Heater core blocked? I'm stumped

[wavinwayne]

HELP, BITOGers!!!....I'm losing my religion trying to diagnose the cause of the almost non-existant heat in my wife's '97 Expedition XLT 4.6L.

My wife has a cousin who was a mechanic at a Ford dealer here in North AL up until a couple of years ago, when he decided to change professions & become an OTR truck driver. This past weekend, he looked at the Expy with me. We ruled out any blend door problems, & the blend door actuator is working fine, too.

Last night, on the advice of the former mechanic, I replaced the thermostat in a last-ditch effort to avoid paying someone to fix this problem for me. Didn't help.

One more thing to note - This past weekend I tried to flush the front heater core, but the way the hoses are routed in the Expy, I think I only flushed a lot of coolant out of the engine block. To make a long story short, I didn't unhook the heater hoses at the firewall; I disconnected them at a "Tee" connection.

Last night, one interesting thing that I noticed after I replaced the thremostat was that one of the heater hoses going to the firewall is not as hot as the other one. One is scalding hot & the other one is just very warm. Does this indicate a partial heater core blockage? Would a partial blockage cause the heater to blow warm but not HOT air?

FWIW, the rear heat has a seperate heater core & the rear heat does get a lot hotter than the front. The front vents only blow lukewarm air at this point. The problem didn't happen overnight; the air from the heater has gradually been getting cooler & cooler, for about a year now.

So, what say the BITOGers?........partial blockage in the front heater core? If so, what would be my best bet? backflush the core with water, or just run a radiator flush kit? The heater hoses at the firewall are a *#@%! to remove on the Expedition.

Sorry for my rambling....Any help would be appreciated.

 

[FowVay]

I am certain that this doesn't relate to your problem but Ford has had horrible problems with repeated heater core failures. The resultant problems have been traced to electrical current in the coolant which has caused corrosion and repeated leaks in the heater cores.

If your vehicle has suffered from such a problem then you may very well have a clogged core.

If you have been running around with the incorrect coolant mixture or a inadequate body ground then this might be a place to start looking. Check the voltage in your coolant with the engine at 2000 rpm. If you record greater than .4 DC volts then you might be a victim.

You're likely looking at a removal and physical cleaning job at the least.

Good luck with this diagnosis.

 

[pajim17057]

Definatly sound like a blocked heater core to me.

 

[theguru]

Ditto.

 

[Mach5]

Some vehicles use a valve to shut off hot coolant to the core when the A/C is on. The one on my car sticks sometimes if the heater hasn't been used for awhile.

 

[Chris142]

Since I work at a radiator shop I see alot of weird stuff.

Got 2 cars in yesterday with a no heat complaint. Neither had enouygh water/coolant in the system to pump up to the core.

Oddly neither ran hot

Another common possibility is that the water pump impellers are rusted away. It will pump well enough to cool the engine but not well enough to lift the water up to the heater.

Replacing the pump on this engine is quite simple. loosen the fan clutch and remove the fan and clutch, remove the belt, remove the pully, remove the 5 or so bolts that hold the pump to the block.

Pull the pump off the block. Thats all there is to it! Since the truck is 8 yrs old you should probly replace the pump soon anyway.

I'm betting that the pump impellers are gone.

 

[jamesn]

i have also had the impellers go out on a toyota truck. heat, what heat? a new pump put it back ok.

 

[andyd]

can you reverse the flow through the heater core? I did this with my Valiant when the core plugged up. I just switched the hoses at the core. It did the trick

 

[wavinwayne]

andyd,

That's a neat idea, but I'm too much of a fraidy-cat to try it. I was going to flush the core today, but it's raining out. I'll try today or tomorrow if it stops raining.

 

[frankiee]

I would disconect the hose from the heater core (cold one) at a accessable place and test for flow.
I would suspect and air bubble at the highest point in the system. (Likely one of the heater hoses to the heater core)
I would cut the hose at the high point of the heater hose and install a tee that is used for flushing. It can them be used for flushing, testing, and purging air from system.

Had it happen this past summer with a 93 Suburban.

 

[chas3]

backflush the heater core. disconnect both hoses (preferably at the block not the heater core). then force fit the nozzle of your garden hose on one of the hoses and direct the other hose someplace safe (like the ground). flush with water. connect to other hose and repeat.

 

[wavinwayne]

I properly back-flushed the heater core today. The heater works again. I'm very happy.

 

[cousincletus]

Glad it worked out for you. FWIW I drain and refill my radiator with 50/50 once a year. Knock on wood haven't had any probs yet.

 

[Dark Jedi]

yeah dodge dakotas has this prob too. the core getting blocked. glad to see dodge isnt the only vehicle that does this.

 

[kc8adu]

i have a hose nozzle with a rubber cone on the end for just this job.
i caught the flush water in a bucket last time i had to do this and it seems to be mostly stopleak.
like bars leak rabbit pellets and sawdust looking stuff.
you should have a ground wire to the rad and core to stop electrolysys.idea is to keep all parts at same potential.