‘72 Mark IV radiator

[Goldstar]

Next up is to flush the radiator and replace the thermostat. I intend to drain the system, flush with distilled water, drain and flush again with rad “cleaner”, drain and flush with tap water to remove the cleaner, drain and refill with 50/50 antifreeze, distilled water. Sound right? Is it best to remove the thermostat so the restriction is less (I’m replacing it anyway)? Thanks for you opinion,
Peter

[TonyC]

If you're replacing the thermostat anyway, then I think it may be a good idea.

Another good idea for a thorough flush would be to remove the drain plugs in the block, to assess and expel as much as possible any rusty crap that has collected down there over the past 49 years. "Regular" flush practices will not remove deposits inside the block, meaning that more-involved flushing is called for, especially for engines that old. Ask me how I know this. Removing the block plugs (the screw plugs, not the press-in ones, the latter are freeze plugs which shouldn't be disturbed unless absolutely necessary) will force out not only old coolant but also the scaly crap sitting in the bottom of the block. If nothing comes out when you remove the plugs, then you know the buildup is bad in there. Break it up with a piece of hanger wire until the coolant pours out steadily; then, with a magnetic probe, poke into the holes to grab stuff that tries to stay in there. Rusty deposits are magnetic, so that won't be a problem. That will guarantee no further mysterious overheat problems and likely spare your engine parts from heat damage due to the oil taking the extra heat-dissipation load that the coolant is supposed to carry.

---Tony

[tomo]

You do not need to use distilled water for the flush. A reverse flow flush is better than a flush by filling the radiator and draining. You can buy a flush kit that will allow you to reverse flush by hooking your water hose to the return side of the heater system.

If you are going to use TonyC's procedure, disconnect the radiator hoses until the block is thoroughly flushed, then replace the hoses. You don't want all of that gunk plugging your radiator.

[Goldstar]

Thanks all. To clarify, when do I use the distilled water? I thought a separate flush of just distilled water was needed, or is it just to be used in the final 50/50 mix? I’ll look into removing the block plugs - hope they are readily accessible.

[action]

You can use distilled water on the refill if you want. NO distilled water needed to flush or clean out.

If the cooling system has been regularly serviced there will be no deposits in the cooling system or in the block to be removed. The need to remove the block drain plugs and the thermostat during the cooling system service is NOT needed in that case. Cooling system service should be done every 3 years no matter how many miles. It is the lack of servicing where junk builds up in the system and becomes difficult to remove. Because the service life of the coolant will only last 4 or 5 years. Regular service is the answer

Action

[Goldstar]

Ok good, no distilled water only flush. I think I will remome the thermostat and hoses, and flush both block and radiator separately without removing the block plugs and see what comes out. It doesn’t overheat so I’m hoping the system is in decent shape. If I get lots of crap coming out, I may remove the plugs and flush the block.
Thanks Boys, most appreciated
Peter

[TonyC]

I agree with Jim, but a little less with Action. It is a good idea to remove the radiator from the equation if you can, keep that block crap out of it. But the engine is 49 years old, and very few of those 49 years were with you. There's no way you can verify whether the prior owners even did regular maintenance; and even if they did, rust will form by itself at that age, making the regular-maintenance matter a trivial point by now. As I said, NO degree of regular flushing practices will remove those deposits from the bottom of the barrel (or block, as the case is). The only way to make that happen is to flush the block directly with the drain plugs removed.

But I know that many here tend to undermine any suggestions of mine, especially since my most recent epic failure; but it's only a suggestion and equally subject to refutation as anyone's. If the block is not overheating, maybe you can get away without doing that. I had to do that myself, so I figured that if I had to, others would as well. But my problems are never the same as others', and I keep forgetting that when I get into a "save the day" mentality, which happens all too often.

---Tony

[Goldstar]

Hey man you’ve saved my bacon a couple times. I value your opinion. I have not yet fully investigated this so let me dive in deeper. If the plugs are relatively easy to get out, I’ll remove them. I’ll get back once I’ve looked at this closely.

[TonyC]

Sorry for coming off as acidic yesterday, I had things on my mind—mainly my own frustrations with Frankenstein's engine, but also the fact that yesterday was the anniversary of my own engine (or, as it's called in biology, "heart") failure...plus a few other things. I still have five days left in this month, so if I come out of it still breathing and conscious, at home as opposed to an ICU, then I come out better than I did last August.

Anyway, yes, that is something I should have also mentioned. Unscrewing the drain plugs for a total flush is contingent on the plugs' accessibility; on some engines they're easy to reach, on others too hard to reach without yanking the engine, still others have no such plugs at all (but I think those are the more modern, cast-aluminum blocks). If you can get to them, do so; otherwise, do the best you can with what you have.

---Tony