I have a 96 D1 with a 4.0 GEMS. I purchased it knowing it was “getting hot” on longer runs with grade increases. It will idle all day and not get hot. PO replaced the fan clutch hoping that was the problem. It wasn’t. By the way, the gauge gives no indication it is getting hot. The only clue is a check engine light. To confirm it is getting too hot I hooked up my code reader and watched the temps. Like clockwork, it gets hot and the check engine light comes on after a few miles on the uphill climb. It cools back off on the way back down.
The radiator has around 150,000 miles on it. I doubt it has ever been replaced or serviced in any way.
I dont know the history of the engine but one head is really clean compared to the rest of the engine. I suspect one head gasket has been replaced or maybe both head gaskets and one head. Aside from getting hot the engine runs strong and surprisingly quiet.
I am about a week away from swapping in another radiator that has 55,000 miles of usage. I will report back when that job is done to see if anything has changed. I will also be replacing the water pump at the same time as it has a very light drip from the weep hole. I will be using a cardone rebuilt pump. I like the rebuilt as it is an OE pump with new seals and bearings. Cardone, in my experiences, have a reliable history. (I purchased it when rock auto ran a clearance on them.)
If I can find an old school radiator shop, I will see if I can get the removed one cleaned out. If not, it is worth about $45 here in scrap metal value. I prefer the original all copper and steel radiators.
Oh, and about the chewed hose. I have seen this from squirrels. (I have purchased a few parts vehicles over the years stored outdoors for long period that became the homes of squirrels. I suspect they are squirrels (maybe chipmunks) as they are very thorough at packing acorns. The last one I purchased they even ate the plug wires.
On a different note, I just replaced the water pump on my D1 with 300tdi. I have no idea how many miles were on the old pump. I purchased a “rebuilt” engine that did not include a new water pump. Puzzling... I purchased it from a UK seller that years ago sold a lot of 200tdi and 300tdi engines. I do not believe he still does. (Turbo was bad, injection pump bad, injectors bad, and the entire assembly was really greasy.) I feel fortunate the engine itself is good.
Three broken bolts later and the new pump is installed. Job took 3 hours half of which was extracting broken bolts.
I should have taken a photo of the backside of the water pump pulley. It was coated in very sticky rubbery tan/yellow substance I have a suspicion was stop leak that eventually failed to stop the leak.