At wit's end!!! :(

[porschpow]

Well, I seriously don't know what going on with my coolant system.

It seems I have no pressure i nthe system.

I changed the coolant (winterized)

Changed to thermostat (and the small hose that goes with it)

Yet, the heater is not blowing as hot as it should

I check if the vacuum canister is holding a vacuum, it does. The vacuum hose that goes with it is sucking.

Yet the heater has no heat!!!!! Well no, the heat is there but not the hotness (max) that it should be

The Thermal block loacout switch is byppased. The vacuum hoses that went to it are SEPARATELY CAPPED OFF

I left the swtich in there cause the wires still going to it.

I finally took that wire harness off and crossed the wires. BUT I LEFT THE SWITCH IN. What I had noticed is that the coolant seemed to be leaking from the switch. I will have to go and buy a plastic hose connector.

BUT WHAT GIVES?!?!?!?!??!?!!?? The AC works, if I put in on cold, its great, just that the heater sucks!!!

[Lincolnmania]

clogged heater core maybe

[85crownHPP]

Reach/look behind your glovebox door for a fat clearish vacuum hose going to a round metal silvery doodad attached to the duct-work under there. Pull the hose off the round thing, and you might just get rip roaring heat. That is the blend door control, if you have ATC climate control, the temperature sniffer goes bad and wont let the system make heat.

[porschpow]

86vicky just changed my heater core last this past summer

[porschpow]

so if I pull clearish hose, and I din't get ripping heat, then the atc sniffer is bad???

What could remedy a clogged heating core?!?!?

[sly]

if you pull the hose off the big can and DO get heat, the "ambient air temp sensor" under the dash pad is bad.

[porschpow]

ok, so no matter how high the heat is, the ambient sensor is bad? I am a little confused. Should I pull the hose while the thermostat is on heat?? What is the right way to check?

[sly]

with the car warmed up and heater running. If it's blowing cool air and you remove that hose from the big can behind the glove box and you get good heat, the sensor needs replacing. If you don't get heat, something has jammed the blend door to cold, the blend door is broken, the blend door actuator (the big can) is stuck/bad, the heater core is clogged, or something else I haven't thought of.

[86VickyLX]

With the car warmed up, put your hands on both heater hoses, if one's hot and one's not, the core is clogged, if they're both cold you have an air bubble in the system. If you have no pressure, top off the reservoir and rev the engine, you'll see the upper hose collapse, this means there's air in the system, the system will suck the coolant in and push out the air. The system will then build pressure, and you should have heat.

[VicCrownVic]

+1 on the possibility of a clogged heater core.

When I got my 91 MGM last year the heat was not warm.
After flushing the heater core the heat was nice and hot for a little while. Once it stopped being warm again I flushed the heater core and the entire cooling system but still the heat was not warm.
I tore into the dash this weekend and could feel that the inlet+outlet hoses on the heater core were BOTH HOT, but no heat in the cabin still. I figured it was the blend door actuator until I realized that was in the correct position.
Since flushing the heater core while it was in the car didn't seem to work last time, I pulled it out and ran the garden hose and shook it up to get the crud loose. I probably did this about a dozen times since each time I shook it more crap came out.
Now my heat works great.

Of course this is a rather time consuming task and I seem to remember it being more tedious on the 89- cars.

For flushing the core I had a good end from a busted garden hose, about a foot long, that I could screw right to the hose. The piece of garden hose was small enough to fit snugly into the heater hose on the core.

[porschpow]

Oh I am dreading this now, I really am. I am really hoping not. I will try these tests .

JUst an additional thing. I unhooked the wires and vacuum hoses to the TBL that runs in the heater hose line, but the actual switch is still there. Would that switch be hindering flow???

[VicCrownVic]

As for the no pressure in the cooling system like you describe, I would follow what 86VickyLX said. I don't have any good ideas on that other than to say when you remove the radiator cap when the coolant is hot it should behave just as you are expecting it to after your 70mile drive from work that you mentioned in another thread.

The engine doesn't seem to have any issues with running too hot does it?
And this might be a long-shot but how old is the water pump? Is it pumping? They are NOT known to break in a way that would cause them to not pump as far as I know but I always try to expect the unexpected.

Also that Thermal Blower Lockout switch will not hinder coolant flow the heater core on its own, it's basically just an inline temp sensor.

[gadget73]

The clear hose should *not* suck. No vacuum = full hot. Vacuum = cold. Pull the clear line off of the can under the dash and see if it gets hot. If it does, its the air temp sensor. They're almost all bad at this point, so its no real surprise. I think mine has been changed at least twice now. The one that I pulled out was bad, and it had a 1990s manufacture date on it.

[jaywish]

If you put the selector switch in any position but "floor" the switch you are asking about is bypassed. So it is an easy test.

The 2 vacuum hoses from the temp switch, are they plugged?

[luddite]

I hope this is not hijacking the thread...
I met my wife (we have been married over 30 years) when some mutial friends suggested to her that I could fix her no heat situation in her Pinto.
I told her that this might not work and that it might make a big mess, but it wouldn't cost anything.
Neither of us had any money.
What i did on the hope that it was a clogged heater core was disconnect the two heater core hoses from the firewall.
Replace one of the heater core hoses with a section of garden hose connected to the garden faucet near the driveway of the house I was living in at the time and turned on the faucet.
A big clump of crap shot out of the other end of the heater core outlet when the faucet was turned on.
I reconnected the heater core hoses. The heater core stayed intact (OMG).
She had heat and we were married eighteen months later.