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Changed water pump in trailblazer blowing out cold air

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You need to bleed the air out of the system. Open the radiator cap while the engine is cold. I like to put a rag loosely over the opening to catch any splashes. Start the engine and let it run at idle. After it warms up you will start getting some "burps". Let it go until they stop. Be careful, the fluid will get quite hot. You may need to add a little fluid when it is done.

Posted on Jan 03, 2017


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Posted on Jan 02, 2017

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SOURCE: 1999 Jeep Grand Cherokee Heat not working

Change your Thermostat.

Posted on Jan 17, 2009

  • 152 Answers

SOURCE: Blowing Cold Air

It sounds like you need to do a process of elimination, by following the travel of the hot coolant.

1. Before beginning, safety must come first, so put on a pair of safety glasses/goggles and a pair of gloves.

2.Open the hood and check the coolant level, and add if needed. If you needed to add then recheck for heat after step # 3

3. Close the hood and start and run the engine to normal operating temp.


5.Reopen the hood and lightly grasp the top radiator hose feeling for heat caused by hot coolant in the hose. Also feel the bottom radiator hose for heat, (you may have to access the bottom hose from under the car) (while down there look for coolant leak...dripping) If heat is somewhat equal between the two hoses move on. If not there are three areas to check
A) Your thermostat may not be opening
B) Your radiator might be obstructed/clogged
C) Your water pump may not be functioning

6. Locate the two smaller hoses that lead to and from your heater core (a small radiator type device located inside cab under the dash that connects through the firewall) (one is connected at the water pump to the heater core the other is connected at the engine to the heater core) one hose may have a regulator (a small mechanical device operated by either cable,electric,or vacuum that controls the flow of coolant into the heater core) attached inline

7. With the hood raised, restart the engine and adjust the heater control to max heat. Locate a safe area under the hood (free of all moving parts) to access and grasp each of the smaller heater hoses, check for heat, caused by hot coolant in the hose, also check the hose before and after the regulator described in step # 6.
If either of these locations are cold to the touch we can safely say we have narrowed the problem down to one or all of three things.

A) If all heater hoses are cold or only the inlet side of the regulator is hot and the other side is cold or warm, its possible that the regulator is faulty requiring a replacement or is not functioning due to inadequate cable,electric,and/or vacuum to operate it caused by a broken cable, electrical short or disconnected/ broken vacuum line, it also could be a defective (in dash) heater control unit or just a fuse if its electrically operated.

B) If the inlet hose to the heater core is hot and the other outlet hose is cold or warm then its possible that the heater core is obstructed/clogged, requiring a flush out or replacement.

C) If all heater hoses are hot (you may also feel a flow vibration in the hoses) then you should have heat, unless the under dash duct work is disconnected or blower fan is not operating.

I hope this helps.....

Posted on Feb 20, 2009

  • 1 Answer

SOURCE: 2002 Lincoln Navigator. Heater is

try changing the thermostat if thats not it check and see if you have water leaking in the passenger side floor board if so then you need a new heater core

Posted on Feb 24, 2009

  • 3740 Answers

SOURCE: car overheating, blows cold air out vents, changed

A couple of things to check because as you describe your symptoms you actually have 2 problems

1. No heat from vents.

Sounds like the heater water flow valve cable is kinked disconnected or the valve itself is stuck You will need to follow your heater core water supply lines to find the valve usually to the right of the center console in the ducting area / large plastic housing for heater and AC internal coils. If the valve works then there is a possibility that the heater core water supply lines have been bypassed on the engine side of the firewall with a coupling due to a leaking heater core. And l;astly the heater core could just be clogged. (quite rare!!)

As for the overheating engine after all of the work you have done.. Perform this simple test.

1. remove radiator cap
2. have someone else start the car
3. watch for water coming out of the open radiator cap area DURING start...
4. have person in the car rev engine gently 2 or 3 times. No need to exceed 2000 RPM. If water rapidly flows out of the radiator during engine revs.. you have some major engine issues.
If it passes all of these checks then the only thing left is improper hose connections on the engine side of the firewall and or a hydraulic water lock in the block that should clear itself by starting and stopping the engine many times with the radiator cap off.

Posted on Jan 27, 2010

  • 11 Answers

SOURCE: rear heater only blows cold air...front of cab

might have dual heater cores rear core might be bad or trying to plug up

Posted on Mar 24, 2010

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hope this helped
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please rate well

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I have water leaking from the engine, but don't know where from. The radiator has been changed the water tested for emmissions, pressure tested and still water is leaking. The heating blows hot when...

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