671 Detroit Diesel Question

SPD748 · March 13, 2014, 06:49:48 PM

Hello all,

We're having an issue that even has my Dad stumped. My mill engine (671 Detroit Diesel) appears to be running cold. No matter what the sawing conditions, the engine will not heat up above 130 degrees. Its blowing a little oil into the exhaust manifold which, on the old DD's, occurs on a cold engine. Once things are all warmed up, the oil 'leak' stops. I removed the thermostat and noticed it to be of the 170° variety. I placed said thermostat in an old pot with water and a thermometer. As it should, she started to pop right open at around 170°.

With the above said, that is, the thermostat is working as it should; why is my engine running cold?

-lee

bandmiller2 · March 13, 2014, 07:34:09 PM

Lee , I would say your not loading the engine enough, too much idle time between cuts and even then its not working hard enough. I would put a 180/190 thermostat in and the quick and dirty cover much of the radiator with cardboard. A better solution would be to build an engine house not too big with doors you can open to service and open in the summer for cooling. When its winter leave things closed until it warms up then open just enough to keep it from overheating. Frank C.

POSTON WIDEHEAD · March 13, 2014, 07:36:58 PM

I learned something here. Thanks Frank.

lyle niemi · March 13, 2014, 09:05:11 PM

you might want to install a thermostatic fan hub on your motor??

SPD748 · March 13, 2014, 09:31:12 PM

Frank,

We're thinking about covering a portion of the radiator and see what happens. I'm thinking though, shouldn't the engine warm to ~ thermostat temperature even if it just idles under no load? My tractors, for instance, will warm to operating temperatures while idling. Heavy equipment that I've operated in the past always warmed to thermostat temps without a load.

-lee

hardtailjohn · March 13, 2014, 09:39:37 PM

Go to a 190 thermostat and cover the radiator. That thing is rated about 238hp and you're not using it hard enough. The best way to run a Detroit is as if you were MAD at it! :D I've got a 6-71 on my rock crusher and even with that, it's not working quite hard enough...even if it's 90 degrees outside, and that's a pretty constant load with both jaw and roll crushers as well as the screen and conveyor.... yours just gets to loaf along.
What Frank said about an engine house will help some too, as you can regulate the exhaust of the air through the radiator....plus it'll make it a bit quieter around there!
John

bandmiller2 · March 14, 2014, 07:16:41 AM

Lee, Detroits are different critters and will not usally warm up Ideling or no load. Lyle has a good, but expensive, idea replacing the fan with a thermostatic one. Build a small shack around it and watch her warm up. With the shack you could duct warm air to the sawyers box in cold weather. Frank C.

giant splinter · March 14, 2014, 07:57:19 AM

I agree with the 671 and 453 Detroits not wanting to warm up under light loads, it is important to run them at operating temperatures and Lyle, FrankC are on the right track as well as John with regulating the exhaust. As your Dad would know, it is also not a good policy to leave them running at idle for long periods of time so that they don't load up. The "Screaming Jimmies" are a great choice of power source and last for a lot of years with proper care. I still have one in a 1941 Kaiser 6X6 G.I. water truck that was converted from multi fuel to a new 1978 Detroit and its still alive and well.

lyle niemi · March 14, 2014, 10:01:44 AM

Quote from: bandmiller2 on March 14, 2014, 07:16:41 AM
Lee, Detroits are different critters and will not usally warm up Ideling or no load. Lyle has a good, but expensive, idea replacing the fan with a thermostatic one. Build a small shack around it and watch her warm up. With the shack you could duct warm air to the sawyers box in cold weather. Frank C.

Might not be that expensive if you go to a truck wrecking yard??

crash · March 14, 2014, 07:25:48 PM

I believe Lyle is on to something there. A thermostatic fan would be a good sanitary solution and can be sourced reasonably from a truck salvage yard.

bandmiller2 · March 14, 2014, 08:35:13 PM

Detroit Diesels don't respond well to thermostats and even fans when running lightly loaded or idling. Very little fuel is burned and the air sweeping through on the exhaust/purge tends to cool the cylinder. Four cycle diesels are a lot easier to keep hot. Everything mentioned above will help, but more load would do the most. Frank C.

lyle niemi · March 14, 2014, 11:42:43 PM

Quote from: bandmiller2 on March 14, 2014, 08:35:13 PM
Detroit Diesels don't respond well to thermostats and even fans when running lightly loaded or idling. Very little fuel is burned and the air sweeping through on the exhaust/purge tends to cool the cylinder. Four cycle diesels are a lot easier to keep hot. Everything mentioned above will help, but more load would do the most. Frank C.

Frank

would a smaller radiator help in this situation???

longtime lurker · March 15, 2014, 06:25:45 AM

You got to drive them like you hate them... and that means more load. Covering the radiator, playing with thermostats and fans will all work but won't prevent the bore glazing up. They loveeeeeeee to glaze up and get all smoky and inefficient if they aren't working.

I'd be looking to fit a PTO and run some hydraulics somewhere in the mill, or hang a big alternator off it for electricity, belt drive a big compressor... anything to soak up some more power. You should be able to hear it working when the blade is fully buried in a cut.

bandmiller2 · March 15, 2014, 08:06:04 AM

Lurker brings up a good point compressed air is handy around a mill for various flippers and cleaning logs and blowing sawdust and the load would do mr. Detroit nothing but good. Frank C.

SPD748 · March 16, 2014, 08:22:38 AM

You guys are the best!

Dad and I were reading over your thoughts when it hit him like a ton of bricks... SAW DUST BLOWER!

A bit on the pricey side but it would solve a pile of problems (sorry, I couldn't resist :D).

It looks like a Meadows #2 or #3 would soak up 10-20 hp and be plenty to carry out the dust. I'm aware of the issues associated with blowers however, I think that with my low clearance and limited space the aggravations of a periodically clogged pipe may be worth it.

Dad is coming over today. We're going to do a little figuring...

-lee

lyle niemi · March 16, 2014, 09:54:04 AM

Good deal Lee!!! That just might be what the doctor ordered 8)

hardtailjohn · March 16, 2014, 12:15:29 PM

One thing you could try Lee, that is quick and cheap, is to just pull the fan and saw a log. Put a spacer (washers for a try) back in place of the fan and run it. That'd simulate the fan clutch, and give you an answer pretty quick. I know on my trucks, the fan actually seldom kicks on, even in the summer. As long as you're watching the temp, you could do some proving pretty easily....
John

giant splinter · March 17, 2014, 12:04:50 AM

This has been a fun project from the beginning and nice work all the way through, that "JIMMIE" was fairly ugly in the beginning and your dad did a great job on the rebuild, the pace has been reasonably fast and the project has come together well. some of the custom fabricating was very well done also. I know that many of us have been following you and your dad on this project and enjoying the build as well as the help that has been offered by so many knowledgable members here on the Forestry Forum. Keep up the great work and hope to see you with a mountain of sawdust very soon.

Bert · March 17, 2014, 09:09:14 AM

I have a very similar setup to yours Lee. We run a 671 on a handset frick with friction feed also. Ours is also turning the blower. It stays a pretty consistent 170 degrees on the guage. Not sure exactly on the pulley size but I believe its about 10" on the PTO and 22 or 23" on the mandrel. Some other mill guys around have commented this will suck up a little more power. I wish I had your skill set. I would add a hydraulic carriage drive.

bandmiller2 · March 19, 2014, 07:43:19 AM

Lee, I kinda forget did you and dad put new rings in the 6-71,if so it will take a wile to break in especially with the amount of use you give it. As I mentioned a small enclose around the engine will raise the ambient air temp. and let it warm up quicker. My first mill had an old cat. D318 and an enclosure, would take no time for everything fuel included to get toasty warm me included in the winter. Just have doors you can open in the summer and to service. I wouldn't loose sleep over a little slober,run it like you stole it. Frank C.