Guys, I have gone through (by way of Search) the posts on the subject. I also bought the Hanes Manual "Ford Ranger Pick-ups 1993 thru 2010 All models" (Not impressed at all.)

There are some things I've tried and somethings I am confused about or lack information. Note I am one of those old-timers who remember adjusting solid lifters as well as points and timing, and when electronic ignition was a new thing, and I just don't know about some of this newer stuff and I haven't ever done much under the dash and with the climate controls.

'99 Ranger 3.0L 5 speed manual 4x2 w/factory AC. Note no overheating problem ever.

I notice poor heater performance when it got cold. I changed the thermostat. Now I have no heat all. I am not sure about the heater hose valve (does it fail open or closed?) so I removed the heater hose valve and put in a T-fitting that is for flusing the system since it seemed like a convenient method. No change.

If I understand it correctly, the heater hose valve is on the return line which goes from the heater core at the firewall to the water pump. The other line goes from the engine just below the thermostat housing to the firewall. Note that both of these lines have a T connection with a hose that goes to the Intake manifold (what is that?) If I read it correctly, the coolant is pumped through the engine and out the heater hose to the heater core and then returned to the waterpump.

I took the cap off the T-fitting I put on the return line, and the coolent comes out slowly. I would expect it to come pooring out. Does this mean the heater core is restricted or blocked? Or is this normal? I read about the possibility of an air pocket in the heater core. (Never heard of such a thing Back In The Day.) How can you tell? I have run the truck with the cap off the T-fitting with the hose elevated to be the hightest point in the system. I didn't see any bubbling, just a slow exit of coolant. I have also run the truck with the radiator cap off. Nothing on this subject in Hanes, btw. I thought they might list a proceedure if this is a common problem.

I have read about a door that opens for the air to flow over the heater core and into the passenger compartment. In a '99 is that a vacuum-operated or electrically-operated mechanism? How can I find out if this is working? Is there a way I can see this operate? I read about an actuator not working when the temperature is adjusted - how do I see that? Does anyone have any pictrues?

My current plan is to disconnect the input line and hook up a hose to the return line and see if I can clean the heater core out. Do I have to be concerned about putting too much pressure through it? The other thought I had was if I just switched the hoses at the firewall since they seem the same size.

Lastly if the water pump is old and not pumping well, wouldn't the truck tend to overheat?

 

The heater control valve is only closed (vacuum applied) when the selector control is set to the off or max ac position. If you lose vacuum, it will default in the open position. However, the valve can get stuck in either position. With this tee installed, you should have gotten sufficient flow through the core for it to warm up. Did you notice if both heater hoses got hot?

Yes, the heater control valve is inline with the return (core outlet) line. The lines going to the upper intake helps maintain it at an overall optimal operating temperature.

If you've replaced the heater control valve with a flush tee, and removed the cap with the engine running you should have had coolant coming out at a fairly good rate. I'd suspect the core maybe plugged. Typically the air pocket forms in the engine when refilling the system after a partial of complete draining of the cooling system.

I believe the blend door is electrically operated. This link should help Blend Door Video

Do not apply full city water pressure (50-60 PSI) from hose to heater core (max about 25PSI). Do not switch hoses at firewall. Just try to back flush the system. If it does not flush out, you will need to replace the heater core. This link might help if you do wind up having to replace it Replacing Heater Core

I would think so.

 

Hey thanks JJ. It's nice to get feedback on my ideas and understanding.

I went to my friendly neighborhood do-it-yourself car wash, disconnected the heater hoses, and ran water into the return line until it ran clear. Then just for fun I ran it in the normal direction. I reconnected the return line and blew the water out of the heater core. I poured coolant mix in the elevated flushing T until it began to come out the inlet. I reconnected that hose and started the engine with the cap off of the flushing T until it stopped bubbling and just leaked coolant. I capped the flushing T.

I then checked in the truck - success! I have good heat now.

 

Glad to hear you got it fixed. Yes, I remember, those days of Points & Condensers and setting the static engine timing with a 12V test light...

If you haven't already done so, and just to play it safe, I'd also recommend you flush the entire cooling system as the radiator may be in about the same condition.

 

JJ, I can't really flush the system right now - we've had temperatures in the teens and I don't have the facilities to do it. That's why I went to the friendly neighborhood do-it-yourself car wash. $2 well spent!

 

LOL, I hear ya...That's one thing I don't miss is those cold winter days.