Temps & Scangauge
 

I am courious about other's experiences with reported temps from scangauge.

I have a Q45 w 4.5L V8

Termostat is 180 degrees (new one installed lasst month, before my trip to tx. old one still was working, mainly just precautionary)

car 'overheats' at 240.
( VERY brief experience 2 weeks ago in texas in standing freeway traffic at 3pm in the afternoon, uotside temp 101 degrees!)
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NORMAL DAY to DAY READINGS:

on a 90 degree day at 55-65mph temp is 197-202
(rarely drops below 193)
around town in traffic temp is 205-218

all is easy to normal driving conditions.

Is it normal to run 20-30degrees over the thermostat 'open' number?

Grill block (your sig) having any effect ?

That sounds like my car when i leave the grill blocks on past winter. mine is also a 180 thermostat. The fan comes on at about 210. Normal driving (45-65 MPH) with temps at 80-90F outside, the car with no grill blocks runs about 184. In town that goes up to 195. I might try putting my upper grill bock back on but I think it blocks too much air.

I had removed my grill block on my trip to texas because orf the 'overheating' (another post - octane).
so these readings are withuot a grill block....

The SG2 will only be recording what the onboard comp is saying which is what the sensor is telling it.

You probably know this anyway from reading your previous stuff but I would start with the cheapest items first - check the thermostat, then the temp sensor and then move onto mechanical stuff.

I had replaced the thermostat prior to leaving. I had put both the old & new one in a pan of water that was on the stove. They both opened at the same time. I didnt think my old one was bad ....but at 205,000 miles and a trip across the mojave dessert and thru ARIZONA w/ 110 degree day........seem like the smart thing to do.
THe thermostat is 180 degrees

I would think thart if a sensor was bad I would get a obdII warninng

A bad coolant temp sensor would only throw an OBDII code if the readings were out of whack in a way that definitely indicated a problem or bad sensor (never warming up). Running a bit hot according to the sensor wouldn't trip a code.

That's normal. There are two significant temperature points - the thermostat and the cooling fan. The engine can run anywhere between those once it's warmed up. On my car the thermostat is 180F, like yours. The cooling fan comes on at 206F. On a hot day and in-town driving, it can rise to 210 or so before the fan can bring the temperature back down. Highway driving keeps it cooler due to the extra airflow.

Some variance, and up to 20* or so above t-stat temp is normal. However, 240* is not. If the car has an electric fan, make sure it's working properly, and not getting weak. If it's a mechanical fan, check or replace the fan clutch.

What you can also do to keep the temp steady is drill a small hole in the T-stat just past the inside of the gasket. That will allow a small bit of hot coolant to leak back to the radiator. I did that on my car and the warm-up time is no slower that before the change but it helps to get the air bubbles out of the heating system and moves some heat out before the t-stat opens. I did two 1/16 holes from what I remember but others have done larger.