ok i know this is a newb question but im lost
my blower works good heater core looks good and all the doors and levers working fine but still im blowing cold air
maybe t-stat ? if so where is it and how hard is i to change

This is the location of the thermostat on my 94. Yours should be the same unless it had been upgraded with the 97 coolant crossover. Then it will have two T-Stats. I don’t know how long you have had your truck or what upgrades the PO may have done. You might also look at the heater hoses and see if it has been fitted with T-valves to stop the flow of coolant to the heater core. They aren't hard to change at all. It has been recommended that you use the AC-Delco T-stat when changing it out.

yea mine is different only had it now like 8months dont know what PO had done
ill see if i can get a pic on here yet

what schwind showed you is the single t-stat setup. my 96 has the dual t-stat setup. if i can find my camera i'll snap a pic for you.

kool

mine is just like this
http://www.dieselplace.com/forum/attachment.php?attachmentid=6938&d=1122611217

so there 2 t-stats in there

Yeah, just buy 2 new ones and change them out. So what temp does your gauge read?

if they are stock t-stats they should be the fail open ones so his truck would most likely be running too cold. i know that how my stock ones failed. sometimes the would stick and not open at the right time(temp would go up a tiny bit) then they'd open and stay open(temp gauge would just sit at 160).

temp nevr moves from around 190 or so
if i push in on either top or bottom hose it moves the anitfreeze in the tank
so im think i might not even have one
i guess im goin to tear it down tomorrow and see

With your temps being at 190 I would say that you have good stats in there. Your heater core not heating is another problem. Possibly shut off valves installed on heater lines or heater core bypassed. At 190 engine temps you heater should be working well.

temp nevr moves from around 190 or so
if i push in on either top or bottom hose it moves the anitfreeze in the tank
so im think i might not even have one
i guess im goin to tear it down tomorrow and see

190 is right where it should be, and the coolant should move in the tank if you squash the hose, sounds like you're barking up the wrong tree. Your thermostat(s) are probably OK.

You say the heater core "looks good"?

That means it's not completely covered in dirt and crap that falls through the defrost holes in the dash, and air can freely circulate through it?

More than likely then, it is plugged on the inside. It receives a low coolant flow and sediment can build up in the twists and turns.

Heated coolant enters from the hose out of the coolant crossover (where your thermostat is) and returns to the upper passenger side of the radiator.

A fairly simple test is to feel the temperature of the hoses into and out of the heater core with your bare hands.

If the one returning to the radiator is not as hot as the one to the heater core, the heater core is probably plugged up, so hot coolant never gets through it, or not enough.

Take off both hoses and flush it with your garden hose.

A little trick that was pass on to me with a clogged heater core was to run draino through it (the liquid type), then flush it well (15 minutes or so)you don't want any to get into the rest of your cooling system. You don't want to do this without hoses hooked to the cores tubes and ran into a bucket. the first thing is to make sure that the flow is restricted like bob said with a water hose 5/8" IIRC.

Heater hoses should be too hot to hold when your engine is up to operating temp.

Just wondering if you have checked the level of your rad. If your low on coolant, it won't heat.

Could also be water pump related. Does it heat at low rpm and not at high rpm?

Just throwing some more ideas out there for ya.

I have had the gear box on the electric valves strip out. It will sound like it is switching modes and really isn't. I would check to be shure the valve that directs the air into the heater core is actually moving. There is a procedure for testing to see if it is the motor or the control in my gm service manual. If a new motor was installed it may not have been timed right.

I had the same problem last fall and found out no heat was due to bad head gaskets.

190 is right where it should be, and the coolant should move in the tank if you squash the hose, sounds like you're barking up the wrong tree. Your thermostat(s) are probably OK.

You say the heater core "looks good"?

That means it's not completely covered in dirt and crap that falls through the defrost holes in the dash, and air can freely circulate through it?

More than likely then, it is plugged on the inside. It receives a low coolant flow and sediment can build up in the twists and turns.

Heated coolant enters from the hose out of the coolant crossover (where your thermostat is) and returns to the upper passenger side of the radiator.

A fairly simple test is to feel the temperature of the hoses into and out of the heater core with your bare hands.

If the one returning to the radiator is not as hot as the one to the heater core, the heater core is probably plugged up, so hot coolant never gets through it, or not enough.

Take off both hoses and flush it with your garden hose.
im letting heat up now to check on the hose's
i took the heater box down was alittle dirty but not bad at all

Just wondering if you have checked the level of your rad. If your low on coolant, it won't heat.

Could also be water pump related. Does it heat at low rpm and not at high rpm?

Just throwing some more ideas out there for ya.
coolent level stay the same right at full mark dont seam to matter low are high rpm

I have had the gear box on the electric valves strip out. It will sound like it is switching modes and really isn't. I would check to be shure the valve that directs the air into the heater core is actually moving. There is a procedure for testing to see if it is the motor or the control in my gm service manual. If a new motor was installed it may not have been timed right.
that what i first thought but tore whole dash apart everything move like it should

I want to change my glow plug system over to manual. Does anyone have any help with this . I know i need to replace my glow plugs with self limit gp.(AC 60g ) from what i understand. Thanks
ummm dont steal my thread

well let it heat up heater core got hot both hose's coming from it get hot
but i seen the hose that goes to rad get hard and the other is very soft

i recently installed a webasto in my truck, and after i had no heat at all. it drove me nuts for days. finally i took both heater hoses off, and flushed water through them to make sure i had good flow. guess what, none at all. i took all the hoses i put on with the webasto, and found a plastic cap stuck in the heater hose between the core and rad. great heat now. i suggest doing the same, that way you know forsure that coolant is going through the core

well let it heat up heater core got hot both hose's coming from it get hot
but i seen the hose that goes to rad get hard and the other is very soft

Not sure when you compared the temps, the best time to do it would be while waming up. The coolant will flow from the engine to the heater core with the thermostats closed.

Once the thermostats open everything will be hot, more or less with hot coolant in both the rad and engine.

Sure sounds like your heater core is plugged. Blow that sucker out with your garden hose. Sounds like the one getting hard is the feed - I'd clean it out from the return side.

DO NOT-- I REPEAT-- DO NOT back flush the heater core, some chevy's have check balls inside of the cores, and if you back flush it, it will stick, and coolant will never flow through. maybe that has already been done to yours and that is the problem. flush it the right way of flow, and then you will know forsure

OOPS - That's good to know. I didn't mean to misslead anyone! Apparently mine don't have the check balls - Worked fine back flushing all 3 of mine - 2 Chevys, 1 GMC.

If both hoses are to hot to hold then you have a blend door problem.

DO NOT-- I REPEAT-- DO NOT back flush the heater core, some chevy's have check balls inside of the cores, and if you back flush it, it will stick, and coolant will never flow through. maybe that has already been done to yours and that is the problem. flush it the right way of flow, and then you will know forsure
which hose is inlet ? so i can do it right

which hose is inlet ? so i can do it right

The inlet is the one from the coolant crossover near the front of the engine. Coolant flows from the engine, through the heater core and back out to the radiator.

kool i try that as soon as it slow down here at work

well i just replace both t-stats still no heat i check the door it moves when i turn it from hot to cold

well i just replace both t-stats still no heat i check the door it moves when i turn it from hot to cold


heater core plugged perhaps? did you try flushing it?

Next slow time hear at work i will try it. Running out of things to try.

UPDATE:double check heat door works fine....took heater core out flushed it .....flushed either cooling sytem . still no heat ...heater core gets hot, hose's all get hot. fan blows strong only thing i see thats not right is the door for fresh air is stuck open instead closed when i push the recycle button.. i trying to this when not busy at work so i used one of the bays

Ok for grinns check to see how strong the coolant mix is 50\50 is best heat 100% coolant is the worst

WOOOHOOOOOO FIXED IT ended up being the heater core was sitting in the bottom of the box. never notice b4 they are to hung mid way to allow ait to past though them. The air was just goin over top of it