Another poor heat scenario!

[wisemank]

I have a 2001 Safari that suffers from poor heat. When the van idles I get cool to warm air at best. When we are driving the air gets hot! Hmmm - Just did a power flush, Replaced (1) vacuum line from throttle body to A/C this summer. Is there another Vacuum line issue to be found? Or a sensor? Please advise. - My wife has lost her patience and I would like to sleep inside!!!!! Just kidding.

[sgtmull]

Yes, there are more vacuum lines to be looked at. If you have a vacuum leak then under more acceleration your vacuum pressure would increase and open the dampers that are closed under idle, low pressure conditions. That sounds like what it might be to me. Since, you replaced the mainline, I would look at the vacuum lines behind the A/C control panel. Can you hear any leak from behind this panel? Another place to check would be Astrosafari.com. They have multiple threads on vacuum issues.

[manmac]

Originally Posted by wisemank

I have a 2001 Safari that suffers from poor heat. When the van idles I get cool to warm air at best. When we are driving the air gets hot! Hmmm - Just did a power flush, Replaced (1) vacuum line from throttle body to A/C this summer. Is there another Vacuum line issue to be found? Or a sensor? Please advise. - My wife has lost her patience and I would like to sleep inside!!!!! Just kidding.

THERE IS A VALVE IN THE TOP HEATER HOSE THAT IS VACUUM CONTROLED,HAVE SOME ONE MOVE THE CONTROLES INSIDE TO SEE IF THIS VALVE ACTUALLY WORKS.THATS MY PROBLEM,ONLY WHEN I PUT IT ON DEFROST THE VALVE WOULD LEAK.GOOD LUCKLET US KNOW.

[old_master]

A vacuum leak in the HVAC system will change where the air flow is directed. Under low vacuum situations to the blend doors, i.e. going up hill, and acceleration, the air flow will default to defrost.
If you are experiencing low or no heat only at idle, I would first make sure the cooling system reservoir is at the "FULL HOT" mark on the tank. If a vehicle looses heat at idle, it is an indication that the heater core is starving for coolant. When a cooling system is low on coolant, the heater core is the first thing to loose coolant. This is inherent with the design to, number one: let you know there is a problem, and number two: keep coolant in the engine block to prolong overheating damage. The reason this happens is because the heater core is the highest point in the cooling system, therefore, care must be taken while re-filling the cooling system to ensure all air is purged out. Once the radiator cap is installed it is nearly impossible for this to happen. Have a gallon of the proper coolant handy and remove the radiator cap. Run the engine at approximately 1500 RPM until the engine reaches operating temperature, (you will notice coolant moving in the radiator, and probably bubbles too). Continue at 1500 RPM while making sure the radiator is full at all times. Brief and quick increases in RPM will help to dislodge any air pockets trapped in the system. Once you're satisfied all air is purged, make sure the radiator is full and reinstall the cap. NOW you can let the engine idle. Fill the reservoir to "FULL HOT" and take her for a test drive. If this doesn’t cure the problem, there is a possibility that the heater core is restricted, in which case reverse flushing it should help. Diagnosis for the core is done while at operating temperature and 1500 RPM. Both inlet and outlet hoses at the heater core should be very close to the same temperature. They will be very warm, but not so warm that you can’t touch them. (You shouldn’t notice a temperature difference touching them with your hand.) Good luck and I’ll watch for replies/questions.

[gizm0327]

My dads 97 safari had the same problem. we also noticed that that temp gage never got above 45 degrees. we changed the thermostat and now the temp gets to approx 90 degrees and we now get heat at all rpms throught the vents. hope it helps.

[wisemank]

Thanks for all the replies.

I just recently power flushed the system and this helped, but not 100%. My wife says she hears air or suction when hard acceraltion. I will check the heater core and try to burp the system for air. Then we dig for vacuum! thanks again, very helpful.

Kip

[old_master]

Kip, it is not a vacuum problem that you're encountering. Unless it’s between your ears (just kidding). Your wife is giving you the answer; she told you she's hearing air or vacuum on acceleration. That's it! You have an air bubble trapped in there. Listen to your wife

[davidreichle]

Old master, Your name suits you well. I had this very problem with no heat at idle today. The engine temp was also running hot. Sure enough my overflow tank was empty. Filling it seemed to take care of the problem. I had changed the coolent about a month ago and thought the level was fine. I am going to check for air bubbles like you said. When you purge the system should the heater be turned on?

[old_master]

[Thank you. While purging the system, coolant needs to flow through the core. Turn the heater control on and the temp to full hot, fan speed is not important. Some vehicles use a water valve to vary the flow of coolant through the core. Not knowing if your vehicle is equipped with a valve, it's best to turn the heater on to be sure there is flow.

[davidreichle]

Old Master, Thank you for the heater tip. I purged the system today and did both freeway and city driving. Both the heater and the water temp looked normal.