My heater will only blow hot air at the front.

Tiny
HENRYR79
  • 2007 SATURN RELAY
  • 93,000 MILES

My heater will only blow hot air at the front while driving and the rear never gets hot, but once I stop even for a red light the front turns cold. What could cause this?

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Sunday, October 28th, 2012 AT 8:06 PM

17 Replies

Tiny
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Sounds like you have a restricted heater core possibly.

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Sunday, October 28th, 2012 AT 9:18 PM
Tiny
HENRYR79
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I am guessing that this vehicle has two heater cores. Am I correct with this guess? I am assuming after readingyour answer that both are restricted, with the back one being totally blocked. Is this a correct thought, since the back seat never gets heat, and the front is hot only while driving and gets cold rather quickly when you stop.

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Monday, October 29th, 2012 AT 1:19 AM
Tiny
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Yes there is a front and rear heater core after the engine warms up heres what I want you to do. Set the front heater to the hostest temp setting with the lowest fan speed. Then see if both heater hoses to the front heater core are getting really hot?Then do the same with the rear heat and see if both heater hoses to the rear heater core are getting really hot?Let me know what you find.

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Tuesday, October 30th, 2012 AT 4:57 AM
Tiny
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Both hoses for the front get really hot if you rev the motor up, if you leave it at idle only one gets hot. At the rear both get hot only if you rev the motor, otherwise both hoses at the rear are cold.

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Friday, November 2nd, 2012 AT 11:00 PM
Tiny
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I first check the front heater core for blockage start there. Have you ever used stop leak in the cooling system since you have owned it?

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Saturday, November 3rd, 2012 AT 12:40 AM
Tiny
HENRYR79
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I have never used stop leak since I bought the van with 43000 miles, of course I don't know the history for the first 43000 miles.

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Saturday, November 3rd, 2012 AT 1:45 AM
Tiny
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Have you checked to see if the front heater core is restricted or clogged?

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Monday, November 5th, 2012 AT 2:58 AM
Tiny
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Not yet, but should I just pull it and try to shoot water through it in both directions from a water hose nozzle? It will be at least next weekend before I can try anything.

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Monday, November 5th, 2012 AT 3:09 AM
Tiny
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You can do that but I wouldn't remove the heater core to check it I use compressed air to check them.

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Monday, November 5th, 2012 AT 5:16 AM
Tiny
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Iuntil you rev the motor?I took the hoses loose from the rear and flushed water from both directions. I saw nothing but clean antifreeze come from the heater core, then I took the lines loose up front before the wyes and flushed from there, still nothing but clean antifreeze. I then put everything back together, started the van, got no heat after warming the engine until I reved the motor. The lines at the back of the van never got hot until the motor was reved up for a while, then they got hot and I could feel heat, but after returning to idle everything got cold again. Do these vans have a problem with the water pump possibly not pushing the water through the heater cores

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Friday, November 23rd, 2012 AT 11:22 PM
Tiny
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Iam not talking about dirty coolant if one hose at the heater core is so hot you cant hold it but the other one is cooler and noticeably cooler you have a restricted heater core. Because if coolant was passing thru the heater core like it should both heater hoses would be too hot to hold. If the water pump wasnt. Working correctly the engine would be overheating.

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Saturday, November 24th, 2012 AT 12:37 AM
Tiny
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Both hoses are cold until you rev the motor then both hoses get too hot to hold. But if you let the motor idle back down both hoses get cold again with less than a minute.

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Saturday, November 24th, 2012 AT 2:19 AM
Tiny
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This is only the rear heater core?Both upper and lower radiator hoses are getting too hot to. Hold?Also have you traced the hoses from the rear heater core back. To the engine and made the hoses were clear the nipples on the engine etc?

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Saturday, November 24th, 2012 AT 2:37 AM
Tiny
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When I took the hoses loose at the back I flushed water through them to the front and reurning to the back. The water seemed to flow fine. Then I took them loose at the quick connect fitttings under the hood and flushed from there, with the water flowing fine again.

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Saturday, November 24th, 2012 AT 2:26 PM
Tiny
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So its only the rear heater not working?

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Saturday, November 24th, 2012 AT 11:07 PM
Tiny
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Both the front and rear heaters are the same, but the rear one never gets warm. The front heater gets warm while driving but gets cold again upon slowing down and stopping.

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Sunday, November 25th, 2012 AT 4:37 AM
Tiny
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Are both the upper and lower radiator hoses getting really hot?

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Sunday, November 25th, 2012 AT 6:05 PM

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