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Cold Weather Thermostat Experiences
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=73827		 Page 1 of 1
Author:  Caddis [ Mon Jan 21, 2013 11:48 am ]
Post subject:  Cold Weather Thermostat Experiences
I have a question for those of you running the OEM thermostat in cold climates. Does your temp gauge always run at the 12:00 position of just a sniff left of it in the winter?
I replaced my OEM thermostat about 5 months ago, but this winter the needle has been having trouble staying at the first hash mark to the left of dead-center. My winter mods include completely blocking the front, removed the air snorkle to the air intake, and removed the whole fan/fan clutch. This morning on a 45 mile drive the outdoor temperature was about -24 the whole way, and my temp needle never quite reached that first hash mark left of center, although cabin heat was pretty decent. Is this this reasonable for these kinds of temperatures in other people's experience? I will say that 10 days or so ago we had an unusually warm couple of days around 40 and my temp gauge was running back up where it's supposed to just a hair left of dead-center again.
I guess I'm just wondering if my relatively new OEM thermostat is already going out or if I'm just experiencing the challenges of keeping an engine warm in a very cold climate.
Author:  nursecosmo [ Mon Jan 21, 2013 12:05 pm ]
Post subject:  Re: Cold Weather Thermostat Experiences
I think you are experiencing normal operation. I have the same Fia grill blanket but I did not remove the fan. Yesterday I had to drive 4 hours in temps from 0 to well below and I could not get any heat out of the blower unless I set the knob to recirculate, which of course, I had to keep changing back to fresh air every time the windows would fog up. I replaced the thermostat about a year ago and the needle would stay just barely left of 12 o'clock yesterday which seemed appropriate but apparently was not enough to heat the cabin. I see an in-line thermostat in my near future.
Author:  papaindigo [ Mon Jan 21, 2013 12:27 pm ]
Post subject:  Re: Cold Weather Thermostat Experiences
nursecosmo - if I am reading your comment correctly during your drive yesterday your temp gauge stayed just left of center but you had little cabin heat except on recirculate; correct? When on recirculate did you have plenty of heat? Coolant is supposed to flow thru the heater core at all times absent an air lock, so to speak, in the heater or a plugged or partially plugged heater core. How much heat you get is controlled by the blend doors in the AC/heater box. If you had a good temp gauge level you should have decent heat input to the cabin unless:
1. there is air in the cooling system which can, apparently cause cylinder head problems. You might consider on a cold engine pulling the front end of the heater hose that runs from the viscous over the top of the tstat to the heater to see if it and the viscous are full of coolant.
2. with the engine hot see if the in/out heater core hoses are the same temp or nearly the same. If there is a big difference I'd suspect a partially clogged heater core which maybe can be reverse flushed gently with a garden hose applied to the heater core return line (i.e. the one that does not go to the viscous). If both lines are hot and about the same temp I'd suspect you have a blend door control problem especially if you get good heat on recirculate but not on the heat setting.

Check those out before considering an in-line. An inline with a good factory tstat might do a bit of good if you get a "hotter" in line (say 195F). Of course if I'm reading you wrong and your temp gauge was not near vertical yesterday that's a different story.
Author:  Maccie [ Mon Jan 21, 2013 12:43 pm ]
Post subject:  Cold Weather Thermostat Experiences
Hmm...I have had some thoughts about this during this winter which is my first with the '02 CRD I bought used this summer.

During all winter, the temp needle has always been exactly at the first hash halfway between zero and the 12 o'clock position - after the engine has warmed up, of course. We are experiencing a quite cold winter and I don't have any winter mods at all.

But since the engine is running well (as far as I can tell) and the cabin gets warm quickly, I have just assumed that all is well.
Author:  dirtmover [ Mon Jan 21, 2013 12:49 pm ]
Post subject:  Re: Cold Weather Thermostat Experiences
Mine sits between 12:00 and 1/2 tick to the left but when it's really cold (less than -25C) it can take a long time to get there.

Now I did add the GDE tune a few weeks ago and I've noticed that it takes even longer to heat up this winter. Last Friday morning it didn't even reach "normal" operating temperature until about 20 minutes into my commute and I got it above 100km/h on the highway.

I'm not sure if this is an expected side effect of the tune but common sense would suggest that better fuel economy goes hand in hand with less wasted heat.

Maybe for fun I'll try reverting to the stock tune to see if it heats up faster.
Author:  TJ2 [ Mon Jan 21, 2013 4:03 pm ]
Post subject:  Re: Cold Weather Thermostat Experiences
This winter I've driven with both fan and shroud removed. I left the shroud off to facilitate tb job and just haven't put it back. I also drive with the front partially or completely blocked off.

I did a 2k mile road trip before Christmas and engine temp stayed about right. There were a couple times it got well below 0 F and as long as I could keep up rpm's, the heat was fine. Pull over to take a nap and engine temp dropped, along with cabin heat. When the rpm's drop the engine cools down.

My biggest headache is driving a nearby mountain pass. It CANNOT be climbed in summer without a functioning t-stat and fan clutch. In winter it's hard to keep engine from cooling down. I start at 4k ft, drive to 6k ft in 2 miles, descend to 5k ft in 1.5 miles, drive 5 miles relatively flat, then climb to 8k ft in the last 4 miles. The return starts at 8k and it's basically downhill all the way.

These are narrow, steep county roads. The descents are slow (low as 15 mph during snowstorms) with speed limits of 30 and 25 mph. I shift into 2nd gear to descend when it's cold and push the rpm's to 2500. If it's not too cold the engine temp will stay in range.

My cooling system is working well, at least it's functioning to its design limitations.
Author:  nursecosmo [ Tue Jan 22, 2013 1:59 am ]
Post subject:  Re: Cold Weather Thermostat Experiences
papaindigo wrote:
nursecosmo - if I am reading your comment correctly during your drive yesterday your temp gauge stayed just left of center but you had little cabin heat except on recirculate; correct? When on recirculate did you have plenty of heat? Coolant is supposed to flow thru the heater core at all times absent an air lock, so to speak, in the heater or a plugged or partially plugged heater core. How much heat you get is controlled by the blend doors in the AC/heater box. If you had a good temp gauge level you should have decent heat input to the cabin unless:
1. there is air in the cooling system which can, apparently cause cylinder head problems. You might consider on a cold engine pulling the front end of the heater hose that runs from the viscous over the top of the tstat to the heater to see if it and the viscous are full of coolant.
2. with the engine hot see if the in/out heater core hoses are the same temp or nearly the same. If there is a big difference I'd suspect a partially clogged heater core which maybe can be reverse flushed gently with a garden hose applied to the heater core return line (i.e. the one that does not go to the viscous). If both lines are hot and about the same temp I'd suspect you have a blend door control problem especially if you get good heat on recirculate but not on the heat setting.

Check those out before considering an in-line. An inline with a good factory tstat might do a bit of good if you get a "hotter" in line (say 195F). Of course if I'm reading you wrong and your temp gauge was not near vertical yesterday that's a different story.


I don't think it's any of those things except perhaps a blend door malfunction. When -20 degree air is coming through the heater core from outside it can only pick up so much heat from the core. If the heater core warms it up by 50 degrees(I don't know what the rise should be), that is still below freezing. I don't think it's a blend door issue because if I put it on recirculate, it will not immediately get warm but will keep reheating the cabin air and eventually the air coming out the vent is warm. I'm not saying that the heat coming out of the vent from outside is cold but it just isn't enough to warm the cabin enough for comfort. It never has been really warm in extreme winter cold even when new and I wouldn't mind raising the temp a few degrees with a 192 degree thermostat.
Author:  papaindigo [ Tue Jan 22, 2013 9:29 am ]
Post subject:  Re: Cold Weather Thermostat Experiences
You might take a look at the heater testing procedure beginning on pg 24-6 of the 06 FSM. I'll abmit the temp rise chart would be a lot more helpful if it went down into a temp range where heater performance really matters (60F is not really cold). That said looking at the curve and projecting, valid or not I don't know, the temp rise seems to go up as ambient goes down such that the temp rise at -20F might be on the order of 70F for an output temp of 50F. I'll admit I've not experienced heater performance at -20F but I have, not locally, had gasser and diesel vehicles in 0 to -5 F and don't recall any heater output problems.

Hopefully some other forum members will post cabin heater output experience from areas that reach -20F. For what it's worth on recirculate I'd expect cabin heat to get more than "warm".

For others:
1. just a reminder that the normal GDE tune lowers the cutoff temp on the viscous heater. This is a good thing in warmer weather as it helps mpg a bit but in really cold weather may impact cabin heat and engine warm up time although now much I don't know. Keith could say but I don't think the impact would be much.
2. in extremely cold weather, absent some sort of radiator air flow block, a drop in engine temp after coming off the road and idling for a while would not surprise me much. How much of a drop I don't know.
Author:  dirtmover [ Tue Jan 22, 2013 12:57 pm ]
Post subject:  Re: Cold Weather Thermostat Experiences
papaindigo wrote:
2. in extremely cold weather, absent some sort of radiator air flow block, a drop in engine temp after coming off the road and idling for a while would not surprise me much. How much of a drop I don't know.


Stock and below -25C it can drop form 1/2 to just above 1/4 waiting for the traffic lights to change. The ECO tune makes it behave like this just a bit sooner.
Author:  LMWatBullRun [ Tue Jan 22, 2013 1:50 pm ]
Post subject:  Re: Cold Weather Thermostat Experiences
When idling at 15F mine never gets above halfway to the top center. Once I start running it gets up to the top within a couple of minutes. If descending a long slope, running the heater causes it to cool somewhat; I would expect that to get more pronounced as temps drop.
Author:  Caddis [ Tue Jan 22, 2013 1:51 pm ]
Post subject:  Re: Cold Weather Thermostat Experiences
Yes, as Dirtmover just posted, idling in extreme cold causes the thermostat to go down quickly, you can just sit there and watch it go down. I drove home yesterday into -50F headwind and the needle hovered between the first two smaller hash marks to the left of 12:00, the cabin heat wasn't hot but definately warm and kept it comfortable inside the vehicle. My opinion at the moment is that my OEM thermostat is not failing, it's just having to deal with rediculous conditions.
Incidentally, and coincidentally, I was talking to a guy yesterday that works for an automotive enginerring group in north-central MN that does a lot of the winter testing for a number of automotive companies. We see their test mules with strange coverings and diagnostic equipment on them quite regularly throughout the winter. We started talking small diesels of course and he mentioned that they are currently testing both BMW and VW diesels, and have had Mercedes diesels in the past (also that mid-size Mahindra diesel pickup that was supposed to be coming over). He said that all of them have trouble running warm enough in these extreme cold snaps and they try all the usual winter mods as part of their testing.
We may not get much above zero F the rest of the week so I guess I'll have a wonderful opportunity to keep making observations.
Author:  woodtick [ Tue Jan 22, 2013 7:28 pm ]
Post subject:  Re: Cold Weather Thermostat Experiences
Caddis wrote:
We may not get much above zero F the rest of the week so I guess I'll have a wonderful opportunity to keep making observations.


Love your optimism. I'm in the Milwaukee area getting the same system. And I get to work outside in it! :pepper:
Author:  MRausch82 [ Tue Jan 22, 2013 8:29 pm ]
Post subject:  Re: Cold Weather Thermostat Experiences
I drove 275 miles today in single digit temperatures through the northern PA mountains for work, and will do so at least one more day this week with the CRD. I did four jobs, and even with the in-line t-stat mod, it struggled to keep at normal temperature. Idling cut the gauge nearly to 1/4, as did decending hills and stop and go (what little I did in Mansfield). The heat worked fine though. Better than the single digit temperatures I was in all day. The temperature fluctuation is normal on these, or any diesel for that matter.

It was about 5ºF here this AM. My wife plugged the Jeep in for me at about 5AM before leaving for work, and I left around 9AM. It started right up. That block heater certainly should be used if possible in these frigid temperatures. I have some white bottle Power Service diesel additive in the tank as well
Author:  nursecosmo [ Tue Jan 22, 2013 11:45 pm ]
Post subject:  Re: Cold Weather Thermostat Experiences
I just ordered the Murry in-line thermostat. The Stant isn't available locally.
Author:  Caddis [ Wed Jan 30, 2013 2:10 pm ]
Post subject:  Re: Cold Weather Thermostat Experiences
Just a quick update in response to my initial question and partially to answer my own question. The temps have been in the upper 20's the last few days and the temp gauge was running right back up where it's supposed to be. So for now I'm going with the assumption my OEM thermostat is functioning normally.
Also, in spite of the cold snap and some driving around in 4WD, I'm averaging between 23 and 24 mpg on the last 4 tanks or so. Looks like I'm on track for 25 or better with my current tank. Pretty darn decent winter mileage I think.
Author:  CATCRD [ Wed Jan 30, 2013 10:10 pm ]
Post subject:  Re: Cold Weather Thermostat Experiences
I have the stant 195 in-hose thermo in both of my CRDs, and according to my scan tool they both run at about 185 on average. They'll cool off to 179 or so just coasting down a small hill or up to a stoplight, but they tend to cycle between 181 and 188 while driving. The gauge sits there half a tick left of center. One stat has a 1/32 hole drilled in it and the other is undrilled. This is with air temp around 20 or 30.
Author:  nursecosmo [ Wed Jan 30, 2013 11:49 pm ]
Post subject:  Re: Cold Weather Thermostat Experiences
I installed the stant this evening and I am reading 188 while driving in 7 degree temps. I can really tell the difference in heat output now that it went from 160 degrees to 188.
Author:  TJ2 [ Wed Jan 30, 2013 11:55 pm ]
Post subject:  Re: Cold Weather Thermostat Experiences
Nice. I've had a Stant sitting on a shelf for a year. May be time to get it down.

Do you anticipate having to remove it during summer?
Author:  ATXKJ [ Thu Jan 31, 2013 9:38 pm ]
Post subject:  Re: Cold Weather Thermostat Experiences
TJ2 wrote:
Nice. I've had a Stant sitting on a shelf for a year. May be time to get it down.

Do you anticipate having to remove it during summer?



I'd pull it in the summer if you're towing - or climbing mountain passes.

flatlands - lightly loaded - 105F outside air temp, got up 205 water temp (Hayden fan clutch - plastic fan)

still only a 15 min, 1/2 quart of antifreeze job.
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