Truck is a 2000 F150 4.6L 2WD with over 130000 miles. Had the heater core spring a small leak on me a while back so I changed it out. Afterwards, I lost my heat. It would work intermittently, but was constantly loosing heat. I changed the thermostat and that didn't help. I read that a lot of people had said that their water pump fins had rusted away so I figured that was probably my problem. Bought the new pump and took the old on off. Not a spot of rust on the old pump fins, BUT one of the fins was broken completely off and is inside the block somewhere. I'm guessing this is causing a blockage and keeping the heater core from getting proper flow. My question is, how do I get it out? I plan on pulling the lower rad hose off and back flushing the entire system, but I'm not 100% confident that will remove the fin, although I'm hoping it will. Anyone got any idea? Thanks!

 

Do your heater hoses from the motor get hot (or warm) at all?

 

The inlet hose gets warm, but not warm enough and the lower hose doesnt get warm. I figure you're gonna lean me towards the blend door, but I've already ruled that out. Thanks for the reply.

 

Oh, also I've already back flushed the heater core a couple times. Sometimes I can hear coolant in the core and other times I cant. I assume that there is a blockage that's letting some coolant flow, just not enough

 

No, wasn't leaning towards a blend door. Just thinking about a blockage as you thought..maybe air bound ??

 

Oh. A lot of people suggest the blend door. Anyway, I've already tried burping the air out of it several times to no avail.

 

I'm trying to think of how a fin could break off ??

They're made of steel aren't they ? Or are they magnesium, white metal maybe?? I could almost swear they're steel tho.

Well, the only way I can come up with is,- if the bearing went out and it got sloppy in there. Being the case, a new one would be in order. So yea, doesn't make sense.

OR Maybe someone was trying to remove the fan clutch with the pump free from the block... You know, then jam the prop either with vise grips or large screw driver. (?)

Now since that is assessed, we can move on
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Which thermostat are you using ? These engines DO NOT like anything below a 192. A 194 , or maybe a 197 is best. They get goofy with a 187 for some reason. No , I don't know why.

At times, you have to burp thru the heater core hoses. Some can be very stubborn. I have a TSB on that somewhere.

 

I don't remember which thermostat I got when I replaced it. Pretty sure it's the 190. As for the fin, I have no idea. As far as I know, this is the first time the pump has been removed and obviously I took the fan off before I removed the pump, which I thought was the only way to do it. I'm at a loss as to how exactly it broke.

 

Also, I believe they are steel. As for the bearing, the pump seemed fine. Turned smoothly and not leaking from the weep hole. I only changed it because I assumed the fins would be rusted off... Not broken

 

Ok guys. It's been a little while since I've worked on this thing. Flushed the cooling system one component at a time (i.e. unhooked upper and lower rad hoses, unhooked heater hoses, flushed the block, flushed the rad, flushed the overflow bottle, flushed the heater core). I never found the broken fin (oh well). Afterwards, I filled it up with coolant and took it for a drive. Parked it on a steep incline and got most, if not all, the air out. The heater worked pretty well. Then I drove it about 50 miles back home and the heat would come and go. A couple days later I parked on a steep incline again and let it warm up, popped the hood, opened the overflow tank and watched for bubbles as a friend hit the gas. No bubbles and it didn't take any more coolant out of the bottle. Now, I have some heat while I'm driving the truck after it's completely warmed up, but if I turn the fan on full blast it slowly cools down until I turn it off for a little bit and then it blows warm air again. So I'm leaning towards a flow problem somewhere around the heater core. When I flushed it, there were no problems pushing water through. I can even blow through the hoses without any trouble. I'm actually wondering if one of the heater hoses has collapsed on the inside and isn't letting coolant pass through fast enough. That's why I have heat if I let it set, but if I turn the fan on high it cools off the coolant in the core faster than it can be replaced. I remember having to twist and bend the lower heater hose a good bit to get it back into place so I'm thinking if one of them is collapsed, it might be that one. Has anyone ever heard of this? Can a heater hose seem ok on the outside, but be trash on the inside and cause a flow problem? That lower hose is difficult to get to to take off the block so I wanted to ask before I try to tear into it. Thanks again!

 

Anyone have any clues? Basically I'm just wondering if the hoses alone could be causing this trouble. I can get both hoses at advance with the quick connects for around $35 so I may just go ahead and change them, I just don't want to go through the hassle if I can eliminate them as the problem.

 

I think, not sure, that the inlet heater hose has a flow restrictor in it to protect the heater core. Might want to start with that one. Maybe pull it completely off and check it for flow with a water hose.

That is just a guess.

 

There is something on the inside of the inlet hose that makes it bigger on the end than a normal 5/8" hose. Kind of stretches it out. Looking inside it, it doesn't look like much, but that could be what you're talking about. I'm really not sure. I guess I may as well change then out. I've already replaced everything else almost.

 

jbrew is the one that would know about that, I think I saw it one time in one of his posts.

My truck only has 200k on it so I haven't had to replace the water pump or any hoses yet!

 

Yeah, I've been hoping he'd hop back in here. Lol