1990 Cadiallac Deville has no heat coming out. Had radiator and heater core flushed by professional and he said all looks good but no heat. Controls appear to be working because it changes from heat to air and all flappers are working. Could water pump be weak not allowing enough water flow through the heater core?
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Re: no hot air from heater, blower runs fine
The heater in your car depends upon a flow of hot coolant going through the heater core in order to get hot air into the car. If the heater core is partially plugged, it will restrict the flow. If you have a head gasket that is putting exhaust into the cooling system, it will eventually get into the heater core. When this happens there is no coolant in the heater core to make the air warm. If the water pump vanes have corroded away the result will be very poor coolant circulation causing the heater to not blow hot air. If your car is equipped with a heater control valve that is not functioning properly, the coolant flow will be restricted. One or a combination of these factors is likely the culprit in your case.
Since you state the 2 things you ruled out, that leaves only the water pump. Is the car running hot? The thermostat may be sticking as well... but im leaning toward the pump.
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If you have no problems with any valve or perhaps the heater blower motor then heater core could be plugged, I have back flushed some successfully by changing the flow of coolant backward and catching back flow in a separate container. Could actually see large amounts of coolant stop leak.
1st thing to check, is coolant level full.
2nd , is the blower motor actually blowing,
Traveling down the road causes ram air to push through the heater as long as the controls are set for fresh air intake.
Remember If allumaseal will not plug a leak then more professional measures must be used. Many radiator stop leaks are so effective like bars leak the stuff that looks like rabbit feed pellets that when used professional help must be found because the radiator no longer has the circulation ability to cool the engine and if a vehicle is run any at all above max operating temperatures it will normally result in costly repairs. I have personally used fine ground black pepper and had good results but it must be very fine ground no matter what is used it must be small enough to travel through the small tubes of the radiator and or heater core. If larger particles are used coolant flow will probably be restricted enough to cause either no heat in the cabin or overheating of the engine which most certainly can cause serious damage the very first time.
The core may be plugged, or it may have an air lock, or the core may be fine and the doors in the heater case may not be opening properly to pass heat.
With the engine at normal operating temperature, feel both the inlet and outlet core hoses at the firewall. If the coolant is circulating both hoses should be hot. If only one is hot, try cracking open the outlet line, with engine running, to get flow started from an air block. (The outlet line will run from the firewall to the front of engine near or at the water pump housing. The inlet for the heater comes off the top of engine from a head fitting and goes to the firewall.) If no flow results, the core may be plugged. To flush the core, take both hoses off at the firewall or off at where they fit on the engine, and put a garden hose into the outlet-flush it backwards-run until clear-let the water run to ground or use a catch can if able to. Some people use compressed air into the core instead of water flushing. Either way, you should see some sediment come out if it had any blockage. Once you get the heater core circulating, any further heater problems need to be addressed at the heater case. Make sure the temperature blend door can open and close-this door opens to let blower fan air pass across the heater core. Good luck.
disconnect the heat hoses going into fire wall , put hose into one with pressure and flush as it sounds like it could be bloked in the heater core,the other thing that could be the problem be the hot ,cold switch as it restricts the flow to makes the heater hoter or colder , it might need tlc or replacing as it is manaul not elec
Feel the 2 tubes at the firewall for the heater core. If they are not getting hot, the heater core needs to be flushed out or replaced. I had this problem with a 1990 Cadilac Deville, it was just a plugged up heater core.
Remember to install sealant after flushing out the system to prevent leaks.
it sounds like you have a air blockage, or the cooling system needs flushed. to flush system go to ( autorepair.about.com/od/regularmaintenance/ss/coolant_f...) click on 3rd one down. remember to bleed air out of system, this works the best. turn heater and blower on high, start adding coolant. start car let it idle till radiator thermostat opens. when top radiator hose gets hot you should have heat. some vehicles have a bleeder to let air from system. when filling putting coolant in system. if it does, then open bleeder while engine running and putting in coolant untill there are no air bubbles coming out. have a good day !! when doing flush if need be. you can go to any auto parts store and buy radiator flush. follow directions on the back ( prestone is best )
Did you mean the only time it blows hot air is under acceleration?
First thing check the coolant level in the radiator. If coolant is low the first hing to stop working is the heat.
If the coolant level is fine but the coolant is muddy I woulds suspect a plugged heater core. You can try back flushing it by removing both heater hoses (engine cold) and then use a garden hose to flush clean water through the heater core. Do this on both pipes going into the heater core. Keep flushing until the water runs clear. Re attache the the hoses, remove the radiator cap, start the engine, let the engine come up to temp and top off the radiator with straight coolant (to comp for the water in the heater core). You may have to repeat this process several times over several days but you should be able to get it cleared enough to get sufficient heat without having to replace it.
The heater core runs off of the cooling system, it is a small "radiator" behind the dash that sits in a box. when the heater core is full of hot coolant, it gives off heat and the blower motor pushes the hot air to the vents.
If a heater core ruptures, becomes clogged with parasites, or gets blocked in a hose (the 2 leading to the firewall under the hood on the passenger side) it causes the car to overheat, and/or leak.
my suggestion is to have the system pressure tested, and flushed if it checks out OK
There is several ways to see. 1. It could still be the heater core, try blowing air in to IN house, if it comes out the OUT hose strong, its not that. 2. It is posible there is an a pocket in the system. Try bleeding the air hose, that could be it. 3. Take the glove box out, disconnect the air bag CAREFULLY! Start the car, And turn the heat all the way up, then all the way down. U should see a arm move back and forth. MAke sure it goes ALL the way shut, and open. 4. It could be that the doors in the dash don't work. I'm not sure how to do this. Hope the other work!!
I had the same problem in my 1991 caddy, and turned out to be the blend door. It is located in back of the glove compartment. There are two kinds, the automatic blend doors and the manuel ones. Since the temperature is automatic and programmed to stay where it is set, it would be an "automatic blend door". Not a hard fix...