HELP! Engine running too cool

joelukex4 · **Joined:** Thu Sep 29, 2011 4:54 pm **Posts:** 386

TURBO-DIESEL-FREAK wrote:

All I know is that the only way to accurately monitor your engine's temperature, without installing expensive equipment, is with an OBDII reader.

I simply do not trust the O.E. temperature gauge... a running temperature "just a tick left of center" does not mean anything to me. You might be correct - being on the highway 95% of the time - that an O.E. thermostat is O.K. for you, joelukex4. But for a proper reading during your time running down the highway you need to hook it up to an OBDII reader, or get an OBDII cable for your smartphone and download an OBDII application.

I am well aware that aluminum heads on iron blocks have been common on gasoline and many diesel engines for many years now. What you do not seen to be understanding is - due to the differences in thermal expansion of iron and aluminum - a properly operating cooling system with a well engineered bypass for even warm-up is critical for long term reliability of the cylinder head gasket.

The fact that the aluminum head/iron block arrangement in engine architecture is now common for both diesel and gasoline engines does not change the facts here. You change the cooling system circuits - especially the bypass circuit - from what the engineers designed, you are playing with fire... end of story.

Let's make an assumption here and no one would know this until the failed OEM t-stat is torn down. If the T-stat fails in a partially closed position where coolant is moving through both the bypass circuit and to the radiator than it could conceivably be acceptable to use an inline stant thermostat. This situation would allow the bypass circuit to function until warm up and when the engine gets hot the stant would then open for cooling purposes. Obviously this is not an optimal situation but would function acceptably.

As far as the temp gauge is concerned it may not be a perfect indicator but I can't believe mine is the only on F'ed up. Everyone else that has shown and tested their gauges in that position are running 195F +/- 10F and I would assume mine is doing the same. I currently don't have the equipment to hook an OBDII reader.

papaindigo · **Posted:** Thu Feb 18, 2016 5:39 pm

I suspect geordi is correct regarding the temp gauge being calibrated so that it does not accurately reflect temp changes when the needle is in the near to or at vertical position. I also agree with TDF that the gauge needle positions do not, at least in any linear sense, accurately reflect temps in degrees. That said according to an old post by IIRC mrmopar64 the temp sending unit is reporting a reading in degrees to the ECU and that determines the needle position which is why you can get temp readings in degrees with a OBDII reader.

As to a temp gauge swinging in the wind so to speak during warm up. I can positively state that it can and does happen. I drove a 1989 Dodge D250 Cummins for a number of years and you could "watch" the tstat (all 3 that were installed while I had this vehicle) open/close by the swings of the temp gauge. In summer time it was less noticeable as the system warmed up quickly but in winter the swinging could last for 10-15 miles depending on ambient air temps until things settled down. Obviously what was happening was tstat would open and direct "warm" coolant to the radiator; cold air flow across the radiator cooled that "warm" coolant so tstat closed; repeat until balance between engine induced heat and radiator induced cool is reached

Mike92104 · **Posted:** Thu Feb 18, 2016 5:58 pm

TURBO-DIESEL-FREAK wrote:

Mike92104 wrote:

TURBO-DIESEL-FREAK wrote:

What you need is one of these...

This is simply the best solution for the issue of cold running Liberty CRDs... nothing else available today comes close.

A disclaimer: I own one of these thermostats, and I believe it to be an extremely high quality, well engineered product. I know that TDF spent a LOT of time researching and designing it. With that said, the quoted post above is nothing more than an advertisement for a product he's selling, and as such violates the spirit of the forum.

Does it violate the spirit of the forum when it was the CRD forum members themselves who asked me to do this?

Yes, because it's a spam post advertising a product you are selling commercially. If you had been patient, I'm sure another member would have suggested your thermostat as an option at which point you would be more than welcome to provide additional information. I hope that makes sense.

TURBO-DIESEL-FREAK · **Joined:** Sat Apr 17, 2010 3:29 pm **Posts:** 1167

Mike92104 wrote:

A disclaimer: I own one of these thermostats, and I believe it to be an extremely high quality, well engineered product. I know that TDF spent a LOT of time researching and designing it. With that said, the quoted post above is nothing more than an advertisement for a product he's selling, and as such violates the spirit of the forum.

Does it violate the spirit of the forum when it was the CRD forum members themselves who asked me to do this?[/quote]

Yes, because it's a spam post advertising a product you are selling commercially. If you had been patient, I'm sure another member would have suggested your thermostat as an option at which point you would be more than welcome to provide additional information. I hope that makes sense.[/quote]

O.K.; yes, I can understand what you are saying, I just do not agree with it.

flash7210 · **Posted:** Fri Feb 19, 2016 8:42 am

Quote:

All I know is that the only way to accurately monitor your engine's temperature, without installing expensive equipment, is with an OBDII reader.

The pic above was taken when I pulled into the parking lot at work this morning.
The TorquePro app shows that coolant temp is 185 and the temp gauge is "one tick to left of center."
The app also shows that coolant temp got as high as 197. This was after I had reached the top of a small hill at 65 mph.
The last two miles into work were at 40mph and I had the heat on, so that gave the engine time to cool a bit before I pulled into the parking lot.

joelukex4 · **Joined:** Thu Sep 29, 2011 4:54 pm **Posts:** 386

Thanks for the pics. This shows exactly what I needed to see. With the stant 195F I was always running with the needle just touching the vertical line. Yours is in the middle of that division and running 185F. With the new OEM t-stat on the interstate I am running at roughly the same position as with my stant. The only time it runs cooler is when at idle in cold weather. Then it runs between the first line to the left of center and where yours was in the picture. Remember I also have a winter front & do most driving on the interstate and "I can't drive 65". You would get passed like you were standing still.

I have no problem currently with the OEM t-stat. We'll see how long it lasts as it is my first one.

TURBO-DIESEL-FREAK · **Joined:** Sat Apr 17, 2010 3:29 pm **Posts:** 1167

flash7210 & joelukex4:

The temperatures discussed in your last two postings are "good", but they are not optimal. Modern diesels should be running over 200 degrees Fahrenheit.

I go back to my experience as a Class 1 driver hauling pipe all around Alberta. The Mack tractor I was using routinely ran close to 220 degrees loaded, and around 210 degrees empty.

ajhill · **Posted:** Fri Feb 19, 2016 11:50 pm

I suppose I'll throw my 2 cents into this discussion, first a little background. I've been a heavy diesel mechanic for a little over 20 years and in my experience all diesel engines perform at optimum efficiency (torque, horsepower, mpg etc) at 200 degrees F or just a little warmer. That being said it is just my educated observation based on my experiences. Using the knowledge that I have acquired and applying it to my recently purchased Jeep CRD I have ordered a housing from TDF because in my opinion it will help my engine run the way that I think it should. I've only owned my CRD for a little over a week and have gathered information from this site to educate me on what I need to look for and where to purchase the parts needed to hopefully make my CRD run for a few more years. Timing belt kit, Weeks kit 1 and 2, GDE tune and a few other parts have all been ordered based on recommendations from this site.

I tend to be a voracious reader so going through numerous forums just like this one I always come across one common issue, people seem to forgot that everything we believe we know was completely foreign to us at some point in our lives. We had to acquired that information from our own experiences, other people or maybe even the occasional dive into a forum on the subject. I guess the point I'm trying to make is that I don't think I've ever learned a thing by bashing another persons opinion.

flman · **Posted:** Sat Feb 20, 2016 7:06 pm

Just ordered 2 HDS tstats today. Going to be nice to have a warm jeep in the winter, and the benefit of engine longevity, increased MPG and power.

papaindigo · **Posted:** Sun Feb 21, 2016 12:50 pm

Only comment I'd offer on the install relates to using a new upper radiator hose. Be careful to measure and cut the new hose based on the old hose so that you don't set the bend in the hose so far back as to touch the viscous heater pulley; remember as coolant warms up radiator hose expands and moves a bit so leave good clearance. Don't ask how I know.

flman · **Posted:** Sun Feb 21, 2016 3:14 pm

papaindigo wrote:

Only comment I'd offer on the install relates to using a new upper radiator hose. Be careful to measure and cut the new hose based on the old hose so that you don't set the bend in the hose so far back as to touch the viscous heater pulley; remember as coolant warms up radiator hose expands and moves a bit so leave good clearance. Don't ask how I know.

What is the case if you use an old hose? Thanks for the insight, I will check my installation 2x.

geordi · **Posted:** Sun Feb 21, 2016 3:52 pm

You shouldn't have an issue reusing the old hose for the top - Using the bend as the center, the long side goes to the thermostat, and the short side to the radiator. That should keep the bend far enough from the pulley for clearance.

Thankfully, the coolant chemistries of the last decade or so have improved amazingly and hoses don't degrade like they used to. I haven't had a burst hose in probably 15 years on many many vehicles. Physical damage is about the only thing that has caused replacement of a hose for my vehicles.

papaindigo · **Posted:** Sun Feb 21, 2016 5:01 pm

X2 - in my specific case on point we were replacing stoutdog's tstat (Kap's version so it had the small diameter upper hose) with turbo diesel freak's tstat (Kap's went to a good home) so we had to install a new OEM diameter hose. Fortunately we stopped for a pit stop about half way from Kearney, NE and Scottsbluff and caught the leak from the cut in the hose just as it started. Duct tape was sufficient to save the day; reduced leak under full pressure to like 1 drip every 5 seconds. We did check for clearance on the initial install but did nor realize how much the hose moved under "load". Hindsight is a wonderful thing.

thermorex · **Posted:** Mon Feb 22, 2016 12:50 pm

What the opponents of TDF thermostat don't realize is that they can't compare something they don't have with something they do have. They speculate. They make assumptions. Assumptions are not facts.

Fact is that TDF thermostat is the best there is, period, talking as a user of both oem and hds thermostats. I can provide an opinion because I used both actually,i do not speculate anything.

I never used an in-line thermostat to patch a partially opened thermostat, because I don't like doing a half arsed job. I either do it right, or I just don't do it, because I don't have time to waste. I had thermostat failure, I replaced with new oem. I then bought another new oem thermostat to keep as spare. And then I got hds thermostat which I now have running with a 190F stant (not the 205F? It comes with). So now I have 1 new oem, one used working oem and the hds. Call me crazy, with so many thermostats I could probably run the jeep another 100k...,not counting hds one. Yes, it's expensive, but I one won't cheap out when I need a good part. I got Suncoast tc vs euro bc I LIKE good stuff. I get brand name tires bc I like quality. I got gde tune and no the free one bc it's plain better. Are all those a must? Definitely no, jeep runs well with custom free tune, with cheap tires made in China, with normal torque converter, etc.

But if one chooses quality over price, it's nobody's business to judge, as it's also nobody's business to judge who wants cheap stuff vs quality. You get what you pay for. Even gde got one hds. Hds holds temperature better. It's customizable. Want hotter? Easy fix. Want colder? Easy fix.

Banning vendors from posting in this forum... Why? Because it hurts somebody's "feelings"? Suck it up and move on. Don't like it, don't read it, skip to the next post. Vendors support the forum and are entitled to advertise. This is why as a society we're in this chaos, we try too hard to not offend anybody. Standing your ground and telling it how it is shouldn't be offensive to anybody.

joelukex4 · **Joined:** Thu Sep 29, 2011 4:54 pm **Posts:** 386

Thermorex - why did you change to a 190F t-stat from the 205F that the HDS unit came with when we are being told that we should run over 200F? I can run 195F with the OEM or in-line stant and save the $500 bills. Just asking.

thermorex · **Posted:** Mon Feb 22, 2016 2:40 pm

joelukex4 wrote:

Thermorex - why did you change to a 190F t-stat from the 205F that the HDS unit came with when we are being told that we should run over 200F? I can run 195F with the OEM or in-line stant and save the $500 bills. Just asking.

I did it because I don't like heating the coolant as much for the only reason of having lower pressure in the coolant circuit. And the temperature is more stable with this hds thermostat. This thermostat plus the elevated idling from gde should go hand in hand. For a bit of mpg increase, I one don't care it runs a bit colder. It's a matter of choice obviously and may not even be a good choice after all, but it's what gives me peace of mind. But your question is 100% legit and logic imo because the engine runs leaner and more efficient with a bit over 200F. In my case I also have a big transmission cooler that contributes to lower mpg, as the transmission never runs over 160F, most of the times is around 100-110F. I am more concerned with not heating than running too cool. I do get about 22mpg winter and 25mpg summer, with best of 30+mpg highway summer at 70mph. This mileage is ok for me.

Plus, I like to be different, lol.

thermorex · **Posted:** Mon Feb 22, 2016 2:45 pm

I'd like to add something, as a personal opinion. For many crd owners, investing in a hds thermostat, or a Suncoast, or any other more expensive part than you can normally get, may not be feasible. It's a 10+ year old vehicle, not a true offroad, nothing fancy, and throwing money for something that has more quality than oem may not be worth. But for whoever wants to keep the jeep for more years, and make it more reliable, better, more pleasant to drive, these expenses have value. I plan on keeping the jeep and who knows, maybe attempt in making it a decent offroad toy in the next years.

geordi · **Posted:** Mon Feb 22, 2016 4:39 pm

I disagree that the cooler a transmission is, that it contributes to lower MPG. Modern synthetic fluids are designed to be stable and operate consistently across a wide range of temperatures, none have ever stated there is a problem with operating too cold or below a certain threshold. Too hot on the other hand.... The temps that you say your transmission is running are perfectly acceptable. The transmission in my TDI has an external cooler as well, and runs about 100 degrees over ambient pretty much all the time except in stop-and-go traffic. Heat is primarily generated from an unlocked torque converter, so whenever you are on the highway, the converter shouldn't be slipping and you also aren't changing gears much, so the transmission is effectively straight through. This is why it isn't generating as much heat either, so there isn't as much of a penalty for fluid that might be too cold.

But the normal operating range of transmission fluid is between 130 and 190 anyway. When you start climbing above 200, the lifespan of the fluid drops off precipitously because breakdown happens very quickly. If your fluid climbs past 230, you should consider replacing it very soon. If it hits 250, the fluid is done immediately.

My transmission runs about 160-170 on the highway, cooler when the ambient temps are cooler... It was running about 130 when driving around NJ a few weeks ago. My mileage has been rock-steady at 36mpg per tank for many months, and that is at a highway speed of 83mph! This is on a 2003 VW TDI wagon with the automatic transmission, so this mileage is pretty much spot-on for the higher-end of the range it is capable of.

I'd always prefer the other fluids be too cool rather than too hot. It's easy to make things hot. Keeping them cool is hard.

flman · **Posted:** Mon Feb 22, 2016 5:12 pm

Engine temp and rad temp are not the same any ways, so tranny should be cooler than engine. If the rad was returning outlet temps the same as inlet, you have problems.

papaindigo · **Posted:** Mon Feb 22, 2016 5:39 pm

All this chat about operating temps and the "accuracy" of the OEM temp gauge got me wondering. Per Stant thermostats have a “rated” temperature such as 180F or 195F which is the temperature the thermostat will start to open, give or take 3 degrees and a thermostat is fully open about 15-20 degrees above its rated temperature. So in theory the OEM tstat starts to open at ca. 175F and is fully open at ca. 190-195F but I don't know what that "means" for the actual operating temp of the engine other than it has to be above 175F. Actual operating temp is influenced by engine generated heat and removal of that heat by airflow across the radiator, EGR cooler, and oil cooler with some extra heat passing across the radiator from the AC condenser when the AC is running, etc. Remember the primary purpose of a tstat is to bring the engine coolant up to a minimum operating temp before that coolant goes thru the radiator and a secondary purpose may be to keep coolant temp at or above the fully open temp; it is NOT to control maximum coolant temp (e.g. once a tstat is fully open it has no influence on coolant temp)

So I guess I'm asking those with the gear to read actual coolant temps direct from the ECU in XXXF what actual operating temps are they seeing with the OEM tstat, inline tstat, and turbo diesel freaks housing with either the 195 or 203F thermostat inserts?

On a related note what is the "ideal" operating temp?

HELP! Engine running too cool

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