I was driving down to my parents place the other day and i noticed my temp gauge climbing, thought nothing of it as it was only a bit above the middle. Made it there and it was at the top of the normal range, not in the red tho. Let the truck cool down for a few hours while i went and bought a new reservoir cap thinking that was the issue. Coolant was still full when i replaced the cap and the same thing happened to me on the way home. got a little warm and started creeping up to the top of the normal range. I'm thinking at this point it's either the t-stat or water pump, truck has 204k on it and as far as i know both of those are original parts. Any body think i should lean towards one part or the other?

 

With those miles, I would do both.
Also check the front of the radiator. Cotton, leaves, ect get in there and block air flow.

 

If your tight on cash I would just do thermostat. The pump to me is a pretty basic part it's either gonna leak or the bearing go out and make noise I don't see it just stop pumping water

 

I'm hoping it's just the t-stat as well, It ran fine 2 weeks ago when i drove to san antonio and back.

 

If the pump isn't leaking, grab the fan blades (preferably with the engine off &#128512 and see if there's any play in the shaft. If not, don't worry about the pump for now. Swap out the thermostat. Sounds like it's your main issue anyhow. Whether it's not opening fully or just sticking, it seems to be the problem. Or the easiest one to begin with.

 

I went ahead and ordered a new t-stat and housing from RiffRaff this afternoon since it's the cheaper and easier fix. Just got the e-mail from USPS that they'll be here weds. Plan on installing them when they get here.

 

Wouldn't hurt to install a real temp gauge either, the stock gauge is really just an idiot light in the form of a needle, and I have seen one factory gauge sending unit go bad and kept reading hot on a F-150 gasser. The owner replaced the t stat, fan clutch and radiator before he realized the gauge was lying. Even a hand held temp gun would've cleared that up. If it gets hot on the highway look for clogged radiator (inside and out) or bad t stat, if it gets hot around town add the fan clutch to that list. But first make sure your idiot gauge isn't lying.

 

^^ Sound advice ^^

 

If i were to do that would i just remove the plug that's below the t-stat to install the sending unit?

 

yes, that's where mine is.

 

Think i'll do that tomorrow evening, how much coolant should i expect to lose when i pull that plug out?

 

Depends on how quick you are. The coolant isn't under pressure, so if you're ready with the sender you should lose only a minimal amount.

 

Cooling issues never seem to be the simple fix. There is just so much that is dependent upon such as scheduled maintenance that affects the systems.

If it's not cooling, there are three area's of concern.

Water not moving - Pump, Thermostat (more often than not, the T-Stat fails OPEN not closed)
Air Not Cooling - Fan Clutch - Blocked Radiator
Weak or not maintained Coolant

Unfortunately, maintenance, or lack thereof, will affect each component.

So, don't be surprised if you have to dig deeper to fix this issue.

I have pulled pumps where the impellers were broken off the end of the shaft where the belt was literally the only thing holding the shaft in place. Removing the tension on the belt caused the fan to fall forward into the shroud.

I've seen radiator cores clogged from mineral buildup which required replacing.

The possibilities are limitless.

Just don't allow yourself to be surprised if you need to go deeper.

Once you get it figured out, I would however suggest you do a complete flush of the system and inspect those three hoses closely. Better to change them now than later and have to shell out the $60 or $80 bucks for Anti-Freeze again.

 

I have just one question:

Does the fan get loud when the gauge climbs?

 

No, it doesn't