Barely any before and after thermostat replacement and coolant flush

Altruism

New Member
Joined
Jun 26, 2019
Messages
6
Location
WV
Howdy,

I've finally given up on figuring this out myself and not quite sure where to go from here.

I have had little to no heat in my 2000, I have flushed and reverse flushed the heater core hoses, and got out a ton of junk. I did this 3 times until it ran clear each time. That improved the blowing power significantly. Both tubes coming from the heater core are hot as they should be, therefore the heater core is working.

I then determined that it was my t-stat as I noticed it had been EATING coolant like it was dessert, and also noticed that the jeep didn't get to optimal operating temperature (195ish) and therefore the t-stat failed in the open position feeding it coolant constant.

So I just replaced the t-stat and now it warms up to the right temp, and the heat is actually warm(er) kinda, but it is still not blowing like how I have seen other TJ's like my best friends where they basically give 3rd degree burns.
I have refilled the radiator and made sure it was topped off, although I noticed I have a ton of dirt in mine so I was going to do a good flush of it this weekend and see if that improves quality.

I do suspect the blend door actuator, but, I also don't because if that were the case then I wouldn't be getting any heat at all, right..? If someone could confirm that, that would be helpful.

I'm not quite sure of where to check next, and any help would be greatly appreciated. Thanks!
 

Mrprez

Jeep Noob
Supporting Member
Joined
Dec 2, 2019
Messages
187
Location
Sneedville TN
I am having the same issue. Replaced the thermostat today, mine didn’t have one at all, and the engine is now running at the right temperature but there is little heat coming from the vents.
 

TrueTexas

TJ Enthusiast
Joined
Feb 7, 2019
Messages
101
Location
The Woodlands, TX
I have a similar issue that it blows lukewarm even though the Jeep is completely warmed up and heat and fan on high. I am somewhat convinced my issue is the blend door but I am not at that part of my build just yet to really be able to confirm.

If the door is stuck partially open, it could still blow warm instead of hot as it is letting a little of the hot air thru to the vents.
 

Oldguy

TJ Enthusiast
Joined
Dec 30, 2018
Messages
284
Location
Easthampton ma.
could be a clogged heater core. Both hoses, inlet and outlet on your firewall should be hot. Inlet a little bit hotter than outlet, If there is a big difference it is most likely clogged up. What i`ve done in the past is get 2 longer pieces of heater core hose and connect THE OUTLET of your heater core to my garden hose reversing the flow and the other as a drain on the other connection. Turn on hose and slowly increase pressure until it blows the crap out. Use clamps on the connections.. Its worked every time for me.
 

Chris

Administrator
Staff Member
Joined
Sep 28, 2015
Messages
42,750
Location
Salem, Oregon
What do you mean by "eating coolant"? As in the engine was burning coolant or mixing it with the oil? That would be a head gasket issue.

It sounds to me like your blend door may be stuck partially open (or closed).
 

TrueTexas

TJ Enthusiast
Joined
Feb 7, 2019
Messages
101
Location
The Woodlands, TX
X1 on blend door issue. That being said...

Although the OP mentioned in the first post that he flushed the HC until it ran clear I do want to caution against using a garden hose to flush a clogged HC. Normal household water pressure is 40-45 psi and can easily hit 60+ psi. The cooling system in your TJ is designed to operate at 18 psi. So if your heater core is clogged and you pressurize it to 45 psi, it may blow out whatever is in there or it may rupture the HC itself. Consider if you are ready to tear the dash out to replace the HC before you hook a garden hose up to a clogged one.

I used a large syringe to lightly flush my 100 percent clogged HC from both sides. It took a while but eventually puked a long turd of who-knows-what and started flowing again.
 

Nimbley

TJ Enthusiast
Joined
Jun 21, 2018
Messages
190
Location
Somewhere in the desert
If the outlet of the heater core is hot then it’s probably the blend door. If the dashpot is getting vacuum and not leaking off it could have something restricting the movement. Use a mityvac to check vacuum supply, the dashpot leakage, and blend door movement.
 

CodaMan

California Prisoner (for only a while longer)
Supporting Member
Joined
Mar 9, 2017
Messages
2,918
Location
California (for now)
"eating collant"? what does that mean? is it going somewhere? Sounds like you need to pressure test your system and find out where it's leaking.