1996 Chevy Lumina Engine runs hot

Tiny
DENNIS BROOM
  • MEMBER
  • 1996 CHEVROLET LUMINA
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 170,000 MILES
1996 Chevy Lumina 3.1 cooling system overheating. Some days I can drive 50 miles before overheating and then other days I can't go 5 miles before overheating. The temperature exceeds 220 degrees. The upper radiator hose is extremely hot to the touch although the lower hose not as hot. The radiator boils over and fills the coolant recovery tank and as it cools the tank replaces the coolant in the radiator. After the engine has cooled down I tried to add coolant with the engine running through the fill tube of the radiator. The system spits and pours more coolant out of the fill tube than I can put in. I have the bleeder screw open to release any air that may be in the system. Over the past 6 months I have replaced the heater core, water pump, and thermostat. I removed the radiator and had it tested and cleaned. Both fans are in good working order. Any suggestions as to what I can do to eliminate this overheating problem. Thank You!
Do you
have the same problem?
Yes
No
Friday, September 12th, 2008 AT 7:37 AM

6 Replies

Tiny
RENAUDTN
  • MEMBER
The top hose being hotter than the bottom hose is perfectly normal since the coolant just exited the engine and hasn't gone thru the radiator. The coolant level being higher in your overflow tank when the engine is hot is normal too.
You should refill with coolant when the engine is cold, and off. Bring your coolant level to the bottom of your radiator neck, and fill the overflow tank up to the cold mark.
Now, when you say your engine is running above 220 degrees, is that the temp you read at the pcm with a scanner or is it what you get with a thermometer?
What I'm trying to say is that maybe your coolant sensor is defective.
Now other possibilities include:
-defective radiator cap (can't hold pressure)
-loose serpentine belt (slips on the water pump pulley)
-leaks (internal or external). Inspect visually your cooling system. Pressure test the cooling system, it should help determining if you have a leak or not. If your system doesn't hold the pressure and you can't see a leak, the problem is inside the engine (do you have an unusual amount of white smoke coming out of your tail pipe?)
-Are you sure the fans come on everytime when they are supposed to?
-Glogged water jackets
-bad hoses (collapsed: restrict coolant flow)
-too much back pressure in your exhaust system (bad catalytic converter, crushed pipe?)
-Make sure that your thermostat opens at the right temp (probably around 195F)

Have you checked for codes? It may give you some hints about what's going on.
Was this
answer
helpful?
Yes
No
+2
Friday, September 12th, 2008 AT 10:51 AM
Tiny
DENNIS BROOM
  • MEMBER
I meant to say the temp is running above 260 degrees based on the instrument panel gauge. At this point the radiator boils over and fills the tank. After a cool down period the tank refills the radiator. During this cool down period I attempt to top off the radiator with coolant with the engine running but it spits and pours out more coolant than I can put in. To say the upper hose is hot is an under statement, it is schorching HOT! And the lower hose is luke warm. When filling the radiator with coolant the bleeder screw releases air. The radiator cap and hoses are good and the fans are working when they should. Why does the radiator spit and pour coolant out the fill tube? Is that a sign of a bad water pump? Where is all that air coming from in the coolant system? Is this normal?
Was this
answer
helpful?
Yes
No
-1
Friday, September 12th, 2008 AT 1:23 PM
Tiny
RENAUDTN
  • MEMBER
One way that can help you to determine if your water pump is not working right is by squeezing the upper hose (engine at idle) when the engine is hot (before it starts overheating though); rev the engine and feel how much coolant goes thru the hose. If you can't feel too much coolant, you could have a bad pump (but not necessarily). With the engine off, you can also try to move the pump. If it wobbles, it's bad and need replacement.

Now, to fill you cooling system, do it with a cold engine and the car off. If you feel like you have air in your system, raise the front of your car so that your radiator cap is the highest point of your cooling system. Top off the radiator and bring the level at 'cold' in the overflow tank. If your level of coolant is too low in this tank, your system will suck in air from the tank instead of coolant which will lead to your car overheating.
Now with the bleeder screws open, turn on the car and let it run with the radiator cap off. Try to squeeze your hose a little bit to get the air out.
The coolant in your radiator should rise slowly to the point where it will start spilling. Put the cap back on.
When coolant starts flowing out of the bleeder screws, tighten them (the bleeder screw close to your water pump should start bleeding coolant pretty quickly after you turn on your car, but it may take longer for the one by the thermostat housing).
Turn the car off, let it cool completely and recheck the level in the overflow tank. If too low add coolant in the tank.

When your engine is cold, your level of coolant in your radiator should be anywhere from the base of the neck to the top of the neck, and your level in the tank should be at least at the 'cold' mark or in between cold and warm. If it's not your case, add coolant to the right level and check for leaks.

If you're absolutely sure that the thermostat, fans, radiator, hoses, radiator cap and water pump are good, that leaves the following possibilities:

-glogged water jacket (debris from the cooling system have accumulated on the wall reducing heat conductivity and/or flow of coolant.)
-leaks (internal or external). An internal leak would likely be a headgasket or crack in the head or engine block.
You should also check your oil and transmission fluid to make sure no coolant is mixed with them. If you have coolant in your transmission fluid, you have a leak in your radiator. If coolant in oil, you have an internal leak. Either way, it's not good.

-loose serpentine belt. Check your belt tension and your belt tensioner (the spring in your tensioner may be too weak and the tensioner need replacement).
-Have you checked your coolant and made sure it's the right strengh? If your coolant is too 'weak' it will start boiling at lower temperature.

First thing you should do: pressure test your cooling system, and make sure it holds the pressure (something like 15 psi for at least two minutes)

If you have an infrared thermometer, check the temp at the thermostat housing; this should tell you if your engine is really overheating. You could have a bad sensor and your car is actually not overheating.
Also, with an infrared thermometer you could tell if you have clogs in your radiator or hoses.

Check for back pressure.

Look for codes stored in your pcm and check the actual temp sent to your computer.
Was this
answer
helpful?
Yes
No
+4
Friday, September 12th, 2008 AT 3:17 PM
Tiny
DENNIS BROOM
  • MEMBER
Now one clue that would led me to belive that the engine is overheating is the radiator coolant is boiling out into the overflow tank. I drove the car tonight 30 miles with no overheating problem. Now I may drive tomorrow morning 5 miles and have a overheating problem. That's what has me puzzeled, it's never the same from one day to the next. I will have the pressure test as soon posible.
Was this
answer
helpful?
Yes
No
Friday, September 12th, 2008 AT 11:27 PM
Tiny
RENAUDTN
  • MEMBER
Yeah, pressure test your cooling system (as well as the radiator cap).
You can also check for exhaust gas in your coolant when your engine is hot.
Do you have coolant in your oil? Is there white smoke coming out of your tailpipe?
Does your car crank for an unusually long time when you try to start it?
These are all signs of a blown head gasket.

You said you drove the car on Friday; did you check your coolant level on Saturday when the engine was cold? If so where was the level at?

What you're describing (coolant leaving the radiator and going into the overflow tank) is normal. Now, if you mean there's coolant boiling out of the overflow tank itself, that's not normal.

Just to rule out another possibility: If you haven't serviced your cooling system in a long time, make sure your coolant is still 'working' and is not worn out (and doesn't have floating debris in it). You can get a coolant tester for $3 at walmart; cheap check :)
When was the last time you cleaned and flushed your cooling system?

Of course all these suppositions I'm making are only relevant if you're absolutely sure that all those parts you replaced or got tested are really working fine.
It doesn't take much for a car to overheat, and a small reduction in the coolant flow (like a radiator or a heater core slightly glogged), a fan malfunction, a defective water pump or thermostat could all end up in the car overheating.
Was this
answer
helpful?
Yes
No
Sunday, September 14th, 2008 AT 7:35 PM
Tiny
KEVIN12881
  • MEMBER
Never have I heard any one so fully describe all the possible problems that could acure in the cooling system causing the car to overheat. If the problem is in your cooling system renaud TN descibed it. However are you sure it is the cooling system? How are you driving this car? Has overdrive gone out and are you driving it in 3rd gear at over 3 grand in the RPMs with the ac on? Is your ac converter locking up causeing problems in the belt? Haynes book also says incorrect ignition timing can cause cars to overheat.
Was this
answer
helpful?
Yes
No
Sunday, September 14th, 2008 AT 8:19 PM

Please login or register to post a reply.

Recommended Guides