1996 4.0 OHV - No heat, will soon replace thermostat, have questions...

[LazyDaiseyFarm]

My Explorer is not reaching operating temperature. Temp gauge stays completely on cold for 20 minutes and then will only just budge about a quarter way up, rather than reaching the halfway point between hot and cold on the gauge like it's supposed to. I know that the main three culprits for running cold and no heat are 1 - stuck open thermostat, 2 - bad blend door actuator, and 3 - clogged heater core, or radiator, or hose... This vehicle hasn't had a new thermostat in 12+ years, so I am assuming that is the best first option to do. I ordered one and should receive it next week. I will change it pretty soon.

My first question is: I switch between 2 vehicles, the Explorer is my winter vehicle. Before I put it in storage earlier this year at the start of spring, I had the oil changed at a shop. I've been driving it even though the temp isn't reaching operating temperature because I only have one vehicle ensured at a time and only recently realized the problem when the heater blew cold. I would say I've maybe put only 500 to 1000 miles on this oil change... But I wonder, since the oil hasn't been getting hot enough to flash off fuel dilution, and to activate the additives, should I change the oil after I resolve the temperature issue? Hopefully the thermostat cures the cold running issue, but it could very well be a clog in the system, however I would have to assume since it is running COLD that the radiator, hoses, and galleries are not clogged, but maybe just the heater core. Regardless, assuming the new thermostat solves the temperature issue, should I just go ahead and change the oil since it's been running too cold to flash off the fuel dilution and to activate the additives? I already have the oil and filter purchased (got it cheap on a Black Friday sale).

My second question is: Assuming that only the cold running temp issue is solved with a new thermostat, (although I am hoping it'll also fix the no heat issue), if she still blows cold air, would the remaining culprits only be either a blend door actuator or clogged heater core? Or is there something else that I am missing?

Thanks for any help.

 

[Turdle]

How is coolant level in radiator? Not asking about reservoir, take off radiator cap and look inside.

 

[LazyDaiseyFarm]

Well shoot... it was low. However, after putting about 3/4 of a gallon in it, I let it run for 25 minutes. STILL stuck totally on C, temp gauge didn't budge at all.

 

[Turdle]

If it was low, you'll still need to burp it,

Park with front raised, try to get radiator cap higher than heater core firewall hoses.

Run engine , select floor and hot on HVAC control, and refill radiator. Although you fill radiator, still need to get coolant up to heater core, and that air out.

Funny thing on these, if coolant is low, there is no coolant for the sensor to sense. The engine will burn up before the gauge moves.

 

[LazyDaiseyFarm]

Much appreciated. I will have to wait until I get some new coolant first. How many gallons do I need to get? And, is it okay to drive it as it is to go buy the coolant?

 

[Turdle]

One gallon distilled water, one of full strength prestone should do.

Use the empty bottle you just made to mix 2 gallons. You'll save $$, and just might need it.

Disconnect radiator overflow tube at the reservoir outlet and let it drain. Flush reservoir with water till all chunks are out. Some will be too large , and need a shop vac to remove. These chunks will let coolant into reservoir, but block passage back to radiator,so you want em gone.

 

[LazyDaiseyFarm]

Okay. I think though that I may as well just wait until I receive the new thermostat, and then do the burping after I put the new one in. Should I drain the entire system before the changing of a thermostat, or just let what comes out come out, leaving the rest in the system, and then adding and burping?

 

[Turdle]

If the coolant is over 2 years old, I'd park opposite, downhill, pull lower radiator hose and use garden hose into thermostat housing while thermostat is out. Parking downhill will drain most of coolant from engine.

Pull hose off lower radiator neck slowly, with a 5 gallon bucket right under joint, allow just a trickle to catch the mess.

You might need more than the 2 gallons of coolant to refill, but I think it'll be close.

 

[LazyDaiseyFarm]

Awesome. I appreciate the help. I feel much better doing that, draining it all out. It's definitely been over 6 years on this coolant so yeah, I will just drain it all when I change the thermostat. I will wait to post again until after I have changed the thermostat. If any problems persist after that I think I could just make a new thread about. So glad for communities like this.

 

[410Fortune]

Also your fan clutch maybe sticking causing the fan to run full time

Not sure a 5 gallon bucket will fit under a stock height sploder! I use a $10 mortar mixing tub from Home Depot

 

[Turdle]

Oh, yeah. Your bucket results may vary. My config allows it but a shorter container as mentioned might be needed.

 

[LazyDaiseyFarm]

@Turdle @410Fortune

Okay, so... I replaced the thermostat and coolant. I replaced a leaking vacuum line. And, I replaced the IAC valve. The cold running issue persists (and therefore, still no heat). Engine idles around 900 rpm but has about a 50 to 100 rpm waver (intermittent, and the dip and rise is slow when it does it) - although I think it always did that, I figured to mention it anyway. Also, has the common lifter tick, read that it's a problem with the oiling system, wanted to ask if that was something I could ignore or if it was a concern?

 

[Turdle]

Does your explorer have the electronic heater controls, or knobs?

 

[LazyDaiseyFarm]

Pulled this off Google Images but this is exactly the same interior:

Spoiler

 

[410Fortune]

Okay so have you messed with the heater control valve at all?
I’m thinking that your cooling system maybe working just fine and the hot water is just never entering your heater core

The other suspect would be the blend door is not moving and is stuck on cold

 

[Turdle]

Do both heater core hoses get warm with floor and hot selected?

 

[Turdle]

Ok, you might want to try an EATC self test, see if blend door moves

 

[LazyDaiseyFarm]

Okay so have you messed with the heater control valve at all?
I’m thinking that your cooling system maybe working just fine and the hot water is just never entering your heater core

The other suspect would be the blend door is not moving and is stuck on cold

No, I haven't yet messed with the heater control valve. Is the coolant temp sensor inside or inline before/after the core? If you're right and the engine is getting warm as it should, why is the temp gauge showing the needle stuck on cold? It will go up like 1/4 past cold and then drop right back down to C.

If it is the blend door, same question as above, how would that make the temp gauge stay on C?

@Turdle To be honest I'm not sure how to check the heater hoses' temps as I am not sure which are the correct lines... Is there a picture or video showing where/which lines to check? And, I don't know what EATC means... sorry. I have only ever had experience with the more usual kinds of mechanic preventative maintenance such as spark plugs, oil changes, brakes, tires, alternators, water pumps and thermostats. I have no experience with heater cores or blend doors.

 

[Turdle]

2 heater hoses going to firewall, passenger side. Both should be warm.

Search for EATC self check. You'll find it

EATC is the type of electronic controls you have for your HVAC. Some models have manual knobs.

You should acquire a scan tool of some type. Amazon has inexpensive elm scan units designed for forscan free software. It would be nice to know real coolant temperature instead of relying on the dummy Guage.

 

[LazyDaiseyFarm]

Is there a scanner that will read real temp data for less than 50 bucks that aren't total garbage?

I will do the EATC self test thing tomorrow. Found a few videos on youtube so that will help.