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I recently took my '77 into the shop after it was overheating and spitting coolant expecting to replace the thermostat. After replacing the thermostat & gasket, they opted to not do a coolant flush due to too much rust & scale, and doing a flush would knock this loose and cause further issues. They also shared the heater core is already plugged.
Looking for advise on what's the best next step. Should I wait for issues to occur, or look for a shop that could tackle helping clear this up? Am I risking further damage by continuing to drive?
You should search for a local radiator shop and have them do a flush, if is extremely clogged and has any leaks they may be able to fix them, a lot less expensive than a replacement radiator.
Just a comment that's slightly on topic. My 68 has never had water in the cooling system since ~1974. My 1997 Ford Thunderbird DD has not had water in the coolant since it was new, Both cars have zero corrosion problems. The cooling passages of the engines don't look rusty, they are covered with a white powder...the silicate additive in ethylene glycol. The other advantage of pure ethylene glycol is that the coolant never pressurizes due to the high boiling point of ethylene glycol. This means if means a tiny leak doesn't become a gusher. It also means you can open the coolant fill cap when the coolant is hot.
Take a look at @interpon's image. You might be better off with a new radiator.
But you should still flush the old coolant out of the engine. There are two drain plugs on the block below the heads that can be removed. It's a lot easier with the exhaust manifolds removed, but you should still be able to get to them. Be ready with a bucket, and perhaps a screwdriver to punch through the crud and get the flow started.
Also, is the spring intact in your lower radiator hose? Missing that can cause overheating, too, and is low-hanging fruit to check and replace.
^^^^
If it was that bad, heater core plugged Id just replace that and the radiator.
They were afraid that radiator would spring leaks everywhere ,Id say its gone. Or worse yet a freeze plug starts peeing.
Flushing the crud out of the block isnt bad. Sediment builds up below those drains in the pic above...leave it alone.
Flush one way...then backwards etc til its nice and clear youre good to go.
To me haveing new cooling stuff is worth the peace of mind when youre out running around...Gauge watching takes the fun out of old cars.
If it does not go to a radiator shop..from the backside of the rad flush the fins out with a garden hose..go easy so you dont bend fins. Hold it up to the light you will be surprised how a visually "good" radiator;s fins are plugged. I do my cars once a year, condenser also. Really makes a difference!
Started doing that with C4s..then my daily..ex's MB elec fan would run an awful lot ac didnt get cold as soon as it should
Thats all it needed was flushing. Fan ran less, ac got cold quicker, win/win. Price? Free.
Just a comment that's slightly on topic. My 68 has never had water in the cooling system since ~1974. My 1997 Ford Thunderbird DD has not had water in the coolant since it was new, Both cars have zero corrosion problems. The cooling passages of the engines don't look rusty, they are covered with a white powder...the silicate additive in ethylene glycol. The other advantage of pure ethylene glycol is that the coolant never pressurizes due to the high boiling point of ethylene glycol. This means if means a tiny leak doesn't become a gusher. It also means you can open the coolant fill cap when the coolant is hot.
Pure antifreeze is designed to be mixed with water, which lowers the freezing point though probably not a worry in Torrance. I use a 50% mix with tapwater,( mostly from a well but last 12 years from city water) just like I have for the last 50 years, never had a corrosion problem.
Once it gets to that point flushing the radiator is likely a waste of time. You could have it cleaned manually, expensive, or replace it, also expensive.
the block and heater core need to be flushed or replace the heater core, nor easy or cheap if you have a/c.
if you just clean or replace the radiator it’ll be filled with new crud from the block in short order. So the whole block, heads, water pump system needs to be flushed. If your top radiator hose was worn out you can bet the lower one is not far behind unless it got changed at a different interval.
I just went through the same thing last month. Replaced the water pump and then found out that the radiator was shot. I decided to replace it with a 4 core "Champion" aluminum with dual 12" electric fans. Yes it was expensive, and yes it is, what some will say, "overkill", but I guarantee that I wont have any overheating problems and wont get stuck on the side of the road with any radiator problems...... The rest of the car is a different story.
Too much rust / scale for coolant flush
