Cold Weather Engine Runs Cold

Boss · **Posted:** Sat Dec 03, 2011 10:01 am

Good Morning
We finally got a snow here in northern New Mexico; wimpy little snow, but snow just the same, we'll take it, and like it. Anyway, it's only 19º and my CRD runs cold; gauge reads ~1/4; heater isn't very warm either. I know it sounds like the thermostat is funky.

I did replace the viscous fan clutch when I replaced the timing belt a couple weeks ago. I guess that was a case of wishful thinking on my part. I mainly did the fan clutch because it was overheating in the Summer witrh the air conditioner on. :lol:

We're still recovering from the price tag for the parts from the timing belt job. Having a brand new water pump sitting in my shop just in case we needed it is also a stretch on our budget. Although with my luck the minute I send it back the pump on our Jeep would spring a leak, so that has to stay where it is. :evil:

The point is we can't spend anything else on the Jeep right now. Should I try blocking the radiator with card board?
Brian Rodgers

racertracer · **Posted:** Sat Dec 03, 2011 10:36 am

If the temperature gauge on the dash reaches near the half way mark, then your thermostat is OK.

You may need a cooling system flush to get the old sludgy coolant out.

viewtopic.php?f=5&t=63883

papaindigo · **Posted:** Sat Dec 03, 2011 10:48 am

But Boss says his temp gauge sits at about 1/4 so while a flush might help circulation in the long run sounds like a new tstat is in order. Boss if you don't want to spring for the OEM tstat right now (about $125 mail order for tstat/gasket/shipping) then you can go for the cheap solution discussed at viewtopic.php?f=5&t=63587&p=705903&hilit=stant#p705903 which seems to cost ca. $10-15 for Stant tstat and an extra worm clamp if you don't have a spare worm clamp.

Boss · **Posted:** Sat Dec 03, 2011 10:53 am

thank you I'll start reading about the alt tstat

Joe Romas · **Posted:** Mon Dec 05, 2011 8:57 am

Have you owned this vehicle through a previous winter??
If not please understand this,
Diesel engines produce less waste heat and that waste heat is what heats the cabin and in our case not so well :JEEPIN:

This should be in the noob guide.
You can let them idel all day and they'll neve warm up in the winter.
Even when everything is perfect you can watch the temperature guage drop while stopped in traffic during the winter. I have owned around 20 diesels vehicles for over 30 some years and they have all been the same :furious:

The first was a new 1978 Rabbit. When you bought a VW Rabbit Diesel you also got a heavy duty heater that I recall cost $154 more and the heater was still cool and those were less effecient indirect injected engines :cry:

You can try cardboard but it never did much good for me.
If your engine remained within 1 tick left of center during the summer months it's as good as it getts :ALONE:

Also any tune offering better MPG's makes them even more effecient and therefore even less waste heat to warm your feet

Boss · **Posted:** Mon Dec 05, 2011 9:40 am

Thanks Joe for telling me like it is, I think :oops:

Yes this is the first Winter for me and the Jeep
Last Winter I had a Isuzu Trooper TD. It got warm, so I don't know
Also have a 82 VW Rabbit NA diesel, coincidentally was a VDub mechanic back in 82, it is sitting outside the shop in the beautiful snow waiting for me to finish the cylinder head replacement job while life keeps throwing curve balls. :shock:

Gorgeous 82 Peugeot 505s turbo-diesel sitting in the driveway also waiting for life to give me a break. :cry:

Wife's 81 Mercedes Benz 300CD in the driveway waiting for her to recuperate from major foot surgery on Friday

And my truck, a dually 92 Dodge D35 6BT Cummins, which I don't drive in the snow cause it don't go in the snow. It has a dump bed that if I get two seconds to rub together I'll finish the PTO and hydraulics, anyway it gets nice and warm. :-)r

I know you didn't ask for my life story, but this has been one very rough year, I'm desperate for something to go easy and cheap
Brian

Joe Romas · **Posted:** Mon Dec 05, 2011 10:27 am

Brian.

Build a bigger shop and bring them all in out of the snow :ROTFL:

Joe

irwinr · **Joined:** Mon Dec 05, 2011 7:34 pm **Posts:** 11

Joe Romas wrote:

Diesel engines produce less waste heat and that waste heat is what heats the cabin and in our case not so well :JEEPIN:

This should be in the noob guide.

This is irrelevant. Less waste heat means longer time to warm up, but if the thermostat is shutting properly then it will eventually warm up properly. The EGT of any diesel at idle is roughly 300 degrees F, plenty hot enough to raise the coolant to 190 degrees with a properly working thermostat.

This is exactly why you *have* a thermostat. The job of the thermostat is to cut off the flow of coolant to the radiator when the coolant is less than 180-200 degrees F. Therefore if your thermostat is working properly when the engine is less than that temperature no coolant will flow to the radiator and thus cooling of the engine occurs which means the engines temperature will continue to rise until the coolant reaches the designated temperature and the thermostat opens.

It's a common problem for thermostats to wear out and stick 'open'. They are actually designed to fail in this way rather than sticking shut which could be catastrophic to an engine.

Joe Romas wrote:

You can let them idel all day and they'll neve warm up in the winter.
Even when everything is perfect you can watch the temperature guage drop while stopped in traffic during the winter. I have owned around 20 diesels vehicles for over 30 some years and they have all been the same :furious:

The first was a new 1978 Rabbit. When you bought a VW Rabbit Diesel you also got a heavy duty heater that I recall cost $154 more and the heater was still cool and those were less effecient indirect injected engines :cry:

You can try cardboard but it never did much good for me.
If your engine remained within 1 tick left of center during the summer months it's as good as it getts :ALONE:

Also any tune offering better MPG's makes them even more effecient and therefore even less waste heat to warm your feet

I've owned/operated dozens of diesels too, and not one of them ever had a problem not reaching the designated 190 degrees. Common sense tells you this can't be true, if the exhaust is over 300 degrees (possibly over 1000 degrees under load), and if the thermostat is shut and no coolant is flowing through the radiator (so the heat has no place to escape) then obviously the temperature of the engine is going to continue to rise until the thermostats opens and allows the engine to cool.

-Jeremy

Joe Romas · **Posted:** Tue Dec 06, 2011 8:41 am

Jeremy

If everything you say is true then why are there viscus heaters installed on CRD's?
And how about the extra 3 glow plugs on VW TDI's?
And you must not have read where I asked him if his crd got to normal operating temperature in the warm summer months. If his thermostat were failing it would not have gotten to operating temperature even in the summer.

It's been the same every winter here, complaint's about cabin heat :BANANA:

dirtmover · **Posted:** Tue Dec 06, 2011 9:04 am

irwinr wrote:

The EGT of any diesel at idle is roughly 300 degrees F, plenty hot enough to raise the coolant to 190 degrees with a properly working thermostat.

I beg to differ. Temperature and energy are not the same thing. The temperature of the average static spark is a few thousand degrees but I defy you to heat your coolant with static sparks. There is no way our engine can heat the coolant to operating temperature at idle when the ambient temperature is much below freezing. At -30C the temperature gauge will drop from 1/2 to between 1/4 & 3/8 in about 30 seconds of idling. Of course, while driving, there is no issue holding the correct temperature.

papaindigo · **Posted:** Tue Dec 06, 2011 10:06 am

For what it's worth:
1. the sole or primary purpose of the viscous heater is to get heat to the cabin quicker on a cold engine which is why the output from the viscous heater goes directly to the heater core. I know the viscous heater stops functioning above a certain temperature but am not sure what that temp is (Note - the GDE tune lowers the cutoff point). Other companies have taken different approaches to providing early heat to the cab for diesel powered vehicles.
2. I won't say a diesel will never reach operating temp from a cold start by just idling but I will say that the ones I've owned won't do so in any reasonable period of time compared to actually driving.
3. a failing as opposed to failed OEM tstat makes a difference. I drove with a failing tstat for over a year. With ambient temps of 75 F or above especially with AC the temp gauge would reach normal operating position. With ambient temps of 50 F or below the temp gauge would not go above 2 full ticks left of center. New OEM tstat holds the gauge at normal operating position under all conditions.

I'll let others debate EGT vs coolant temp but the bottom line is if the tstat is functioning properly then coolant temp should reach normal levels.

Boss · **Posted:** Tue Dec 06, 2011 1:11 pm

some good info, some silly, I ignored the arrogant sounding stuff, like I said, this has been a rough year for me, starting with my Isuzu diesel throwing a dampener and a head gasket, dad dieing, then my dog, my mom. I'm just explaining why I'm short on patience.

not doing a lot of :ROTFL:

lately sorry
right so the thermostat is bad, I can live with it for a little while longer
Brian

papaindigo · **Posted:** Tue Dec 06, 2011 1:49 pm

Understood best wishes and hope things improve. As for the tstat the $11 fix seems to be the Stant tstat in hose mode probably with a 3/32" or 1/8" hole drilled in the tstat skirt to move a bit of coolant while the engine warms up, see viewtopic.php?f=5&t=63587&start=40

Boss · **Posted:** Tue Dec 06, 2011 7:50 pm

thanks everyone

irwinr · **Joined:** Mon Dec 05, 2011 7:34 pm **Posts:** 11

Joe Romas wrote:

If everything you say is true then why are there viscus heaters installed on CRD's?

Like I said, lower waste heat means it takes *longer* to heat up. The viscous heater helps warm the cabin until the engine does warm up.

Joe Romas wrote:

And how about the extra 3 glow plugs on VW TDI's?

Seriously? Glow plugs are to assist with starting the engine. They shut off very soon after it starts running.

Joe Romas wrote:

And you must not have read where I asked him if his crd got to normal operating temperature in the warm summer months. If his thermostat were failing it would not have gotten to operating temperature even in the summer.

Somewhat true, but it's not as obvious. When the ambient temp is 90+ degrees, the amount of heat lost through the radiator is much less than when the ambient temp is 0 degrees. Plus in the summer with the A/C on the A/C condenser heats up that air before it enters the radiator. Thus the coolant temperature gauge will read much lower in the winter which makes the bad thermostat much more obvious to the driver in winter months.

Joe Romas wrote:

It's been the same every winter here, complaint's about cabin heat :BANANA:

Sounds like this is a common problem for the CRD and some on this very forum are suggesting the thermostat should be replaced every 50k miles. So it's not "normal", it's just something that has to be replaced every so often. It shouldn't be ignored because operating under the 180-200 degree window that is considered optimal for internal combustion results in lower fuel mileage.

In fact it looks like one of the forum members has started a little business modifying thermostats so they can be replaced with $15 generic thermostats instead of paying the $150 for a jeep one. Obviously these things failing is common in CRDs.

dirtmover wrote:

Temperature and energy are not the same thing.

Definition of temperature from wikipedia: Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot. Heat spontaneously flows from bodies of a higher temperature to bodies of lower temperature. No net heat will be exchanged between bodies of the same temperature; such bodies are said to be in "thermal equilibrium".

The important part of that: "Heat spontaneously flows from bodies of a higher temperature to bodies of lower temperature."

This is a basic principle of science that most of us learn in high school...

Engines heat up because of the heat generated during combustion. In this case the 'body of higher temperature' are the exhaust gases, which even at idle are 300 degrees as they leave the engine. That's after they've already lost some of their heat to the metal components inside the engine... The body of lower temperature is the coolant which is supposed to be kept around 190 degrees by the thermostat. Most of the waste heat of combustion goes out with the exhaust, but as the cylinder walls are exposed to those hot exhaust gases constantly, they will continue to raise in temperature until the temperature of the cylinder walls match that of the combustion gases inside. Now I mention 300 degree EGTs because that's what's *left* after combustion is finished, but at the peak of combustion the temperatures are much greater inside the cylinder, easily exceeding 2000 degrees at top dead center even at idle. So this notion that a diesel can't heat it's coolant to 190 degrees is *only* true if the coolant is being cooled somehow... such as by running through the radiator, which should not be possible while the coolant temp is less than 190 degrees with a properly functioning thermostat.

Let's see how confident you are about this. Go drain your engines coolant and then start it up and let it idle and see how long it takes for it to overheat. It may take a couple hours but it will continue to heat up until the engines safety measures kick in and shut it down.

dirtmover wrote:

At -30C the temperature gauge will drop from 1/2 to between 1/4 & 3/8 in about 30 seconds of idling. Of course, while driving, there is no issue holding the correct temperature.

No Diesel vehicle I have ever owned or operated has exhibited this problem, or at least, if it did it no longer did after replacing the thermostat.

Joe Romas · **Posted:** Thu Dec 08, 2011 8:21 am

irtroll
I suggest you take a good look at the water outlet mounted on the head of a VW tdi :dizzy:

You'll see 3 glow plugs.
Check this link :roll:

http://www.metalmanparts.com/product.sc ... egoryId=38

Mine does not yet have 50K miles and the thermostat showed signs of failing at about 35k.

Cold Weather Engine Runs Cold

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