Hey all what's up??

I have a concern and I would like some opinions on it. I jumped in my 2000 Ex 4.5 the other day and I was driving around with the heat on real low so that it would get warm before I increase the blower. I get to my first destination and I realize that the blower is shooting out cold air....... So I check the controls to see if I made some bonehead move and left the AC on. Nope all looks good so I turn it off and let the Ex idle for a few. I turn it back on and nothing. So I get out to check the fuses..only to learn the Ex doesn't list the fuses like most. I look around and decided I would wait until I get home to test the fuses. So I jump back in and I figured I would rev the engine a little......I don't know why........
I get it up to around 4x RPM's and then all of the sudden the heat starts blasting out.??????!!!

Anyone have ideas as to what happened ?? Thanks for the responses.

Lloyd

 

Thermostat stuck closed until you revved it up???

 

A stuck closed thermostat would cause it to quickly overheat. If it stuck in any position it would have been stuck open and constantly cycling the entire cooling system through and taking a long time to get up to temperature. If this was the case a good rev probably wouldnt h ave made it snap shut and warm fast enough to get instant heat.

Have you ever added any stop leak additives to your cooling system by any chance? Sounds like something may have been a lil plugged up and coolant finally pushed through it with the added RPM possibly.

Do you have the digital climate control, or the older manual *****? Could have been a sticking valve somewhere as well. Have you ever had your coolant system flushed?

 

I have the older manual *****. Now that you mention it though I would like to upgrade to digital. Is that possible???? Also Since I have owned it I haven't put any stop leak it but the previous owner may have. The engine temp was fine did not overheat and was not low!! If it was the stop leak it should be good....as far as the heat goes right?? Thanks for the responses!

Lloyd

 

IF someone added some stop leak for any reason in the past it has a tendancy to clog stuff up especially small passages in heads typically causing minor hot spotting. With all I have learned over the years I am very anti-stop leak additive in any form unless its a junk car your about to send to teh junkyard or your too broke to fix the real problem and dont mind possible other future problems.

I'd suggest a coolant flush if youve never had one as it probably needs one anyway. You can buy test strips to dip in teh coolant and itll tell you if its time to swap if your not sure now I believe. Typically it should be changed every 2-3 years.

I have a feeling the valve that controls coolant flow/or the door in the dash that physically moves to change the direction of air flow are probably sticking. Next time it happens try cycling the ***** form cold to hot a couple times, and change where its blowing, like defrost/vents/floor etc and see if you get heat suddenly. Thats one way to try and diagnose it, or get you headed in the right direction if your not too mechanically inclined.

If the excursions dont have a valve to control coolant flow to the heater core when you reved it and let go of the gas the sudden loss/spike of vacuum may have jarred the mixing door into position as its vacuum controlled and in the dash. Do you ever hear a loud single slamming sound from the dash? Like a gremlin in your dash just got mad and went in his room and slammed the door? lol

As far as swapping to digital, I would bet $ you could not do it without MAJOR changes. But I am not sure, if it was offered in your year truck it may be a straight forward swap, if it wasnt an option yet the wiring is most likely not there and as I said MAJOR work to make it work.

 

Never heard any slamming...but I will keep an ear out. I will also go ahead and flush the coolant. I would rather be safe than sorry. I am fairly mechanically inclined I am just a rookie Ford owner. I have torn down many engines before now and have never hesitated to do something on my own that could save me a few hundred...I like money and don't want to give it away if I do not have to...lol!! Thanks for your input.

Lloyd