New radiator or unclog a partially clogged one?

You could take it to a radiator shop and ask them to flush it.
They can put higher pressure and volume through it than you can.
And usually they will warranty it. Unless it's in bad shape, they will tell you.

Before you pull it, you can disconnect the hoses try flushing with a hose. It should flow
out almost as fast as you put it in. Let it drain, then block the lower hose fitting,
and fill it with white vinegar and let it sit for an hour or so... Some people have had
good luck doing that. You should also do that to the heater core.

 

Someone here emailed one of the stop leak manufacturers, and they recommended to fill the system with a 50/50 mix of white vinegar and distilled water. It worked a charm for them: dissolved the clumps. Now whether that would work with your stuff you would need to test. If you can get some of the goop out, test by dropping it into such a mixture, see how it reacts.

Assuming it does work, dissolves the goop: drain both the radiator and the block*, and maybe disconnect the lowest hose on the exhaust heat recirculation system. Try to get the system as emptied as possible. Then fill with the mix, leaving the engine coolant bleed bolt open to vent as you pour it in (it's a black/white contraption on a hose directly above EGR cooler. You might want to remove wipers and cowl (if you haven't already), for access to the bleed bolt and the block drain.

Try to catch all the drain, and measure how much you get. It comes in handy, to calculate coolant/water percent later.

Run the engine in Maintenance Mode, squeeze hoses and top up as needed. Be sure to have your cabin heat set to high. Keep going till the radiator fan cycles on/off.

Then let it cool down, drain again, as completely as possible. Then it's a bit of a quandary: you have a relatively cleaned out system, but a "certain" amount of water/vinegar residue still in there. If you just refill with 50/50 Super Long Life Coolant, it's going to be somewhat diluted, and contaminated with vinegar.

Maybe do one more fill and drain with straight distilled water. And again, when draining carefully measure what comes out, compare with the system capacity spec (7.3 liters, 7.7 US quarts, see attached also). Compare the drained amount with system capacity, to determine how much water is still trapped in the system. Then refill with full strength Super Long Life Coolant, not the premix (if you can find it), or Long Life Coolant (which comes full strength I believe), diluted with distilled water just enough to achieve 50/50 mix. Or maybe 55/45 (coolant/water) mix. The latter is the spec for Canada, might be good to err slightly on the "strong" side.

Keep in mind the change interval for Long Life Coolant is shorter, maybe half? So maybe just run that for a couple of years, then drain and fill one more time with Super Long Life Coolant, the premix.

* The engine block coolant drain is a small bolt with a spigot directly below it. It's up fairly high on the block, on the rear side, towards the passenger end. It's in the vicinity of the oil temp sensor and timing chain tensioner, just a little over. You can just see and reach it from below, with the car raised and engine under panel under. Push a 5/16" hose onto the spigot, and loosen the bolt to start the drain.

More than once it's been said here that hardly anything comes out when you drain the engine block point, but I've yet to do it, would want to see for myself.

 

Glad the heater core is clear. And hopefully, the rest of the system. Maybe a new thermostat?
Since you have it out anyway, cheap enough to replace.

I personally wouldn't use anything but what Toyota calls for. Different coolant don't always mix well.
I would flush it as Mendel says above, and then maybe twice with just water. And leave the thermostat out
so the water can circulate throughout.

Then install the thermostat and fill with the coolant Toyota calls for, the 50-50 mix.

 

If time is an issue, and you can't obtain the Toyota SLLC, then Zerex Asian Car coolant is an alternative. HOAT coolant is specified. But again, Toyota SLLC will let you sleep best.

2 Best Options For Coolant On Your Toyota Prius | Torque News

 

Toyota Long Life Coolant (without the "Super") is approved I think (need to check), just shorter change interval. Again, (need to check) but believe it's full strength.

 

Links to some (Canadian) info for the two Toyota coolants:
Toyota Genuine Long Life Coolant | Markville Toyota
Toyota Genuine Super Long Life Coolant - Markville Toyota

The long life appears to be full strength. Maybe phone a dealership part department. I believe it was spec'd for gen 2, at least earlier years.

That insistance on pre-mixing the SLLC is a bit of a pain, if you need to do a water flush you're kinda screwed: very hard to evacuate all the water.

 

With that many miles and head gasket info, I’d go with ride til it dies and keep building the emergency saving to save up for a non hybrid vehicle with medium miles.

 

The only way to get ALL the water out is to rebuild everything.
ORrrrrrrr, hook an air hose up to the radiator and blow air through the system for a few days...
You don't need to get ALL the coolant/water out. He just wants to saw the radiator if possible.
Flush it with the vinegar, then 2 rinses with just water. That will be good enough. 3 or 4 if that will
make you feel better. The little bit of vinegar left won't do anything.

 

Easier method, put the entire thing in a ziplock bag with rice in it.

 

Have you ever seen what happens when you put tap water into an Aluminum-block car engine. Have you seen one literally melt and crumble away before your eyes?

Me either, but the way you see some internet writers follow the letter of the specs on that, you might wonder.

So I would not worry so much about using distilled water during the flushing phase. And once it is pretty much clean of any antifreeze, you might try repeated flushes with hose water, monitoring what comes out.

After doing a full final drain before the actual re-filling, I'd assume some small amount of water (hoped to be pure enough) remains, so adding 50/50 may not be the best thing. So aiming for 50/50, I prefer to put in 100% equal to half the specified cooling system capacity, and fill the rest with distilled water.

I still have the original coolant in my Prius, and will probably go to the minor effort of getting the specified Toyota coolant when flushing both systems as needed. But I saw your pic of the Peak. If it is significantly more convenient for you to get that now, I'd use it. I use that in many of my cars, and it is convenient to use the same coolant (or ATF, engine oil, etc.) when possible, for different cars just so you don't have so many different half-full bottles on the shelf.

The true main thing you need to be concerned with when changing coolant is for compatibility between the new and old fluid - you do not want any reaction between the two. But most ethylene glycol coolants (like that Peak and like the Toyota stuff) are probably compatible and not likely to gel into a solid, or even catch on fire. BTW, all the different colors are artificially added. So it's not like the green stuff and the pink stuff come from different planets.

I believe the main reason there are so many different specs out there (esp. from European cars) is that different countries will have their own special environmental regulations, and some, like Germany, may try to continually out-do the previous administration with something even "greener" to appease the tree huggers (can I say that here? ). At the end of the day, none of these coolant options are designed to melt aluminum on contact. Virtually anything will work.

OK internet. Fire away.


And separately from the coolant issue, a radiator should be pretty cheap, and given the miles it has already given you, I'd probably just replace it if it were my car.

 

....But most ethylene glycol coolants (like that Peak and like the Toyota stuff) are probably compatible .....
Probably.....

 

That's hands-down bullet-proof.

 

One head scratcher: the Owner's Manual (and Repair Manual) say "system capacity" is 7.3 liters (7.7 US qts). I think that's the starting-from-dry, how much it'll take capacity. But not 100% sure. Pretty sure though.

If you're dealing in US qts, and have done a thorough water flush, this is what I would do, following @2012 Prius v wagon 3 's lead:

1. Drain the sytem.
2. With air bleed bolt open, Add 4 quarts* of Toyota Long Life Coolant (the 100% stuff, not the "Super" pre-mix).
3. Continue filling with distilled water, burping the coolant hoses, till you've got the coolant level stable at the top mark in reservoir. At whatever point in the process coolant starts coming out of the bleed bolt, quickly shut it.
4. Follow @NutzAboutBolts coolant change video from there on, topping up as needed with distilled water (not pre-mix).

The one downside: the Toyota Long Life Coolant is rated (IIRC) to be good for only half as long. I would just use it for maybe 2 years, then do another exchange with Super Long Life Coolant (the pre-mix). That is if you've still got the car, lol.

* System capacity is 7.7 US qts. multiply that by 0.5, is roughly 3.85 qts. Mutiply by 0.55, is 4.23 qts. The latter is the Canadian SLLC pre-mix percent, so I'd think just using a full 4 quart bottle is both convenient and "in the ballpark".

 

With all the flush and vinegar or acid flush you cannot do it as a new one.
I think buying a new radiator is something you should consider...
You can find from 100 usd to 400 usd on autozone

 

This is why it's best to know ALL the information before giving a diagnoses...
Which is hard to do here.
I understand why the previous own did what they did. But they didn't understand
the damage they were doing.
I hope this works for you!