Heater core clogged?

[MikeO]

Learning as I go...

Little or no heat.
Trying to flush heater core. Neither water or air will go through hoses.

Please advise.

Also, the Jeep has been running cool. OBD says 185.
I replaced thermostat, but would a blocked heater core affect coolant temp?

 

[Jerry Bransford]

A blocked heater core will not affect the engine temperature. Did you install the correct temperature thermostat which needs to have a 195 degree rating? 165 and 180 degree thermostats are incorrect for the TJ.

I'd keep at using a garden hose to flush out the gunk that is block it, go back & forth from both sides and eventually it should clear out. Don't be afraid to use full hose pressure.

 

[Link]

Definitely odd. Shouldn't affect running temp although side note...if a vehicle is running hot and assuming your heating system is working properly, you can turn your heat on with the fan at full blast and it'll help remove heat from the engine...at a cost of your comfort.

 

[MikeO]

A blocked heater core will not affect the engine temperature. Did you install the correct temperature thermostat which needs to have a 195 degree rating? 165 and 180 degree thermostats are incorrect for the TJ.

I'd keep at using a garden hose to flush out the gunk that is block it, go back & forth from both sides and eventually it should clear out. Don't be afraid to use full hose pressure.

Yes, both thermostats were 195 degree. Now with the new thermostat installed. OBD shows coolant temp at 204 degrees on highway, not sure why cooler than 210, but better than the 185 degrees before swap. (new MOPAR water pump installed too.)
However, the OBD is showing a PO118 code. not sure what to do about that.
Kept at the heater core flush with the hose, eventually got rusty, dirty water that cleared after a minute; went back and forth on both sides until all clear.
Got heat now. Thanks again.

 

[sab]

It sounds like you had two problems and fixed one of them:

1. ECT voltage too high (P0118)
2. Plugged heater core

Here's the description of the P0118 code from Jeep (caveat - this is from the 2005 Powertrain Diagnostic Procedures Manual, and the PCM is different from the one in your 1998, so it might not be correct):

You need to diagnose the possible causes above to find out why your ECT is sending more than 4.96V to the PCM. Whatever it is, that should solve your temp gauge issue.