48 D 24 -Rad and Block Flush Questions

[Norm Tatlow]

Hello from Calgary, Canada. I haven't been on the forum since it was expanded, years ago. Good to get back. 48 D 24 Fluid Drive. Engine temp is always good, in 180 - 200 F range. I drained the rad and block to change coolant after 4-5 years. At the engine block drain hardly anything came out. I expected it to drain the water in the water jacket, even tried it before draining the rad in case of draining back that way. This is #1 mystery to me. Also my info says the cooling system capacity is approx. 15 quarts. I only got about 6 quarts from draining the rad. That fluid was a bit dirty but no sludge or rust pieces. And runs fairly cool always. Overheated in a very slow parade, hot day once. I used Prestone Super Flush and filled and drained twice. ANY IDEAS why nothing from block drain and why 6 quarts vs. 15? Thanks.

[Young Ed]

You need to pull the lower core plugs and remove all the sludge that builds up there. Nasty job but I guarantee you need it. The last one I did was full up to the drain.

[Reg Evans]

Yes, Here are a couple examples of what I have found.

[Norm Tatlow]

Thanks guys,

When it is so sludged up, why does the temp stay normal?

[Niel Hoback]

The sender is up high on the head where there is no sludge to impede the flow of coolant. It doesn't tell you the temp lower down in the block where the water isn't moving.

[Young Ed]

and 180-200 is kinda high if you ask me. both mine rarely go over 160.