Cooling system problems on 2000 F150

I have a 2000, F150 V6 truck with 150, 000 miles. On a recent two-hour trip I noticed the temperature gauge was indicating hotter than normal. If I drove the truck faster than 65 mph, the needle would get a little over three quarters of the way up to the hot symbol. If I kept a speed of 60 mps or lower the truck ran at its normal temperature, which is slightly just below the halfway mark on the gauge. I drove the entire distance, roughly 100miles in each direction without the any warning lights neither coming on nor the needle ever hitting/pegging the hot mark. The truck never overheated, no water was lost, no smell of overheating, no leakage from the water pump or strange noises and once again, no warning lights!

I pulled over several times to check the fluid and every time I opened the reservoir for the radiator I noticed there was no pressure as indicated on the cap, ?caution 16 lbs of pressure when hot? and the water temperature in the reservoir was extremely reasonable to the touch, you probably couldn?t even heat much less boil and egg or pasta. I thought this to be very odd? I had the radiator flushed almost to the exact day a year ago. The fan runs and cycles while idling and the temperature runs normal. In my genius state of mind I decided to experiment and pushed the truck to 75mph and the gauge would get a little closer to the hot mark, but never seemed to quite overheat. The truck temperature would drop off at a steady pace as I backed off the speed, almost matching but not quite.

I dropped the truck off an auto shop and was shocked to hear that they want to replace the radiator, water pump and thermostat for a cool $1,000. As you can imagine I was a bit shocked. This is my seventh car and has been babied since mile one. Everything has been done when called for without any hesitation, as this was my first new vehicle. I have worked on cars in the past, (no master mechanic type jobs) and found it odd for all three things to be replaced. Any suggestions or comments are very much appreciated.

Get a second opinion from another mechanic. Although your “baby” is old enough to start showing problems, considering the year old flush, the list of replacement parts seems a bit much; unless it wasn’t flushed properly. When was the thermostat changed? I change mine every two years. I assume the coolant was changed when the flush was done. Good luck.

" had the radiator flushed almost to the exact day a year ago"

There is your problem. You are supposed to get it flushed annually and you are a day overdue. Seriously, I would ask the shop how they know this stuff needs to be done. It looks like they are throwing parts at it and it is a slow week for them.

If the cooling system was been kept up, I doubt the water pump or radiator would need replacement. This vehicle could have come with green or gold (G05) coolant. Ford seems to have switched back and forth ( I hope you changed it at least every two or five years respectively, as recommended. I was going to suggest that the t-stat might not be opening all the way. Has it ever been replaced? If you have no pressure, you should test or replace your pressure cap. The system should be pressurized at that temp. The coolant was not boiling regularly or you would be low on volume.

Low rad coolant temp and high engine temp indicates a likely incomplete opening t-stat or other limited flow to the rad. Less so a clogged rad, IMHO. You would have noticed it the rad was externally clogged with trash or there was a lot of crap between the rad and AC condenser, right?

The coolant was changed when suggested but not the therm. I noticed when i last had the rad flushed, the fluid seem darker/dirtier than what was in before. Anyhow i started by replacing the rad cap today with a new one a realized the old cap was missing the rubber gasket! After putting the new one i went for a 35/40 minute drive running about 75/85 mph and the needle moved slightly toward the hot icon but not nearly as much as before, a considerable difference. Prior to the recent event, i could drive around 80/85/90 mph (normal driving speed for me) without the gauge ever moving from center. After getting back from the drive i slowly opened the rad cap and yet again, no pressure. Tomorrow i change the therm and possible have the radiator flushed. If this doesn’t work i suppose i could swap out the rad for a new one and hope that is it. There is still no visible sign of the leaking coming from the water pump. Any suggestion of doing a rad flush myself, good/bad idea?

My bad, i forgot to thank you both for your responses. THANK YOU!

I would definately say that your problem lies with your water pump. It makes sense because at a higher speed and rpm the engine demands more coolant to stay at operating temperature. So the water pump produces but only to an extent. Making it not pumping as much coolant than needed at those higher speeds. So i would replace the water pump first off, the thermostat is cheap and really no problem to replace anyways. Most people replace the thermostat when replacing a water pump or radiator anyway.

Here is the latest update. I had the rad flushed and the therm replaced, still no water loss from the pump. I took the truck out for a long drive at a higher than normal (legal) speed and everything is back in working order. All in all I paid $165.00 versus the quoted $1000.00 for an entire cooling system replacement. I am grateful for everyone?s responses. Have a great day!