3406 high coolant temps

Anyone ever try a coolant system pressure test yet rank, to see if it hold's pressure? Another very dumb question...have you replaced the radiator cap itself? I bet you have though. That will blow your mind what that does if the cap is junk.

I know what you're going through, it ain't fun.

I just had a bad day with my 3406A PCTA last week coming up out of Alabama in Tremont, Pa. on I-81. I was whistling along just fine, when she started rapping like a bearing was spun. Got it way off to the side and looked things over, blowby was severe and was definitely rapping. Shut her down, and 9 hours later my buddy was there to the rescue with another lowbed and a spare tractor, and we got it home.

I just pulled the motor yesterday and am replacing it with a 400 B, and was able to back the truck into the shop under it's own power and when cold, the rapping isn't even present until it warms up a little. So the 3406A PCTA is for sale now for some enthusiast who might want it for a restoration along with the spare parts motor I have...

But the underlying issue for this debocle I think, was the fact that mine was running hot lately too. Lately if loaded even lightly, that thing would climb to 210, even 220* with the fan running...I flushed the radiator 2 months ago with that solution that Cummins sells, and it seemed to be slightly better. I blew the core out with air and pressure washer until I thought it was clean, but evidently it must have been an internal flow issue because it always ran hot the past 2 months.I think that attributed to the final demise last week.

The mysterious thing was that it never used one lousy drop of coolant, never even pushed a drop out the overflow the whole time. Heck, I drained the radiator Friday to pull it and it was chuck full still, after the piston issue even.

My son donated the yellow 3406B to the cause out of his 1982 Freightliner FLC until I find another motor to replace that one for him, and we pulled both of them out Friday and Saturday. He just has the truck around to look at...not running it because he's actually a LOT smarter than dad is.

I got the radiator being recored, and next is I have to dress that B model engine out with the stuff off of the A, like the a/c bracketry, fan clutch, brand new turbo that's coming off the A and onto the B, and a new clutch. Not something I needed right at the moment. But when is it ever a GOOD time?

I can't complain one bit though. I bought this truck last February, took it apart, changed a bunch of stuff to make it what I wanted, put a water pump and thermostat on it before I put it to work, and just sent it. Had to do some work to it after I dyno'd it at 303 HP (was a 375 HP factory rated,) and it woke it up a bit, but those A model's just aren't built to give you the best torque nor fuel economy in the long run. Been good to me thus far for a 40 year old truck with a LOT of money into it, LOL.

 

Restriction in the block isn't something to rule out either. My buddy (a Cat authorized shop,) found a couple doing what yours is doing with casting sand plugging the coolant channels with the sand they use to cast the block with.

 

Man, I hope you come back with a report tomorrow that you put a $14.00 radiator cap on it and it's running 180* pulling Cobleskill Hill on 88 now.

 

7 psi on the cap. As said have for sure seen a cap make a big difference

 

You might want to pull the front elbow off the oil cooler and check for debris plugging the tubes, all coolant must pass through the oil cooler to get to the block.

 

Every pound of pressure in the cooling system raises the bowling point 3 degrees F. If the liquid every boils cooling is a lost cause.

 

I'm with DDS .

I bet your oil cooler is plugged up on the coolant side. This would cause very low flow .

 

I'm leaning towards the oil cooler more so than anything else too. But in these situations, it's best to start with the cheap stuff first and work your way up to the spendy stuff...and a little luck helps too.