Not-so-great heat, running a little cool (I think)

[qslim]

Been driving around during this cold snap and realizing that the heat isn’t so great. It was 12 on the way in this morning and I wasn’t impressed. This is my first TJ winter so I don’t have anything to compare, so I’m wondering you think I’m out of regulation here.

I overhauled the cooling system this past spring IAW all the part #s on this forum (Mopar pump, stant thermostat,etc...) due to a small leak. I never really payed attention to temps because everything runs like a top, but the temp gauge has always stayed just a tad left of the 210 mark. Now in this cold it’s further left, so took a pic of the gauge and also a reading I took of the temp sensor on the tstat housing. This is after I got home from work, about a 10 mile drive, ambient temp is around 32. I’m planning on grabbing another tstat, any thoughts?

 

[Leinhit]

my temperature gauge runs right on 210. When you replaced all your parts did you put in a new heater core or did you flush it out at least?

you might be very surprised at the improvement if you take the two heater hoses going to the heater core off and flush out the heater core if not the entire system.

I noticed a vast improvement in the amount of heat coming out of the vents after flushing the heater core. So hot that I can't hold my hand in front of the dash vents it's too hot.

Also even though I have very hot air coming out the inside of the Jeep always seem very cold to me even with a hardtop on.

So far it is a huge difference going into this winter. The only other thing I did different was coat the inside of the tub with a rubberized undercoating spray and I suspect that it must have insulated it and holds the heat better as it certainly holds the noise out better than it ever has.

Huge difference in how warm it is inside now.

 

[TJ4Jim]

What thermostat temp did you install during the overhaul. Should be a 195 deg.

 

[Jerry Bransford]

Been driving around during this cold snap and realizing that the heat isn’t so great. It was 12 on the way in this morning and I wasn’t impressed. This is my first TJ winter so I don’t have anything to compare, so I’m wondering you think I’m out of regulation here.

I overhauled the cooling system this past spring IAW all the part #s on this forum (Mopar pump, stant thermostat,etc...) due to a small leak. I never really payed attention to temps because everything runs like a top, but the temp gauge has always stayed just a tad left of the 210 mark. Now in this cold it’s further left, so took a pic of the gauge and also a reading I took of the temp sensor on the tstat housing. This is after I got home from work, about a 10 mile drive, ambient temp is around 32. I’m planning on grabbing another tstat, any thoughts?

View attachment 122551

Yes, either you installed a "failsafe" thermostat and it has failed in the open position as happens regularly, or you installed a 165 or 180 degree thermostat instead of the correct 195 degree thermostat. Stick with a good brand like Stant and avoid ANY thermostats claiming to be "failsafe" which only means they tend to fail in the open position (which renders them useless) instead of the closed position.

 

[qslim]

Yes, either you installed a "failsafe" thermostat and it has failed in the open position as happens regularly, or you installed a 165 or 180 degree thermostat instead of the correct 195 degree thermostat. Stick with a good brand like Stant and avoid ANY thermostats claiming to be "failsafe" which only means they tend to fail in the open position (which renders them useless) instead of the closed position.

Thanks Jerry. I did install a Stant, copied down all the PNs from another thread of yours here... I figure I fat fingered something and installed the wrong one. Oh well, I needed something to do this weekend anyway, just wanted to verify that this is indeed out of spec. Thanks as always.

 

[RobertJ]

I'd avoid anything other than OEM Mopar and always use them on the 4.0s. They are still cheap enough.

 

[Ericict]

At 20f, mine was running just left of the of the 2 but not touching. The heater was very hot and we had to run it turned off of max heat to about midway. I did use a stant 195 when I OH the system this past spring.

 

[Ericict]

Been driving around during this cold snap and realizing that the heat isn’t so great. It was 12 on the way in this morning and I wasn’t impressed. This is my first TJ winter so I don’t have anything to compare, so I’m wondering you think I’m out of regulation here.

I overhauled the cooling system this past spring IAW all the part #s on this forum (Mopar pump, stant thermostat,etc...) due to a small leak. I never really payed attention to temps because everything runs like a top, but the temp gauge has always stayed just a tad left of the 210 mark. Now in this cold it’s further left, so took a pic of the gauge and also a reading I took of the temp sensor on the tstat housing. This is after I got home from work, about a 10 mile drive, ambient temp is around 32. I’m planning on grabbing another tstat, any thoughts?

View attachment 122551View attachment 122552

With 175 at the housing, you should be getting hot fluid into the heater core. Are you sure your diverter door is working properly? Are both core lines hot? Plug?

 

[tworley]

I echo the recommendations of replacing the tstat. Mine is just ever-so-slightly left of the 210 mark since I overhauled my cooling system.

Edit:just saw the no-so-great heat comment. Definitely give the heater core a good flush. The heater in the TJ is pretty darn good. Mine cooks me out after a while.

 

[Goatman]

Flush the heater core, then swap the hoses into the core so you flush it backwards also. This will do a lot better at getting larger pieces of crud that won't flush thru the core in the normal flow direction.

 

[Ericict]

Been driving around during this cold snap and realizing that the heat isn’t so great. It was 12 on the way in this morning and I wasn’t impressed. This is my first TJ winter so I don’t have anything to compare, so I’m wondering you think I’m out of regulation here.

I overhauled the cooling system this past spring IAW all the part #s on this forum (Mopar pump, stant thermostat,etc...) due to a small leak. I never really payed attention to temps because everything runs like a top, but the temp gauge has always stayed just a tad left of the 210 mark. Now in this cold it’s further left, so took a pic of the gauge and also a reading I took of the temp sensor on the tstat housing. This is after I got home from work, about a 10 mile drive, ambient temp is around 32. I’m planning on grabbing another tstat, any thoughts?

View attachment 122551View attachment 122552

what did you find?

 

[qslim]

With 175 at the housing, you should be getting hot fluid into the heater core. Are you sure your diverter door is working properly? Are both core lines hot? Plug?

Yeah, heater hoses are hot. I flushed the core when I redid the cooling system earlier this spring and replaced all the hoses. When I say it's not great I don't mean it's lukewarm, it's just not would I would expect a normally functioning heater to be. At full blast from a warmed engine while driving I'd think it should be uncomfortably hot even if its 15 deg F outside and instead it's just enough to keep the interior warm. Maybe there's still some junk in there though, can't specifically recall that I flushed it both ways.

what did you find?

Nothing yet.. Not the daily driver so it'll be a little bit. I ordered another thermostat and when I get around to replacing it I'll flush the heater core too. I shall report back with findings.

 

[Goatman]

You have to remember that the whole interior of a TJ will help suck heat out. The thin single ply metal on the body has no extra (or any) insulation like regular cars do. And lacks the addition of the inner panels that create a dead air space that helps hold heat in too. Also the hardtop is a thin single layer. No headliner to keep heat in either. So while the heaters in Jeeps are legendary for their mediocre output, the way the body is constructed is also a large heat suck.

 

[qslim]

I'm resurrecting this thread because after installing a 3rd Stant 195 t-stat, replacing the heater core, radiator & doing some other engine work my temp is still in the same place. I'm not really concerned about it, but from what I understand on the 4.0s they're supposed to run at 210 so I don't want to run the engine long-term under its optimal temperature.

The temp gauge always stays about 2 needle widths to the left of center, and after driving around for a few days recording live data the highest reading I get from the ECT sensor is 196. I'm not sure I should really give that much of a shit about it, but it annoys me.

 

[RMETeeJay]

I'm resurrecting this thread because after installing a 3rd Stant 195 t-stat, replacing the heater core, radiator & doing some other engine work my temp is still in the same place. I'm not really concerned about it, but from what I understand on the 4.0s they're supposed to run at 210 so I don't want to run the engine long-term under its optimal temperature.

The temp gauge always stays about 2 needle widths to the left of center, and after driving around for a few days recording live data the highest reading I get from the ECT sensor is 196. I'm not sure I should really give that much of a shit about it, but it annoys me.

Is it possible that your fan clutch is engaged at all times (spin while cool to test)? Did you test the stats before installing?

Running too cool is more than bad MPG. If you run rich all the time, it will eventually dump enough fuel into the oil that you won't get optimal lubrication, etc.

 

[qslim]

Is it possible that your fan clutch is engaged at all times (spin while cool to test)? Did you test the stats before installing?

Running too cool is more than bad MPG. If you run rich all the time, it will eventually dump enough fuel into the oil that you won't get optimal lubrication, etc.

Forgot to mention I replaced the fan clutch as well.

 

[RMETeeJay]

Forgot to mention I replaced the fan clutch as well.

It could really only be a few things:

1. Bad coolant temp sensor (you could use an IR temp gun to verify what OBDII is showing).
2. Bad or incorrect stat (unlikely since you've done 3, but I always test in a pot on the stove before installing).
3. Bad (locked) fan clutch (not sure how to test, but I don't think it should spin when engine is cold?).

 

[Ericict]

Mine runs under 210 also. Ive confirmed that the temp sensor (OBDII) is very close to thermal reader (+-) a degree or 2; 196-198. Ive stopped worrying about it and wrote it off to he all the different components at the extreme of their specs. I did check my stat when I installed it with a thermal reader as well and it opens at 195ish. Mine does cook me out in the winter though. Its hot. I couldnt find a spec in the SM as to what a spec might be for the coolant system.

 

[Ericict]

It could really only be a few things:

1. Bad coolant temp sensor (you could use an IR temp gun to verify what OBDII is showing).
2. Bad or incorrect stat (unlikely since you've done 3, but I always test in a pot on the stove before installing).
3. Bad (locked) fan clutch (not sure how to test, but I don't think it should spin when engine is cold?).

From the SM. Ive always just checked to see if it spins or doesn't when cold. I dint think this is his problem, but it is good info to know.

TESTING If the fan assembly free-wheels without drag (the fan blades will revolve more than five turns when spun by hand), replace the fan drive. This spin test must be performed when the engine is cool.

For the following test, the cooling system must be in good condition. It also will ensure against excessively high coolant temperature. WARNING: BE SURE THAT THERE IS ADEQUATE FAN BLADE CLEARANCE BEFORE DRILLING.
(1) Drill a 3.18-mm (1/8-in) diameter hole in the top center of the fan shroud.

(2) Obtain a dial thermometer with an 8 inch stem (or equivalent). It should have a range of -18°-to105°C (0°-to-220° F). Insert thermometer through the hole in the shroud. Be sure that there is adequate clearance from the fan blades.

(3) Connect a tachometer and an engine ignition timing light (timing light is to be used as a strobe light).

(4) Block the air flow through the radiator. Secure a sheet of plastic in front of the radiator (or air conditioner condenser). Use tape at the top to secure the plastic and be sure that the air flow is blocked.

(5) Be sure that the air conditioner (if equipped) is turned off. WARNING: USE EXTREME CAUTION WHEN THE ENGINE IS OPERATING. DO NOT STAND IN A DIRECT LINE WITH THE FAN. DO NOT PUT YOUR HANDS NEAR THE PULLEYS, BELTS OR FAN. DO NOT WEAR LOOSE CLOTHING.

(6) Start the engine and operate at 2400 rpm. Within ten minutes the air temperature (indicated on the dial thermometer) should be up to 88° C (190° F). Fan drive engagement should have started to occur at between 74° to 85° C (165° to 185° F). Engagement is distinguishable by a definite increase in fan flow noise (roaring). The timing light also will indicate an increase in the speed of the fan.

(7) When the air temperature reaches 88° C (190° F), remove the plastic sheet. Fan drive disengagement should have started to occur at between 57° to 82° C (135° to 180° F). A definite decrease of fan flow noise (roaring) should be noticed. If not, replace the defective viscous fan drive unit

 

[Winks42]

Forgot to mention I replaced the fan clutch as well.

I had the same issue, replaced fan clutch, tStat, flushed heater core and even fixed a broken blend door and nothing worked. I recently spent the $20 and go a new coolant temp sensor and it fixed my issue.