Respectfully disagree, you are correct that a water pump could do it. Given the age, and the feedback that water does flow in and out of block, if I had a single guess it would be plugged radiator. Core/replace, I give it 90% odds of cure.If the thermostat is out, the radiator is not clogged, and the fan has its blades and spins when running (loose belts), it points to a water pump that the impeller may be slipping or have a shear pin that has been sheared or more likely the belt is broken/missing or too loose.
If the system is at least reasonably clean, the fan turns, and the thermostat is out, it is almost surely the water pump impeller or belt preventing the coolant from circulating.
My night to be a disagreeable turd, sorry. Stop leak in little diesels, with small water jackets should be a last ditch effort. And you should be aware you are taking a better than fair chance of making a small problem a big one.Have you considered a leak either in the head gasket, the seals between a cylindar and the block. Try using a sealer. You might have a leak so small it's undetectable in the exhaust. You've also indicated it seems to gert hotter with time, indicating engine expansion is expanding the leak. engine sealant - Google Search
Hey 4570Man, what do you have against taking the Radiator to a shop ? 🏻️
In an effort to be slightly more agreeable Not sure what can or can't be un-soldered cored and sealed back up, that is why I carefully said cored/replaced. All my older/bigger stuff is so over cooled it can probably work with 40-50% plugged radiator and still be fine. The little/newer stuff seems to fight so hard to save a buck and a pound, that everything is on razors edge. That is not a provable fact, just my observation.Interesting about getting the rad recored. Never had either rad out of my M9's, ever. One is a 2002 with 2500 hours on it. The other is a 2004 with 6000 plus hours on it. I run Prestone 50-50 pre mix in both. I'd run straight water with Purple Ice if it didn't get below freezing here but it does, so I don't.
I do keep them clean, they get blown out every day when I come in from the field and at least weekly I use a Radiator Genie with water to clean the rad of any accumulated stuff that might be in there.
Of course I wasn't aware you could recore a radiator with sonic welded on plastic tanks top and bottom but then maybe you can. of you can I sure don't know about it.
Company says: Shell Rotella
- Protection against overheating – Excellent heat transfer properties allow heat to transfer more effectively, protect against freeze and boil-over and help keep engines running cool