So, I have a 98 ls1 camaro ss and the coolant temp gauge never moved past 100 degrees. I thought it could be a couple things: coolant temp sensor, the gauge, or the thermostat stuck open. I ruled out the thermostat because the heater blows hot so the coolant is obviously hot.

I replaced the coolant temp sensor and flushed out the system. I started the car and the gauge started to climb while the car was warming up as normal. The gauge hit 210 and stayed there, then I was letting the air bubbles out of the system (coolant level was full) when the low coolant light came on and the gauge started dropping and then stopped back at the 100 degree spot. I shut the car off and restarted it, the coolant level light went off but the gauge still won't go past 100.

Does anyone know what might cause this problem? Thanks.

 

Nobody has any ideas?

 

I would try a thermostat. It sounds like the temp was rising before you got the air bled out, as the thermostat will not function until the system is fully bled. Once you finished bleeding the system the thermostat opened and the temp dropped to the same spot it was maintaining before the ect sensor swap. It sounds to me like the thermostat is just opening too early.

If you have access to a scan tool you can check the temp on there to see if the gauge in the dash is functioning correctly.

 

Does a scan tool show the temp to be 100 degrees too ?

If so, it might be a wiring problem with the connector/wiring for the temp sensor, which I've seen before... They get smushed easily especially when working on exhaust/headers.

Top of the radiator cap and the top radiator hose getting hot ?

Rob (Bad30th)

 

Going to use a scan tool on it tonight and I let everyone know the results. Although, the connector did look fine when I pulled it off to change the sensor.

 

Usually the thermostat has a fail safe, when it goes bad it will stay open thus not letting your motor get hot.

 

Yea, I know, but my heater blows hot so I figured the coolant is hot too. But we will see tonight when we use the scan tool.

 

Scan tool says coolant temp stayed at 174 degrees all the time even after hard runs.

 

If your water temp was really 100F you would never go into closed loop. I didn't know the gauge read a value that low. Are you using an aftermarket gauge.

 

Its the white faced 200mph gauge cluster, the lowest value is 100F.

 

does the car run ok or is it sluggish or surges soundin like the sensor but the car shouldn't run good if the sensor was readin like that ohm it out

 

acually i may be wrong does the ls1 have 2 sensors one for gauge one for the ecm i'm not sure

 

Does anyone know where the sensor for the gauge is because obviously the ecm is reading correct, but the gauge is not. I replaced the one on the driver side head.

 

98 model cars have a 3 wire ECT - one wire for 5 volt ref, one signal to ECM, and one signal to the gauge. 98 model cars have a wire going straight from the sensor to the cluster. If you replaced the ECT sensor and the gauge is still showing lower than actual temps it may be a faulty gauge or a problem with the wire.

99-up model cars only have two wires on the ECT - a 5 volt ref and the signal to the ECM. In the 99-up cars the ECM sends a data signal to the cluster which operates the coolant temp gauge.

No LS car or truck has two separate ECT sensors.

 

Thanks for the help.. Must be a gauge problem since the ecm is getting proper reading.

 

man i got this same thing. but my scaner and guage are reading the same.
97*F. changed t state already too.. both upper and lower hoses are hot.. wat gives...

 

Both hoses are "HOT" to the touch? Maybe so, but is the temp gauge in your hand accurate enough to tell the difference? I doubt it unless there is a considerable difference. Better to use a IR thermometer. Black things like rubber heater hoses have good emisivity so you will get an accurate reading from the hose surface. I once tried an experiment to see if I could lower my water temp even more after installing a low temp thermostat. I tried removing the thermostat alltogether thinking the flow would increase even more. It did to the point that the water was rushing through the radiator so fast there was no time for the cooling fins to carry the heat in the water away. The water temp actually went UP not down as a result. You must have a restriction(not enough flow) OR not enough restriction(thermostat not contolling flow rate). That's one thing most people don't think about. Your thermostat has two jobs to do. Determine at what temp the water BEGINS to flow and once it opens fully it then determines flow rate.

 

Hi Elmer,

When you remove the thermostat from an LSx, you leave the bypass port open... this provides the coolant a path of less resistance compared to the radiator, so most of the coolant takes this path (pump recycles hot coolant back into block rather than thru radiator), this is why it ran hotter without the TS... if you block off the bypass when you remove the TS, you will find it runs cold enough to prevent closed loop fueling.

The TS's third job is to minimize flow thru the bypass port when TS is open (i.e. make the bypass port be the higher resistance coolant path compared to radiator).

 

I didn't know about the bypass port so I pulled the thermostat to look for it and couldn't see it. I found the heater core ports(feed and return) and the port for the water returning from the radiator, but didn't see another port for bypass. How is the bypass plugged and where the heck is it located? Is it normal for the heater core ports to be located on the return side of the radiator instead of the side going into the top of the radiator where the water is hotter? Why don't they tap the heater water before it goes into the radiator where it would heat the passenger compartment quicker?

 

Look at the end of the thermostat, there is a spring loaded disc.

The bypass port is the round hole between the heater in/out ports.