Uh-oh, heat not working

sgbuick · #1 10-13-2009, 12:26 AM

I put the heat on for the first time this year (96 caprice), the air coming out gets the slightest bit lukewarm, just enough to not be the cold outside air, but defininitely not strong heat. Checked coolant level in the recovery tank, it's OK, and temp guage is about 1/4 above the C under normal driving. No heater core leaks or coolant on the floor or anything like that. Any ideas as to what might cause this? Thx.

Blue Bowtie · #2 10-13-2009, 12:38 AM

Entrapped air, plugged heater core, or water valve failure.

Check the heater hoses under the hood once the engine is warm. If only one is hot, or if they are only barely warm, there is inadequate coolant flow through the core. You can try to flush the core with clear water if you suspect clogging.

sgbuick · #3 10-13-2009, 12:10 PM

Where is the water valve located? Is that the same as the vacuum controlled heater control valve on the older cars that was under the hood by the AC?

305caprice · #4 10-14-2009, 02:33 PM

it could aslo be the thermostat ive seen that happen a couple of times and every time we just changed that part and boom nice heat

j cAT · #5 10-14-2009, 10:16 PM

Quote:

Originally Posted by sgbuick

Where is the water valve located? Is that the same as the vacuum controlled heater control valve on the older cars that was under the hood by the AC?

your vehicle has even on the hotest days coolant flowing thru the indash mounted heater core...this heater core for some reason gets plugged with crap....I've been there done that before...so when I replace my dexcool every 3years approx...I make damm sure I flush out That heater core and on all my other vehicles the same ...when my vehicle was new back in 96 the heat was poor...those damm GM sealant tabs plugged it up...no problems with heat now ...maybe too hot usually run on 50% ...

use of air pressure is a good way after the heater core flushing to get every thing in there out...

how often do you do this coolant replacement ? do you do it or some repair shop? I doubt the repair shop will do it takes more time ...

jd-autotech · #6 10-14-2009, 10:45 PM

yep take off your heater hoses at the firewall and shove a garden hose on one of th e heater core tubes and then the other go back and forth til you got nothing but clean water coming out in both directions then do it some more for good measure thenput it back together and top off your coolant and if still nothing thermostat time

sgbuick · #7 10-15-2009, 12:24 PM

One more thing I noticed is that the temp. guage only goes up to about 1/4 above the C. Should it be higher than that? ALso, when stuck in traffic it tends to climb toward the middle until you start driving again, then it quickly goes back to 1/4 above C. What should the guage read during normal driving?

j cAT · #8 10-15-2009, 06:12 PM

Quote:

Originally Posted by sgbuick

One more thing I noticed is that the temp. guage only goes up to about 1/4 above the C. Should it be higher than that? ALso, when stuck in traffic it tends to climb toward the middle until you start driving again, then it quickly goes back to 1/4 above C. What should the guage read during normal driving?

this is normal 1/4 to 1/3 thats it....like I said my heater will burn your feet...if the heater core is clean....this with the 1/4 temp reading...this never changed since nov 1995...

463 · #9 10-15-2009, 08:58 PM

one more for you to look at is a weak rad cap that is releasing presure before the rated 15 psi Pressure Rating (SAE Range 14-18 psi) will not let the temp stay at the normal temp of the Thermostat thats in the car. a weak Thermostat also will give low temp.

j cAT · #10 10-15-2009, 10:19 PM

Quote:

Originally Posted by 463

one more for you to look at is a weak rad cap that is releasing presure before the rated 15 psi Pressure Rating (SAE Range 14-18 psi) will not let the temp stay at the normal temp of the Thermostat thats in the car. a weak Thermostat also will give low temp.

this system is 15psi...if the 15 psi is not available you use the 14psi..If you use 16-18 psi. this will blow out the radiator...

the only reason you use this pressure cap is to prevent boiling at temps above 212deg F...once the coolant boils the engine overheats due to air in the WATER pump...can't pump air...

another member suggested bleeding the system this is a possible cause...as an air bubble could be traped in the heater core though on this vehicle I have never seen it..but on other vehicles it is common..

because he has the correct temp readings I believe this is the typical plugged heater core very common with these vehicles..

463 · #11 10-15-2009, 11:21 PM

Quote:

Originally Posted by j cAT

this system is 15psi...if the 15 psi is not available you use the 14psi..If you use 16-18 psi. this will blow out the radiator...

the only reason you use this pressure cap is to prevent boiling at temps above 212deg F...once the coolant boils the engine overheats due to air in the WATER pump...can't pump air...

another member suggested bleeding the system this is a possible cause...as an air bubble could be traped in the heater core though on this vehicle I have never seen it..but on other vehicles it is common..

because he has the correct temp readings I believe this is the typical plugged heater core very common with these vehicles..

j cAT FYI: the % of coolant in the system determines when it will freeze/boil. the rad cap psi is set to release coolant at it's 15 psi and let coolant back in to the closed system when the system cools down. if the cap did stick it will blow out the weakest point. a weak rad cap will not give the proper pis for the heater core to run at the optimun heat output for under -30 temps. all good infro on the heat problem to date.

sgbuick · #12 10-16-2009, 12:53 AM

463, by radiator cap, I am assuming you're talking about the cap on the recovery tank, no cap on the actual radiator on 96's? If the coolant level in the tank is low would it affect heater performance?I felt the heater hoses to see if they're cooler than the lower rad. hose, but all 3 seemed to be just mildly warm (maybe because it's 35 degrees outside today??)compared to the upper rad. hose which I think was hotter, will have to check again.If the thermostat was running too cool, would the temp. guage also show too cool?

j cAT · #13 10-16-2009, 09:22 AM

Quote:

Originally Posted by sgbuick

463, by radiator cap, I am assuming you're talking about the cap on the recovery tank, no cap on the actual radiator on 96's? If the coolant level in the tank is low would it affect heater performance?I felt the heater hoses to see if they're cooler than the lower rad. hose, but all 3 seemed to be just mildly warm (maybe because it's 35 degrees outside today??)compared to the upper rad. hose which I think was hotter, will have to check again.If the thermostat was running too cool, would the temp. guage also show too cool?

your problem is with the heater core...the heater core hoses need be hot...the thermostat with this vehicle works very different than most engines..hot coolant will continually flow thru the heater core...the thermostat is special for this engine and it is possile someone installed the wrong type of thermostat...the temp should be 180deg F...

the correct thermostat costs more and some install the wrong type..
once again with your temp readings it is most likely the heater core..

with this system 50% minimum dexcool coolant with distilled water only..I use 65% dexcool with distilled water...this will protect the metals from damage and reduce any restrictions to flow of coolant thru the engine...better heat transfer to radiator etc..

one thing you must Be careful of is do not spill any coolant on the front cover of the engine as directly below the thermostat housing is the distributor,which if coolant gets into it will not be good...many have damaged there distributor by spilling coolant on it..

as I stated before this flushing of the heater core is required at every coolant change,,,especially if you live where it is cold....

there is no magic fix...it you do this work you will have to get DIRTY..
GOOD LUCK

sgbuick · #14 10-16-2009, 12:19 PM

One more thing, as I prev. mentioned if you run at idle for a few minutes the temp. needle starts heading toward the middle. I tried doing that to see if the heat would get stronger and the heat did not improve very much. Does this mean it's not thermostat related?

j cAT · #15 10-16-2009, 01:49 PM

Quote:

Originally Posted by sgbuick

One more thing, as I prev. mentioned if you run at idle for a few minutes the temp. needle starts heading toward the middle. I tried doing that to see if the heat would get stronger and the heat did not improve very much. Does this mean it's not thermostat related?

that is also a very normal condition ....when the ac is off and idlling for a period of time the temp gauge will climb to about 50% area then one of the electric fans will come on that,, is if your engine has the fans.... some do not depending on the type of cooling system that was install when the vehicle was produced...the HD tow pkg has the non electric fan clutch ..

this as described condition points to the heater core because with a higher coolant temp the heater is still not hot ,,,also the heater hoses are the same temp as the radiator hoses if not then this to indicates lack of flow...

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