Cool Down

[tlarkin530]

Just bought a '67 Kaiser M35A2. Has the Hercules LDT 465 4D. My buddy said that every time I go to turn the engine off I should wait five minutes at idle to let the turbo cool down, otherwise I'll cause "serious damage." I've heard this before, but also know that on newer diesels it's irrelevant.

What do you all do? Had any problems just shutting it off? How long do you sit at idle?

Thanks!

 

[Flyingvan911]

You should let it idle and warm up for atleast 5 min and let it cool down for 5 min before shut down to let the turbo warm-up and cool down. And to let the rpm's come down after driving. If I'm driving slow and easy around the neighborhood, I'll let it cool down for a few minutes. If I'm on the highway or using lots of power in town, I definitely let it cool down 5 min.

 

[plym49]

Our turbos run on plain bushings, not ball bearings, so I am sure that the extended idle before shut-off will help cool the turbo if it just have been run hard. Once the motor is shut down, the turbo is still spinning and no more oil is coming in. If the turbo is that many degrees cooler, compared to when it was higher rpm and motor under higher load, equating to higher temps - then the bearing clearance is going to be a little fatter and that has got to help once the oil flow stops. Also it will be spinning at a lower rpm, so it will come to ao stop more quickly.

Me, I give it the five minutes as often as possible. However, if I am driving at idle speed (with no additional throttle opening) at all in the period immediately before shut down, I count this time as part of the five minutes.

 

[jeffhuey1n]

All three of mine get the 5 minute cool down. I can't say i read it in the book, it's a big book. it was suggested sometime in the past after i joined SS and have followed the procedure every since. Hasn't hurt anything and I'll keep doing it till evidence to the contrary shows it's not needed.

BTW, welcome to the madhouse where OD green rules!

 

[gunboy1656]

Mine always gets the 5 minute warm up and 5 minute cool down...sometimes longer if I am taking stuff out of the back after a show.

Oh and even if it is not in the book, there is still (or should be ) a data plate in the cab warning you to do this.

 

[kc4wd]

5 min 5min

 

[wikallen]

Section 2-17 of your operators TM will even tell you to let it idle for 5 minutes before turning off the engine.

All my turbo vehicles, new and old get a cool down before shutting off, as they should be.

 

[mightymanx]

There is not a production vehicle ballbearing turbo I know of and letting the oil cool it applies to ball bearing turbo's as well

the turbo gets hot as heck the moving parts are cooled by the oil that runs throught the center cartaridge where the bushing(s) is

you shut off the truck while after giving the turbo a workout and the oil stops flowing the heatsoak from the hot (exhaust) side starts to heat the heck out of the cartridge and the residual oil in there will burn. ( just like burning oil in a frying pan). That cakes up on the shaft and surfaces and can gall the shaft and bushing(s) this can also cause the ceramic and or ball bearings to sieze due to being gummed up from sticky burt on oil.

Will this happen instantly No will it accelerate your turbo wear Yes!!!

The modern vehicle does not need that BS that is in the owners manual is exactly that BS It is thought that the new synthetic oils are impervious to this but I can tell you I have taken apart enough late model turbos to know that is a load of baloney.


Now for a deuce with a 1950's junk turbo it will probably last longer than the newer ones being abused because it is sized improperly so it spins much slower and has very sloppy tolerances so it can eat more crud.


Either way I let it idle for a few minutes If I have been under 1000 rpm parking and pulling in I count that as idle time.

It is also good practice for a non turbo engine as well to pull some heat out of the heads.

 

[gimpyrobb]

If you have a pyro, you'll know when its "cool" to turn off your truck, otherwise, 5min is good.

 

[Clay James]

I always idle down for 5 min. For warm up I don't do 5 minutes, usually roll out once the air pressure is full, but it takes me a few minutes to get down the driveway and through the gate so that gives it the rest of the time since it's low RPMs and idling.

 

[nk14zp]

R.t.f.m.

 

[rlwm211]

Having done a test series with both pre and post turbo pyrometers, you would be amazed at how much heat remains in the turbo even after youi have stopped working the engine.

The manifold/turbo assembly can reach upwards of 1200 degrees perhaps 1300 when you are working the engine hard. 1300 is considered the upper limits of EGTs.

The turbo and manifold store a lot of heat and the best way to cool them is to allow engine exhaust gasses to do this as it is a gradual and even reduction of the temperatures.

I remember the first time I pulled a long hill with the two pyrometers and let off at the top and coasted down the other side and saw the pre-turbo temps in the 400-500 degrees and the post still up over 1000.

Letting your truck idle after working it is just good driver practice.

 

[mudguppy]

i don't wait 5 minutes; i have an EGT gauge. by the time i'm back thru the neighborhood, at my house, and idling into park position, the EGTs are down to almost 300°; that's about as cool as it will get. if it isn't there yet, i may wait until it is but it doesn't take more than another minute at that point. i take that time to walk around the vehicle and see what (else) has started leaking.

just be smart about it - if you just come off of the interstate to get some fuel and was at full power a minute ago, then you should give it some time to cool off.

and, yes, it does apply to newer vehicles as well.

 

[Chevyman_15237]

Its cheaper to idle/warm up for 5 minutes and idle/cool for 5 minutes rather than replace a turbo or other parts. I usually do a good walk around inspection before and after driving anyhow... that's how I roll

 

[Srjeeper]

Read this..

http://www.turbosafeplus.com/news_clips.html

 

[Ridgerunner]

Most Deuces have a plaque right on the dash that state to warm up 5-min, and cool down 5-min. They put that on there for a reason.

 

[randini]

I alway try for 5 min, pre and post driving. Honestly if the engine is cooler and the outside temp is cooler, and I have not had my foot in the gas..i let it idle and call it good....BUT IF it summer, the engine is 190+ and I just got off the freeway, with 3 tons in the bed, I would wait over 5 min.. Use your head. you'll be fine...

 

[dmetalmiki]

Cool Downs

That's the bennifit of a "pre-lube" Pump. As I shut down my engines After a 3 minute cool down I allways switch on the the Pre-Lubes. and wait a further Minute with the the Engine oil at around 20-30 P.S.I. Engine Stationary. Comforting feeling that! pressure before starting & After Stopping Engines.