Issues with Hvac and heat

[Rushin]

Greeting and Happy Holidays!

Have two issues, possibly related possibly not.

Issue #1: When under any sort of acceleration i only get heat to defrost setting. All other vents cut off. When i am going down hill or idling i get heat or ac to any went i want. I suspect vacuum leak or bad check valve. I only know of one check valve. One that comes off the manifold. I tested it and it works fine. I might replace it anyway. Any thoughts on what else could be causing this? What are some tests i can run?

Issue #2: When its really cold out. The engine only warms up to about one bar below 210. When under a lot of load going up long mountain passes it will creep closer to 210 but still quite a bit below it. Bellow is a phone of where the gauge is usually when going down hills or cruising at speed. Do i have an issue with my T-stat? The engine does not take long to warm up or anything. I know for sure t-stat stays closed when engine is warming up.

Any input is appreciated.

 

[87manche]

you have a vacuum leak. The most likely culprit is the line that runs to the vacuum reservoir up front on the passenger side.
When the mode door loses vacum it defaults to defrost.

temperature gauge is not to be trusted. Check the thermostat housing with an IR thermometer.
It's possible that it's at the correct temp and the gauge is wrong because of a sender or wiring issue. Make sure the gauge is correct before worrying about it.

 

[RedHeep]

The big graduations are 25 degrees apart, the little ones are 12.5 degrees apart. Your 195 degree thermostat will post on that little line because 185 plus 12.5 is 197.5. You see a different result in the summer because the ambient air temperature makes your radiator less efficient while in the winter your thermostat is opening and closing to maintain heat in the engine at the 195 degree mark.

 

[cruiser54]

 

[Rushin]

You guys are awesome! Thank you!

Any ideas why heat blows barely warm? It does get a bit warmer when engine gets hotter. If I turn the fan up on the heater I can see temp drop even more on the gauge.

I recently replaced the radiator and flushed the coolant system with a water hose a few times. I did not flush the heater core so I am suspecting heater core might be partially blocked.

 

[RedHeep]

I would guess your thermostat needs replaced. If you're getting a large temperature drop by turning the heater fan on, your thermostat probably isn't closing like it should. The heater core shouldn't have that much effect on your engine temperature.

A partially blocked heater core wouldn't be effective enough to create additional engine cooling. You can run water through it and see, but I'm guessing you need a new thermostat.

 

[Rushin]

Alright. I guess a new t-stat is what i will need. I do think running blower motor makes a big difference on engine temp. I do it in my turbo miata all the time. On a track i often run heat on full blast to cool the engine. I have an aftermarket gauge and it makes a significant difference when i run blower motor. Like 10-20 degree difference.

 

[cruiser54]

Get a good 195* stat in it. Dealership one is best although pricey.

 

[87manche]

made in Israel motorad ones don't suck either.

you can get them at a parts store if you can't make a mopar dealer.

 

[Rushin]

Didn't get the new t-stst yet but did do IR test on the housing. While idling after a good 15minute drive i temp is between 180-185. If I rev the engine it drops even more. The electric fan is not on only the mechanical one is.

I would think that after t-stat opens there is not much difference if it's a 195 or a 180. Am I wrong?

 

[cruiser54]

Didn't get the new t-stst yet but did do IR test on the housing. While idling after a good 15minute drive i temp is between 180-185. If I rev the engine it drops even more. The electric fan is not on only the mechanical one is.

I would think that after t-stat opens there is not much difference if it's a 195 or a 180. Am I wrong?

You are wrong. A properly working thermostat MAINTAINS the temp in the engine.

 

[87manche]

You are wrong. A properly working thermostat MAINTAINS the temp in the engine.

this.

It shouldn't be fully open until after 195, and it sounds like yours is open @ 180ish.

someone may have put a 180 in it, because people think that a cooler thermostat fixes overheating for some strange reason.

 

[Rushin]

I woke up in the middle of the night thinking about this. And what I said makes no sense. So yeah I see what my issue is here. I bet it has a 180 t-stat. If only it was a bit warmer out to swap the t-stat. Its been freaking cold as shit here in CO lately and the jeep wont fit in the garage anymore with the 3" lift...

 

[RedHeep]

I woke up in the middle of the night thinking about this. And what I said makes no sense. So yeah I see what my issue is here. I bet it has a 180 t-stat. If only it was a bit warmer out to swap the t-stat. Its been freaking cold as shit here in CO lately and the jeep wont fit in the garage anymore with the 3" lift...

One ratchet wrench, a couple hose clamps and 10 minutes. I can change a thermostat before my fingers get cold.

Take it off, take it in the house, clean the sealant off, put new sealant on, take it outside and put it on.

 

[dan1977p]

I woke up in the middle of the night thinking about this. And what I said makes no sense. So yeah I see what my issue is here. I bet it has a 180 t-stat. If only it was a bit warmer out to swap the t-stat. Its been freaking cold as shit here in CO lately and the jeep wont fit in the garage anymore with the 3" lift...

Don't use that as an excuse. I shoveled my driveway, backed the jeep out, flushed the cleaner out of the core, block and radiator and replaced with 50/50 coolant all in 18* weather. Already replaced the thermostat due to overheating and crappy heat from 180* thermostat the PO put in. It was worth the effort as I don't overheat going over mountain passes anymore and I was in similar conditions.

 

[87manche]

I did a waterpump @ -5 last year.

cheap chinese waterpumps.
You know you literally can't buy a made in the USA waterpump for a 4.0 anymore? Amazing that the first one went 13 years, but i've done two in 3 after it failed.

 

[Rushin]

I might give it a short this weekend