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94 caprice heat does not get hot

11-15-2006, 12:16 PM
I have a 94 caprice classic ls the heat does not get hot only warm sometimes heres what I have done so for.

changed thermostat
changed heater control valve
flushed anti freeze
changed heater control unit

heater hse to heater core gets hot, top radiator hose is warm lower raditor hose is cool. could it be poor circulation i.e. water pump. any ideas will be greatly appreciated

Blue Bowtie
11-15-2006, 12:43 PM
Welcome Aboard!

"Warm" and "cool" are relative terms. "Warm" in my area would probably be considered "cold" in some places, like Florida or SoCal. Today it was about "warm" enough to snow. Much cooler and we wouldn't get any.

As for the radiator hoses, the hot coolant leaves the engine via the top radiator hose whenever the thermostat allows it. The lower hose should be cooler, since the radiator is supposed to extract heat from the coolant. Again, these are all relative terms.

If the ambient temperature in your area is below 40ºF, the radiator hoses should have a significant difference in temperature. If both heater core hoses are hot, we can presume that the coolant is being pumped through the core, at least in some volume. If you suspect that the core is clogging, you can reverse the hoses so the coolant flows in teh opposite direction through the core - The core really doesn't care which way it goes.

If the core is being heated, it is also possible that the air control dampers in teh ventilation system are not operating as they should. If the heat/cool door is not closing fully, the hot air from the heater core will be diluted by the cooler air bypassing the core.

If the car has a temperature gauge, there may not be numbers, but there should at least be markings. If the temperature registers at least 1/3 of scale on the gauge, the coolant should be hot enough to make heat for the passenger compartment.

Another piece of information which might be helpful is the temperature rating of the thermostat you installed. AFAIK, the stock rating for both L99s and LT1s is 185º (not 195º). Anything lower than that could be contributing to the problem.

12-28-2006, 03:56 PM
My '94 4.3 v-8 - same thing. Reverse flushed the heater core. This helped, and later I reversed the heater core hoses for a couple of days, then returned them to normal. That flushed the core enough to get it working very well.

02-10-2007, 01:50 PM
slip on a new rad cap as the old one may be to week to hold the cooling system up to the 15 to 16 lbs of psi. there may be a vac leak in the ac/heat vac pots that operate the doors in the dash.

02-12-2007, 10:50 AM
thanks will try the cap and reverse the hoses on the heat core. will post a reply if it helps

1968 Pontiac
02-16-2007, 08:31 PM
If I remember, the only thing a rad cap affects is the actual coolant temperature before it starts to boil. This effect can best be seen if running straight water: it will boil at 212 Deg F without a cap, but the water temp can go higher with a pressurised system before the water will boil. In the end it really won't help your heat as your thermostat should really be opening before the temp even gets to 212 Deg F, thus your heat will be effected more by the thermostat than by the cap. Back in the stone age, if you were really inclined you would put a 195 Deg thermostat in for the winter and 165 or 175 Deg for the summer.

01-20-2009, 09:04 PM
I'll tell you what was wrong with my 94 Caprice when it wouldn't put out much heat. After I flushed, (forward, backward and sideways) the cooling system and heater core, new 180 thermostat, checked hot/cold door in dash, new 195 thermostat, eliminated inline restrictor in input hose of heater core, then installed new one, tried it in the in and out lines of core -nothing helped. eventually realized while installing new heater core there is supposed to be a foam seal between the heater core and ductwork (incoming air side). mine was gone, either from mice, or some one before me had replaced the heater core and not resealed. anyway, enough air leaked around the core to make for a cold ride. Few layers of foam tape and car is warm for our nice MN winter.

01-21-2009, 11:43 AM
I have the same problem with my 94 5.7, the other day it was -5 outside and I personally think it was colder in my car.

03-05-2010, 07:45 PM
problem was still there went to carwash and power flushed heater core heat works great now

j cAT
03-07-2010, 10:48 AM
problem was still there went to carwash and power flushed heater core heat works great now

your replying to your posting after 3 yrs ?

03-07-2010, 11:42 AM
sorry, but believe it or not just fix the problem about aweek ago. no more post under this sorry

j cAT
03-07-2010, 05:36 PM
sorry, but believe it or not just fix the problem about aweek ago. no more post under this sorry

its been years since I learned that replacing the coolant means flushing the heater core..never had any problems with heat after that whenever someone asks for me to do this work this is always done and they do indeed feel how hot the heater air can get...

complaints too hot !

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