Hey guys,

So today I am sitting in the drivethru for about 20 minutes, it's around 115 outside, and as I get ready to go, I notice the temp gauge is pretty high up on the Navi. Probably 75-80% of the way to the H. As I start to go the temp drops pretty much immediately. Within 1000ft it was back to normal. But when it dropped it dropped in what appeared to be step increments, not a smooth gradual move until it got closer to nominal.

Nominal is just above the horizontal line. The drive home, about 8 miles it never creeped up, the fan clutch was engaged the entire time. I could hear the fan howl taking off from each red light.

So I'm thinking this may be a Thermostat issue, or possible a temp sensor issue. Anyone have anything similar happen before?

Thanks,

Matt

 

Have you checked coolant level lately?

115, hmm you must be in my back yard.

>>>>>>>>>>Action

 

As a post script on the thermostat.

The function of a thermostat is to restrict flow to heat up the engine until a certain temp is reached. Once the temp is reached basically the thermostat is open and not really supposed to close again because the coolant is hot and stays that way. If you are driving in 115 degree weather the coolant is always hot. If the temp gauge gets to normal temps and stays there for any length of time the thermostat is open and not in the picture. There are 2 likely failures for a thermostat. Stuck open or stuck closed or partially close.

If the thermostat is stuck in any closed or partially closed position you will know that quickly because the temp gauge is high, stays high and goes higher because the the engine is generating more heat and there is low to no coolant circulation. If the thermostat is stuck open the engine will struggle to get heated up. When it finally heats up the coolant stays hot and in the normal zone. It is the job of the radiator, water pump and coolant to cool down the engine.

So to your issue - gets hot with vehicle at low RPM and nearly zero air movement from a moving vehicle. When the vehicle is blasting down the road at speed the air movement through the radiator is sufficient to remove heat from the coolant. Just as long as the coolant moves through the radiator. When the vehicle isn't moving there needs to be a way to make air move. That is called a fan. And you said you heard the fan. However if the coolant is not moving fast enough through the radiator (water pump issues) OR there isn't enough coolant in the system then the cooling system is going to struggle at the time there is the most heat load.

Hot engine
Hot ambient temps
Low air movement like parked at the drive thru

>>>>>>>>>>>>>Action

 

Hey Action,

Thanks for the reply, I understand the function of a thermostat. And do understand that the temp will rise when standing still. I would havery thought the fan would be designed to pull enough air at idle over the radiator, and the water pump designed to push enough water through. But that may be me being optimistic

To answer your questiin, I checked the coolant level as soon as I got home and it was right where it should be. I also looked around the engine bay, don't see any leaks and all the hoses look good.

I was a little more concerned over the temp step down, which could be that once I pushed the thotter a rush of cooler water hit the sensor.

In general, I always keep an eye on the water temp in the summer. A faulty tstat could roast an engine pretty quick here.

I'm in Phoenix AZ. Driving around at 7pm tonight it was still showing 113 out, definitely in the toasty time of year.

 

The coolant, water pump, radiator and fans cool the engine down. If they are not functioning correctly the engine will heat up or over heat. And yes the vehicle is designed to provide enough cooling when standing still at 110 or 140. If it does not keep the system cool there are issues with the coolant, water pump, radiator or fans.

If the coolant level is correct there my be an issue with the water pump, radiator (partialy plugged interbally or externally) and or fans. Since you state you hear the fans that might be eliminated. When was the last time the cooling system was serviced?

My Navigator temp gauge will not move significantly if at idle, middle of the day with AC on and vehicle motionless.

>>>>>>>>>Action