Brother-in-law ask me if I would put a thermostat 195* in his 98 F150. As it is not getting any heat, the temperature guage is in the normal range. I figured id help him out. Easy job, get it all done, run it to get it warmed up [17minutes], still no heat, it's a luke warm but no change from before, He also has a serpintine belt I put that on. No leaks top of the resorvoir. Noticed that the top rad hose isn't getting hot as usual as well as the heater hoses. Took the stat out check to see if it's opening fully or what, and did the hot water in pot test open right up water was at 197.6 digital meter, so that confirms the t-stat is good, now i'm thinking water pump but I would think the vehicle would overheat if that was the case but it is not, we made some dinner and let it idle for 1/2 hour temp guage normal, coolant full, top hose not hot, but warm. Scratch'in my head here. I'm gonna take the water pump off and look at it. I've never seen one for these engines, I'm a 78-96 bronco guru. But can fix anything. Are the pumps known to not last for this in these engines, It was replaced 9,000 miles ago as was the whole top end including the heads (stock). He fork a bunch of money to a idiot garage, only to take it back again for oil leak YIKES!. - Bob

 

Makes me Pine For the Good Old Days! The '92 E150 I'm retiring has a brass radiator & w/cap off you can see water circulating to judge water pump, thermostat functioning & see if core is full of crud.

Presume you did a Search of this popular topic? There's been a variety of common faults discussed. Recall debate whether temp guages might've been neutered into on/off 'idiot lights' like oil pressure guages. One thing remains for certain, running engines get hot. A bad pump usually leaks or makes noise, most seem to keep pumping. The symptom is overheating from coolant loss, it would circulate if there was enough. Note that heads leaking via cracks or gaskets can fizz, creating a bubble inside the water jacket that can airlog heater cores & disrupt circulation. What were you saying about "a idiot garage"?

Air trapped in the motor or heater core was what 1st came to mind. In 10 years the heater core could be blocked by corrosion if the coolant wasn't changed. They also can get blocked externally from debris that blows in.

Perhaps the fan clutch has zhit the bed & is running excessively. Its designed to regulate how much to slip, depending how warm the air is behind the radiator. Common failures can make them stick more than slip, look for any sign of fluid leaking.

Common Poor Heat gremlins also involve the 'door' that selects heat, AC or fresh air failing & the dash **** coming lose & just sliding when you turn up the heat!

You don't have a Miracle motor-the heat is going someplace.

 

The temperature gauge on these trucks measures the head temperature...NOT the water temp. And from what everyone says on here...it is fairly accurate.

 

Yes I read over 126 posts, over three days didn't find any pertinent info. The fluid has been changed when he had the top end replaced/fixed 9,000 miles ago. There are no head leaks to this day. Nothing but the power steering cooler leak. The garage he used to do his motor work, was a bunch of crazy morons, theuy charged him over 5K to shave heads, new water pump , timing, fan clutch put it all together only to take it apart two weeks later because one of the heads cracked! So he has new stock headsin there. He called me this morning and said he had a little more heat than last time so well see. I will keep an eye on the pump and see , it looks easy to do.-Bob

 

Sorry to hear that.

Not sure what you can expect from "a bunch of crazy morons" & a 10 YO motor that has had to be apart so many times. Still don't suspect "the pump" however IF, trapped air, fan clutch, blocked up heater core & heater control issues are not "pertinent" I'm afraid nothing else comes to mind. Let us know what the 9,000 mile pump looks like. In really cold conditions a motor could idle w/o a pump & even drive at some level just by thermal convection cooling thru radiator. I've seen SAABs & even tractors used to plow, that relied thermosyphon effect to circulate coolant. Also seen failed water pump impellors made out of cast iron, stamped sheet steel, diecast, rubber & plastic.

IMO these F150 heaters should come on like Jack the Bear. Running, coolant circulates thru heater core constantly & once warmed up, when you demand heat that control door should open by vacuum & provide a nearly instant blast of heat.

Wild thought. Could also have an AC issue. You know AC is enabled in every control position except Off, Panel or Floor? For heat only you should try Panel or Floor. For instance if you select Panel & Floor the AC could be running, even in cold weather, if it's low limit was NF.

 

Alright, checked the old pump was smooth operation so I put it back on. The fan and clutch seem to be good as the resistance seems normal. I had him buy another T-stat and o-ring NOT from PEP BOYS this time from the dealer, Did the hot water in pot thing again and compared the two stats. I couldn't believe it- the motorcraft one opened up way more than the pep boys one. So I had him get his money back for that one. I've never had a problem with the "Stant" brand name till now. Everything works good. This isn't a daily driver vehicle He only had put 9000 miles on it in 2 years. Them Fords just break more when they sit than run, just like my Bronco! OH well it fixed now, thanks for the help!!

BTW- There is a huge space between the motor and the intake on the modular engines Is there anything under the runners? Hoses electrical? Just curious. looks like a good place for ford to put something that needs replaced often. -Bob

 

That huge space is for storage... I've got a couple of sockets, an extension, and a few extra nuts and bolts in mine. If ford coulda figgered out how to put the spark plugs in there they would have!

 

I am having the same problem on a 4.6 Expedition! I have change two t-stats. I have been buying the ones from Auto Zone. My coolant is just not getting hot enough. My top hose does not get hot enough. You got a Ford t-stat and it fixed your problem??

 

I am having the same problem on a 4.6 Expedition! I have changed two t-stats. I have been buying the ones from Auto Zone. My coolant is just not getting hot enough. My top hose does not get hot enough. I can put a finger down in the coolant after 30 min of idle and it barely feels warm. You got a Ford t-stat and it fixed your problem??

 

So I thought, I had him call me back yesterday with the same problem- we went on a road trip through the city at stop and go for hour or so, The guage was reading normal, the heater was warm but not hot. I checked to see if the A/C came on Panel and floor positions and it didn't. This is a stumper. The hoses coming from the core and returning to engine are both hot! It must be the pump, or the core is partially blocked and allowing flow through the top which is why both lines are Hot. I'm not convinced the fan clutch is the problem as I can't see it over cooling enough as the hoses are Hot. I will post what I find and the solution.

 

If both heater hoses are hot and staying that way even while the heater is only putting out lukewarm air, you're working on the wrong side of the firewall.

Steve

 

Well i did another flush today. started it up let it warm up, kept topping off the fluid level and burping the top rad hose. And....it seems to be working fine. I put a thermometer in the panel duct and I got 140 deg out of it as well as the floor vent. I dont know if it will continue to work, but I am calling it fixed now. I am not sure what fixed it tho. Thermostat, multiple flushes,topping off the fluid to max, new rad cap??? I just dont know??

 

That's what I keep telling myself, but refuse to listen. Looks like I need to take that dash apart. He said he had the core replaced a few years ago and everything worked fine, just don't use the vehicle much anymore. Oh well, Sounds like a weekend project!- Bob

 

The coolant is full and the hoses are hot but, no heat in the cab, I think the blend door (if it's called that on this year is not working.) Won't know till I get it apart.

 

My 97 has the same problem...I've found if I hit a few potholes after warm up, the heat usually comes on due to the blend door jarring shut. Its like there isnt quite enough vacuum pressure to close it due to it sticking or something, but the vibration of the potholes causes it to unstick and close.