Hi to the group and sorry to make my first post a long, complex one. 2006 explorer 4.0 57,000 miles automatic XLT. Never any problems-knock wood.

This summer wife's SUV started acting up. She described as very loud fan noise or maybe noisy A/C compressor. Have not put a dime in this vehicle other than very good regular maintenance and tires. She lead me on the wife to husband typical wild goose chase! I work on all my own vehicles so she had me believeing that if she shut off A/C noise went away. Best guess compressor getting ready to depart this world.

Then she starts saying that it would make noise even with A/C off and feels like tranny is "revving". I decide fan clutch and some cooling system parts. Tranny revving she then describes when I push as hanging in third and not wanting to go to OD. Temperature gauge going way up and then coming back down by itself FAST. I do radiator, thermostat, coolant temp. sensor, water pump, electric fan clutch as I noticed overflo tank using some fluid fairly regularly. When I go down below, I see coolant along bottom of radiator. I basically completely do cooling system. Coolant usage goies away, but temp gauge going up and then back down continue. Fearing tranny issues too, I took it in and they claim planatary gears are almost welded together, it had to be dragging down the engine, and new tranny is needed. I have rebuilt tranny put in. Taking car home, it is shifting beutifully, but temp gauge still goes way up and this time it sprays coolant everywhere. Went got car next day, added coolant as radiator was bone dry and fluid all over top of engine. drive can home no event. No leaks in garage when warm. strange. Take it back to tranny shop and they install another rebuilt tranny just to be "sure". Test drive car beautiful. Driving home on freeway I observe gauge leave midpoint and head for red. Then, it dropped quickly and erractically to midpoint and never did it again rest of way home. I suspect cooling system needed to be burped. Monday, wife drives to work and it does same thing ONCE. Gauge went to red after about 15 minutes and then right back to mid-point fast. Did once coming home. Typically a boiling pot of water on stove does not come back down in 3 seconds! Today it drives fine. No incidents.

After each event, radiator is full and over-flow is 1/2 way as usual. I now can only guess tranny had issue and over-heated car for real. New tranny has cured one issue, but head gasket leak might explain that combustion gases are flowing into coolant as air and causing rapid gauge movement to full hpt and back to middle in 2 seconds. Suspect bacd head gasket only occasionally lets combustion air into coolant, but not necessarily coolant into cylinder.

My question is has anyone experienced and how can I test compression that may not be leaking back into coolant all the time. I see no coolant in oil. $3500 later I have a gauge that raises to red and then falls like rock back to middle. Does not happen every time. When gauge does go up, fan clutch definitely engages full! HELP!

 

I would suspect a faulty thermostat......

Use an IR gun and run some readings on both sides of Thermo housing, Make sure there is no air in system.....

Pressure test the cooling system and do a full compression test.

Warm engine, All sparks out. WOT, fuel and spark disabled, Dry/wet, fully charged battery.. .. Philip

 

Interesting. I changed the thermostat when I did all the rest so it is new, but the bubble is the only explanation. Either from bad bleed or from a blown head gasket that is causing super hot air (combustion air) to be forced into cooling system. It went hot on wife today and stayed hot for about 60 seconds ....as soon as she pulled over the temp dropped right back down to mid-point. RPM seems to play in somehow. Change in rpm up or down can put a stop to high temp. If it were from a bad bleed, it should have worked its way out on its own would it not? You think I got a bad thermostat cause bthey take about 1o minutes to change. Is there any special procedure to bleed? Is it possible that combustiob air can go into the coolant, but coolant not go into the oil or out the tiailpipe? Not using any coolant anymore It acts like an air bubble forms right under the temp. sending unit. I don't have access to an IR gun, but I'm beginning to think this superheat condition is real and the cooling system has pockets of very hot coolant. I have a tranny and an entire cooling system into this problem and the last tranny had melted planatery gears. This vehicle went from a no problem, lo mileage great SUV to a real 'fuser. Thanks for the help and keep the ideas coming. Does the explorer have any special process for bleeding? The manual says nothing except something about a
RADKITPLUS???

Bill

 

2 ways to bleed air,

• park nose up on an incline run until air is out
• install a flushing T in the highest heater hose, loosen it to expel air...

another possibility is a bad water pump, blades corroded off..... Philip

 

Again, I replaced entire cooling system and pressure tested ok COLD. My older BMW bleeds with two bleeder screws and the "on edge" thermostat is even recommended to get a small hole drilled in in at 12 O'Clock position. With exploder having a flat thermo, never expected air to stay anywhere. I will try idling with heat/blower on full and cap off until coolant starts to swirl out meaning thermo is open. All is new-Read, thermo, WP, fan clutch (electric $$ ouch) belt, Thermostat housing, coolant temp switch, snap ring, by-pass hose...normal stuff. Not using fluid from over-flow.

 

It is a pain when people post this long, complex issue and then never post the conclusion, so I will! I bought a second new thermostat. I was fully prepared to drill a small hole in it if I needed to, but the third time was a charm. I bought a third thermostat and a radiator cap, and as soon as I installed the second new thermostat, the exploder stopped the over-heating immediately. I can only guess the second one was not tested. It cured it immediately.

Now on to the dreaded "tire sensor fault" that comes and goes! Thanks for the help guys.

 

Thanks for reporting back, sometimes it is the simple things that we have already checked.... Philip

 

You may have to break down the tire and check/clean the pressure sensor.. Philip

 

Testing of thermostats before replacing...Simple. Stick thermostat into pan of cold water. Use a thermometer.

Watch as it gets hot. When thermostat opens..what is the reading on the thermometer?

 

Do the Ford tire sensors have replaceable batteries? Do you know what they can be bought for at the right places? Thx.

As far as the thermostat...yes, we all know how to check one. This one was very close to 190 degrees, but would allow the temp to run through middle of gauge and keep going to almost full scale and then would quickly drop to mid-scale and never go there again on that trip. The newest one opens more fully a little sooner. Since I bought both at Autozone, I could return the second one.

 

How Do Tire Pressure Sensors Work? | eHow.com

 

Since yours it intermitent, maybe just needs resetting..

Ford

• 1 Check the tires before you reset the tire pressure sensor to ensure you inflated the tires with the suggested tire pressure according to the owner's manual.
  
  
• 2 Turn the ignition of your Ford to the "Off" position.
  
  
• 3 Press and release the brake pedal.
  
  
• 4 Switch the ignition from the "Off" position to "Run" three times. End in the "Run" position.
  
  
• 5 Press and release the brake pedal once again.
  
  
• 6 Turn the ignition to the "Off" position.
  
  
• 7 Switch the ignition from the "Off" position to "Run" position three times as you did before, ending in the "Run" position. The TPMS light will flash and the horn will beep if you performed this procedure correctly. If your vehicle has a message center, you will see "Train LF Tire" as the TPMS learns the new pressure settings. Then the message "Tire Training Complete" will appear on the display.
  
  
• 8 Turn the ignition to the "Off" position to verify the training's success if your vehicle does not have a message center. Repeat the entire procedure if the horn beeps twice after you turn the switch to the "Off" position.
  
  

 

I have the 3 part large, thick, blue mechanical service book on my 2006 and it does not give as good detail as you have. Thanks a ton. I will try in the morning. the "run" position means positio0n 2 I am sure "0" is off "1" is next Then "2" is the position that if you go any further, you will hit the starter and start the vehicle. What a convoluted way to perform this task! How did this get discovered if the manual does not even refer to it??!!

Thanks as the tires are all fully inflated yet the under-inflated picture of a tire starts to flash about 20 times and then the tire inflation failure or whatever it says exactly comes on and the flashing tire quits. Don't know if this sounds like a classic bad calculation from my recent tire rack purchase, but that is when the whole deal started. Tire rack people should encounter tire sensor system 10 times a week at least.

Thanks again-friendly forum and helpful folks here. Must go with the vehicle as I also have an old E39 BMW and that forum is full of smart asses and now that the older BMWs have come down so far in price, every other question is about how to put a Bimmer on the ground or will 22s fit!

 

Make sure you include the spare when you perform the air-up/reset.....

It also a good time to ensure the under body cable is in good shape and lubricated... Philip

 

I thought I read somewhere that the spare had no sensor! Hell, that could very well be my problem. Thanks!