I don't know if this is an issue or if it's normal so, I thought I'd post this on here.

My '04 Ranger has over 240k on the odometer. Runs great and has never given me any issues. Everything checks out OK - all the fluids, filters, and whatnot are in good shape. No CEL or any other indication that anything is wrong (except for maybe the IAC valve and clutch slave.)

I've noticed, though, that when I fire it up in the mornings to let it warm up while I scrape the ice and snow off the windows, the heat/defrost will not blow warm air. It doesn't matter how long I let it sit, it will only blow ambient air through the ducts.

When I get going down the road, however, the heat kicks in, after a bit, and works very well!

I've not found anything that would indicate an issue with the blend door or any other component and this is the first vehicle I've had that did this.

Is it normal for a 4.0 SOHC Ranger to do this? Or is there something I'm missing?... It's not really that big of a deal, but I do find it a bit odd that it would do this.

I mentioned the IAC above - I think it's "sticking" every once in a while and, when it does, I'll hear a loud "thump" right before it idles down to around 1k rpm. I can't see how this would affect the heat, though...

Anybody have any ideas about the heat?

Thanks.

 

What does your temperature gauge show? Is is sitting on Cold while the engine is idling? What does the temp gauge show when it is blowing hot air? What do the hoses to and from the radiator feel like? What do the hoses to the heater feel like?

Two thoughts come to mind:
1. your thermostat is not working properly, or
2. your heater core is plugged up.

Do some more checking and let us know what you find.

 

The temp gauge never gets past the halfway mark. I will have to check to see if it gets up to that mark at idle - my memory is failing me right now. I can check it tomorrow along with the hoses.

If it were a plugged heater core, wouldn't it just not work? When it starts working, it works very well - almost cooks me out of the truck. I also do not get an antifreeze smell nor is there any indication of a leak that I can see...

I can believe that the thermostat might be the culprit - I have no idea when it was serviced last so, I'll have to check into that...

Thanks for the ideas - I'll report back after I've had a chance to check things out tomorrow...

 

Does the thump sound like it comes from inside the cab around firewall area? Maybe the blend door is sticking and the thump is the door seating.

 

It does, and I did think of that but, what's throwing me off about that is that it only happens when the truck kicks down from high idle to curb idle - first "thump" then idle kicks down.

Also, it doesn't do it every time - only once in a while. It hasn't done it in a while...

Last night, I was driving home from a friend's house - it was around 5*F and it didn't seem that the heat was as warm as it should have been.

I'm waiting for it to warm up a bit outside before I go out and tinker with the truck...

 

I had a 03 SD that made the thump after starting the engine if the heater controls were in a certain position.

 

OK, I'm thinking it's the thermostat...

Here's what I came up with:

While I was doing this, the outdoor temp went from 18*F to 28*F.

• 11:02:30am - Started the truck. It ran smooth at 1500rpm.
• 11:03:03am - The idle kicked down to just above 1k rpm. No "thump".
• 11:13:02am - The temp gauge climbed to the halfway mark and stayed there. It was still blowing ambient air and the hoses were cool to the touch.

I let it sit idling for a while to see if anything changed. The upper radiator hose and supply hose for the heater core started feeling warmish, but not warm enough - it wasn't enough to open the valve on the heater core supply line to let the warm water through.

While it was idling, I got in behind the glove box to check things out - the door to the right of the AC box seems to be working fine - I worked the control from AC to Off to Heat and that door opened and closed just fine with no issues. I couldn't see the blend door - it seems to be buried - but while working the temp control from hot to cold and back, I could hear the door open and close - it didn't sound unusual (no weird noises) and didn't appear to be sticking from what I could hear. All controls work normally - no issues to report.

• 11:42:01am - Went for a drive to warm the truck up. I also had some errands to do while I was out.
• 11:43:48am - Warm air started coming out of the defrost.
• 11:53:51am - Temp in the cab started getting comfortable.
• 11:58:40am - Temp in the cab started getting rather toasty.
• 12:03:20pm - While stopped at a store, I checked the hoses and they all felt normal - the upper radiator hose was warm but not excessively hot - same for the heater supply hose and the temp on either side of that valve was the same (what triggers that valve to open? Temp?). The return line from the heater core was slightly cooler than the supply line indicating to me that the heater core is fine.

After getting back home, I let it sit at an idle for a bit and the air coming out of the ducts started cooling back down to just above ambient. Controls had not changed.

Coolant level is fine.

This is all telling me that the thermostat is stuck open but is still providing just enough restriction to allow the water to warm up for the heater while the truck is being driven around - just not at an idle...

Sound about right to you guys?

 

Is this something that just started or was it the same last winter?

 

I can't recall if this was happening last winter or not. I know I didn't have any issue over the summer - even with the AC running...

 

I don't know what the thump could be, but I vote on a bad thermostat.
With the A/C running, the only coolant temp indication would be on the gauge. You wouldn't have flow through the heater core, I don't think.

 

I'm not familiar with the system on the 04, but normally if there is a heater control valve in the heater hose the valve is opened by vacuum. When the temp contol inside is put in a position requesting heat vacuum is sent to the valve to open. Most systems don't use the valve. The blend door inside is all they use.

 

OK, that makes sense. There is a vacuum line attached to the valve but nothing else so that's what made me wonder what triggered the valve to open.

It seems to me, based on what I saw today, that something would have to monitor coolant temp in order to determine when to send vacuum to that valve to open it - but I'm not used to working on such a "newfangled" vehicle and staring at all those gadgets and gewgaws under the hood gives me a headache...

I'm still leaning toward the thermostat being the culprit - it just seems to be the most logical choice... The problem is that this cold weather tears me up and I can't be out in for too long so, I'll have to wait until it warms up a bit before I can swap it out - luckily it's an easy & cheap swap...

 

Thermostat could certainly need looked at.
However, I have to ask, what was the blower setting when the air output started getting cooler @ idle?
I know that with the 2.3/2.5L engines, you can cool the engine to nearly cold in very short order by running the blower on 3/4 with the engine idling. I'm reasonably sure that even the 4.0L will cool down with the heater blowing on a higher setting, with the engine just idling, after a while.

 

Thats a good point. Thermostats usually stick open or closed. They don't normally stick somewhere in between. Replacing the thermstat wouldn't hurt and its not a costly repair. I'm begining to think what is happening is normal considering how cold its been. It will take longer to heat up idling with the blower running than it would driving down the road.

 

Sounds logical - I can see that...

But, I very rarely run the blower past 2 - haven't had any reason to and the noise from the fan at the higher speeds annoys me...

Whether the blower is on 1 or 2, the effect is the same...

I had also considered that it may be because of the outdoor temp - that maybe the engine was containing all the heat and the cold outdoor temp was keeping the heat from being transferred to the coolant... No clue... It's been getting down in the negative temps at night and it doesn't seem to want to get past the freezing point during the day - it's supposed to be like that for at least a week... Brrrr...

The heat issue really isn't that big of a deal for me as it does warm up nicely once it gets going down the road - I'm more concerned about the engine running at the correct temperature...

I'm attempting to contact the security company in Montana that owned this truck prior to see if I can get any idea of the maintenance history...

Thanks for the help guys!