Cool Heat At Idle, Hot Heat At Higher RPM's
- Thread starter PhillipA
- Start date
Wanted to provide an update: Brought the TJ back to the shop, the heater is just too cold. Shop installed a known, good mixer box unit, swapped T-stat, burped cooling system etc. Still only luke warm. They did replace the water pump, but state it's fine. I'm picking up the TJ tomorrow and have a Mopar water pump on the way. I've heard to many stories of poor flow on aftermarket pumps. Anyone here experience that?
Really sucks, heat worked fine until we brought the TJ in to have a leaking heater core replaced.
Really sucks, heat worked fine until we brought the TJ in to have a leaking heater core replaced.
Is your thermostat a 180 degree or 195 degree thermostat? You are getting up to normal operating temps?
On the water pump, I have never used an aftermarket unit so I can't comment and never had a problem.
On the water pump, I have never used an aftermarket unit so I can't comment and never had a problem.
MrMark52
TJ Enthusiast
This statement gives some good insight into what might be wrong - "Really sucks, heat worked fine until we brought the TJ in to have a leaking heater core replaced.".
When you replace a part of a system to fix one issue, and the results are that the system no longer operates as it did before that part was replaced but the original problem was fixed - chances are that part might be the problem.
In this case, the heater core was leaking but the heater provided plenty of heat. So the heater core was replaced and now it's not heating good.
So why are we looking at all the other things? Was new heater core "exactly" the same design as the old? Was the coolant flow rate measured through the new core? Maybe there is a restriction in the new core that is limiting how much coolant goes through it.
It could also be that when the old core was removed, some trash or something in the coolant may have broken free and got into the coolant circuits which are also restricting coolant flow.
But changing all the other parts (thermostats, water pumps, etc) when they were fine before the heater core change would not have changed because of the heater core change.
When you replace a part of a system to fix one issue, and the results are that the system no longer operates as it did before that part was replaced but the original problem was fixed - chances are that part might be the problem.
In this case, the heater core was leaking but the heater provided plenty of heat. So the heater core was replaced and now it's not heating good.
So why are we looking at all the other things? Was new heater core "exactly" the same design as the old? Was the coolant flow rate measured through the new core? Maybe there is a restriction in the new core that is limiting how much coolant goes through it.
It could also be that when the old core was removed, some trash or something in the coolant may have broken free and got into the coolant circuits which are also restricting coolant flow.
But changing all the other parts (thermostats, water pumps, etc) when they were fine before the heater core change would not have changed because of the heater core change.
Allseasonrider
New Member
Heater core is fixed! Ordered one from Brass Works, swapped out myself. Removing the dash is not a light task, took me about 3 hours to get the HVAC box out. The heater core the shop used seemed fine. Didn't have much faith swapping in the Brass Works unit would produce heat, but it does!
I had to know why so I took the plastic tank off the removed heater core. There are plastic twisted support things in all the tubes! No doubt to keep the tubes from getting squished while being assembled. BUT, seems like they should have removed them before putting the tank on. These essentially blocked 80% of the flow. No wonder it didn't produce heat.
Had the old leaky factory core and removed the tank, sure enough, no plastic things. Going to see if I can get a picture posted.
I had to know why so I took the plastic tank off the removed heater core. There are plastic twisted support things in all the tubes! No doubt to keep the tubes from getting squished while being assembled. BUT, seems like they should have removed them before putting the tank on. These essentially blocked 80% of the flow. No wonder it didn't produce heat.
Had the old leaky factory core and removed the tank, sure enough, no plastic things. Going to see if I can get a picture posted.
Aftermarket on the left, I pulled one of the twisty things out. Factory on the right. I've heard some owners say they swapped out for another aftermarket unit and it magically worked. I'm wondering of this is a quality control in manufacturing? Twisty things inserted to keep soft tubes from getting squished? Once the fins are on and tank is ready to install, twisty things should be removed.
Factory unit didn't have them.
Factory unit didn't have them.
I stand corrected, found an interesting post on them:
https://www.wranglerforum.com/threads/twisted-plastic-in-heater-core.2426525/Supposed to be in there or not, they don't seem to improve anything. If my old factory unit didn't have them and produce amazing heat.
The Brass Works heater core is more like a radiator. It takes a little longer to get saturated with heat, but it produces some very nice hot air.
https://www.wranglerforum.com/threads/twisted-plastic-in-heater-core.2426525/Supposed to be in there or not, they don't seem to improve anything. If my old factory unit didn't have them and produce amazing heat.
The Brass Works heater core is more like a radiator. It takes a little longer to get saturated with heat, but it produces some very nice hot air.
I learned something new today, looks like a few folks have found pieces that made their way out of the core and into the system. Zoinks!
https://wranglertjforum.com/threads...6-tj-unlimited-4-0-coolant-system.5771/page-2
I can see possibly one that almost lines up with one of the hose connections getting pushed or sucked out, but not the rest.
The plastic turbulators are so thick they take up about half the tube area easily. If they were metal and thinner, maybe the core would have produced heat?
https://wranglertjforum.com/threads...6-tj-unlimited-4-0-coolant-system.5771/page-2
I can see possibly one that almost lines up with one of the hose connections getting pushed or sucked out, but not the rest.
The plastic turbulators are so thick they take up about half the tube area easily. If they were metal and thinner, maybe the core would have produced heat?
They don't need them because it's built like a little radiator. The tubes are thin and flat seems like creating a lot more surface area. The Brass Works was $360 and 3 month wait, but worth it.
Sorry for the fuzzy picture, Brass Works had 3 more rows.
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