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Old 01-04-2010, 12:43 AM   #1
mech12
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Cool heating problem


I have 2001 saturn sc coupe 1.9L and the car is blowing cold air. I replaced the thermostat because it was running very cold on the temp. gauge. It was also low on coolant. After replacing the thermostat, is there a way of bleeding the air out of the system? After running there is hot water going into the core but the hose coming out is cold. It might be a somewhat plugged core but, there is hot air coming out if I rev up the engine for a period of time. Also this a stumper, hot air is coming out of the center vents but switch to defroster and the air is pretty cold. There is a water shut-off valve under the dash that controls the water flow to the core I think. This one works with a cable and it seems to be working, because it changes the air temp. when turning knob for heat. So any help on this problem would sure help. Thanks much Mech 12

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Old 01-04-2010, 01:07 AM   #2
Ssicarman
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Welcome to the Board.

There is no water valve in the system.

Your symptoms are typical of a blocked heater core. Back flushing the heater core would be the place to start.
Disconnect the heater core hose at the coolant tank and the one that goes to the engine by the t-stat. Run a garden hose to the heater core hose and let the water run through the heater core and out the engine hose. This should unplu the heater core. Run the water through the other way as well.
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Old 01-04-2010, 01:18 AM   #3
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The system bleeds itself as the resevoir is the high point of the cooling system. There is no water valve. Hot water always circulates through the heater core. The lever you are talking about actually operates a damper that regulates the amount of cabin air circulating through the heater core. I've worked on a lot of Saturns and I've never had a problem with a clogged heater core (cracked and split, yes). I suppose if someone had dumped a lot of stopleak in the system you might have legitimate clogging problem. I must admit I have seen alot of heating issues, on the forums, only recently. I had a water pump where the impeller was completely rusted away, causing similar symptoms (it wasn't on a Saturn though). Also if you don't have enough antifreeze in the system, those long skinny heater lines are the first to freeze and the last to thaw.Just because its green or pink or orange doesn't mean you have adequate protection. Keep us posted.
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Old 01-04-2010, 03:53 PM   #4
mech12
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I drained the freeze when I changed the thermostat. The antifreeze was murky light brown. I guess I could let the car run with the cap off he resivoir and see if that helps burbing the system of any air trapped in the system. Very cold here to run a hose through the core now. I think the inlet for the heater core comes from the resivoir and then goes through the core and then back into the engine by the firewall. The hose by the thermostat {small} in under the thermostat housing goes back to the resivoir, correct? This is the one I disconnect and flush? Hopefully I can do this when I here from you guys if I am correct. Thanks Much Mech12.
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Old 01-04-2010, 08:58 PM   #5
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As mentioned already the system is self bleeding.

The coolant flow is from the engine to the heater core to the surge tank.
The hose that you want water to go into for a back flush is the one from the heater core that runs to the coolant tank along the frame.
The hose that you want the water to come out of is the 5/8 inch or so one by the t-stat housing.
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Old 01-04-2010, 10:49 PM   #6
mech12
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Thanks so much for the quick answer. I will try it when it gets a little warmer. Just too cold wright now to run water through the core and down my driveway. I realise I had it just backwards on the flushing after I read it again. Also when the water pump impeller goes out would't the engine run hot from no circultion? Food for thought on that one. When idle, if the pump was bad, water would not flow as easy and there would not be so much heat and if I were to race the engine more water flow and more heat. Am I right to think that? Just when I did race the engine {at a stand still} the heat did seem to rise on the thermometer I had in the heater vent. When I was driving the car it seemed to go down on the thermometer. Like I said before the center ducts where giving heat and the defroster ducts where not when switched to defrost. I hope I am not going on to much about this, but would really like to clear this up soon. Thanks much again Mech12.
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Old 01-05-2010, 12:19 AM   #7
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I have never seen a water pump impeller go bad on an S-series. If it did the temp would peg very quickly and you wouldn't get any for heat out of the heater because the coolant would not be moving at all.

You will get better heat from the system when you rev the engine because you have a higher coolant flow. With a restricted heater core you remove the heat from the coolant faster than hot coolant can move into the heater core.
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Old 01-05-2010, 02:04 AM   #8
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Water will circulate naturally in a closed system. Warm water is less dense so it rises and is displaced with cooler water-simple physics-the term is thermosiphon.Lots of farm tractors had this type of system (no water pump), and they are still operating. Water pumps insure that this process takes place. The post also stated that the rusted impeller was not on a Saturn. Water pumps also force the water to go to areas that natural circulation would not, like heaters and heater lines.

Last edited by hoseppi; 01-05-2010 at 02:19 AM..
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Old 01-06-2010, 12:25 AM   #9
mech12
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I want to thank you guys for the info. I guess it comes down to the heater core. So flushing we will go when it gets a little warmer. Is it hard to replace the core on this Saturn? Looks like it is under the dash and that would have to come out I suppose. Any Idea how much to repair if I took it in? Thanks again mech12.
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Old 01-06-2010, 11:31 AM   #10
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It's not a bad job. The most difficult part is getting the hoses off. It's in an awkward work location so do your stretching before you jump in there. I've only had to do it one time on a S car. I had to replace the core because the antifreeze was diluted to the point of marginal protection. It froze and split the heater core. Replacement should be your last resort. If it is not leaking, I would flush it a few times and make sure nothing else is responsible for the problem, before replacing it.

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