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View Poll Results: Do you let your car WARM UP before driving?
I don't warm it up, I just hop in and drive. 22 23.16%
I let it run for a moment, then drive. 53 55.79%
I let it warm up to the 40 marker, then drive. 17 17.89%
I let it warm up fully, past the 80 marker. 3 3.16%
Voters: 95. You may not vote on this poll

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  #31  
Old 11-19-2002, 05:43 PM
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It is not a good thing to let the car idle and warm up slowly. It is also not good to fire it up and have a lead foot on a cold engine. Both have bad effects. The optimum procedure is a compromise. Start the car, and start driving it within 30-60 seconds or so, but DO NOT put a heavy load on it (more than half throttle, or half of max RPM, approximately) until the temps are at LEAST on the scale (40C+) and preferably above 80C. Look at the late-model BMW's for an example. When cold, the redline is limited to about 4k, as it warms up, the redline slowly rises until it's at normal (8k or so) at operating temps. Great idea, I think.

The comments about driving with cold, thick oil, and also about turbo cooldown & coking, are largely irrelevant if you use synthetic oil. Mobil-1 15W-50 will pour faster at 20 below zero than any dino oil will at 20 above zero. And it has such a high flash point it would be difficult to coke it on the turbo bearings unless you were really abusive on it, like a 100F ambient day, climbing a mountain at full throttle, high engine temps, then just killing the motor. But for normal driving, with synthetic, you can mostly forget about all that silliness! Plus you get extended drain intervals and less engine wear!




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  #32  
Old 11-19-2002, 07:16 PM
fahrgewehr
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Like most posts I read regarding oil or something engine related that isn't an exact science, I have simply become more confused. I am no mechanic (but have stayed at a Holiday Inn, or something like that...), but I would assume that moderation would be the best way to go...wait a minute before tearin off, but don't wait all morning.
I think all would agree that no one ( with the possible exception of a few professionals..) really knows the answer to this debate.
With that said, I would like to say, threads such as this are very entertaining---I like to wait about 30 seconds before taking off.... I'm sure this will lead to longer engine life.
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  #33  
Old 11-19-2002, 07:18 PM
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fahrgewehr - you're not confused, it sounds like you understand perfectly. Keep doing what you're doing, it's perfect.





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  #34  
Old 11-19-2002, 09:30 PM
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psfred: turbo cool down

Fred:

I've known about the turbo cool down for gas engines for a while now, and yes, it absolutely makes sense. I ALWAYS did this on a Shelby Dodge engine I had and it paid off (too bad the car didn't last as long as the motor). Knowing this, I often wondered why MB never put a water cooled bearing jacket on the turbos in the 123 series, considering the coking problem, and never mentioned cool down in the owners manual (not the one I have, anyway).

People on this site informed me that the diesel turbos generally do not run as hot as the gas jobs because of lower operating revs, and that diesel exhaust is cooler than gas. Therefore, the water jacket wasn't necessary.

I figured MB being what they are, that they would have installed a water line if needed (and even if not, just to be safe). Since MB chose not to, perhaps the coking problem really wasn't all that likely on these engines?

I have to wonder if turbo paranoia is entirely necessary with a 123 diesel after driving, save for an extreme run down the interstate on the hottest day of the year, maybe.


My two cents.

Gil
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  #35  
Old 11-20-2002, 12:57 AM
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Quote:
I figured MB being what they are, that they would have installed a water line if needed (and even if not, just to be safe). Since MB chose not to, perhaps the coking problem really wasn't all that likely on these engines?

I have to wonder if turbo paranoia is entirely necessary with a 123 diesel after driving, save for an extreme run down the interstate on the hottest day of the year, maybe.
Exactly correct, once again. Turbo failures on MB diesels are extremely rare, and usually involve worn oil seals or broken wastegates. But almost NEVER burned up bearings, at least on engines where people change the oil every now and then. The MB turbo & oiling system is well designed and under stressed. Note there is an oil cooler in the system yet it often doesn't even function, as the oil thermostat needs to get quite hot before it opens the circuit. Barring extreme circumstances, like racetrack use, I fully believe coking/cooldown is a non-issue on stock MB turbodiesels...

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  #36  
Old 11-20-2002, 02:26 AM
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I'm with gsxr on this. If you are using synthetic oil, once pressure is up off you go. Keep RPM/load moderate until the temp is pretty much fully up. The key here is the expansion rates of different metals as they heat up. This almost doesn't matter on the 123 iron block and head engines but it can on the later cars with alloy heads. The block/head/pistons/liners/valves etc. all expand at different rates as they heat up and it's not wise to really stress them until they are all fully hot. At the same time, in really cold weather it takes too long to warm up at idle so you are better off driving slowly to speed the process along. This is especially important on gas engines as the increased blowby on startup lets gas vapor in your crankcase which doesn't help the lubricating properties of your oil.

The turbos on our diesel are pretty bulletproof, mostly because they don't get as hot as gas engine turbos. I once owned a Merkur turbo and stopped for gas after a long hard run in the desert. I left the engine running, put the hose in the tank and opened the hood. The turbo was still bright orange! When I first got my 123 turbo I figured it would be that same but it wasn't. I did almost the same run and checked it immediately and there was no color at all. Diesel exhaust just isn't as hot. Cool down doesn't hurt, but it's probably not necessary.
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  #37  
Old 11-20-2002, 04:46 PM
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Open the Garage Door First

Please open the garage door first Jassper else you will have a gloomy look on the walls in no time if you start the engine first.

On my diesels, I always mean to plug in the elec heater but somehow it has yet to happen! On most mornings I start the engine, when it comes to life, I put it in reverse back outa the drive and let it glide down the hill great engine brakes on really cold mornings!!

Then keep it <40 till I see the temp go to 80C after that its open season.

On the cooling of turbo, I have a large veh which is a turbdiesel, and yes I generally slow down well before I have to stop after a freeway run, but in cases where one has to stop suddenly it is a good idea to let the oil circ about and cool the trubo and let the engine coolant temps also come down before you shut down the engine.

Its funny to see all the cars at the restarea taking letting off steam and fluids while the owners are doing the same!!

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