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Discussion Starter · #1 ·
Hey guys, I've search on this for over a month. In the mornings I crank up the jeep, it reaches 210 on the dot after running for a bit, never over heats, fan speed on slow I have nice hot heat.

However if I turn the fan on medium to high settings it blows hot for a few minutes then gets as cold as if the jeep wasn't warmed up. At first I thought this was a heater core issue. I flushed it out a few months back, some gunk did come out but it flowed extremely freely.

Now I keep reading about the heat not working on different settings being the switch or the resistors. However my fan blows on all settings just fine, the heat just doesn't come out on the medium to high settings. Once the air goes cold if I put the fan back on low after a few minutes the heat returns.

It's almost the same symptoms you get with too low of fluid however it does it rather you have throttle on or not. One thing I did notice was the return line coming from the heater core doesn't seem to be getting hot. (Top line hot, bottom line cool enough to touch) So basically like the H/C is clogged.

I'm at a complete lose with this one guys, shy of just tearing it all completely down one part at a time till it works again, hopefully someone here can save me some time / money / aggravation / or my sanity.

Thanks ahead of time.
 

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It does sound like the H/C is clogged or there is some kind of restriction. Try flushing it again even with plain water. Flush it both ways (back flushing) including though the hoses. See how well the water flows out as you flush it. Maybe some more of that gunk is now loose in there.
 

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Discussion Starter · #4 ·
I'll check the vacum lines again. However all the functions work correctly. A/C works just fine heat works fine, though not as hot as it used to be, in all setting except the top two blower notches which make it ultimately turn cold.

Would a thermostat even give me an issue like this if it was stuck in some weird position? From the look of things there is a side channel that feeds the heater core anyways so it shouldn't matter what the thermostat is doing right?

Guess sometime this week I'll probably go ahead and do another flush on the heater core. Is it possible it's already got in bad shape again from just a few months back? The reason I flushed it last time was because of this problem and nothing seemed to change.

Thanks guys I'll check everything out this week and see what I come up with. Anyone have a good suggestion on the easiest / fastest / best way to flush this thing?
 

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The vacuum controls the flaps & is not related to fan speed.
The return hose not being hot is the key symptom.
You defiantly have a flow problem. Remove both heater hoses from the engine end. Attach a garden hose to the end of one of the hoses. You can find a garden hose fitting intended for a quick disconnect fittings at hardware stores or Home Depot. Attach it to the G hose & push the other end into the heater hose & clamp it with a hose clamp. Turn the water on slowly & see how the water flows out of the other hose. Reverse the process to back flush the system. As you turn up the water pressure you should be able to see the out flow increase accordingly. If you don't, there is still a restriction in the H/C. Depending on what you find you may need a new H/C but at least that is how to test it & hopefully get it opened up.

One affect the thermostat has is to help cause back pressure in the system (restriction) to increase the flow through the heater. The other is if it sticks open the heater won't heat because the engine isn't hot either. You say the engine comes up to temp so there is a thermostat in there & it is not stuck.
 

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Discussion Starter · #6 ·
Rbui4MyMrs ok so basically if that thermostat is messed up one way of the other the engine temps would be all screwed up regardless. If that's the case it isn't the thermostat then. It warms up around 210 and sets there. Never stays cool or overheats. Checked vacuum lines today as well as ensuring the heating controls functioned correctly everything there seems fine as well.

So I suppose the next trick will be a reflush on my heater core. I don't think I did a reverse flush last time on it. The heat didn't return last time to it either, well it did for a short while when I was trail riding and worked for about another day or so but then never again. The more I think about it the more I'm starting to think it was what I originally thought it was, the heater core.

Thanks guys for the help, I'll take a trip to Home Depot and see if I can find a hose spout that would fit into that hosing. What is the size of that hosing? 5/8"? (It'll probably be Thursday before I can get back on it now unfortunately and it rained all day today...grr, the Jeep gods aren't liking me right now.)
 

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Discussion Starter · #7 ·
OK guys finally got around to it, work has had me busy. Anyways, reverse flushed and regular flushed the entire system, and the heat core separately. Now I have no heat at all, versus a little bit of heat?!

The engine does heat to 210, doesn't over heat at all. Everything seems normal. My input line to the heater core is still not getting hot. It got dark before I could move along to the next step. However I went and picked up a thermostat and gasket tonight. Going to try that in the morning.

Surely this is it right? Seems like the only thing left that could be a flow problem with it. I checked the control panel to make sure it was indeed swapping over and it seems to be working correctly. These 30-40 degree mornings are really starting to get to me.

Thanks for the help so far! Is there anything else in the system that could be causing this issue? It seems to me the thermostat / heatcore would be the only things that could be blocking it. Thanks again!

*Edit*
Just a quick update, going to get started early tomorrow after finding this thread: http://www.wranglerforum.com/f5/heater-core-wont-get-hot-89993.html

Maybe it's the water pump as well, never even crossed my mind since it doesn't overheat, guess this is now a possibility.....crap.
 

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That is very interesting. That guy never had overheating! Hard to believe but possible, I guess. Let us know what you find.
 

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Have you checked the thermostat?
 

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Feel the heater hoses to make sure they are hot. If you have heat there but not in the jeep, the problem is in the heater blend door control.
 

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Discussion Starter · #11 ·
Ok update, the problem is solved. So short break down here. I had a heating issue where I would get a little bit of heat but when I would turn the fan on high it would blow cold. I reverse flushed the entire cooling system as well as the heater core separately. Some gunk came out but not really enough to matter.

I cranked and tested, no heat. So I swapped out the thermostat, cranked and tested, still no change. And then, just like the thread I posted up previously, I changed the water pump. I now have heat. This was the weirdest way I've ever had heat do in a vehicle. I still don't understand how it wasn't overheating. Especially considering the condition of the water pump.

I also found out this thing had the original thermostat and water pump in it when it was manufactured in May of 1997. Simply amazing the about of years this lasted before giving up the ghost.

Attached are what I found. Images are large, I didn't have time this morning to resize them.
 

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Wizard of Brakes
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The reason it didn't overheat is due to BELIEVE IT OR NOT, the robust nature of the cooling system and the fact that you aren't in a hot environment right now.

I drove our 04 in 110° heat here in SoCal in the middle of summer for 10-15 miles before it overheated to the point that it blew up the radiator. I was trying to do too many things at once and forgot to raise the fan shroud which pinned the fan blade.

The only airflow the radiator was getting was when the rig was moving. So yours not overheating doesn't surprise me at all.
 

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Discussion Starter · #13 ·
I've been having a heating issue, first noticed in August, while we were in 110 degree temps!! I did a flush a fill on the system back during the summer month and decided to go full heat/defrost to see if I could get it to burp more and I had no heat what so ever then. Kind of forgot about the issue and I thought I had a clogged up heater core and did a flush on it alone back then and did have quite a bit of stuff come out. Come winter time I realized it still wasn't fixed. And as above started troubleshooting.

Even in cool temps, 50 degrees around here as of right now ~30 in the mornings, it would still over heat without something circulating water. I had the same issue back ~8 years ago with a Ford Ranger I had at the time. In the middle of winter it over heated. And to top it all off I've been doing a lot of trail riding in the last few months. I'm totally surprised I never had an issue. All this started back at the beginning of August when my radiator basically blew the top of it off, large crack all the way across the top of it.

Weird indeed, if I wasn't sold on Jeep reliability and build quality by now, I definitely am now!
 

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Wizard of Brakes
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I've been having a heating issue, first noticed in August, while we were in 110 degree temps!! I did a flush a fill on the system back during the summer month and decided to go full heat/defrost to see if I could get it to burp more and I had no heat what so ever then. Kind of forgot about the issue and I thought I had a clogged up heater core and did a flush on it alone back then and did have quite a bit of stuff come out. Come winter time I realized it still wasn't fixed. And as above started troubleshooting.

Even in cool temps, 50 degrees around here as of right now ~30 in the mornings, it would still over heat without something circulating water. I had the same issue back ~8 years ago with a Ford Ranger I had at the time. In the middle of winter it over heated. And to top it all off I've been doing a lot of trail riding in the last few months. I'm totally surprised I never had an issue. All this started back at the beginning of August when my radiator basically blew the top of it off, large crack all the way across the top of it.

Weird indeed, if I wasn't sold on Jeep reliability and build quality by now, I definitely am now!
You should go back to your first post in this thread and compare it to the one you just wrote. I believe very strongly that will help you greatly in the future if you try and get some help diagnosing an issue via the written word. :D
 

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Discussion Starter · #15 ·
Huh? I did just what I said in the first post? I tore it down one part at a time till I fixed it? Not following you here.

The only symptom was the return line on the H/C wasn't hot originally which lead me to believe it was a blocked/clogged heater core. The top line, coming from the thermostat was hot originally. Over the past few weeks it got to the point neither was hot.

I did a flush of the cooling system and the heater core once again, not as dirty but some stuff did come out. Still no heat. Swapped the thermostat, still no heat. Swapped the water pump, I got heat. I got suggested a vacuum problem and a blend door problem. Someone also suggested I swap out the thermostat.

When I said "Even in cool temps, 50 degrees around here as of right now ~30 in the mornings, it would still over heat without something circulating water." was meaning with my thinking it would still over heat if the water pump wasn't working, but it wasn't. Then gave the reasoning because I had a Ranger which got a bad water pump and it over heated in the winter time, despite 30 degree temps.... Maybe that's the confusion you are having??

You show up after I gave an update to say what fixed it saying your's overheated due to a clutch fan being stuck in place? I have no clue the correlation you are putting on what you are saying, and what I did to fix the issue or ask for help?
 

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Wizard of Brakes
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Huh? I did just what I said in the first post? I tore it down one part at a time till I fixed it? Not following you here.

The only symptom was the return line on the H/C wasn't hot originally which lead me to believe it was a blocked/clogged heater core. The top line, coming from the thermostat was hot originally. Over the past few weeks it got to the point neither was hot.

I did a flush of the cooling system and the heater core once again, not as dirty but some stuff did come out. Still no heat. Swapped the thermostat, still no heat. Swapped the water pump, I got heat. I got suggested a vacuum problem and a blend door problem. Someone also suggested I swap out the thermostat.

When I said "Even in cool temps, 50 degrees around here as of right now ~30 in the mornings, it would still over heat without something circulating water." was meaning with my thinking it would still over heat if the water pump wasn't working, but it wasn't. Then gave the reasoning because I had a Ranger which got a bad water pump and it over heated in the winter time, despite 30 degree temps.... Maybe that's the confusion you are having??

You show up after I gave an update to say what fixed it saying your's overheated due to a clutch fan being stuck in place? I have no clue the correlation you are putting on what you are saying, and what I did to fix the issue or ask for help?
Calm down, I was merely pointing out that you left out some pertinent information and repeatedly stated that you did NOT have any kind of an overheat issue. Had you brought that up in your first post, I think the responses may have been different.
 

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Hey guys, I've search on this for over a month. In the mornings I crank up the jeep, it reaches 210 on the dot after running for a bit, never over heats, fan speed on slow I have nice hot heat.
However if I turn the fan on medium to high settings it blows hot for a few minutes then gets as cold as if the jeep wasn't warmed up. At first I thought this was a heater core issue. I flushed it out a few months back, some gunk did come out but it flowed extremely freely.
Now I keep reading about the heat not working on different settings being the switch or the resistors. However my fan blows on all settings just fine, the heat just doesn't come out on the medium to high settings. Once the air goes cold if I put the fan back on low after a few minutes the heat returns.
It's almost the same symptoms you get with too low of fluid however it does it rather you have throttle on or not. One thing I did notice was the return line coming from the heater core doesn't seem to be getting hot. (Top line hot, bottom line cool enough to touch) So basically like the H/C is clogged.
I'm at a complete lose with this one guys, shy of just tearing it all completely down one part at a time till it works again, hopefully someone here can save me some time / money / aggravation / or my sanity.
Thanks ahead of time.
im having the same problem you are to the t!!! ive never had the heater core flushed so im going to start there.
 

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Discussion Starter · #18 ·
Calm down, I was merely pointing out that you left out some pertinent information and repeatedly stated that you did NOT have any kind of an overheat issue. Had you brought that up in your first post, I think the responses may have been different.
Calm down? I'm not mad? You seem to be having a problem interpreting postings this morning. What pertinent information did I leave out of the first post? I fail to see what you are talking about and how you are correlating anything. The only thing I left out was a previous flush, which I said I did again, and a radiator change. It wasn't the radiator. I didn't have any sort of over heating problem, at all, 210 on the dot all the time. The cracked radiator wasn't from overheating. Hence I left it out.

I also had no problem with the responses I received. Everyone gave me help to look at different things, like the blend door actuator and manually moving the flap to see if it changes anything, swapping the thermostat, flushing the system, and checking for vacuum problems, before I tore into the motor to swap the water pump. Everyone was very helpful. You seem to me misunderstanding the entire posting......

im having the same problem you are to the t!!! ive never had the heater core flushed so im going to start there.
Yes crawlr, I would suggest starting with a good flush(basically free or cheap with the exception to antifreeze), it's the easiest thing to do. If nothing changes try the thermostat($2.99 for it / $1.50 for the gasket). If it still doesn't change I would check on the blend door actuator motor first! Sorry I don't have a link off hand.

If all else fails take a look into the water pump. Are your heater core lines hot after your thermostat opens? Plenty of fluid in the system etc.?
 

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Thanks for posting the results. Also for posting the link you found that pointed you to the water pump. That will help others in the future. I would not have guessed a pump like that would circulate enough to keep the engine at normal temps. THANKS again.
 

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Discussion Starter · #20 ·
Rubi4MyMrs, yeah when I saw that thread I thought, "there is no way this is a water pump issue." Asked for help here and several other places and with people that I know. Everyone pointed to either the thermostat or heater core. I thought the same thing, going through the process and it still not fixing it I stumbled across that thread and picked up a water pump. I figure why the heck not, at 98K miles it probably needs one anyways and it's only $35 so why not right? And it fixed it! So I figured I would defiantly post up what I found with those pictures so if anyone else had this issue they wouldn't be pulling their hair out like I did.

Hopefully this helps someone in a bind at some point in the future.
 
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