Heater Core Revisited.

[JBDive]

I've asked this before without any clear answers so once again this year I have the same problem and looking for the same answers.

Is the heater core design one in which the fluid is forced to go from intake to output or can fluid bypass the coil and pass directly from in to out?

I had my engine replaced, when doing so they found lots of jelly in the system so insisted on replacing the radiator and I specifically told them to flush the heater core which they swear they did. Well it's cold today and the heat *****.

When I have back flushed it I would at times get a plug or some other junk out of it but sometimes not and always the flow of water was unrestricted. If water can pass through the core without passing through the actual coils this would explain that, if not then WTH!?

(No, fluids were never mixed in this Jeep nor was any antileak crap used. engine guys suspected the cleaning agent at the factory was never fully removed from inside the engine and it mixed with the antifreeze to cause this buildup. In the engine itself there was a paste along all the bottom of all coolant channels)

 

[tjkj2002]

The coolant can bypass 95% of the heater core if it's at all plugged in anyway.

Flushing may return 5%-10% for a very short term fix.

 

[JBDive]

So some follow up and why I really don't feel like this is a heater core issue.

Sitting in the driveway with engine idling, temp on high, fan on low I took the temps of the heater core hoses, heater vents, engine block where bleed valve is. Outside air was 55 F

Bleed valve - 175
Heater hose intake - 175
Heater hose outflow - 165-168
Vent tempts - 90-105

Rev'd up engine to 2000 RPM, vent temps 120-125

Tomorrow I will check vents while driving but I suspect I won't see anything over 80 degrees travelling at 60MPH in probably mid 40's temps.

On the 02 I was told Jeep has to use a programming tool to check the blend door and verify the hot/cold is moving as it should. The self programming by moving the dial left and right doesn't work on this year. Right?

Talked to three more mechanics and a "radiator guy" today and none of them were sure if antifreeze can pass through a clogged heater core on an 02 by bypassing the core proper, they think that is the case.

 

[JBDive]

The coolant can bypass 95% of the heater core if it's at all plugged in anyway.

Flushing may return 5%-10% for a very short term fix.

I suspect that is the design as well, basically a small radiator with an open section across the top. That said though if it can bypass how does it work in the first place as water always seeks the path of least resistance so straight from in to out would happen all the time.

 

[tjkj2002]

I suspect that is the design as well, basically a small radiator with an open section across the top. That said though if it can bypass how does it work in the first place as water always seeks the path of least resistance so straight from in to out would happen all the time.

You must be registered for see images

 

[JBDive]

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No image.

I spoke with a parts person at Jeep today and they know their stuff generally and they are pretty sure there is no "bypass" in the system.

 

[JBDive]

So I was reading on some of the other car forums of people that have reversed their hoses and driven that way for a few days to a week. Some did it with a cleaning solution in the whole system, others just to reverse the flow.

This sounds like a decent idea to a point and I can see doing it AFTER a flush of the core but clearly it would then flush whatever is in the core into the rest of the system. A week's worth of hot, pressurized antifreeze should free up anything it can get to.

 

[tommudd]

No image.

I spoke with a parts person at Jeep today and they know their stuff generally and they are pretty sure there is no "bypass" in the system.

LOL you are not reading it
the antifreeze will " bypass " going into the heater core when plugged, not that the heater core has a " bypass "
Read what tjkj wrote
Now on to the next, what works on " other car forums " does not always translate into great results on a Jeep for instance
Have seen some rather amusing results ( but expensive for the car owner ) over the years listening to Bubba down the road next door to your other brother Daryl.

 

[tommudd]

So I was reading on some of the other car forums of people that have reversed their hoses and driven that way for a few days to a week. Some did it with a cleaning solution in the whole system, others just to reverse the flow.

This sounds like a decent idea to a point and I can see doing it AFTER a flush of the core but clearly it would then flush whatever is in the core into the rest of the system. A week's worth of hot, pressurized antifreeze should free up anything it can get to.

Not if the core is plugged up it would just bypass and not go down into the core

 

[TomB985]

Are you sure your blend door is functioning properly? You could have a perfectly functioning heater core, but minimal air going through it.

 

[JBDive]

Are you sure your blend door is functioning properly? You could have a perfectly functioning heater core, but minimal air going through it.

I think so as A/C was great this year after cleaning the filter under the dash. I'd like to get the dealer to do a check but I keep getting mixed answers for this model (02). I asked if they didn't have a diag tool which told them the positions the door was opening to and closing to as the 02 doesn't do the right/left/right trick to calibrate. Can't get a straight answer from them.

 

[JBDive]

Not if the core is plugged up it would just bypass and not go down into the core

So I am back at the beginning asking the same question. Can a backflush of the HEAT CORE ONLY bypass the heater core tubes? and pass from one side to the other? When flushing and you get no restriction in the water flow can the core still be clogged, can water just flow across the top of the core to the exit side or is it forced into the circulation pattern?

 

[JBDive]

So flushed again this past weekend. Again I had a snail size tube of jelly come out along with some minor scale. I then did a closed loop running CLR through the system, backwards and forwards for about 15 mins. I would have gone longer but the drill pump from Harbor Freight started disintegration and throwing CLR all over the place. I follow this with a clean water flush both directions along with air, some scale came out, nothing large after than initial jelly.

Heat temps now are better but not as good as new I don't think. We have only had mid 40's so it's been rather hard to test however:

Outside Temp mid 40's, highway speed, fan on low, vent temps 120-135.
Outside Temp mid 40's, city driving, fan on low, vent temps 130-140.
Turning the fan higher than second speed drops vent temps pretty fast, 90 or so.

 

[Aceofspades]

I think so as A/C was great this year after cleaning the filter under the dash. I'd like to get the dealer to do a check but I keep getting mixed answers for this model (02). I asked if they didn't have a diag tool which told them the positions the door was opening to and closing to as the 02 doesn't do the right/left/right trick to calibrate. Can't get a straight answer from them.

Seriously there’s a filter under the dash?

 

[Aceofspades]

So flushed again this past weekend. Again I had a snail size tube of jelly come out along with some minor scale. I then did a closed loop running CLR through the system, backwards and forwards for about 15 mins. I would have gone longer but the drill pump from Harbor Freight started disintegration and throwing CLR all over the place. I follow this with a clean water flush both directions along with air, some scale came out, nothing large after than initial jelly.

Heat temps now are better but not as good as new I don't think. We have only had mid 40's so it's been rather hard to test however:

Outside Temp mid 40's, highway speed, fan on low, vent temps 120-135.
Outside Temp mid 40's, city driving, fan on low, vent temps 130-140.
Turning the fan higher than second speed drops vent temps pretty fast, 90 or so.

My 02 is the same way. Very long time to warm
Up compared to the 03 with far less miles on it
I feel like it takes longer for the core to get “heat soaked” which is usually the time it takes to get to work

 

[uss2defiant]

Seriously there’s a filter under the dash?

chicken wire 'filter'.

 

[HoosierJeeper]

Seriously there’s a filter under the dash?

chicken wire 'filter'.

It keeps produce and rocks from blowing inside:happy175:

 

[TomB985]

Outside Temp mid 40's, highway speed, fan on low, vent temps 120-135.
Outside Temp mid 40's, city driving, fan on low, vent temps 130-140.
Turning the fan higher than second speed drops vent temps pretty fast, 90 or so.

Have you correlated these with the actual engine temperature readings? An inexpensive OBD bluetooth adapter would make this easier.

Either you've got an obstruction or a stuck thermostat. The dash gauge isn't specific enough for this. My money is on the heater core, though. :blah:

 

[ltd02]

My 02 is the same way. Very long time to warm
Up compared to the 03 with far less miles on it
I feel like it takes longer for the core to get “heat soaked” which is usually the time it takes to get to work

The solution is simple, you just need to move further away from work... :gr_grin:

 

[JBDive]

Seriously there’s a filter under the dash?

Somewhat and yes it needs cleaned. I had really horrible airflow when recirculating air was selected, I assumed a bad actuator. Pulled the glove box and in the upper right area you will see a "filter" or mesh and if you have never cleaned it out it will be pretty much clogged. Just stuff a shop vac hose in there to clean it out. I posted about this on another thread, let me see if I kept the image, nope, but here is the thread and the thread I referenced in finding the "filter".

http://www.jeepkj.com/forum/f202/c-heat-air-volume-vents-fix-64081/