Hi folks,
Apologies in advance for any redundancy in my posting. I've seen a couple similar threads, but their solutions were a little unclear to me.

I'm replacing a few coolant hoses that were not replaced by the previous owner of my '96 D1. I would imagine that after replacing the hoses and refilling I'll have some air in the system. What is the best way to bleed air out of the 4.0L D1 cooling system? It was fairly straightforward on my D2, as it has a dedicated bleed screw in the top hose, but no such bleed screw exists on the D1. I've heard about the method of angling the front end up an incline and opening the radiator bung... Is that the best way to go about things? Any advice would be really appreciated. Thanks!

That is a good way, but I usually make sure I am simply on level ground, loosen the reservoir cap, run until t-stat opens (hot hose), let it cool down then check level. The level marker (seam) in the reservoir is even with top of the radiator on level ground. Filling at the radiator is a good way to get that last little bit of air out.

I also noticed the D2 forum seems to have a lot more trouble with this than the D1.

I usually run it up on a steep hill with the radiator higher than the motor, fill it at the radiator warm, then let it cool down and check it over the next few days.

- pull the top plug on the radiator and the reservoir fill cap
- add 1 gal slowly (about 1/3 of what will be needed for a complete fill), wait 2-3 minutes
- add another gallon slowly, wait 2-3 minutes
- add coolant until the radiator is full and coolant is near the top plug.
- replace the radiator plug
- top off until you cover the 'X' in the reservoir
- run the engine at 2500 rpm with the cabin heat on full until heat is felt from the vents or 60 seconds (whichever happens first)
- check fluid level. top as needed
- go for a ride around the block
- check fluid level. top as needed

Thanks for the quick responses! It’s all sounding fairly simple. I just wasn’t sure if there were any weird quirks to the D1, but doesn’t sound like there is!

By the way, it really helps me to have an opaque reservoir to see the level from the outside. Used to have a black one, and an old tan genuine. Swapped those out for see-through (All-Makes I think) to check level at a glance whenever the hood is open.

Another tactic some use (me too) is to loosen the reservoir cap and run unpressurized. Good posts for that option in the Forum, lots of plusses, a couple minuses, depending how the truck is used.