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Unread 02-26-2015, 05:15 PM   #1
1999-Wrangler
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No Heat

I have read several threads on multiple websites. I just bought from a friend a 1990 Wrangler Sahara. It is going to need a frame swap, but I cannot do this until April. In the mean time, I am fixing other smaller problems. He told me when I bought it that the heater had quick working. He had replaced the radiator in the last six months. Due to the cold, I pulled it in my garage and flushed the heater core using a recirculating pump. I flushed with Vinegar and Hot Water. At first, I only got a trickle through the core. Eventually I had a really good flow. Every time that I changed the water, I would notice new rust flakes coming out. I done this for over 6 hours. Each time flushing both directions, I would see Rust Flakes. I put it all back together and no hot air. I pulled apart and repeated process. Got a lot of crap out again. Hooked it all back up and got luke warm air. I flushed again getting a lot of crap out again. I realized how bad of shape the whole system must be in. I bought an in line T and flushed the entire system until the water was clean. I hooked all back up and no warm air. I flushed core again getting flakes out. Hooked back up and no warm air. I burped the system and no warm air. Last night I drained system and put Prestone Flush in it. I got Jeep hot last night. The reservoir was filthy with stuff caked on sides and bottom, so I pulled off and cleaned. Today I warmed up engine up since it still had flush in it. Still no warm air. The outlet hose from core was not hot like the inlet. I pulled the hoses off. I used a funnel and poured some water in to the inlet hose. Water immediately started running out of the outlet hose. This leads me to believe that the core is not clogged, but doesn't explain why the outlet hose is not getting hot. I am getting luke warm air at best. On defrost, the air on passenger side is luke warm, driver side is cold. I have also used an air compressor to blow it out, I am stumped and getting frustrated. What do I do?

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Unread 02-26-2015, 05:27 PM   #2
Jeepsr4me
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The water pump has a small tube coming off it that supplies water pressure to the heater core, it can stop up there and not allow the water to pass.
Check the lines coming from the heater core and see if either are hot.. If they are the air divert-or in the ac box is not closing to allow the heat part to work
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Unread 02-26-2015, 05:37 PM   #3
1999-Wrangler
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The inlet hose to the heater core gets hot. The out let hose does not get hot.
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Unread 02-26-2015, 05:46 PM   #4
Jeepsr4me
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Then your heater core is stopped up...Cause there is no valve that shuts off flow of the heat to the core..

Get another core... I like to pressure check it before I put it in too... Easy to just hook the 2 lines to it under the hood and run the jeep for a few... Nothing sucks more than finding a leaking core after you buttoned up everything...

can do it with air too... but.
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Unread 02-26-2015, 06:08 PM   #5
chris142
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Quote:
Originally Posted by Jeepsr4me View Post
The water pump has a small tube coming off it that supplies water pressure to the heater core, it can stop up there and not allow the water to pass.
Check the lines coming from the heater core and see if either are hot.. If they are the air divert-or in the ac box is not closing to allow the heat part to work
You have it backwards. The hose on the thermostat housing is the feed and the wp is the suction.
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Unread 02-26-2015, 06:24 PM   #6
1999-Wrangler
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Not arguing, trying to understand. Why can I pore water in the inlet and it run out of the outlet if it is stopped up? Since the inlet is hot and outlet is cold, I agree it is stopped up. Don't understand why water with no pressure can pass through.

If I have it correct, the big hose coming out of the top of the motor at the thermostat housing to the top of the heater core is the inlet. The smaller hose coming from the bottom of the heater core is the outlet.
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Unread 02-26-2015, 06:32 PM   #7
Jeepsr4me
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The core can get a clog that will let low pressure by but when you add more it closes. I put a home water hose on the end of the heater hose and turn it on full blast... it will blow out any crud or blow up the core, either way you got to do it..


I knew the flow went one way or other... Does not matter in this case..
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Unread 02-26-2015, 06:41 PM   #8
1999-Wrangler
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I can get this kind of flow through it when it is not hooked up to vehicle. As soon as I put it on and start the truck, only the inlet hose is hot.
image.jpg  
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Unread 02-26-2015, 06:59 PM   #9
chris142
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Check the return hose and pipe for a restriction. Then move onto the wp impeller.
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Unread 02-26-2015, 07:05 PM   #10
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Hadn't thought about it being in the water pump. I can see the thermostat is working. How would the water pump be bad but the jeep not over heating? Trying to learn here.

Last edited by 1999-Wrangler; 02-26-2015 at 08:01 PM..
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Unread 02-26-2015, 08:37 PM   #11
chris142
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I have seen water pumps with missing impellers that never overheated! I can't explain why.
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