With no turbo timer and no gauges how long should you let your truck idle before shutting it down? And, should it be done every single time?

David

 

I believe it should be done all the time. Outside air temp will play into how long you need. The colder the air, the faster the cool down. Now, with temps in the 60s, it takes about 30-45 seconds to see the egts drop below 400. On days when it is 85+, It may take as long as 1.5 minutes to get that low. Many like to see temps aroung 300 before shutdown, but I may get flogged, but I don't have that much time.

 

If you are just idling around than you only need to give it a minute or less it wont be very hot. If you are pulling a heavy load and get to the top of a hill and want to shut it down may be good to give it a couple of minutes.. The 4" turbo back you have will help out alot.. Best way would be to add a guage if you are concerned. Hope this helps out

 

IMHO, only when you have *REALLY* worked the turbo does it need to be cooled down. Like, you wouldn't want to to be pulling 15k for three hours, pull off the highway, and immediately shut the truck off. For 99% of daily driving, I don't see a need to a turbo cool down. Some folks like to see the EGTs get below some level (like 300 or 350) before killing it. If you pull heavy, let it idle for a few minutes before killing it -- 5 or 10 should be more than enough even after pulling the heaviest of loads. If it makes you feel better, a minute or so normally brings my EGTs below 300 (no load), but that's probably way over and above what's needed (and I don't do that all the time).

 

ive been told it depends on how long/hard its been running. i wouldn't say "everytime i gotta let it idle for 10 min. before shut down" that just would waste fuel or apparently Gold whichever term you like. i usually wait about 25 sec after i put in park.. but thats just me if i come home from a good run i'll wait a min or two.

 

I been thinking about getting one of those turbo savers but they are kinda pricey so I'm still just waiting for it to cool down before I shut it off.

 

On a related topic- where/when is the trade off between "idle down" and "wet stacking?" I did some research a few years back before I bought my 95 (when I was also considering a PSD but couldn't afford one) and there was a lot of talk about idle down vs. wet stacking at that time. I've recently read somewhere that our trucks won't wet stack... anyone have an educated opinion on this topic?

 

I'm pretty sure with the new computer controlled engines that's been eliminated. Maybe someone else will chime in....

 

The way I understand wet stacking is this: Deposits of unburned diesel fuel are passed into the turbo and accumulate. As I understand it it occurs most commonly when the glow plugs are not allowed to get to the proper temperature to before starting the truck or excessive idling. Now, I'm no Tech so I'll stand corrected if I'm wrong. Maybe this won't occur with the computer controlled engines. I don't know.

As far as cool down times I wonder to be safe and not shut down with too high EGT's and at the same time not to burn excess fuel without need and to prevent wet stacking if a turbo monitor would be better than a turbo timer. I have always made sure that after long trips at interstate speeds or when towing I would let the truck run 3-5 minutes before shutting it down. I guess for me the unknown with not having pyrometer was whether I needed to do this with just everyday driving around town?

David

 

From what I read and recall, wet stacking is actually unburnt fuel piling up on top of the piston, which is caused by excess idling while the engine temps are lower. There is supposed to be a balance between "idle down" (letting the turbo/EGT drop to a safe temp) and wet stacking. Not arguing with anyone or saying they are wrong, but this is what I remember and I think it will make a good discussion.

 

I didnt think that our trucks "Wet stacked" maybe Im wrong. Also thought high idle helped stop it.

 

As far as I know the computers have eliminated the wet stacking . High idle did help stop it , what wet stacking is ,Excessive unburnt fuel in the cylinders the fuel washes down the cylinder walls removing the oil causing excessive wear to the rings and cylinder walls as well as contaminating the oil.

 

I don't believe wet stacking will occur on these modern engines. The high idle will kick in and raise the rpms to heat the cylinders. If you cranked it on a cold morning and let it warm up for a half an hour you MIGHT start having a problem, but the high idle kicks the rpms up to heat the cylinders to prevent this. On letting it cool down, it can't hurt and I do it. It usually will take less than a minute to lower the EGT to below 350*. If you have the AC on it will take a little longer. If you have just pulled off the expressway, pulling the travel trailer, with the AC on, 90* air temps, It has never taken over 4 - 5 minutes for it to cool down to below 350*. Turn the AC off and it takes about 3 minutes or less.
Joe

 

You may be exactly right. As I mentioned I am certainly not a Diesel Tech. I am only repeating what I read once before. You won't get any argument out of me either cause I don't know enough to argue

Hopefully someone will come along with some knowledge and help us out. (Well seems like they did. They posted the above info while I was typing mine)

David

 

Cooldown: The purpose of a turbo timer or turbo monitor is to prevent coking issues when shutting down the engine while the turbo is still extremely hot. With the oil that many of us use today, coking is very rare. Many of the heavy duty oils, and especially synthetics, are much more resistant to coking at higher temperatures than we used to see. The old 300 degree rule of thumb is actually no longer needed. There are some who will disagree with me, and state that you should never shut down the engine until the turbo cools to 300 degrees (or 350). That's fine, and if you do that, there's really no harm. However, there's also no harm in shutting the engine off at say 400 degrees. Your turbo will last just as long. Very few PSD owners actually monitor their turbo temps and regularly shut the engine off at a lower temp. Very very few of them. A vast majority don't care or don't know, and shut their trucks off at any temp. If coking was a big issue, we would see it on a regular basis. We don't.

Wetstacking: Yes that's another event that you don't see. As was stated previously, high idle mode, and even the EBPV, all play a part to keep this from happening. Extended idling is useless anyway, and wastes fuel. With the price of diesel where it is at, I don't think anyone is up for extended idling anyway. There are guys in Alaska who idle their trucks for long periods of time due to the extreme cold weather, but we still don't hear about wetstacking issues with them.