Overheating Car Question

[Schrödinger's cat 87]

My sister in laws 2002 Chevy Imapala overheated. I checked the upper and lower radiator hoses and there are no cracks or leaks as far as I can tell. How would I know if the water pump is broken or if it's the thermostat ? What else would cause a car to overheat ?

[robot_hell 72]

If the thermostat is easy to take out, put it in a pot of boiling water. It should open as it heats up. If it doesn't, that's the most likely cause, and cheap to replace.

[Malsua 1,422]

Does it have electric fans, do they run?  If not, it's a sensor or maybe a fan.

 

If the return pipe doesn't get hot, it's a flow problem...thermostat or pump.     If your fluid is low and you've added fluid, it may need burped properly.

[alec.mc 180]

probably has electric fans....are they running? If not - likely a relay or something. 

[GRIZ 3,369]

Did it overheat while driving or while going slow or stopped? Check:

 

Coolant level purge air if needed

Electric fans should come on when car is stationary and getting hot. Fans are usually off when cruising along. Some cars turn on fans automatically when you turn on AC. Not sure if yours does.

Water pumps will usually leak before they stop pumping. With full coolant idle car over dry driveway and if pump is leaking it will drip on driveway.

If you can get your hands on the water pump pulley see if it wobbles. It shouldnt.

 

These are all things you can do before pulling thermostat.

[CageFighter 236]

check ur oil, do u have a milkshake?  if so, grab ur ankles and hope they use Vaseline. 

[NickySantoro 211]

My sister in laws 2002 Chevy Imapala overheated. I checked the upper and lower radiator hoses and there are no cracks or leaks as far as I can tell. How would I know if the water pump is broken or if it's the thermostat ? What else would cause a car to overheat ?

Under what conditions did it overheat? If it was at idle, likely the fans didn't come on. Run the car at idle, AC off, and watch the temp gauge. At some point the fans should come on. If they don't, turn on the AC. If the fans come on the problem is likely the coolant temp sensor.

[Schrödinger's cat 87]

check ur oil, do u have a milkshake? if so, grab ur ankles and hope they use Vaseline.

Lol. How would I know if there is coolant mixed in the oil ?

[Schrödinger's cat 87]

Under what conditions did it overheat? If it was at idle, likely the fans didn't come on. Run the car at idle, AC off, and watch the temp gauge. At some point the fans should come on. If they don't, turn on the AC. If the fans come on the problem is likely the coolant temp sensor.

It was during local driving. I'll ask and see how long the car was running before it overheated.

[Schrödinger's cat 87]

Thanks guys, I'll bleed the air, check the pulley for wobble, and see if the fan turns on while idling and when I turn on the AC.

[Schrödinger's cat 87]

 

If the return pipe doesn't get hot, it's a flow problem...thermostat or pump. If your fluid is low and you've added fluid, it may need burped properly.

I'm not sure where the return hose is. I'll try to find it and make sure it's hot.

[CageFighter 236]

Lol. How would I know if there is coolant mixed in the oil ?

 

open the filler cap, you'll see the white creamy stuff!  

[Malsua 1,422]

I'm not sure where the return hose is. I'll try to find it and make sure it's hot.

 

It's the one connected to the thermostat, usually the top hose although some cars can be the other way.  Essentially if it doesn't start heating up pretty quick, it's not flowing out of the block and into the radiator which means either the thermostat is stuck closed or the pump is shot.  You usually know right away if the pump it shot as you're spewing fluid all over or you hear gawd awful noises, but weird things can happen.  

[1LtCAP 4,267]

My sister in laws 2002 Chevy Imapala overheated. I checked the upper and lower radiator hoses and there are no cracks or leaks as far as I can tell. How would I know if the water pump is broken or if it's the thermostat ? What else would cause a car to overheat ?

1. check coolant level. cold.

2. fire engine up. turn on a/c. when clutch cycles on, fans should cycle on too. if not, look for fan relay or fuse problem. if they do fire up, then kill a/c. if it doesn't fire up, then you need to check to be sure you got power to it. check the connector too. they've been known to burn up.

3. monitor temp gauge, and keep an eye on fans. they should come on around 210f, and go off around 219f. if you have ANY way to watch the actual data, that would help.

 

 water pump, while not common, could go bad. not common on these though. head gaskets are common, as are cracked cylinder walls. thermostat while annoying to get at isn't that hard. on a cold engine, you should be able to have it out and new one in in about an hour.

[Schrödinger's cat 87]

So here what I see so far. There is nothing creamy at the top of the oil tank. The upper radiator hose does get hot although it took about four minutes or so. There is a pretty bad grinding noise coming from from seems to be the water pump housing but it's hard to know for sure where exactly the sound is coming from. When I put my hand on the water pump I feel vibration but that may not mean anything.

 

Here's the thing, the car has been on for about a half an hour and I don't see the rad fans go on. I had the AC on for like ten minutes. The temp gauge is at the half mark so I think that's like (?)95 degrees (it starts at 60 and goes to 125)

When the clutch goes on and the belt turns faster the grinding sound is much worse.

[Malsua 1,422]

You may have multiple problems.

 

The grinding noise could be the pump or the tensioner pulley could be shot.

 

The thermostat could be stuck open but the fans aren't working, meaning the car will overheat if you stop for any length of time. 

 

If the fans don't come on when the AC is on, it's possibly a fuse, a relay, a sensor or the fan itself is bad.     They should come on whenever the AC is on.  That they aren't means something there is messed up.

 

You're probably going to have to take it to someone with some familiarity with those vehicles.

[GRIZ 3,369]

If it's the water pump also replace the belt tensioner whether it seems good or bad. Not doing so is false economy. Improper tension on the belt will cause belt failure and/or wear. It can also cause damage to the water pump. New pump = new belt and tensioner.

[Kevin125 4,772]

If you end up changing a tensioner pulley or pump you should probably change the serpentine belt unless you know it was recently changed. If its got crack, get a new one. They aren't expensive.

 

Some are a little tough to do and you need to make sure you know the correct path. Probably worth finding a helpful You Tube video on the belt change procedure. I did two recently and some forum posts showing the process were very helpful.

[Schrödinger's cat 87]

You may have multiple problems.

 

The grinding noise could be the pump or the tensioner pulley could be shot.

 

The thermostat could be stuck open but the fans aren't working, meaning the car will overheat if you stop for any length of time.

 

If the fans don't come on when the AC is on, it's possibly a fuse, a relay, a sensor or the fan itself is bad. They should come on whenever the AC is on. That they aren't means something there is messed up.

 

You're probably going to have to take it to someone with some familiarity with those vehicles.

Thanks malusa, I agree. I believe the water pump is going but that is not the problem. IIRC I seem to remember hearing the grinding noise a month ago. The bleeder screw above the water pump is also cracked, I'll probably replace it if and when I change the water pump.

The problem seems to be the fan. I was thinking of taking an electrical meter and checking if there is power in the wire harness that clips into the fan. I was also going to try to jump the relays and see if they are burnt out. Is that a good idea ? I see three large relays and one smaller one. Both fans aren't working so I have to see which one controls both.

 

I'm not sure what you mean about the thermostat being stuck open. Why would you think that that's the problem and not an actual problem with the fan ?

 

Thanks about the ideas about the tensioner and belt. I've changed it quite a few times on my own car so it should be easy.

[Malsua 1,422]

The fact that the return pipe stayed cold for a period of time, then got hot suggests that the thermostat probably is ok.

 

That said, if it's stuck open and the car is only idling and not under load, it's possible that it's not getting hot enough to turn the fans on.   It could also be opening too soon.  The AC should turn on the fans though, so that's a bit of a mystery.

 

You really need to put a reader on there that can watch live data and see what the water temp is.  Watching live data should show it climb to 190 or so, then drop down briefly when the thermostat opens.   The $100ish hand held code readers generally can read live data.  Also  ELM327 readers + torque pro can read it as well.

 

Jumping the relays is a bit iffy.  You could rig some wires directly to the battery to see if the fans go.  If they dont run full blast, maybe one has a bearing problem.   Some fans are "smart" and you can't just apply power and ground.  You risk blowing something out without a schematic.

[1LtCAP 4,267]

So here what I see so far. There is nothing creamy at the top of the oil tank. The upper radiator hose does get hot although it took about four minutes or so. There is a pretty bad grinding noise coming from from seems to be the water pump housing but it's hard to know for sure where exactly the sound is coming from. When I put my hand on the water pump I feel vibration but that may not mean anything.

 

Here's the thing, the car has been on for about a half an hour and I don't see the rad fans go on. I had the AC on for like ten minutes. The temp gauge is at the half mark so I think that's like (?)95 degrees (it starts at 60 and goes to 125)

When the clutch goes on and the belt turns faster the grinding sound is much worse.

sounds like you've got more than one problem.

1. upper rad hose got hot in 4 minutes? as in almost too hot to touch? that's WAY too quick. poss. stuck open thermostat

2. the fans should've come on when the a/c compressor cycled. if not, you gotta find out why.

3. the grinding noise may be bad bearings on the a/c compressor.

 

 you could pull that water pump off. they're relatively simple to remove. before that though, remove the belt, then spin each accessory by hand( with the engine off)

[1LtCAP 4,267]

If it's the water pump also replace the belt tensioner whether it seems good or bad. Not doing so is false economy. Improper tension on the belt will cause belt failure and/or wear. It can also cause damage to the water pump. New pump = new belt and tensioner.

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this. i work on a small police fleet. i try like a $#%^& to save them money on their vehicles. every single time i tried a shortcut like mentioned above, they ended up having to bring it back to have the shortcut un shortcutted. they're not pissed...they know i'm trying to save em money......but i've stopped doing that now.

[1LtCAP 4,267]

Thanks malusa, I agree. I believe the water pump is going but that is not the problem. IIRC I seem to remember hearing the grinding noise a month ago. The bleeder screw above the water pump is also cracked, I'll probably replace it if and when I change the water pump.

The problem seems to be the fan. I was thinking of taking an electrical meter and checking if there is power in the wire harness that clips into the fan. I was also going to try to jump the relays and see if they are burnt out. Is that a good idea ? I see three large relays and one smaller one. Both fans aren't working so I have to see which one controls both.

 

I'm not sure what you mean about the thermostat being stuck open. Why would you think that that's the problem and not an actual problem with the fan ?

 

Thanks about the ideas about the tensioner and belt. I've changed it quite a few times on my own car so it should be easy.

before you jump any relays, swap the fan relay with an identical one from another position. use a basic test light at the 2 wire connector at the motor. one should be hot if the fans are driven on.

[AMScott 3]

Sometimes the water pump impeller comes unfastened from the impeller shaft resulting in poor cooling circulation and noise from the pump....

[1LtCAP 4,267]

Sometimes the water pump impeller comes unfastened from the impeller shaft resulting in poor cooling circulation and noise from the pump....

that used to be stupidly common on volkswagens

[Schrödinger's cat 87]

sounds like you've got more than one problem.

1. upper rad hose got hot in 4 minutes? as in almost too hot to touch? that's WAY too quick. poss. stuck open thermostat

2. the fans should've come on when the a/c compressor cycled. if not, you gotta find out why.

3. the grinding noise may be bad bearings on the a/c compressor.

 

you could pull that water pump off. they're relatively simple to remove. before that though, remove the belt, then spin each accessory by hand( with the engine off)

Thanks John, yes, I don't remember if it was after the four minutes but eventually the upper rad hose became super hot. I'm sure the fact that it's above the radiator that was not being cooled by fans also made it hotter. When I spin the AC and water pump pulleys what I'm checking for is wobble and a grinding feel correct ?

[Schrödinger's cat 87]

I'd just pull out the thermostat and put it in water to see if it's stuck, it's really easy to get to but if the trouble is the fan I may leave the grinding noise alone for another time. It's a pain to fully drain the coolant and then refill and bleed if I don't know that's the problem. The fan should be turning on when the AC clutch cycles whether the thermostat is working properly or it's broken.

[1LtCAP 4,267]

Thanks John, yes, I don't remember if it was after the four minutes but eventually the upper rad hose became super hot. I'm sure the fact that it's above the radiator that was not being cooled by fans also made it hotter. When I spin the AC and water pump pulleys what I'm checking for is wobble and a grinding feel correct ?

thing is, in that car, the coolant leaves the engine through the upper radiator hose, flows through the radiator to shed its heat, then re-enters the engine through the lower hose. that's why i was so concerned over a 4 minute heat up time on that hose. that one shouldn't feel that hot for at LEAST 10-15 minutes if you're just idling.

 

 yes. you'll either feel or hear a "Rumble" sort of if one of them is making the noise. also, the water pump has a weep hole behind the pulley that will often leak slightly when the bearing starts to go bad......