But how does it know whether it's taking longer to warm up because of a 1/16" hole in the Tstat or if it's just a cold vs. warm day, or if you have the heater controls off or on? Just curious, I don't work on new stuff, couldn't fix one if I tried.
It KNOWS what you did last night!!!! It's a timed event with logarithmic tables. That particular vehicle does know the outside temp, the coolant temp at start up, and if you have the heater on or off. Some geek figured out exactly how long it should take to reach operating temp with all those variables and put them on a computer map. When the actuall readings fall outside the programmed expected projection, it throws a code. Example and out of my *** for explanation. Let's say the computer wants to see 1* rise in coolant temp for every 30 seconds run time. Doesn't really matter if its - 30* or 80* and im sure the rise vs time is on some type of bell curve. If its out of that range, the computer throws a DTC code.
A 1/16 hole will only flow .2 gpm at a 10psi differential. At idle, with the heater valve open, the pressure is likely much lower. I've never had a problem with it but there could be programs capable of detecting it. A smaller hole will still allow air to p*** through and cut back coolant flow.
On new cars, they "know" weather or not it is hot or cold out side with an ambient temp sensor. It also "knows" how long it should take to warm up. If it takes too long it throws a code. Chevy trailblasers are terrible for this. (trailblasers are just terrible). My boss taught me an old trick similar to the candy trick except he used to use an asprin to hold the stat open. Plus the car would never get a head ache!!!!!!!
I drill a hole on older non computer controlled systems, but never had to do that to a flathead. I've had some new cars that were nightmares to purge, it was a combo of lifting the front end, the coolant funnel, driving and re checking.
The Jalopy Journal
