Overheating Issue - Chevy Impala SS Forum
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post #1 of 7 (permalink) Old 10-19-2014, 07:32 PM Thread Starter
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Overheating Issue

Ill start with whats been done
1 tstat
fans wired to a switch
bypass tee
replaced expansion tank (coolant resivior)
Was still having issues would only start getting hot after I was on the interstate for 20?30 min and the it would use all the coolant in the tank.
Had a pressure test done it held pressure and found no leaks. Oil is clean not milky , no white smoke or steam when its started also motor doesnt miss even if it sits for a few days so Id say head gasket is not the issue.
Tried new water pump now it starts getting hot at idle after 5/10 min been bleeding system noticed very little improvements. The hoses have a lot of pressure on them like something is restricting somewhere. pulled both rad hoses stuck hose iin the top and had a good flow out of the bottom. same thing for the heater core lines. kept bleeding sytem started getting heat again and it didn't get hot until after 30 min. hoses were real hard again. cracked the cap on the coolant tank it relieved the pressure and temp started going down did this several times and kept opening the bleeder. also when the car is cool if I pull the cap off the coolant tank and throttle the motor it pushes the coolant out of the tank instead of pulling it in. I'm stumped and in need of help. someone had something about a steam line that goes between the heads that may have air in it. sorry for the lengthy post just trying to cover all the things I've done and give as much info as possible.
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post #2 of 7 (permalink) Old 10-19-2014, 07:55 PM
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What is the actual temperature of the coolant, and how are you measuring it? If you're just going by the gauge on the dash, they are known to be inaccurate.

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post #3 of 7 (permalink) Old 10-19-2014, 08:17 PM Thread Starter
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It's getting hot enough to boil the coolant, I also replaced the tps sensors while back.
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post #4 of 7 (permalink) Old 10-19-2014, 09:34 PM
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Have you or anyone else pressure tested the expansion tank cap? If the cap holds more than the rated pressure then it could start to get hot and likewise if the cap isn't holding the rated pressure.

How old is the radiator? The radiator could be getting plugged up and that will definately cause the engine to get hot.

Have you changed the thermostat yet? The thermostat could have failed or isn't working properly as it should and once again will cause overheating.

1996 DGGM Impala SS

Last edited by 4x4high; 10-19-2014 at 09:37 PM.
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post #5 of 7 (permalink) Old 10-20-2014, 02:51 AM
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This is confusing. Are you saying that taking 20-30 minutes on the highway to get hot is good or bad? By hot do you mean "warning light" hot or just heat coming out of the heater?

You said you tried a new water pump and it got hot in 5 minutes at idle. That's because you needed to bleed out the air.

Then you bled the system over and over (good) and now it gets hot in 30 minutes ... again, hot as in "warning light" or hot as in ouch.

Do your fans come on automatically, or just with your switches?

What exactly is the problem?

The hoses should feel very hard when hot. Like a rock depending on the brand. This is normal.

The coolant will expand when it gets hot causing the air in the coolant tank to become compressed (max 16psi). Coolant does "not" compress ... air does. You MUST have air in the top of the coolant tank.

Expecting the coolant to "go down" measurably when you accelerate is incorrect ... unless you have a lot of air in the system. You should not really be able to see the level change much till it gets hot. It will then rise and without the cap, spill over.

Running the engine hot without the cap is not advised. This coolant will hit boiling and not be able to cool the engine. The cap lets the temperature get above boiling.

And of course, never remove the cap when the fluid is hot. If the temperature is over boiling, you will see a violent explosion of fluid in your face.

Did you put the correct t-stat in? It is a two stage device with a small bleed hole. It matters.
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post #6 of 7 (permalink) Old 10-23-2014, 11:01 AM
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You probably got the wrong mixture of coolant or too much which is probably damaging the pressure cap.
Your doing something that is wrong , that may be just a simple fix instead of trying all new parts like you have.

1995 SS ,
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post #7 of 7 (permalink) Old 11-15-2014, 07:50 AM
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Originally Posted by Devs93 View Post
It's getting hot enough to boil the coolant, I also replaced the tps sensors while back.

these caps do get plugged up on the pressure relief section. if the hoses are too hard then replace the pressure cap with the same or clean the relief valve on the cap. I suspect that the pressure tank is dirty and this debris does this. too much pressure will damage the cooling system components.

if the coolant is boiling then you have no pressure. the coolant will boil at over 260deg F with 15 psi..no pressure 212 deg F or lower .

Last edited by j cat; 11-15-2014 at 07:54 AM.
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