Hey guys...I've been absent for quite a while I just realized. Been busy with other hobbies, school, life, bla, bla, bla...LOL. Anyways...having a new cooling issue with the truck. My cooling performance/capability has really dropped off in the past 10 months or so, and has really showed up now that summer has set in. First things first, I have real temp gauges (oil, water, and tranny) so I know what's going on, and I know what's supposed to be normal for my truck. Coolant level is good and pressure in the system is good. I have dual 16" electric fans and a F250 LD radiator...cooling has NEVER EVER been an issue on my truck, even pulling my X thousand pound toy hauler.

But here lately, she struggles to stay at what would otherwise be a normal temp for my truck. So here's some numbers...

Normally, outside air temp has no bearing on the water temp on my truck. Without going into too much detail, with the fans on, my truck ALWAYS ran right up against the closing temp of the thermostat; about 195-198 or so. Never ran above 200. I very, very, rarely had to even use the fans and even then, I only needed fans while towing, or in town in extended stop and go traffic. Any sustained speed above say 35 mph or so and the fans were not needed no matter how hot out it was; she'd hover right around that 200 mark.

Well, here lately, that's changed. I'm running the fans all the time just to struggle to keep her below 210. Cruising down the highway at 70 with no trailer no load or anything, and she's struggling to run at 200. Even if you climb a hill going down the freeway, that'll cause her to start to warm up. Driving under any type of load (accelerating normally, etc) generates heat that mandates the fans to be on, and even then I'm seeing 210 or better until the load is reduces.

It doesn't act or seem like a thermostat because when it's cool out (night time) or not too brutally hot, it'll run against the thermostat closing of 195-198. Clearly it's not stuck open either since I can somewhat control the temp. So indications are it's not that.

Based on the way it acts, I'm thinking it's a circulation problem of either a bad water pump or the radiator clogging and really reducing flow. I read a thread on here one time where a guy replaced his water pump and the fins/veins in the pump were soo corroded and eaten away. it wasn't circulating anything. Is this possible? I've got 175,000 on the stock water pump. Also contributing to the circulation thought is the fact my oil temp is up in relation to this problem. Seeing 10+ degrees higher on the oil on average in comparison.

What would you guys try first? I'm thinking a good flush and see if I can see anything particular with the radiator...maybe get it out and see how well water flows through it? Water pumps aren't that expensive...throw one on it for safe measure?

 

How often have you been changing the coolant? Where did you get the radiator? Used? How old? New?
If you shotgun it, I would suggest changing the thermostat first just to be sure. I suppose the underdrive pulleys slow down the water pump?

 

Coolant get's changed on average about every 1.5 years. Radiator was brand new; forgot where I got it from. It's 7-8 years old. Underdrive pulleys are irrelevant in my case...they have been on there forever.

 

FYI. I once saw a GM car (Camaro?) where the vanes on the water pump had completely corroded away so there wasn't any coolant flow to speak of. Also on one of my old cars the spring in the radiator cap partially rusted away so the cap wasn't holding the amount of pressure that it should have so that caused the boiling point to be too low and caused over heating. Also a blown head gasket has been known to vent through the cooling system and cause it to overheat. Blown head gasket could also cause a loss of power.

 

It isn't running lean is it? A lean condition could cause a temp rise under the situations you described.

I will assume that you checked the radiator for air flow and bent fins.

As others have said it could be the pump. I have over 330k on mine and it has the original pump, so I would run down the other avenues first.

 

Radiator fins are fine. I didn't physically inspect it yet, but AC and tranny are running super cool...so clearly the fans are drawing plenty of air all the way through. I don't think it's running lean; it runs great. There's been no change in driving performance or fuel mileage, or any other symptom to indicate such.

Yea, I can't find the thread where one of our members had the bad water pump...forgot how many miles were on his when it happened too. Think I'll start with a flush. I may just buy a water pump anyways considering the prices; less than $50 from RockAuto.

 

I would start with the thermostat. It maybe cycling off and on but not opening all of the way which is why it cools when the ambient temps go down at night. Yeah, the veins of a water pump can certainly corrode and cause issues but you should be seeing crap in the coolant from it. It will usually have a metallic noise at the pump when it starts going south. Might also check the radiator for voltage. If your meter reads more than .2 volts, you have stray voltage in the system and yes, it will eat a water pump and everything else including the thermostat housing in the system. It will continue to eat until you solve the issue. Hopefully, you've never used anything like Water Wetter in the system. If so, sell the truck.....and no, that's not a joke. Water Wetter cannot be removed and yes, it causes excess voltage in a system. That's better known as electrolysis. The fix is a new cooling system, new heater core, new hoses, new engine. It ain't a cheap date to fix.

 

I had to replace my water pump at 22x,000 miles, it wasn't leaking, but the truck started to try to run hot in drive thru's and lights that held a while,, and sure enough the impellors were completely gone. I'm pretty sure it was the original pump.

 

I have electrolysis. I've had it for years. Chased it forever. Finally gave up. That was years ago as it was driving me insane and it caused zero cooling issues. Haven't checked the voltage in a long time to see where it's at though. Oh well.

Have never heard that about Water Wetter though. Can't say I've heard anything bad about that at all over the years.

https://www.f150online.com/forums/v8...tric-fans.html

 

I would remove the water pump and look for one or more impeller fins missing. They can and do break off sometimes. Even one missing will cause a cooling issue because the loose fin will migrate to the lower block water passage just above the oil filter adapter/lower hose connection and get stuck there. It will then restrict coolant flow generating a condition such as you are experiencing. Seen this numerous times.

 

Heater core clogged causing a restriction?

I've seen lower radiator hoses internally collapse under the inlet side of the water pump. It's "negative" pressure on the inlet side. Dual layer rubber hose that the inner layer pulls down and can cause a restriction with no out word signs.

Radiator bottom clogged (can be verified with IR temp gun)

If you have trans cooler in radiator tank only, could even be a trans issue adding too much heat into the coolant

 

So when it comes time in the future to sign up for the annual F150 giant DORK awards, you guys might as well just stay home cause you don't stand a chance of beating me this year!!!! So I was just about to devise a plan to start taking **** apart...pull the radiator and flush it out, pull the pump and inspect it, test the thermostat, etc. But I decided today to just look it over and check the obvious simple stuff, like say...oooohhhh...IDK...maybe the water level?!?!?! It was low. Well, let me add some...yes...great idea. Just under two gallons later she was right back up where she needed to be. (bang head on wall here). Can you believe that ****??? From me of all people. Oh well! Hope you guys get a laugh at my expense. Stop and go traffic today on the freeway, 91 degrees, barely reaching 30 mph at times and never had to turn the fans on at all. She never got above 205 or so. And now we return you to your regularly scheduled program already in progress, lol.

I guess there is the unanswered question of where did almost two gallons of coolant go?? I know Patman and Labnerd know how I am about my truck...there's no leak and certainly one that went unnoticed.

 

Hopefully not head gaskets.

 

Yeah, losing that much coolant with no visible leaks doesn't sound good. May have a bigger issue than water pump? Could the radiator cap be failing to hold pressure? If so, the coolant will boil at a lower temp and you could be losing coolant that way. But, with the overflow bottle, you might would notice if that happened?

An almost new 67 Mustang my new bride was driving on our honeymoon way back when started missing when she pulled out to pass on the interstate. I looked over and saw the temp gauge was pegged high. We pulled over and I filled it up with ditch water and drove to the next gas station where I flushed it out with tap water. A new cap fixed it up and since the 200 cu in six was all cast iron, it didn't blow a head gasket. That was before the dawn of overflow bottles.

 

A friend of mine said that when his dad let him start driving he told him "You better always make sure there is oil and water in the car, but I don't care how much you drive without any without any gas!" That was about 50 years ago and I think still applies today.

I hope everything checks out good after that.