Before I drive her off a cliff here is what the symptoms were when first purchased, and what repairs have been done involving the cooling system:

Truck never quite reached normal operating temps, heater barely blew lukewarm air. Switching to all the way cold and it would pass through cold air as cold as outside (with no AC running) So the blend door is working.

1. Replaced thermostat, truck reaches normal operating temps.
- now the truck will vary between blowing nice hot air to warm air after running for a while and under load. IE: once exiting the highway, the heat starts to cool off. Operating temps are still perfect. If she's idling, heater blows barely warm if she's already been on a drive and you apply throttle.

2. Burping the system. Revving and holding the truck at 2k produced some small bubbles, squeezing the upper rad hose on passenger side several several times seemed to work out some more air.

3. Upper heater hose going to firewall is hot. The return is warm, not as hot as the other one.

4. no coolant inside the truck under the dash or passenger carpet, no leaks that can be seen. Not having coolant go missing either.

5. Oil looks like oil, coolant looks green with the exception when you release the throttle the return fluid in the degass bottle look a bit murky/dirty.

I'm thinking the core is plugged/clogged or something...


Is it normal to have a hissing (like pressure being relieved) from somewhere by the passenger firewall when you shut the truck off? It only lasts a few seconds - like a purging of some sort. I'll see if I can get a clip unless that's normal. (you probably wouldn't notice it with the hood down.

 

Plugged heater core. Disconnect both hoses and use a garden hose to reverse flush the core. Be careful not to overpressurize it. If that helps, then flush the entire cooling system and put some fresh coolant in.

 

Ok so, I already have a t-fitting in the upper hose from the previous owner... where do I disconnect the other one? Looks kinda cramped there.

Any tips on this or a how to other than don't over pressurize it?

 

If you already have a T-fitting, use that to flush the whole system. Use a hose adapter to connect the hose to it, open the radiator drain and remove the degas bottle cap.

 

I'm going to need to do a back flush on this system. The inlet hose is easy to remove from the motor and attach another piece of hose to let it drain.

The outlet hose however.. holy. Whats the easiest way to accomplish that one? Looks like it wraps down behind the motor somewhere...

 

sure does behind the intake if it were me id put another t in that hose might be a lil redneck but one you dont have to pull the intake and two you can hook up a hose to it and drain it out instead of blowing it all over your motor and causing more problems

 

I'll probably end up going that route. Knowin me I'll end up breakin off the core ports or something if I try to get the hose off...

 

Blue Point, the cats *** ~

http://buy1.snapon.com/catalog/item....re&dir=catalog

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Anyway, just a little info for yuh. You may end up replacing that core.

How they Flow, when in question ~



Ford Motor's Bleed Procedure TSB ~



If you still can't seem to skin that cat, well, if you know how a dishwasher's discharge line is set up (the old LoopDLoop), you get it.

 

Nope! Lets see what year, (?) -a 2000 5.4L. Well there's more than just one thing back in that area that could be discharging after shutdown. The only part that normally does that on occasion is up front and that's the EVR. It's suppose to. If you place your hand on top of that part while your hear the noise and you feel it vibrating, -you found your noise maker.

Back by the pass side firewall, - could be the PCV system as well as the heater core lines. Pressure can build with partial blockage problems and it usually finds it way out. I bet it;d making the noise while it's running, you just don't hear it. Could also be your heater vacuum system behind , -(firewall by battery box area).

Some cooling systems also have a bypass passing thru from the heater core hard-line back by the firewall, then pass side of the TB. Called the CCS Cold Climate System.

Track it down, but if I had to guess, the cores spent.

 

Thanks for all the help so far fellas and here's an update as of a few minutes ago:

1. Rigged up the heater core hoses for a backflush.
2. ran one 6 foot heater hose down into a brand new squeaky clean bucket, the other outlet heater hose has the garden hose attachment on it to shove water through it backwards.
3. Initial backflush, somewhat dirty coolant but not too bad. Small debris can be seen.
4. next 3 buckets are crystal clear water with some debris flushed out.
5. after another bucket or so, swapped the hoses to flush it in normal coolant flow direction - all clear. I might have got a grand total of a palm full of sediment or whatever it was.

One thing I might add, the flow through the core appears to be great. Water come through almost as if there's no core inbetween the tap and the end of the hose. So I think my core is flowing good.

She still gets nice hot air then back to cold, to back to warm etc etc.

Waterpump?

jbrew: I wouldn't have thought a spent core would at least dish out some blistering hot air for a few moments...

 

Just some more details, as this problem is really frustrating me...

Each time the heat comes and goes, my temp gauge stays perfect. So, wouldn't that mean the waterpump is pumping correctly?

Also, could it be that the fins/blades in the heater core are clogged but fluid still passes through the core with no problem? My inlet hose is hot during operation, and the outlet is not as hot. It's not cold either. It's above warm.

What if I poured some flush with the core hoses disconnected and let it sit over night? (so the flush is sitting in the core...)

Grasping at straws here as the cold mornings have already started...

 

So today on the way home I turned on the rear heater controls since I never really checked what those vents do while I'm having this problem.

Even when my dash vents blow really hot air for a few moments, the rear vents are always blowing cold.

Not sure if I mentioned this earlier, but it seems like if I turn the heater completely off in the front and then turn it on again moments later it'll blow some warm air out of the dash vents for a very short period. I have the auto HVAC controls too.

I'm throwing this out there before I launch this truck off a cliff.

 

So I'm not feeling too good about this truck now.

After the flushing etc and driving it - I've come to find my degass bottle now smells like exhaust. If that's the head gasket, which I believe it is, pretty sure it's the passenger side head.

Might go roll her off a cliff now. *&(#*&^@*&%$&!!

 

You can confirm by doing a hydrocarbon test on the coolant.

 

Is there any other way it could smell like exhaust and it not be the headgasket? Other than I have a leaky manifold on that side.

I was also thinking this may have something to do with the hissing I hear after I shut her down that's somewhere near the passenger firewall.