RPegram

My company just purchased a 2001 2500 4X4 6 speed manual extended cab long bed truck with 237,000 miles. We purchased knowing it needed a clutch, but found out the trans was bad due to a failed pilot bearing. When the clutch and transmission were replaced I removed the adapter plate and replaced the rear crank seal. I did not notice any signs of a water leak then. The freeze plugs on the outside looked like new. While everything was apart I put the left motor mount bolt back in its slot (previous mechanic must have loosened it for some reason) and had the starter rebuilt. I saw no signs of leaks new or old while doing all this. I spent a lot of time under this truck while waiting on the rebuilt trans to arrive. After driving truck for a couple of days I noticed a couple of drops of coolant on the bottom of the adapter plate between the trans and engine block. I have never seen more than a couple of drops and have only once seen a drop on the pavement below the truck. The radiator stays full, but in a thousand miles of driving I did have to add a little to the overflow tank. The block casting number is "55". I have no prior maintenance records from the prior owner now do I have any way of contacting him. The truck runs and drives great. It has a pac brake exhaust brake, pac brake 4wd lockout, fuel-boost-exhaust temp pillar gauges. Aftermarket lift pump mounted under bed (maintains 12-13 psi WOT). I have found no other modifications to the truck. It appears previous owner used it to pull a fifth wheel camper. I also replaced the stock pilot bearing with a sealed unit ordered offline. Had to have the flywheel machined for new bearing, but well worth the cost!

I was wondering if anyone else had ever experienced this and what they did to remedy the problem.

high bid

On the current 53block thread it's mentioned taking a measurement of the block inside a freeze plug to determine the thickness. This is relevant for those w/the 53 block. Would it be possible that it is a thin walled block even w/the 55#?
OR
Did the prev owner not have enough coolant and it popped a freeze plug?
Possibly the headgasket? If they towed and strained the motor w/out letting it fully warm up could it blow the gasket?
Check the oil for coolant
Just some ideas. Hope it's an easy fix.

RPegram

I changed the oil when I installed the new clutch and transmission and since then the oil has remained fairly clean looking (turned a little darker), but definitely not milky in any way. The leak is so small I cannot trace a path from where it is coming from. I have run a pressure test on the radiator and it might drop a pound a minute. When under pressure it is still just a drop hanging off the adapter plate, but not dripping. After temperature comes up, if the radiator cap is slightly loosened, it still has pressure. When everything was exposed I saw no signs of improperly installed/moved freeze plugs. Everything looked extremely clean and the thought even crossed my mind that this was a fairly new engine. Areas normally not cleaned when a vehicle was sold, were actually clean (under intake, behind head, etc.) The only oil on engine is around the crankcase breather bottle around the front of the vacuum pump. When at freezing temperatures, the engine will fire before it makes a complete turn with the starter. There is no miss or even a weak sounding cylinder while running. The only smoke I have seen is when it first cranks, there is a little puff of black.

Does anyone know if the "55" casting was used in 2001? This truck has rear drum brakes so I figure it is an early 2001.

Thanks for any and all input.

1-2-3

I beleive there's a small freeze plug on the back of the head. I'd get a mirror and look at it as step 1.

D2 Cat

Had a tractor with a small leak, like yours, and with the cab and loader it was real difficult to see much. Added a bottle of red food coloring to the radiator and it made it much easier to find.