Coolant age and type is unknown on this truck so I decided to follow the workshop manual versus the simpler “drain from lower radiator hose” method favored on the forums. Be warned….this is a messy job.
Have a lot of drain pans ready because when you remove the engine block drain plugs, coolant sprays everywhere.
The plugs are a little hard to find. Here is the left plug.
And here is the right. This one is inside the engine mount so access was tight
The plugs are 3/8″ square so connecting backwards to a 3/8″ drive socket worked well. Here is the combination of extensions I used on the left plug. There is a lot of coolant that comes out, and your plug will likely get shot across the garage….it wasn’t fun looking for it.
The right plug is really hard to get to, so I finally came up with using a low profile ratchet designed to have sockets mount inside a 7/16’s head. Again used a 7/16″, 3/8″ drive socket backwards and that worked really well.
This tool makes quick work of all the Disco coolant hose clamps.
Removed the radiator bottom hose and let drain.
Removed the hose going into the top of the thermostat housing….
….and bent it down as low as possible to let it drain. Used the garden hose to flush low pressure water through until it came out clear.
The manual calls for Loctite 577 which was not available at any of my local parts stores. I had some Permatex high temp sealant that I used instead. Comparing the tech sheets, 577 is a superior product, so I might order some up for next time I do this. No chance of getting a torque wrench in there, so snugged them tight.
Reconnected all the hoses, and then removed the bleed screw.
The expansion tank simply clips out and can be moved around once you disconnect the bleed hose from the battery box.
Decided on this coolant as it seemed high quality, met all of the workshop manual spec requirements and is popular on the Disco forums.
Filled the expansion tank until it stopped draining, then lifted it about 8 inches up to help it drain. Kept doing this until coolant started to come out of the bleed hole. At first the coolant bubbles out as the air is being removed and then it comes out in a steady stream. While this is happening, kept the expansion tank elevated and screwed in the bleed screw. Completely filled the expansion tank, then ran the engine until warm and refilled to the cold fill line. After driving around a bit, the level dropped so waited for the engine to cool down and filled again to the cold fill line.
Plan to change out the coolant every year. Should help the head gaskets last a little longer.
