I just bought a 92 Celica GT convertible today. for cheap. when i was test driving it, i noticed the temp gauge was getting hotter and hotter. so i decided to have it towed home, just in case. well i was driving it around my neighborhood and the gauge would go all the way into the red and then sometimes it would drop back down to the middle and climb right back up. the fans arent kicking on unless the A/C is turned on. I'm wondering if its just a faulty gauge or sensor and the reason the fans arent kicking on is because its actually running at normal temp. whatcha guys think?
thanks.
1. A thermostat stuck in the closed position (very possible if a convertible isn't used in winter, thermostat is closed, and it becomes stuck from non-use).
2. Water pump is worn to the point where there are hardly any fins on the rotor anymore to move coolant (very unlikely, but possible).
3. Air in the cooling system to the point where there is no coolant flow.
I wouldn't drive it hot, or risk it.
A good way to check is to start the engine after it has been sitting all night - then turn the heat on full blast right after it starts. The air coming out of the ducts should be cold. As the temp gauge climbs, the duct air temp should warm up. Does it?
If it does, your water pump should be good and you likely don't have an air bubble in your system (coolant is circulating within the engine well). This would point me to a thermostat that is stuck closed. If you don't get warm air, you may have a worn water pump or you may have air in your cooling system preventing proper circulation.
It's possible the sending unit or gauge are bad, but if the gauge reads cold when the engine really is cold, then gradually climbs as it should when the engine warms up, it sounds to me like your sending unit and gauge are working properly.
The thermostat is easy to get at. If you get heat out of your heater, I would recommend you check on the thermostat first. Replace it with a Toyota thermostat and gasket and get any possible air out of your cooling system, and see what you have after that.
I would start with the basics first check coolant if you never replaced the thermostat nows a good time to do it and any noise coming from the water pump ?? And yes don't drive it till you get it fixed you don't want to find out what will happen if the engine over-heats.
I'm gonna change the thermostat first along with a full radiator flush with brand new coolant. If that doesn't help next guess would be the coolant temp sensor. Im new to this engine so if there are any links to help with this procedure I'd appreciate it. Thanks guys
Remember, you can check a symptom of a bad water pump before going to the expense of changing it (and on this engine, it is expensive).
If you are positive the new thermostat works, and there is no air bubbles trapped in the cooling system, the heat from a running engine isn't getting dissipated in the radiator for some reason. If the water pump is bad, then there is no coolant flow to push the hot coolant into the radiator and to draw out the cold coolant. The same would be true of your heater core (is also is a radiator).
So, start your engine, let it warm up a little, and turn your heater on full blast. By the time your temperature gauge reaches its normal operating temperature, are you getting plenty of hot air from your heater?
If you are getting heat from your heater, your water pump is pumping coolant very well and is not the problem. Then the only explanations I can think of would be a defective thermostat (which you already changed) or a plugged radiator core.
If you are not getting any heat at all from your heater, your water pump likely is not pumping coolant at all, so nothing is flowing to the heater core or the radiator.
Your water pump is driven by the timing belt. Your labor cost would be right up there with the cost of changing the timing belt. If you are approaching 60,000 miles since the last time you changed your timing belt, if you need a new water pump, then get your timing belt and any other necessary parts changed at the same time (camshaft seal, crankshaft seal, tensioners, etc.).
I warmed it up to normal operating temp and turned the heater on full blast. there was warm air coming out but not exactly hot air. it def wouldnt have been warm enough to warm you up on a chilly day. means i need a new water pump?
as for the thermostat. i replaced it with a new one and the problem was still happening. so i completely gutted the thermostat, i took the valve and the springs out of it. its virtually a big metal washer with a gasket. hoping that this would fix the problem and allow coolant to flow freely at all times.
If your coolant at your water outlet is hot (where your temp. sensor is located), you should be getting hot air from the heater vents. If only slightly warm, another step you could have taken was feeling the heater inlet and outlet hoses. If the inlet hose was hot, but the outlet cold, that would tell you that you have very little flow going through the heater core. But with no thermostat there now, this wouldn't be a worthwhile check to make.
Hopefully it will run cool enough to use for a while without the thermostat. I wouldn't run it very long that way, especially in summer, if this resolves your hot temp. problem now. You may not have enough coolant flow to keep things cool when the outside air temperatures warm up.
Have you had a new timing belt installed recently that coincided with your temperature problem? Just wondering if they did something wrong (like putting the smooth side of the timing belt around the water pump pulley instead of the ribbed side, if this is even possible).
I've heard of plastic blades on a water pump breaking, which could be your situation. I thought Toyota pumps all had metal blades, so the chances of blade failure or worn blades was almost non-existent. But I could be wrong.
sorry. i posted that kinda out of order. ive had that bored out thermostat in there for a couple days. still running hot. is it possible i have to replace the radiator? i think i'd rather have to do that than the water pump.
Thermostats are important. They equalise the heat throughout the engine.
Without one, the cold water comes in and then runs straight out again without having a chance to pick up any heat from the engine.
Some parts of the engine will be nice and cool but other parts (away from the pump) will be even hotter than before.
Blown head gasket, warped head, cracked block are soon to follow.
To test the thermostat, place it in a pot of water with a thermometer and bring to a boil.
Note the temperature at which it opens (somewhere around 90C or 180F, usually labeled on the thermostat itself).
I'm thinking of just taking it to the stealership and getting them to properly diagnose it. I've drained it 3 times now. I'm tired of having totry something and then refilling it and draining it again. If they can tell me what's wrong then I'll just fix it myself
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