Yesterday, yeah thanksgiving day I noticed a strange thing happened on my car while I was driving on the highway. The outside temp was around 30 degree, maybe below due to wind chill factor, but the water temp dropped from normal or little bit under half of meter to nearly end of bar. The car was running ok at the first or shall I say under 55mp or when I stopped for pumping some gas. However again, when I drove back at the night, same thing happened again, it started fine with normal water temp, but after I speeded up around 65mp, the temp dropped bit above the end of bar... till I had bumper to bumper traffic when the temp came back to the normal. Is that strange?

So, what's wrong? I know car can be overheated, but never heard of the other way around or temp drops when in the cold weather or driving in the cold weather. Please help me. Thanks a lot!

 

I've had problems w/my temp gage toally and intermittently bottoming out but I think it's a loose connection (a bang on the dash helps) you could have a faulty coolant temp sensor. Part is about $22 and easy to replace.

 

Any idea where the sensor is located? Any picture and how to remove/install it? Where to get it?


If it's sensor, then nothing to worry about it, right?

 

It's more likely that your thermostat is stuck open.

 

how to fix it? Does it do any harm to the car if don't fix?

 

That's what mine was initially... But when I replaced the thermostat, it still does it.
It also gets a little colder inside, just not as extreme as it did BEFORE I replaced the warped thermostat.

 

Theres no real easy fix. You just have to replace it. If you have a VG I belive it's located right above the water pump.

 

Whatever you determine, both parts are easy to replace. I am a novice mechanic at best and had no problems at all. Both thermostat and thermal sensor can be purchased thru partsamerica.com (kragen/checker direct). Thermostat should be about $18.00.

On my 89 SE to replace thermal sensor:
„h Drain out a little coolant
„h Locate sensor on where top radiator hose enters the engine block. It is red or yellow in color and has a connector w/4 ? wires to it, covered in shrink wrap.
„h Take pin off connector from side w/needlenose pliers (don¡¦t drop it!)
„h Disconnect connector.
„h Wrench out the old thermal sensor.
„h Wrench in new one, reverse process to complete job.

Thermostat
„h Located in housing at bottom of bypass hose.
„h Drain out a lot of coolant (maybe good time to flush)
„h Remove bypass hose (and upper radiator hose...makes it easier to work)
„h Remove housing (4 bolts). Removed housing will contain thermostat.
„h Scrape/clean gaskets on housing.
„h Bead gasket maker around lip where thermostat goes, put new stat in, and let it dry at least one hour.
„h Bead gasket maker around housing, stick it on, and bolt it in (don¡¦t torque down to much...just seat the bolts in firmly). Let dry 1-2 hours.
„h Reconnect all hoses and run to normal temp, look for leakage.
„h Good-to-go!

 

also invest in a hydrometer, for coolant systems, not batteries.
their dirt cheap so you dont need to worry about that, but it will give the ability to mix you antifreeze correctly.

The Cooling system rules:
1. Too much water and it will boil. If it boils, that is BAD! It can ruin your engine. Also upto a certian point, it will not be able to cool quick enough.
2. Too much antifreeze and it will not be able to disapait the heat as good. Overheating happens.
3. Not enough antifreeze and your engine coolant will freeze. if this happens you will probably be screwed! the outsides freeze before the insides of the pipes will (think ice cubes in an icecube tray). If It freezes, you have a new planter, cause that block is cracked (or radiator if your lucky, but since it can cool faster than a block, you probably gonna be a gardner.

best bet, Buy a hydrometer and a gallon of anti freeze for $10-$15 bucks and enjoy the pride you will have in knowing your car will not become an icecube.

Also, Redline makes a product called Water Wetter. It enhances the cooling properties of water. I recommend it.
MrGone

 

Heh, I'm not worried about overheating these days. I'm more worried about getting a hypothermia or frostbite inside the car! It does take forever for my car to warm up (temp gauge to move to the normal position) these days. Sometimes going to work I'd arrived before the temp gauge reaches normal or any heat coming out of the vents. And it's gonna get colder! I already blocked the grille openings, and that helps.

But the radiator fans are not running though, that means the thermostat is working, right? That's the only thing that the thermostat controls, right? I'm wondering if the car's just designed more with Death Valley in mind, more than Siberia anyway.

 

Over heating is a problem, but freezing is a bigger one.
The reason why your not getting heat is because the heater core is not getting warm. the coolant flows through the heater core, which is like a radiator, but trying to accomplish the oppisite task. the air flows though the heater core to heat up and go into your car.

anyway, atleast you wont be getting "heatsoak" any time soon
MrGone

 

My understanding is that the temp control sensor actually controls the radiator fans....this is what originally led me to replace that item. However, if your thermostat is not opening up, the temp will go up and prompt the sensor to signal the fans to engage so it could indirectly control the fans thru the temp sensor.

For $40 and a couple hours of time you might try to replace both it beats the hell out of a breakdown. If you need the replacement part numbers let me know on this board.

Beerguy

 

I have same problem with a 93. Replaced the thermostat but still engine returns to cold reading while driving. Stopped at an idle the engine returns to normal operating tempature. My car has the electronic heater/ac controls where you choose the tempature. Is the fix different for the electronic heater? Is the sensor the problem? How can you test or know for sure?