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Temperature Gauge/code 25 ?


misterkni
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I have a 1991 Lexus Ls 400. The temperature gauge jumps around. It starts at normal then jumps all the way to high. It'll stay on high for awhile then come back to normal. It does this continuously while driving. I've replaced the Temp switch, radiator (needed replacing anyway), and thermostat and it didn't correct the problem.

The check engine/trac off light is also on. I had the code read and it's code 25 (lean). I think this code also have something to do with the temp sensor.

The car was running pretty good, so I wasn't going to worry about it. Until yesterday, It fell dead while I was waiting at the Wendys drive thru window. I could not restart the car. I opened the hood and could smell coolant. I let the car sit/cool for about 30 minutes then it started.

Has anyone had this problem? Any ideas on how to correct the problem?

Thanks

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from what i gather, your temp guage is giving a correct reading. the problem is most likely your thermostat. i know you said that you just replaced it but it can still be bad. it would appear that your thermostat is "sticking". a thermostat is a metal spring and as it heats up from engine heat, it expands and opens the floodgate for the coolant to circulate. your thermostat is not expanding like it is supposed to, staying shut, causing your engine to overheat. i had the same exact problem in my 94 mazda 626.

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you need to blead the air out of you cooling system, especially after you changed everything. Take the plug of the thermistat housing and use that to fill the engine, also remove the drain plugs on each side of the engine to try and get rid of all the air in the block, when you finally think you have it all out, start the engine and with the thermistat plug off and the resivoir cover off, let the engine warm up and it will spit the rest of the air out, just when you get clear flow out of the thermistat, put the plug back on and fill the resivor up and you should be done purging the air.

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does coolant flow out of the rad res ?

I doubt it is air in the system as it would need tons to be that much of a difference, so unless you have a head gasket leak and are lossing coolant i wouldn;t think air.

rad caps are also a small possibility but still one, make sure your fan is working first

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No, I'm not losing coolant. Also, the fan seems to be working fine. Does anyone know what controls the temp gauge. Could it be the Coolant Temp Sensor?

Even 10 seconds after I first start the car the temp gauge jumps all the way to high.

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Even 10 seconds after I first start the car the temp gauge jumps all the way to high.

sk is right. if thats the case then i retract my statement about the thermostat. your cooling system is definitely not the problem. its not possible for air in the system, improper amount of coolant, or defective thermostat to cause such a large fluctuation in actual temp. there is something wrong with wiring like sk said or the sensor or something.

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the sensor for the o2 may be fine it may be both wires are damaged, as the sensor makes a lean reading when it gets hot as the resistance is raised , so if the wires are snipped it can ground them and give inacurate readings

the gauge might be another option for the non overheating problem

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