SuperDave69

Having an issue with temperature spiking suddenly then returning to normal. It does this intermittently but when I’ve checked the fans, they don’t seem to be blowing excessively hot air from the radiator. I have replaced the thermostat and the problem persists. Could this be the “mapped temperature” or auxiliary water pump I’ve heard about on this model? Any help would be appreciated.

hellride

The auxiliary pumps are to get coolant to your transmission and heater core. They typically throw a code and shouldn't impact your normal circulation. How far and how fast are you seeing this temp fluctuation? Sounds like your temp sensor.

SuperDave69

Happens at all speeds. Will go from normal to pegged in about 2-3 seconds, stays for around 4-5 seconds, then back to normal in 2-3 seconds. Seems to do it more after I’ve gotten into the throttle.

TheoRR

Symptoms you describe sounds like either clogged radiator, sticking thermostat, or sensor related. I would suggest to review all those again, even the thermostat you just replaced.

Also, is anything showing up when you do a VCDS scan?

Jibsymalone

Does it do this when idling? Can you use an IR thermometer to corroborate the temperature being reported is the actual temperature of the coolant, or at least close to it? That should help rule out a sensor issue pretty quickly?

SuperDave69

I’m gonna pull codes when I get home. I saw one before about an intermittent open circuit on something on the cooling system but before I could write it down I messed up and deleted it.

SuperDave69

Doesn’t seem to matter whether it’s idling or driving down the highway at 80. Only difference is it doesn’t drop the temperature back down nearly as quick at idle.

SuperDave69

Is the plug that connects to the thermostat for temperature readings or is it to control the thermostat?

TheoRR

I think the thermostat flow control is all mechanical. Looking at Erwin, the thermostat (F265) is connected to ECM (J623). I think the plug sends temperature data to the engine ECM.

Jibsymalone

Well that's good, I was worried it would only show when moving, and it is kind of hard to shoot an thermometer under the hood when hurtling down the interstate ☺