98 blazer little or no heat

[flame1234]

if it isn't one thing its another with this truck. had starting problems etc., seemed to have fixed that. now the wife gets home tonight and says the blazer has no heat. " my toes are numb" she says.

i went out a looked at the gauge. it was not all the way up to 210, but it was certainly off cold. coolant is not down in the resevoir. it was at the full hot line. checked the oil to see if i night have a head gasket problem, and the oil was clean. i read some previous threads on heater cores and such, could this be my problem? it sounds like a real pain in the butt to change myself, don't really have that much time to do it anyway, and would more than likely be beyond my ability. how much would it cost to have it done?

btw we did put a water pump on it months ago or so, but i don't have any coolant on the floor of the garage at all now so i don't think i have any leaks.

any ideas.......

thanks

[old_master]

Once the engine is at operating temperature, set the heater to full heat, leave the engine running, open the hood and put your hands on the two hoses at the heater core, (passenger side on the firewall). They should be very warm but not so hot that you can't hang on to them. There should be very little, if any, temperature difference between them. If they are both cold, you've got an air pocket in the core and the cooling system needs to be bled or "burped". If you can notice a big difference in temperature between them, the core is restricted and needs flushing or replacement.

[flame1234]

Originally Posted by old_master

Once the engine is at operating temperature, set the heater to full heat, leave the engine running, open the hood and put your hands on the two hoses at the heater core, (passenger side on the firewall). They should be very warm but not so hot that you can't hang on to them. There should be very little, if any, temperature difference between them. If they are both cold, you've got an air pocket in the core and the cooling system needs to be bled or "burped". If you can notice a big difference in temperature between them, the core is restricted and needs flushing or replacement.

thanks for the response, i will try and post results

[VanillaGorilla]

flame.... Have you checked the thermostat????? My 2000 blazer had no heat one cold day and drove 30miles for turkey day.... The Thermostat was stuck... On the way home i tapped the thermostas housing and headed home...

I had heat going home....

With a bad heater core you should smell anti-freeze or maybe your defrost will fog up the windows......

Also check fuses and heater lever linkage.....

[travis2822]

I had the same problem with my 99. I did a quick fix and this spring I am going to do it right. I went to the car wash and pulled off the 2 hoses that go to the heater core and sprayed the hell out of it. My heat is hotter than it ever was. Not the correct way but certainly takes care of the problem short term.

[flame1234]

Originally Posted by VanillaGorilla

flame.... Have you checked the thermostat????? My 2000 blazer had no heat one cold day and drove 30miles for turkey day.... The Thermostat was stuck... On the way home i tapped the thermostas housing and headed home...

I had heat going home....

With a bad heater core you should smell anti-freeze or maybe your defrost will fog up the windows......

Also check fuses and heater lever linkage.....

my wife drove the truck to work today, and i called her to ask if she smelled anti freeze or anything else strange. she said no. could it really be as simple as a thermostat?

[Southern Comfort]

FUNCTIONAL TEST
1) Idle engine for about 20 minutes until warm or until
thermostat opens. Ensure coolant temperature is about 194  F (90  C).
Select vent mode. Move temperature lever to coldest temperature
setting. Select high blower speed. Air should exit instrument panel
outlets and should be about the same temperature as outside air. Air
should not exit floor outlets, defrost nozzles, or side window
defogger outlets.
2) Select heater mode. Move temperature lever to hottest
temperature setting. Most air should exit floor outlets (should be
hot), with remaining air exiting defrost and window defogger outlets.
Air should not exit instrument panel outlets.
3) Select defrost mode. Most air should exit defrost and
defogger outlets, with a low volume of air exiting floor outlets. Move
temperature lever to coldest setting. Air temperature should decrease
to about the same temperature as outside air.
4) Slowly turn blower motor speed control knob toward OFF
position, stopping briefly at each intermediate position to check
force of airflow exiting instrument panel center outlets to hear
blower speed. Airflow and blower speed should decrease noticeably at
each intermediate position.
HEATER OUTPUT TEMPERATURE CHECK
1) Remove radiator cap when engine is sufficiently cool.
Select heater (floor) mode, high temperature setting and high blower
speed. Idle engine until coolant can be seen flowing in radiator.
Install radiator cap.
2) When engine is warm, after about 20 minutes, drive vehicle
at 30 MPH (48 km/h). Measure ambient air temperature and floor outlet
air temperature using a thermometer. If floor outlet air temperature
exceeds minimum specification, heater output temperature is considered
sufficient. See HEATER OUTPUT MINIMUM TEMPERATURE SPECIFICATIONS
table.
HEATER OUTPUT MINIMUM TEMPERATURE SPECIFICATIONS

Ambient Air Temp.  F (  C) Floor Outlet Air Temp.  F (  C)
0 (-18) .................................................. . 130 (54)
25 (-4) .................................................. . 139 (59)
50 (10) .................................................. . 147 (64)
75 (24) .................................................. . 155 (68)
INSUFFICIENT HEAT DIAGNOSIS
1) Perform HEATER OUTPUT TEMPERATURE CHECK. Go to next step.
2) Common conditions for insufficient heating are as follows:
* A leak in the cooling system.
* A low coolant level.
* A loose or worn drive belt.
* A leaking or kinked heater hose.
* A cracked or missing radiator cap seal.
Repair condition(s) as necessary and recheck heater
operation. See HEATER OUTPUT TEMPERATURE CHECK. If heater system
operates normally, system is repaired. If heater system does not
operate normally, go to next step.
3) Turn ignition switch to ON position. Set mode control to
floor/heat position. Set blower speed to HI position. Set temperature
control to full hot position. If airflow from floor outlet is high, go
to next step. If airflow from floor outlet is not high, go to step 7).
4) Move blower control through all positions. If blower speed
changes, go to next step. If blower speed does not change, go to step
11).
5) Perform HEATER OUTPUT TEMPERATURE CHECK. If temperatures
are as specified, go to next step. If temperatures are not as
specified, go to step 12).
6) Inspect following areas of vehicle for cold air leaks and
repair as necessary:
* At cowl, below windshield.
* Inside heater case, at door seals.
* Inside outlet vent ducting.
Perform HEATER OUTPUT TEMPERATURE CHECK.
7) Perform FUNCTIONAL TEST. If system operates as specified,
repairs are complete. If system does not operate as specified, go to
next step.
8) Check airflow from instrument panel vent outlets. If
airflow from vent outlets is high, go to next step. If airflow from
vent outlets is not high, go to step 17).
9) Move mode control to floor/heat position. A small amount
of air should flow from defroster outlets. If airflow from defroster
outlets is as specified, go to next step. If airflow from defroster
outlets is not as specified, go to step 18).
10) Remove floor air outlet and check for obstructions.
Remove or repair obstructions as necessary. Move blower control
through all positions. If blower speed changes, go to step 9). If
blower speed does not change, go to next step.
11) Check following components of blower motor controls and
repair as necessary:
* Blower motor switch
* Blower motor resistor/relays
* Blower motor system wiring harness
Perform HEATER OUTPUT TEMPERATURE CHECK. If temperatures are
as specified, go to step 6). If temperatures are not as specified, go
to next step.
12) Turn temperature control to full hot position. Check
temperature valve position. If temperature valve is fully closed, go
to next step. If temperature valve is not fully closed, go to step
22).
13) With temperature control in full hot position, start
engine and allow to idle. Check temperature of both inlet and outlet
heater hoses. If temperature of air around each heater hose is about
the same, 85  F (24  C), go to next step. If temperature of air around
each heater hose is not the same, go to step 23).
14) Remove heater hoses at heater core and check that heater
hoses are connected properly. If hoses are properly installed, go to
next step. If hoses were not properly installed, go to step 25).
15) Backflush heater core and service cooling system.
Reconnect heater hoses and refill cooling system. Start engine and
bring it to normal operating temperature. Recheck temperature of both
inlet and outlet heater hoses. If temperature of air around each
heater hose is about the same, 85  F (24  C), go to next step. If
temperature of air around each heater hose is not the same, go to step
23).
16) Replace heater core. See appropriate removal and
installation procedure in appropriate HEATER SYSTEM article. After
heater core replacement, perform HEATER OUTPUT TEMPERATURE CHECK.
17) Set mode control to defrost position. Check airflow from
defroster outlet. If there is little or no airflow, go to next step.
If airflow is okay, go to step 10).
18) Move blower control through all positions. If blower
speed changes, go to next step. If blower speed does not change, go to
step 11).
19) Check for obstructions at blower motor inlet and at
plenum. Repair as necessary. If obstruction was found, go to HEATER
OUTPUT TEMPERATURE CHECK. If obstruction was not found, go to next
step.
20) With blower motor set to HI position, move temperature
control from full hot position to full cold position. If change in
airflow is present, go to next step. If change in airflow is not
present, go to step 26).
21) Check for restrictions between heater case and instrument
panel outlets. Repair as necessary. Go to HEATER OUTPUT TEMPERATURE
CHECK.
22) Re-index cable or actuator. Inspect temperature valve,
cables, and linkage adjustment. Repair or replace as necessary. After
repairs, perform HEATER OUTPUT TEMPERATURE CHECK.
23) Check thermostat for proper installation. If thermostat
is installed properly, go to step 27). If thermostat is not installed
properly, go to next step.
24) Reinstall thermostat properly and go to step 13).
25) Reinstall hoses to proper positions and go to step 13).
26) Inspect the following components and repair as necessary:
* Temperature valve
* Control assembly
* Blower motor wiring harness
Go to HEATER OUTPUT TEMPERATURE CHECK.
27) Replace the thermostat. Go to HEATER OUTPUT TEMPERATURE
CHECK.
I hope this will help.
SC

[maineskibum]

Originally Posted by old_master

If they are both cold, you've got an air pocket in the core and the cooling system needs to be bled or "burped". If you can notice a big difference in temperature between them, the core is restricted and needs flushing or replacement.

How do you bleed or "burp" the system? I have had heating problems for a while now and don't know how to permenently fix it. I have flushed my system about 5 times now (twice doing an acid flush) and it has worked after each one. But after about 2 weeks to a month of having heat it goes away again. I have also changed my thermostat. My friend told me that I might have a air pocket that needs to be released but I thought it was probally the rust/gunk build up in the core. At this point I want to try everything and anything to make it work (its cold in Maine),and I don't want to have to end up getting a new heater core or radiator. Please I need help, I am about to send myself to the mental ward trying to figure this out. Any responces will be greatly appreciated!!!

[flame1234]

had the core flushed and it is better, but replacement was recommended. i called around to get prices on that, and 800 bucks was about the norm. so i decided with that $800, a potential fuel pump problem..$800, ball joints that are going bad, not to mention anything else in the front end..$600, and after 87,000 miles we have the original exhaust on it still, so when that goes i'm sure the cat is going to be plugged..so another say $400. $2600 to fix all this stuff?

NOT

we just traded the damn thing in on a new jeep wrangler. i'm done with it. thanks to everyone for their responses and help!!

jamie

[friesza]

I agree flame1234 I am at my wits end with just about all newer Chevy products...they know of the problems but refuse to remedy them...then they wonder why the foreign cars are selling better thatn the American made...first my hood cable broke...next the front hub bearing went out...then the actuator for 4 wheel drive and now no heat....after replacing thermostat...I am going to fluch it good and if it happens again it is either gonna be traded in or to the scrap yard....And to top it off it has only 50000 miles on it and its a 2000...I dont off road it or abuse it...it is maintained very well...oil is changed every 3 months or 3000 whichever is first....usually 3 months..I love this little rig but its irkin me bad right now....
OH AND Southern Comfort....How do I Re-index cable or actuator. Inspect temperature valve,
cables, and linkage adjustment.
Love all the help I get Here

Thanks

[travis2822]

Just on the note of bad GM products. Most of my vehicles have been GM. I have had a few foreign vehicles but GM has been good. Only minor problems that I can usually fix. Foreign cars have there own problems. If something breaks it is usually a lot more expensive. I give a thumbs up to my 99 chevy blazer. I would by GM over any other American manufacturers and most foreign. Just my 2 sense.

[anotherblazer]

Great advice guys.I thought it was my waterpump untill I read all your comments.I flushed the heater core with my garden hose and a couple hose clamps.The heat works great for now.I hope it keeps working.