1997 4.6 overheating issue

[debago7778]

Just got a 1997 XLT 4.6. has 136,000 miles. Truck runs great. But has a few issues that just popped up.
1) No heat at all, cold AC. Just no heat at all on any setting, front or rear
2) The truck just started overheating. It will drive fine. The suddenly peg the temp gauge and the oil light will come on and the truck goes into a "limp mode" I'm guessing. I immediately pull over and turn off truck. there will be some water loss from the filler cap area. Filled water up. Cranked truck and drove fine.

It did this once Sunday and twice last night. The upper radiator hose was hot to the touch, and when i went to take out and check the thermostat, there wasnt one.

I tried searching on here some, but havent found an exact issue. Should i try the t-stat first? Or is a waterpump or blockage more likely?

Anyone have an online manual or .pdf I can get a hold of?

thanks!

devon

 

[Racenut]

Just got a 1997 XLT 4.6. has 136,000 miles. Truck runs great. But has a few issues that just popped up.
1) No heat at all, cold AC. Just no heat at all on any setting, front or rear
2) The truck just started overheating. It will drive fine. The suddenly peg the temp gauge and the oil light will come on and the truck goes into a "limp mode" I'm guessing. I immediately pull over and turn off truck. there will be some water loss from the filler cap area. Filled water up. Cranked truck and drove fine.

It did this once Sunday and twice last night. The upper radiator hose was hot to the touch, and when i went to take out and check the thermostat, there wasnt one.

I tried searching on here some, but havent found an exact issue. Should i try the t-stat first? Or is a waterpump or blockage more likely?

Anyone have an online manual or .pdf I can get a hold of?

thanks!

devon

Does your REAR heat work?

If your REAR heat is working then I would say it sounds like a plugged heater core for the front, but it could also be the water pump.

If the REAR heat DOES NOT work, then I would say change the water pump first.

Either way you go I would definatley run a good cooling system cleaner thru it ( such as the one that Prestone makes ). Just make sure after using the cleaner to "FLUSH" clear water thru the system 2 -3 times before adding any antifreeze, because if you do not get all the cleaner out of the system it will "eat" the hoses from the inside out.

 

[debago7778]

Thanks! I will check as soon as I get off work!

 

[debago7778]

No rear heat either last night after work. I topped off the coolant before leaving work and again before headeding to work and it seems ok. Just no heat.

 

[Racenut]

Try running the cleaner thru the system and if it does not clear it up then change out the water pump. While changing out the pump, I would also put a thermostat in it.

 

[debago7778]

thanks. i will grab a cleaner tonight!

 

[debago7778]

I ran a flush through it (just a cheapy Barr's) and istalled a new thermostat. I have not had another overheating issue, but still no heat in cabin, front or rear. I did notice the new gasket for tstat is leaking this morning, so need to fix that tonight. Also I know notice a rushing water sound when i cut the car off. Sounds like it is behind the glove box area. There is no leaking anywere inside the cabin.

 

[Racenut]

A rushing water sound from behind the dash usually indicates that you have air in your cooling system.

 

[debago7778]

air in system? ok, I will drain and refill it tonight after replaceing thermostat gasket and see if alleviates the problem. Whats the best way to get all of the air out of these systems? Run it with cap off overflow tank or what?

 

[Racenut]

air in system? ok, I will drain and refill it tonight after replaceing thermostat gasket and see if alleviates the problem. Whats the best way to get all of the air out of these systems? Run it with cap off overflow tank or what?

Try to park on an incline with the front of the Expy higher than the rear ( or put it on ramps ) that way any air will " burp " itself out because the filler is higher than the rest of the system ( once you get it full, "bounce" the front end a little bit by hand and that will work the air out ).