overheating, I'm stumped. Options

[6strngs]

so today, I drive my car home from work. get out of the car and notice a strong coolant smell. I let it cool down for a while, then went out to check it. The radiator was still full with coolant, but the overflow tank was kinda low. so I poured some coolant in (pre-mixed 50/50). anyway, so I go to drive the car again and after a short trip, only a couple miles, I'm hearing this weird whining sound. I glance down and see that the water temp gauge is reading HOT! like, it was all the way into the red! I pull into the closest parking spot and shut off the car. I let it sit for about half an hour and decide to drive it back home. I start the car up, and the temp gauge jumps to 1/2 way. normal. and as I start driving, it starts climbing. it gets to about 3/4 of the way to hot and then very suddenly just drops back down to half. then it stays there the rest of the way home. I pull into my garage, and get to work. I tried my best to track down a leak and decided it appeared to be that the hose that feeds coolant to the throttle body was leaking. so I replaced it. so after a couple hours of work (decided to do some other stuff too since I had everything taken off anyway) I go to drive it again and same thing. the temp gauge reads normal, then it will climb in temperature, then drop back down to normal, then climb again, then normal. anybody have any ideas? thermostat? water pump? malfunctioning sensor and/or gauge?

[alltracman78]

It sounds more like you have an air pocket somewhere in the coolant.
It certainly won't hurt to replace the therm just in case though.

After you replace the therm, put the front of your car up on jackstands SECURELY so it won't fall [this includes pulling the ebrake] and let it run with the rad cap off. Keep topping off the coolant if it drops. Keep your heat on full the whole time.


Also, just FYI for you guys, overheating doesn't actually damage the HG, what happens is it CAN warp the head. Which then doesn't allow the HG to seal properly. So you get a BHG. But the overheating itself doesn't damage the HG.

[hatchy_gt-s]

It sounds more like you have an air pocket somewhere in the coolant.
It certainly won't hurt to replace the therm just in case though.

After you replace the therm, put the front of your car up on jackstands SECURELY so it won't fall [this includes pulling the ebrake] and let it run with the rad cap off. Keep topping off the coolant if it drops. Keep your heat on full the whole time.


Also, just FYI for you guys, overheating doesn't actually damage the HG, what happens is it CAN warp the head. Which then doesn't allow the HG to seal properly. So you get a BHG. But the overheating itself doesn't damage the HG.

i dont know where to start with this an air pocket isnt going to do **** seeing as it always has air going threw it, the second is the second you start the car without a rad cap on it will spray out seeing as it needs presure to run the coolent, and yes overheating the engine will blow a head gasket because the gasket of course is made out of a rubber substance and the header is aluminum so heat from the engine will weaken the gasket and the preasure from the enclosed engine will blow the head gasket.

[alltracman78]

i dont know where to start with this

You obviously don't.....

You're not supposed to have ANY air in the coolant system. If "it always has air going threw it" then you have a problem.
An air pocket can cause a temp sensor to read incorrectly, and cause the heater core to not work right. As well as cavitation in the water pump, hot spots, ect, ect, ect.
Bottom line, you DON'T want them in your coolant.

The only pressure in your coolant system is from it heating up. When it gets hot, it expands. The rad cap controls how much pressure stays in the system.
So if you start it/run it cold, there will be NO pressure. Rad cap on or not.
And when it's cold the thermostat is closed, so the flow from the pump doesn't effect the radiator. Once it reaches temp it will slowly rise above the level of the rad, assuming it's full. When this happens you can put the cap on and let it pressurize. But it won't build ANY pressure until the cap is put on. It will just overflow.

A Head Gasket is NEVER rubber. It would melt.
A "header" is an exhaust manifold, so throw that term out the window when talking about a head gasket.
Yes the head is aluminum. Has nothing to do with overheating, other than it warps easier than cast iron. File that away for a minute.
Heat doesn't damage head gaskets. Normal coolant temp is 180 - 220*F [roughly] How hot do you thing your coolant is when you overheat? 280*F? 300*F? 500*F?
CONSTANT temps in your combustion chamber are WELL over 1500*F. It can spike to over four THOUSAND *F during combustion.
Do you honestly think even 500*F coolant temps [which you shouldn't ever see] are going to damage the gasket?
Now detonation/preignition CAN damage a HG. But not from the heat. From the pressure.
Back to the overheating/BHG.
When the coolant in the head/block can't get to the rad to cool itself off, your engine overheats. When this happens much of that extreme heat in the head cannot escape anymore. So the head gets hotter and hotter. When you heat something, it can change shape. Aluminum is much more susceptible to this than cast iron. Which is why you don't hear about old school cast iron head engines blowing HG from overheating very often...

When the aluminum warps, it no longer has a flat sealing surface with the block, it's now warped, or rippled.
Which means the HG no longer has flat pressure all over it. Without the pressure it can no longer hold in the pressures from the oil, coolant, and combustion. so it leaks.
Blown HG.


I wasn't trying to be a dick, just to help you out.
I've worked on cars for 8 years. I currently work for a Toyota dealer as a tech.
That doesn't mean I know everything, nor am I always right.
But what I posted is basic stuff. Which I have down pat.
Please do some research before you jump on my case next time.

Batman!!!!!!!

I'm working on an answer. I have most of it, just checking on one more thing.

Back to thread.

The reason I recommended you raise the front of the car up BTW, is to create more pressure for any air bubbles in the system to come to the top. This makes the "burping" more effective.