Weird overheat issue - opinions wanted (1 Viewer)

[Dan04TLC]

Guys,

Would like your opinion. Background info - 2004 w/166k. Up to date on all maintenance, wife's vehicle. Drove it the other day, ran great. Stopped for a minute and sat idling while wife picked up kids. Probably sat idle for 8-9 minutes. As I went to pull away, temp gauge was almost to the red, started moving forward a bit, and it crept up into the red. We were only a couple blocks from home, so I decided to turn heat to max and limp it home. As soon as I turned the heater on, temp gauge fell back down to normal. I went home and parked it. Couple hours later drove it around, let idle, etc. Could not replicate the issue. Any thoughts? Think the t-stat stuck? Bad sensor? It was cold outside, around 32 degrees.

 

[Rolocado]

Air in the system? Did you open it up for a service? I’m assuming coolant levels are fine?

 

[TXLX100]

Has the thermostat been replaced? The thermostat and broken heater line connections are the only issues I've heard that will cause initial overheating on a 4.7.

 

[94SRUNNER]

I'd be curious as to the coolant systems history. I know you said you are up to date on all maintenance...does that include the coolant system?

As said above, the thermostat is an easy check. Additionally, could air have gotten into the system?

 

[TheDan]

Id check for air first personally by parking nose up on the steepest incline you can find, and with a cool engine running at this incline with the radiator cap off, let it run until the thermostat opens and coolant flows/burps. Keep your heater on during this as well to make sure you dont trap air within there as well.
Never take off a radiator cap if the engine is warm/under pressure though for safetys sake (for those reading who arent aware)

 

[TheDan]

Another thing to look for is if anyone has added a radiator flush/solvent in the past. If it is not completely flushed out and air is in the system-- there can be bubbles/suds within the cooling system that are hard to get rid of until you flush with ALOT of water. (This happened to my dads car about 10 years ago when he got bad maintenance done by a shady mechanic he trusted)

 

[gatormark91]

Fan clutch uses viscous silicon oil that is temp sensitive. Wondering if the fan clutch could be an issue?

Air bubbles sounds like the most plausible suggestion to me, though? Especially if the issue went away as soon as you turned on the heat.

 

[Dan04TLC]

update, it was air in the system, and found the thermostat housing was leaking. All fixed now.