I was wandering how long and when I should let my engine cool down?
Ford says to let it idle for 8-11 min. after you pull or run it at high speeds for a extended amount of time. I have been told by a few people to not let it idle at all and some say to let it run all of the time. So what is the correct answer.
Thank You in advance
Russ

 

Russ, I idle My engine for five minutes normally, but when pulling, I usually idle for about ten minutes. I think three minutes would be the shortest amount of time under normal conditions. The opinion of no idle time is all wrong, especially for a turbo charged diesel. One of the reasons for the idle time is to equalize the engine temperature. The other opinion, just let it run all the time, is all wrong.

 

How long I let mine idle is dependant on the EGT's. If I'm coming home from work, pull into my driveway, and see that my temp is 325*, I don't idle at all. I rip the key out, and go inside. If I'm on the freeway and Mrs. Quadzilla wants me to pull off into a rest area, I'll let it idle until the temps get down to 350*, but with my intake and exhaust, that only takes a minute, if that.

Quadzilla
'95 F-350XLT Crew Cab SRW 4X4 PSD, 35X12.50X16.5's, Limited slip 4.10's, Hypermax downpipe, gutted EBPV, "Catless" in Seattle, "Renegade" 4" exhaust system, CTFD sticker, Air bags on all four corners, TYMAR intake, shimmed fpr, Diablo Delta chip, Fumoto valve, Autometer pyrometer, Sonnax valve, Tricumulator springs, Tru-Cool, HX mod, Magnefine tranny filter,
4R100 pan, Red Line synthetic in transfer case and both diffs, reverse shackle kit, big 'ol grin on driver's face.
And a wish list that gets longer every day.
(Thank God for a wife that likes big trucks.)
[link:www.community.webshots.com/user/quadzilla100|Pictures]

 

I don't have the in cab gages. This is what I did to determine how hot my turbo was in certain typical driving circumstances. This summer when the ambient in Alabama was about 95 F. I drove down the freeway 2,000 RPM's, 71 MPH, 20 miles, my usual drive home. I just pulled off the road, left the engine running in Park, got out and opened the hood. Using a hand held laser pointed pyrometer I could determine that the turbo case temperature at the turbo outlet was about 360 F. Probably took me about 60 to 90 seconds to pull off stop take the temp. I am quick for an old guy. The next day same distance, speed, RPM and aprox. ambient temperature. I got off at my exit, waited at the ramp light about 60 seconds then drove slow, not over 1500 RPM to fuel up at a station about a block off the freeway. Checked the temp the same way, 290 F. Later that week, I got off the freeway, drove one mile to my subdivision entrance, at aprox 1500 RPM's, then the last mile at 20 MPH, slow zone to my house. Got out checked the temp same turbo outlet position, 245 F.
Using that as a quide: If I drop off the freeway to fuel up I let it idle while I fuel up, or 3 to 5 minutes if I am going into a store. If I have been just creeping around at low RPMs for the last 10 minutes I shut it down as soon as I get parked and get my belt off about a minute sometimes two.
For those that tow or haul heavy, you need gages for continous monitoring, MO. However, the company I used to work never had a turbo problem on the F-350's or F 450's. The construction guys would run them hard 80+ ,(swapping drivers cross country) pull into the lot, shut it down without any intentional cool down. Gages don't do any good if you ignore them. I have seen them do that after hauling four passengers, a (F-350) Miller Big Blue 400 Amp diesel welder air compressor combination and 500' of cable in the bed, oxygen cylinders piled up to the bed rails and the back end down on the spring stops. Over 200K miles on the trucks, nothing but brake (no surprise) problems. These trucks are tough, that is why I bought one for my personal use.

 

Ditto QUADZILLA, with my intake and downpipe, I haven't had to let it idle more than a minute. I haven't done any prolonged heavy hauling yet with the new set up, so well see if that changes anything.

 

When people are telling you not to let it idle they're not talking about cooling the engine down. You should idle to let the engine coole down, like you mentioned, but avoid idling to warm up or while running. The engine will not warm up anyway if you just let it idle.

 

>The engine will not warm up anyway if you just let it idle.

Ain't that the truth !

 

It will warm up if you weren't part of the 95% that took out that exhaust back pressure valve

 

>I was wandering how long and when I should let my engine
>cool down?
>Ford says to let it idle for 8-11 min. after you pull or
>run it at high speeds for a extended amount of time. I have
>been told by a few people to not let it idle at all and some
>say to let it run all of the time. So what is the correct
>answer.

Russ,
You have received some good replies to your question. I will throw in a little more to confirm what has already been said.

If you have no pyrometer and cannot see how hot the EGTs are allow the engine to run between idle and 1000 RPM with NO load for four or five minutes. This allows the engine and turbo to cool and also permits the turbocharger to spool down (slow down). After four or five minutes, shut down the engine. This is a good general rule to use if you had just pulled off of the freeway and had been working your engine under a load. Stopping a turbocharged engine immediately after high-speed operation without allowing a sufficient cool-down period may cause damage to the turbocharger, as it will continue to turn without an oil supply to the bearings.

Whenever possible, avoid unnecessary idling. During long engine idling periods the engine coolant temperature may fall below the normal operating range. The incomplete combustion of fuel in a cold engine will cause crankcase oil dilution, formation of lacquer or gummy deposits on the valves, pistons, and rings, and rapid accumulation of sludge in the engine. Other bad things happen as well. I hope this has helped somewhat. Good Luck.

 

I use my PSD mainly to pull my trailer x-country. My rule of thumb is that when I pull off in a rest area, I just let it run. I'm usually only there 5 minutes or so.

When I pull off to fuel, I let the engine run while fueling, then pull away from the pumps to park and pay, when I shut down. Maybe 10-15 minutes idle time.

Not very scientific.

 

>It will warm up if you weren't part of the 95% that took out
>that exhaust back pressure valve

Actually I still have my backpressure valve, but my engine won't warm up driving slow or idleing. I have actually watched my temperature gauge go down while driving through town after being on the highway (in winter).