First TD winter, running cool

[MusicMech]

Hey, so this is the first winter I'll have encountered with my 1994 Golf 1.9TD.  Engine starts and runs great in the cold, and the heater starts cranking out some heat fairly quickly.  However, it never makes it up to what I assume is a normal operating temperature.  The dash gauge used to make it to between 80C and 90C when warmer weather was happening.  Now, even after long periods on the highway or in town, I can't get it to warm up past about 75C.  Is this a sign that the thermostat needs to be replaced, or should I do something for the winter to reduce the efficiency of the radiator? 

[libbydiesel]

It has nothing to do with the radiator unless the thermostat is not working correctly.  Any time the thermostat is less than fully open, the coolant temperature in the radiator is completely irrelevant to the temperature of the coolant in the engine.  You engine may be running colder due to more cold air rushing over it tho. 

[TylerDurden]

My 89 Jetta has the condenser removed and warm-up takes forever; so I block the grille, which allows the fan to still pull air through the radiator if it gets that warm.

[libbydiesel]

You would be better off blanketing the engine instead of the radiator.  Not only will it have a greater effect (unless the issue is a dysfunctional thermostat) without creating the potential for overheating. 

[Hoble]

Diesels are way more effecient compared to a gas motor meaning that less heat is made during the combustion process. Where I live we often see -10 C and sometimes -25. Tdi's can't even make it to full temp down the highways. You often have to block off a good chunk of the radiator with cardboard or what ever. My mk4 daily idleing for a while in 3*c won't stay at full temp, drops from half way to about a third.

So your problem depends on the temps you are in.

[8v-of-fury]

Yes. The coolant does not flow through the radiator unless the thermostat has opened. When the thermostat opens you should notice a susbllbstantial decrease in temperature as all that cold coolant enters the engine, but it will come back up to and hover around the thermostats temperature rating assuming the engine makes enough waste heat to keep that coolant hot.

You will probably notice that in the winter the engine will run a ton colder, this is not because of the rad. It is because of the engine block and aluminum head acting as a very large surface area heat sink. The coolant is not flowing through the rad but is not being heated enough to maintain a hott enough coola t temps with cold air directly blowing on the engine itself.

I found last winter with my 1.6NA and .71 5th gear cruising at 2300rpm was making no heat and i had trpuble keeping ice off my windshiled.

[8v-of-fury]

Diesels are way more effecient compared to a gas motor meaning that less heat is made during the combustion process.

Not that they make less heat.. Its that they waste less heat.

[rodpaslow]

Unless you're really cruising on the highway, using a lot of fuel & boost, you will not have it reach full temperature.  I live in a bit cooler climate than you do in Toronto, with the grill closed off and just putting around Saskatoon, the engine will take forever to heat up.  I can idle it and it and it will actually cool off to about 160° until I start driving it again.  With these IDI's i've found with a good heater core, I have no problems with heat.  I have friends with TDI's that complain about not having enough.

[Hoble]

Diesels are way more effecient compared to a gas motor meaning that less heat is made during the combustion process.

Not that they make less heat.. Its that they waste less heat.

That's what I was trying say, but couldn't find the correct words. That's what came out haha

[R.O.R-2.0]

Diesels are way more effecient compared to a gas motor meaning that less heat is made during the combustion process.

Not that they make less heat.. Its that they waste less heat.

That's what I was trying say, but couldn't find the correct words. That's what came out haha

they are ~15% more efficient..

so, 15% less heat from the heater.. lol.

[JamesT]

75°C is probably the point your thermostat opens, and it's nearly hot enough for normal engine operation. If it runs at that temperature for too long, my worry would be moisture accumulation in the oil, but that would be pretty minimal at air temps much bellow zero.

[lloydbiker]

Well well, welcome to the club!  I am currently running a 2004 24V 5.9 Cummins, and a '97 AAZ Jetta (380Kkm)(also in past owned a 12v Cummins (600Kkm), an '87 1.6 TD Jetta, and an '83 Merc 220D). All are/were difficult to keep warmed up in winter, unless 'working', with the Cummins 24V being the most stable. I would love to be able to get a 'Radiator Blind' setup, similar to that provided on 50s/early 60s Volvo (like a roll-up window blind without the ratchet, manually operated via a pullchain under the dash), to fit the AAZ, but most just look at me like I'm talking a different language. My solution, in the meantime, is to cut a panel of corrugated cardboard to fit over the top of the engine bay, for the winter. Nothing under there gets hot enough to start a fire, and the panel helps to slow heat loss.
With the old Merc (in Prince George BC at -35c) I would hit the top of 'Airport Hill' at full 'Operating Temp' and coast downhill (about 1 mile), only to see my temp drop to 'Cold'.    

[homerj1]

Last winter on the way back to PEI from Montreal I got stuck in a "traffic jam" for 1/2 hr (due to an accident) and watched the engine temp slowly go from hot to cold.

Really demonstrated the thermal efficiency aspect of my AHU TDI.