Heater Problem

[Mike92STX]

On the wifes 94 Explorer 4.0 it blows warm air but it doesn' get hot. I'm thinking it is a sticky thermostat but I'm looking for other ideas from some people that knoe more than I do. I had it running with the air blowing as warm as it gets and when I move the temp adjustment to cold it gets cold and the back to warm when the lever is moved back. I think that means the blend door is working? I want to change the thermostat tomorrow but if somone thinks it is the water pump I would rather do it at the same time.
It has 205000 miles and alot of rust so we want to replace it soon. Will be fore sale if anyone wants to part it out when we get somthing else. She got hit by a uninsured driver a couple of months ago so it has a hood and grill and the passenger side fender is bent.

 

[CajunPwnStar]

When was the last coolant flush? I'd do that, check and replace the thermostat if needed, and also flush the heater core. If the blend door is working, I'm almost positive it's a clogged heater core.

 

[RonD]

Watch your temp gauge, if engine is not showing above 1/4 after 10 minutes then yes thermostat may be stuck open, or feel upper rad hose as engine warms up, it should NOT get warm, it should only get warm after thermostat opens, so about 8-10minutes after cold start.

If these seem OK then Heater core is probably getting clogged up.
Heater core is the by-pass for the cooling system on the '94, so always has coolant flowing thru it.
You can try Back Flushing it, Google: Back Flush Heater Core
Or you can just replace the core.
On a '94 there are 2 hose clamps and 4 screws you need to remove to swap out the core, so very easy to do, first time it will take you about 45min, if you ever do it again maybe 20min.
New core is $15-$25

 

[Mike92STX]

Thanks for quick reply, I changed the heater core about 2 years ago. It might be plugged. I will try the flush and change the thermostat.
Thanks Again

 

[Mark_88]

It could also be just low coolant...so if you haven't already done so...top up the fluid before anything else...

 

[Mike92STX]

Well not going to work on her Explorer today. she is going out to lunch with some girl friends. I topped off the antifreese and started it earlier it warms up in about 10 minutes and blows warm air but still not warm enough? There is a slight squeak but it sounds like it is a bearing in the alternator. Hopefully it will not get worse before next weekend because I won't have time to work on it durring the week.

 

[Mark_88]

OK...I seem to remember someone saying the 4.0 is the hardest to burp because of the angle of the hoses or height...I forget which one. Air in the system will/can result in low heat in the cab because the coolant doesn't flow properly...

I'd have to say my memory serves up a post about someone saying to park on a slight incline (facing upwards), pop the rad cap off, and run the engine till it warms up...about 7 minutes...then top up the fluids again...and something about squeezing the upper rad hose or pushing it down till the air comes out...

Now I'm not 100% sure about the method, or whether it applied to the different versions of the engine...but I would hope someone chimes in if this is a possible solution...

 

[Metalcrack]

It could also be just low coolant...so if you haven't already done so...top up the fluid before anything else...

Same problem in my wife's Corolla. Whichever method is the best in this model for burping....incline etc. Try that as cheapest and easiest option.

 

[Mike92STX]

I tried the burping this morning and didn't get any air out of the system. The hoses going into and out of the heater core are both hot so I don't think it is plugged. Going to get a thermastat today and replace it, must be sticking open part way? When I was trying to burp it the cooliant in the radiator looked like it was flowing good.