Ever since I did my headers and exhaust, the temp gauge has read about 50 degrees low. It seemed to work fine before then

The fan comes on when it should, at 193 degrees, but I went ahead and changed the sending unit, anyway. No help.

Does anyone have any ideas?

Thanks

 

Hellooooo?

 

Exactly how do you know it's reading 50 degrees low?

 

taking readings with lazer thermometer on the thermostat housing

 

Ok, depending on where your sending unit is installed you could easily see that much difference between the two. Some sending units are not as accurate as others either; have you tried swapping it out with a new one?

 

I've owned the car for over 14 years. The temp gauge has always worked fine.

Put headers and exhaust on it, and it reads 50 degrees low.

In the original post, i said I'd changed the sending unit. If anything, it's worse.

 

I'd suggest verifying the sending unit/gauge operation as per this article and go from there.

http://www.madelectrical.com/worksho...mp-gauge.shtml

 

headers can lower the temperature at the sending unit location, especially if they're coated. 50 degree difference in actual temps may be stretching actuality but are certainly within the degree of accuracy of the stock gauge.

keep in mind that the stock gauge is not linear, as evidenced by the spacing between dial readings. at some ranges a relatively small difference in actual temperature at the sender may appear, on the guage, to be more.

consider the stock gauge to be more of an 'educated guess' as to the actual state of nature at the sender.

 

I've had several cars with SBCs, put headers on them, and had the temp gauge continue to work fine.

Moreover, I've searched on here, where literally hundreds of guys have put headers on virtually identical cars, and haven't experienced this problem.

I can't see it as some kind of general side effect of putting headers on third gens.

Seems like I remember a discussion a long time ago about it having something to do with a pigtail, but I can't find the thread.

 

apparently your temp gauge is much more accurate than the stock gauge installed within most of these cars

from the certainty of your post it also must be reading exactly 50 degrees lower at all ranges of operating temperatures, which would include a cold engine that hasn't been started

we can thus rule out any correlation between any heat removed by the headers and your 50 degree lower guage reading.

can't help you there

 

Well did you move or remove the temp sensor? Auto temp sensors are thermistors which have reduced resistance with increases in temperature (called a negative temperature coefficient). Could something be adding resistance to that circuit? Did you replace the sensor with some sealant that could add resistance?

Something with an entire new exhaust system could be there was some kind of heat riser/ restriction that got removed with the old exhaust?

Now in theory when the exhaust restriction is reduced when new headers/pipes the engine breathes better making it somewhat leaner at same RPM. And IIRC a lean mix is hotter than a rich mix burn. So that would be opposite of what you are seeing. I really think the problem is with the temp gauge and it's circuit.

Hope this helps.