over heat

[tntb83]

I have 99 Alero 3.4 engine seems to over heat & boil/blow all the water at of reservoir before fans come on.
Fans will come on, just late.
Any ideas?

[biv343]

First thing to consider would be a stuck thermostat. It's an inexpensive part to change, and it if hasn't been replaced its probably due. But, it's not a very easy part to get to to change.

[xeroinfinity]

No First I would consider having an air pocket trapped in your cooling system.

Thiers an air bleeder on the recirculator tube on top of the water pump. Let the car warm up, then open it slightly to bleed out the air.

It helps to have the front of the car elivated too

[BNaylor]

Just to clarify did he say water? I sure hope this person is using the right mix of coolant (antifreeze).

It takes a bad cooling system problem to overcome the 15 psi rating of the cap of the coolant reservoir and have coolant blow out the overflow hose. May even be bad lower intake manifold gaskets, especially if they have never been changed with the improved ones.

[tntb83]

I have changed thermostat twice & right now I am running without it.

I have tried with or without coolant, no change.

Car only overheats when idle for A long time (depending on outside temp)
Runs just fine while going down the road which kinda rules out gasket I think.

Now what do I do??

[tntb83]

I was told about the bleed plug & have done that many times so I don't think it is an air pocket either.

need more ideas please.

[xeroinfinity]

So when you say "over heats" is the temp up above 220 deg?

I would say you have LIM problems.

also running straight water thruogh the system will cause it to over heat, and it will cause rust in your system which isnt good

[gbryan]

For whatever reason, Dexcool cools better. Are you using dexcool or some other coolant? I ran Prestone "mix with anything" coolant and my 99 alero ran hotter when idling. Quit running hot when I put the dreaded Dexcool back in. Also you need to know whether your coolant is getting about 220 - 225 degrees, this is where the fans come on. You need to know whether it is really getting hot or something else is happening.

[xeroinfinity]

gbryan, I believe he stated using straight water :

The fan #1 comes on @ 220 deg.
Fan #1+#2 comes on at 240, or when your AC unit is on, both will run.

Dex gets that extra 10 degs with a type a sodium molecularly bonded to the glyco atoms.
dont ask how I know this

My SE is full sythetic(w/dex too), no problems for over a year. My GT has Green prestone it runs fine and no problems with the temps anymore.

Though, I am running a 180 thermostat to keep those temps way under the usuall 200 deg running temperature.

here is a pic of the gauge 1 is fan one.
2 would be the temp where both fans should run.

[tntb83]

I'm not real sure just how hot it is getting but when it gets A little above the normal line is when it blows the water out.

I have put the dex-cool in twice but same thing happens.

[xeroinfinity]

Try replacing the resivour cap is something inexpensive and if yours is bad it will blow out when its at running temp.

If it still blows it out, I'd bet the head gasket(s) or LIM is about to go.

Good Luck!

FYI the term "overheating" usually refers to it maxing out the temp gauge.
What you are experiancing would be "running Hot"

[tntb83]

I have changed cap, no change.
It just seems like if the fans would come on at the right time then I wouldn't have A problem.

But at any rate i'm tired of messing with it and hoping to get rid of it next week.

Thank you to everyone that tried to help.

[BNaylor]

Do the fans come on with the A/C on? What does your temperature gauge read? At what mark on the gauge when the suspecting overheating occurs.

BTW - Ours indicates around the middle marker and a little below in all driving conditions...A/C on or off now since the weather has gotten cooler.

[xeroinfinity]

I still say the LIM is bad or soon will be.

My SE w/195 deg thermostat always ran straight up, aroound 200, and the gaskets/heads everything was new.

Good Luck !