down" and then out the bottom connection.

 

Other times the "regular" flow of a radiator is from the top hose into the side of the radiator and then "across" the radiator and then out the bottom connection.

 

So if regular is top/down, turn it upside down. If regular is from the side/across, turn it so the outgoing side is up.

 

Then connect a water hose to the bottom connection (now on top), wrap a rag around the hose so it will force water through the radiator, and run the water until it runs clear out the other end.

 

(The water is flowing backwards through the radiator and this can unclog "gunk".)

 

If this does not work, get a new and/or larger radiator.

superman072000 Enthusiast

superman072000

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Have you checked the fan clutch for proper operation?

 

It turns when hot. I tried to check how hard the resistence is but i really have nothing to compare it to... its turns when engine is one and there is some resistence when trying to spin it..... how much agin no comparision.

 

Radiator is clean I will try and remove it today and try the flush thing.

 

Is the pressurized sytem different? I dont seem to have a drain plug..... there is just a hole where the haynes says it should be. But I have never had any leaks or anything...

builderpaul Enthusiast

builderpaul

Posted
Posted
Have you checked the fan clutch for proper operation?

 

It turns when hot. I tried to check how hard the resistence is but i really have nothing to compare it to... its turns when engine is one and there is some resistence when trying to spin it..... how much agin no comparision.

 

Radiator is clean I will try and remove it today and try the flush thing.

 

Is the pressurized sytem different? I dont seem to have a drain plug..... there is just a hole where the haynes says it should be. But I have never had any leaks or anything...

 

 

You will hear the fan pulling more air when the fan clutch engages. (When engine gets over heated). This is a very noticeable sound. The first time my fan engaged I thought I had a problem till I saw the engine temp rapidly go down.

superman072000 Enthusiast

superman072000

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OK so i flushed the coolant system radiator engine block, everything. It is still over heating. I couldnt get to the end of the block with out it over heating. While I wa sin there I changed the thermastat again and made sure coolant was mixed exactly 50/50. top radiator hose is hot. I am still iffy on the fan blade clutch I mean its turning all the time. I dont notice in difference if its supposed to go into a higher speed or something. Is it supposed to spead up? go faster than normal? And The coolant system didnt even take 2 full gallons... is that normal?

txab Senior Enthusiast

txab

Posted
Posted
OK so i flushed the coolant system radiator engine block, everything. It is still over heating. I couldnt get to the end of the block with out it over heating. While I wa sin there I changed the thermastat again and made sure coolant was mixed exactly 50/50. top radiator hose is hot. I am still iffy on the fan blade clutch I mean its turning all the time. I dont notice in difference if its supposed to go into a higher speed or something. Is it supposed to spead up? go faster than normal? And The coolant system didnt even take 2 full gallons... is that normal?

 

You're not going to get all the water out of your block when flushing, some will remain trapped. Find out what the total capacity of your system is. After the flush with clean water, start by adding 50% of your total capacity of pure coolant back to the system. Your fan clutch will engage and disengage as needed. If engine and air temp are very warm it should be fully locked and you should definitely hear it pulling air, it should almost roar. It's not uncommon for clutches at your mileage to begin to get lazy. With all that you've done there's not much else it can be at this point, IMO. Fan clutch or clogged radiator.

bill190 Enthusiast

bill190

Posted
Posted

Various things...

 

Did black "gunk" come out of the radiator when you back flushed it? Or was it clean water?

 

Be sure the thermostat is installed the correct way. There is an up and down.

 

Then I don't know if you can somehow see that it is pumping water and water is flowing when warm. On one vehicle I had, the radiator cap was near the top hose. I could leave the radiator cap off and run the engine. Then when it got warm, you could see water begin to flow as the thermostat opened up. It would start to bubble out the radiator cap opening, then I would quickly put the cap on.

 

Is it actually overheating as in it is bubbling up water out the radiator cap (cap on)? Or the temperature gauge is indicating overheating and no other signs?

 

If just temp gauge, might want to take a temperature gauge and measure the engine block temperature. But when I have had the temperature gauge not read accurately, usually it reads too cool.

 

If you have a gauge, be sure it reads cool when the engine is cool and gradually rises as the engine warms up. Not always hot or a sudden jump to hot.

 

Is the heating working when on full blast? This needs water to circulate for it to work. Just another clue.

 

Then hot water should go into the top radiator hose, flow through the radiator, hot air should be blowing out the engine side of the radiator, then the bottom hose should be much cooler.

 

If the water coming out the bottom hose is as hot as the top hose, then the radiator or fan is not doing its job.

superman072000 Enthusiast

superman072000

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Top radiator hose is hot bottomw cooler. Fan is spinning. And yeah I can HEAR it pulling air through the radiator like a wind tunnel. When it gets REALLY hot smoke comes in through the AC vents. Very faint smoke but smoke. When I flushed it it was mostly clean water a little rust particles but nothing I think to be alarmed about. I am baffled. I made sure to mix the dex-cool 50/50 no if ands or buts about it. Its 50/50. With the pressurized system you can see inside the radiator the only lip is on the surge tank and the liquid isn't boiling but I think there might be air in the system. so I am trying to bleed it the best way I know how right now. But still running hot. Whats normal tem for a 2500 hd 4x4? I foudn that the radiator isnt like most it has no official drain plug and way to drain it. I was trying to do it pure haynes but there was no plug to take out so I just did it with the hose.

bill190 Enthusiast

bill190

Posted
Posted

Generally the temperature should be about the center of an instrument panel temperature gauge. Read what your owners manual says about what the temperature should be for *your* vehicle (if you have a temp gauge on your instrument panel).

 

So far as the "smoke" coming out of the A/C vents, this could be a leaking "heater core" and this would be steam if that was the case and it would happen with an OK operating cooling system (steam coming out).

 

So is it in fact smoke? Smells like smoke? Or is it steam and the windshield gets steamed up, but smells like heated antifreeze? (Nasty smell, but not burning smell.)

 

How do you know it is overheating?

 

Just the "smoke" from inside?

 

The temperature gauge is pegged all the way to red hot? If not, what does the temperature gauge read?

 

Any other symptoms?

superman072000 Enthusiast

superman072000

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It does smell like anti freeze, the smoke, And the gauge has pegged at 260 red. Now its staying right around the middle of 210-260(210 is dead center and what I always thought was normal, with minimal fluxuation) The temp gauge is what i am going buy and the smoke from the vents.

bill190 Enthusiast

bill190

Posted
Posted

Ok, it sounds like you had two problems and perhaps the first caused the second problem.

 

It sounds like the engine was overheating, but now that is fixed if it is around 200, and this is the center of your gauge, it is not in the red, and your owners manual says this is normal.

 

Whatever you did to get the gauge to move from the red zone to the center was what fixed the overheating problem.

 

When it overheated, this would have caused the coolant to be extra hot and have a higher pressure. And this is what may have caused a leak in your heater core or a hose connecting to the heater core. Basically hot coolant leaks out inside the vehicle as steam and this rises, fogs up the windshield, and is hard to clean off.

 

The heater core is just hot water/coolant going in one hose to the inside of your air system to a small radiator like thing, then back out another hose to the engine.

 

It is also usually a ROYAL PAIN to fix/replace a leaking heater core or the hoses (whichever is leaking). But I have read of some easy fixes above on the "Fullsize Truck & SUV" area. I seem to recall reading where someone was able to replace a leaking hose from the engine compartment? I don't remember.

 

I would suggest you post a question up there in the "Fullsize Truck & SUV" area about fixing this leak and maybe someone can tell you easier ways to attack this problem for your specific year/model vehicle.

superman072000 Enthusiast

superman072000

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I wasnt satisfied and installed a new radiator today.... Because it would still kinda move up a little bit in the temperature gauge. No biggie..but you neverr know. so now running with ac full blast at 4pm today when it was about 85 degrees. The gauge didnt move above 210.. i think all is good

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