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Old 12-22-2012, 12:43 PM
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No Heat while driving 2003 Laredo

It's getting cold here in Indiana and I need to get this fixed, quick!

My vehicle starts fine. Idling there are no issues. The temp gauge rises fine to 210 and heat comes from whatever vents I choose without any issues.

However, once I start driving the air comes out, still in full force, but the air temperature drops drastically. The temperature gauge also drops. Last night driving home from work, it was about 32 degrees out and the temp gauge was bottomed out at 100 and nothing but cold air was coming from the vents.

Coolant levels are fine. I changed the thermostat about 2 years ago (doesn't mean it's not bad).

I am sure this is something that I can handle, but I am unsure on where to start to try to fix the problem.

Thanks in advance for your help!
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Old 12-22-2012, 02:35 PM
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Re: No Heat while driving 2003 Laredo

When the coolant temperature goes down that much, for sure the thermostat is sticking open. Low coolant temp = low heater output. So you probably need a new thermostat.
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Old 01-02-2013, 05:07 PM
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Re: No Heat while driving 2003 Laredo

Thank you for your response. I replaced the thermostat and the old one was indeed stuck open. I put everything back together and took the Jeep for a test drive about a mile down the road. The heat was coming through great! I thought I nailed it!

Short lived excitement. As soon as I pulled in front of the house, the heat went cool. The temp gauged showed it was right where it should be about 210 maybe even a little over. I am getting a little steam from the engine, but I am assuming that is a little burn off from the little bit of radiator fluid that I spilled when installing the thermostat. Coolant levels are fine. I am not sure where to go from here.

I didn't drain the radiator fluid before installing the thermostat. Would that matter?
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Old 01-02-2013, 05:31 PM
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Re: No Heat while driving 2003 Laredo

Well, upon further inspection, it appears as though the steam is coming from the gasket where I changed the thermostat.

Could it be that the thermostat shifted while I was tightening it or that I possibly tighten the bolts too tightly and damaged the gasket?

Would any of this even be the cause of why I still have no heat?
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Old 01-04-2013, 11:18 AM
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Re: No Heat while driving 2003 Laredo

Update:

I falied to tightened the bolts completly after changing the thermostat resulting in a small amount of engine coolant to leak, causing the steam. This is now fixed.

The jeep heats up well (temp gauge) and the fan turns on appropriately. When I turn the heat on, it's ice cold. I am assuming I have air that needs to be "burped". So my question now: What is the best way to burp the cooling system?

I let the engine idle with the radiator cap removed and squeezed the upper radiator hose, however that did not seem to fix the no heat problem.

Again, Thanks in advance!
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Old 01-04-2013, 12:51 PM
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Re: No Heat while driving 2003 Laredo

Are you sure that the small dearation valve on the thermostat is pointing upwards? Not sure if that could cause no heating problems, but for sure it can create an air bubble when not pointing up.
Which engine do you have? For the 4.7 you have to remove the bleed plug, close to where the upper hose connects to the engine piping. Remove it on a cold engine and fill coolant into the radiator until it overflows from the bleed plug. Reinstall it again and let the engine run. Sometimes putting it on an up slope could help in getting air out.
When you feel both heater hoses when the engine is hot, are both hot as well?
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Old 01-04-2013, 01:09 PM
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Re: No Heat while driving 2003 Laredo

The engine is 4.0 so no bleed plug. I'm not sure about the valve on the thermostat. I put the thermostat in with the spring in the engine block. I didn't know anything about the valve or what way it should face.

Both hoses are hot when the engine is hot.

I've read that you top off the radiator when the engive is cool, let the engine idle and then repeat several times. I will see if that does the trick.
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Old 01-04-2013, 05:45 PM
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Re: No Heat while driving 2003 Laredo

All fixed. Topped the radiator off three different times and let it idle and I am in business. Thanks to all for the help!
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