Z24 coolant flush and replace

[mTeryk]

This has probably been covered before but I can't seem to find much info on it. I just replaced the water pump on my 1985 720 4wd. I didn't keep track of the volume of fluid I drained out but it seems that for both the flush and the final fill I put it in less than 2 gallons when it should take 2.6.  After draining the radiator using the petcock, I filled it to the top, ran it till it warmed up and then topped it off. I'd say I put about 1.75 gallons in each time. 

 

Am I missing something? It's not running hot so I suspect it has enough fluid in it but that I am not fully draining the system. If this is the case, how do I get the rest of the coolant out. One thing I noticed is that my radiator cap is weeping a bit, maybe that the system isn't coming up to pressure?

 

Thanks for any help on this 

 

Teryk

[DanielC]

It is almost impossible to get all the coolant out of the cooling system, with the engine in the car.  There is usually at least one plug on the engine block, that can be removed that will drain more water out of the engine.  The heater also holds some water, and even when water keeps running out of a radiator, it still retains some water.

 

On my project truck, when I finally got it running, I noticed the coolant looked rusty again, after I flushed the cooling system.  I ended up flushing the system again, and that helped get a lot more rust out of the engine cooling system.   I took the radiator completely out, and drained the remaining water out of it.  Then I ran a hose onto both the bottom and top of the radiator, and with water in the radiator, shook the radiator and got more sediment out of it.

I disconnected the long heater hose, by the water pump, on a L-16, and  used a hose to flush clean water through the system, with out the radiator in the truck.  More rust came out.  I took the thermostat out, put the cover back on the engine, and then again used a hose to flush both forward and back through the upper and then the lower radiator hoses, and more rust came out.  

Then I took an air hose, and with clean water running into the lower radiator hose, from a garden hose, blew compressed air in to the open heater hose, more rust came out.  I then removed the block plug, just above the starter on an L-16, and blew compressed air out that, with a hose running fresh water in to the lower radiator hose.  This block plug is near the back of the engine, and the compressed air stirrs up sediment that settles back there, and even more rust came out.  This is after all the flushing I already did.  

then I put the block plug back into the engine block, reattached the heater hose, and put the empty and flushed radiator back in the truck.

The cooling system on a 521, with a L-16 holds around 1.8 gallons of coolant.  I put a gallon of antifreeze in the system, and filled the remaining up with water.  If you have hard water, with dissolved minerals in it, use distilled water.

[mTeryk]

Thanks for the response. I certainly didn't go that far to flush my system. I'll save your post for next time when hopefully I'll have more time and space.