We just got my car back together and when we started it up and let it warm up we noticed the gauge was not reading right. The car runs good and drives like it did before we took it apart. During the down time of the car could I have messed something up? Maybe a sensor on the block or head I can check. I did take the head to a machine shop to have it looked at and when it was there I had them clean it up (some type of washer they have). The gauge use to come up about half way or so but now it just goes over the C mark on the stock cluster. The car is a 99 civic si if that gives you any idea on how the cluster looks. Should I even worry about this at all cause it isnt affecting the driveability of the car at all. Its just weird when I look down and the temp gauge isnt where it use to be. Thanks Guys.

 

Yes, it will affect the vehicle. If the gauge is reading correctly, the ecu will think it's still cold and stay in warmup mode. I would check the thermostat to see if it is stuck open, cause that's what it sounds like to me.

 

The gauge and the ECM don't use the same sensor. They don't share information.

If the gauge is correct, then the engine's not reaching proper temperature. T-stat stuck open, and the ECM will know about it from it's own sensor (ECT sensor).

If the gauge is wrong, and the engine is actually reaching the proper temperature, then the ECM won't be fooled. Chech the sender for the gauge or maybe the gauge itself. I don't have a '99 si so my Helm books aren't gonna help you much.

Do you have a Helm repair manual??

 

yeah I think its a stuck thermostat as well. Im just gonna order a low temp thermostat and install it and see what happens. After all, even if it isnt the thermostat its not a bad idea to upgrade it anyways.

 

i never understood the idea of a low temp thermostat.

just order an OEM honda thermostat...as honda designs their engines to run at the correct engine temperatures.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by chet &raquo;</TD></TR><TR><TD CLASS="quote">i never understood the idea of a low temp thermostat.

just order an OEM honda thermostat...as honda designs their engines to run at the correct engine temperatures.

</TD></TR></TABLE>

yeah i guess you have a point. Im just gonna get a OEM one and save myself like 50 bucks over the Mugen one. I mean its not like my car has ever over heated so why would I need anything different than what I have.

 

The Engine Temp gauge is affected by 3 things: +V which comes from Fuse 25 (7.5A Meter), Ground which comes from G401 which is located in the left front kick panel area, and finally the sending units input.

The sending unit is located right by the ECT sensor. The sending unit has only one wire, which is yel/grn, while the ECT sensor has 2 wires...just so your not confused as to which is which.

Since the odometer/speedometer/tachometer/fuel gauge all share the same +V and ground, unless these other gauges are screwing up, I'd point my finger at the sending unit/its wiring/possible air bubble in the coolant system.

And as far as the thermostat goes...just stick an OEM unit back in there and be done with it.