Ok so here is my story. I bought a 1998 Ford Ranger XLT about 1 month ago. The temperature kept shooting super high at idle but would regulate driving. So here is what i did so far. I replaced the water pump, thermostat, fan clutch and all new radiator fluid. So this took care of the over heating problem as there where no fins on the water pump. So here is the next issue that arrived. I get heat every now and then. I flushed the entire system multiple times, Does anyone know what the temperature should be on the lines to the heater core? i am assuming 195. I also did the blend door mod and the door is shut and still no heat. Here is what is happening now. the truck has normal temperature and runs great. the heat will be super hot until i drive for like 20 min then will turn cold again. then after 20 min it will get hot again. this happens all the time. When we checked the temperature of the hoses that go to the heat core. it was 130 on the inlet and 95 on the outlet side. cant figure out what is happening. maybe the heater core is clogged cause of the temperature difference. Someone please help as i live in Chicago and its cold....lol....

 

The heater core isn't clogged because the you would be getting no heat at all, but you do have heat every 20 minutes.

Run the truck until you have good heat in the cab, while the truck is running disconnect the vacuum line to the dash controls and block both ends off.
The line can be found on the passengers side crossing over the exhaust manifold.

If the heat stays on, then there is a problem underneath the dash where the vacuum is turning the heat off even though the control is turned all the way into the red.
A bit of along shot if this is the problem.

Have you got the heater water hoses connected correctly ?
I don't have a diagram and my truck has the engine out of it, so I can't advise you there.

I'm thinking that the thermostat is closed when you drive the truck for the first 20 minutes (this is normal). Coolant circulates through the engine and heater matrix, but none of it goes into the rad _ you have good heat.

Eventually the thermostat opens to cool the engine and the coolant should still circulate through the heater matrix while flow is diverted to the rad.
What I'm thinking if the lines were put on wrong, all flow to the heater matrix maybe getting blocked off when the thermostat is opening.
Maybe not all the flow, but a good chunk of it when it opens.

Another possibility if the lines are connected wrong then, the flow is going to the rad first when the thermostat opens and then into you heater matrix.
Wit this situation, you will get the fully "cooled' coolant running directly from your rad into the heather matrix, this would explain the very cold temps in the cab.
Hot coolant from the engine should always come from the engine itself.


As for the temp of your lines, they should be hot, but I don't know what the temps should be.
Seems 130 and 95 are too low.

 

Possible air pocket, hows the coolant level in the radiator and overflow?
The heater control valve is another possibility

 

bled the system mutiple times. cant figure it out. I have two close buddies that are both mechanics and cant figure it out. I will check the vacuum lines and see if that is the problem. I will also check to make sure that the lines are hooked up correctly. The only thing that i could think is that the acuwaiter on the inlet hose is bad and as it warms up it is closing and when it cools its opening? can i delete that.

thank you guys for all your help in advance as my friends and I are stuck....

 

heater core valve the one with the vacuum line correct and goes in and out on a little arm. can i delete that and run just striaght hose and see if that works?

 

Yes, you can remove the heater water control valve. My son did that on his 1999 and it causes no problems. Personally, if that solves the problem, I would replace the valve with a new one (that's just the way I roll LOL).