Letting the engine idle...

greentdi

Veteran Member
Joined
May 4, 1999
Location
Lexington, MA
TDI
'99.5 Jetta (sold)
I have heard that for traditional diesels, it is better to let the engine idle for a few minutes rather than shut it down and start it up again within a minute or two, as this wastes fuel. Does anyone know if the same is true for the TDI engine?
 

cage

Top Post Dawg
Joined
Mar 25, 1999
Location
lakewood, ohio
I think that is true for any engine these days. The reason I say that is because the catalytic (spelling?)converter should be kept as hot as possible to work. + I think restarting the engine just increases wear on the starter and everything else since the oil drains back down into the pan again.
 
M

mickey

Guest
Yep, you spelled it right! Generally speaking, gasoline engines hate idling, but diesels would love to do nothing but idle. I don't have an opinion, really, since I work 65 miles away from home. Once I start an engine, it tends to run for a while.

-mickey
 

Craig

Veteran Member
Joined
Apr 8, 1999
Location
Kitchener, Ont., Canada
One other thing to consider is oil pressure. When I bought my first VW diesel a co-worker warned me not to let a diesel idle for prolonged periods. He had experience with a farm tractor that was left idling in the field for extended periods. The engine wore out prematurely do to lack of oil pressure. My last VW had an oil pressure guage and at speed the oil presssure was several times that at idle. Even a fast idle was twice the pressure of idle.
 

diesel_freak

Veteran Member
Joined
Apr 7, 1999
Location
Troy, Ohio
I would not worry about it and drive it like a gas engine, except when stopping right after some spirited, high rpm driving. Let the engine idle for a minute or two to allow the turbocharger to slow down back to it's normal speed corresponding to engine idle. If you don't, the turbo bearings will be spinning longer than normal withour oil. Very bad for your wallet in the long run.
 

Tazzman

Veteran Member
Joined
Apr 19, 1999
Location
Great White North ( south of N. Bay )
Ive driven deisels for a long while. trust me
Running the deisel is the best thing. The longer they run better they do.
What hurts them is if your stopping and turning them off, frequently.
A deisel will run for ever if it doesnt have to stop.
And they dont like the cold. Keep them warm in the winters. especialy with a rad blocker of some kind theyll run better.

Tazzman
 

Switca

RIP, Gone But Not Forgotten
Joined
Mar 29, 1999
Location
Flat lands of Delaware
Tazzman:

At what temperature should we think about blocking the radiator? How much should we block?

16vforever:

I'm still on my first crankcase of oil and wait at least 2 minutes before shutting the engine off. Do we have to do this with synthetic oil?

It's not a major problem for me, but my girlfriend does not understand why we (at least me) has to sit in the car for 2 minutes. I tried to explain it to her. Big mistake.
 
M

mickey

Guest
Here's my take on the turbo cool-down question:

The turbocharger actually takes very little time to stop spinning, or at least to slow down to a point where it's not a problem. (Maybe a few seconds or so.) The reason to wait before shutting down the engine has little to do with lubrication, and more to do with the fact that the turbo bearings are cooled by the flow of motor oil. The instant you turn off your engine, the flow of relatively cool motor oil stops. Whether the turbo is spinning or not, the temperatures inside the turbo are extremely high just after a high-speed, full boost run. Synthetic oil is an excellent choice in turbocharged engines because it can handle much higher temperatures without burning and forming nasty carbon deposits, which will ruin your turbo. (And the rest of your engine, too.) I think two full minutes of idling is MUCH longer than necessary! If you come screaming into your driveway at 90 miles per hour with the turbo at full boost, you might want to wait a minute for the turbo to cool down. If, like me, you spend a couple of minutes driving gently through your neighborhood at speeds barely above idle after you've left the main highway, the cooling problem is already solved and you can shut down immediately. Synthetic oil will take care of the rest. Just use a little common sense.

As for blocking the radiator, I wouldn't worry about it if you own a New Beetle. I think the flow of air through the radiator is close to zero until the cooling fan starts up. I'm not sure about Jettas or Golfs; they seem to have a more direct flow of air through the radiator grill.

-mickey
 

Tazzman

Veteran Member
Joined
Apr 19, 1999
Location
Great White North ( south of N. Bay )
I find deisel work anything above 15 c
Once you get below in the single digets constantly is when you should block off the rad intakes.
Most after markets have kits for winter blockers for deisel engines.
especially for the big one's.
You find that even when you block the front of the rad air flow will still make its way through from under. Since the temp is so much colder you dont need the max air flow for cooling.
Hope this helps out.
 

bob kowalchuk

Member
Joined
Mar 11, 1999
I dont agree with blocking off the radiator on any car. As long as your thermostat is working, the engine will get up to the proper running temp, on the highway anyway and you wont risk a meltdown. As far as low temp performance goes, my tdi will confidently start with no block heater at temps down to -40F which we get for about 7 to 10 nights a year here in southern Quebec. I use 0W30 oil and I keep the tank quite full, over three quaters full at all times plus a little shot of gas line antifreeze in the winterized diesel.
 

Peter Cheuk

Gasser :P
Joined
Aug 31, 1998
Location
Daly City, Calif., USA
TDI
'06 Jetta GLI
I had blocked off my radiator during the winter months and experienced slightly quicker warm ups. The motor never gets hotter than normal and seems fine. And we never saw anything less than 30 degrees F. Even in stop and go traffic the car ran fine. I only blocked the upper portion of the grill between the headlights. Down below there's a large opening that allows air to flow in and cool the radiator. I did notice that the fan would be going more often when I got home and parked in my garage, but that happens anyways even when not blocked, though less often.

I'm currently not running a blocked radiator because it's warmer and because, I feel, the added stress on my motor from the Hopa module warrants the extra cooling.
 
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