Ok here it is , ive been reading and can not find an answer.
I am in canada its minus 35 all this week and my heat sucks . I took to garage today after running for two hours they hoses were cool to cold they told me best place to start is with thermostat i agreed. so they did that put new thermostat housing on as original was a little rusty again i agreed . the tech noticed the the sensor for temp to ecm was a cracked suggested a new one again for 20 bucks i agreed (that should help with gas milage) anyway they call me in heat is working amazing nice and hot temp gauge for once is reading dead on hoses are hot everything perfect im happy. NOW here we go i leave garage head on park truck go back to it and temp gets up and my heat is gone its cool again . I go back to garage he removes rad cap with engine hot seems to be no pressure so he puts on new rad cap.. bleeds system tops it up and there is heat again awsome tech takes truck for a ride comes back now he lost heat . lifts front end on hoist bleeds system some more tops up great heat again sends me on my ..

I am happy later on go to pick up my son from school as im sitting there waiting my heat feels again cool not hot anymore ive lost my heat again .

NOW i do not seem to be losing a drop of antifreeze in the past 4 months ive been driving it they have bled the hell of the system and i watched my self no more bubbles , just as i would assume my self system was ready..

BUT AGAIN I HAVE NO HEAT , Little better as i rev it up but not hot by any means .... i put in a 195 stat as i should for my area so i should have great heat ....
so any HELP PLEASE . I DO NOT WANT TO GO BACK AND KEEP PAYING BY THE HOUR TO HAVE THEM MESS AROUND GUESSING WHAT IT MIGHT BE

one tech at garage suggested head gasket and with this suggestion i would agree but i have not lost a drop of anti freeze or oil or anything in 15000 kms never had to top anything up so im going to say head gaskets are fine because if something is coming in something has to go out in exchange

SO PLEASE HELP ME IM SO COLD .................

 

Vacuum leak?... no vacuum, the mixer/blender door wont work.
It had been so long since I had used heat, I think the foam seal on the door had it stuck shut... took many cycles of the switch to get it to break free.

 

well at -35, working on it won't be any fun.
check a couple of basic things-

is the coolant overflow tank full. (should be) if not, top it off to slap full. if coolant is low, it will starve the heater core of hot coolant. the engine will pull in coolant to top itself off.

is the temp gauge sitting on normal, about 195* (should be)

when temp gauge is 195*, feel the 2 heater hoses that go to the passenger side firewall. are they hot? (should be)

with engine cool ONLY, open radiator cap and check fluid level. is it full?

 

Done all that is perfect ..... everything is topped up bled as best i can see it being done and new stat all done today.....

 

Not totally sure about a vacume leak but i do know if i switch to cold it goes straight to real outside cold air .. so i do know its moving from open to close ...

 

I could use help w/ this also.
Went to use truck for the first time all month. Truck warmed up to temp. but heat was cold. drove around the block, came home, sat in driveway. Heat turn hot.
Went out several hours later and drove truck for 2hrs heat worked fine. Stopped at gas station. truck idled 2min while i ran in came back out and heat is cold.

When I switch from heat to cold on control I can deff feel the difference in coldness.

Any help suggestions would be great. thanks

 

What year is your truck?

For the 95, you prolly have an air bubble in the heater core, or, the core itself is clogged.

 

You could try disconnecting the hoses going to the heater core and flushing it out with a garden hose. I got a whole lot of crap out of mine doing this and the heat worked much better afterwards. Don't want to use too high of pressure though or you may finish off an already weakened heater core. You'll have to bleed it again after you hook the lines back up which also can be a pita but there are several tips on how to do it if you search. I tried jacking the front pass side up but ended up having to park on a steep hill to get all the air out.

 

I appreciate everyones help very much but did anyone read what i even wrote ?
i mean suggesting i lift front end and burp it , has be done i took the truck to the garage i watched this happen . i know i may need to do it more because of air bubbles and i will try

and suggesting heater core is clogged ? this is not an issue of not getting any heat , its an issue of not being able to keep it ... if the heater core was clogged i would just not have heat period

i get great heat . then its gone almost like i bleed it and somehome air is being reintroduced to the system ??????????????

does that start a fire for anyone .....??? i hope it does please help

 

So answer the question. WHAT YEAR IS THE TRUCK?

It DOES make a difference.