Radiator flush or not??

Drain/fill is fine. However, an independent shop not specializing in Prius may have trouble due to the coolant heat recovery system which includes an electric pump and the thermos container.

 

Its hard to do properly unless you have the proper equip. You need this:

MityVac - Automotive Vacuum Pump Kits - Radiator Adapters - Cooling System & Pressure Testers Kit - Fluid Evacuator

to properly vac. If you dump all the motor coolant including pulling the thermostat it will be an overheating/ sloshing sounds under the dash nightmare unless you evacuate all the trapped air. Its a dealer or a very savvy mechanic deal. Do what I do yourself. Dump the rad.contents only. Put just distilled water back in it. Run it till it reaches op temp with heat on full blast. Let it cool down. Repeat.
Then final rad dump then fill up with factory coolant. That will get you real close to a complete flush.But stay with it. Do what I've listed all in one day. Don't let it slide and run it without factory anti-freeze as it might corrode.
Done this in alot of cars and had good results and will save you some money and horrors of horrors will keep it off the dealer rack.Good luck

 

In the old days coolant was based on Inorganic Acid Technology (IAT) for corrosion protection. It was great stuff and offered very good corrosion protection. It did have one major drawback - a 30,000 mile 2 year service length. When it was let go longer, as many consumers did, bad things could and did happen.

In order to get a longer life, GM lead the way to longer service life with Organic Acid Technology (OAT) antifreeze. GM's version, brand name DexCool can last 5 years/150,000 miles. There was one problem - DexCool can weaken certain rubber and plastic gaskets/hoses/parts due to one of the major ingredients (2-ethylhexanoic acid known as 2-EHA ). So nobody but GM (and Saab, IIRC) uses coolant with 2-EHA in it. BTW, Preston long life any color any make uses 2-EHA.

Toyota switched to a long life antifreeze using a Hybrid Organic Acid Technology, and like all Japanese manufacterers they use no silicates and they do use phosphates. The Toyota Pink is good for 100,000 miles/10 years and 50,000 miles/5 years afer that.

So, at 80,000 miles you still have 20,000 miles of life left in your antifreeze. I would not worry about until the 100,000 mile mark.

The longlife HOAT technology variations that everybody besides GM went to contains silicates and no phosphates (European makers do not like phospahtes) - Ford's G-05 is an example. GM's DexCool has no silicates and no phosphates but has the dreaded 2-EHA that everyone else hates. Only the Japanese make a HOAT based longlife antifreeze with no silicates, no 2-EHA, no amines and low phosphates (the Japanese have long used phosphates).

The only place to get a Japanese style longlife antifreeze is the dealer, and given how hard it is to remove all the old antifreeze from the Prius, I would recommend staying with the Toyota "pink" longlife antifreeze when your Prius hits the 100,000 mile mark. Under no circumstances should you risk using a 2-EHA based antifreeze with it's known gasket compatibility issues in your Prius - which rules out DexCool and Preston long life any color any make coolant.

Rumple

 

1. Yes, the radiator has a drain cock. The engine block also has a drain cock on the side that faces the rear of the vehicle. Further, the coolant heat storage tank (which contains hot coolant) can also be drained, and the associated coolant pump should be disconnected during this process so that you don't have an accident. When refilling, one challenge will be to run that coolant pump so that the tank can be filled and air can be purged out of that system.

2. Yes

3. Since your car has 80K miles, this is a good idea. You will also need to replace the rubber O-ring that seals the thermostat housing.

I suggest that you use Toyota Super Long Life Coolant which is premixed with distilled water. This has the correct pink color and is ~$20 per gallon.

I also suggest that you download and study the Hybrid12 Engine Control System.pdf file that can be found at Automotive Training and Resource Site, especially pages 2-4 to 2-7. If you need more tech info after reading that, go to techinfo.toyota.com and download relevant repair manual pages for your model year.

If you are still inclined to DIY, you may decide to forego draining the coolant heat storage tank; however this will result in keeping ~30% of the old coolant in the combined system.

Good luck.

 

Hi Ed,

A problem with this suggested approach is that the correct coolant is the pink Toyota SLLC which is already premixed 50%/50% with distilled water. Hence the use of distilled water during the intermediate drain/flush steps means that at the end, the coolant that remains in the system will have an insufficient % of antifreeze and an excess % of water. This results in reduced anticorrosion and antifreeze protection.

 

you must have missed the last line about adding factory coolant in the end...

i like that approach... a distilled flush.

 

The problem is you will have great trouble getting the proper 50/50 distillation with the water "flush". Since there is a significant amount of water in the coolant system, when you add 50/50 you will end up with something *less* than the required 50/50.

Rumple

 

then don't add 50/50... buy pure. they sell it.

 

Yes, you can buy red Toyota Long Life Coolant from your friendly Toyota dealer. This coolant is not premixed and consequently costs less than SLLC. However the service spec for changes using the red LLC coolant is 30K miles compared to 50K miles (after the factory-fill coolant has been replaced) for the pink SLLC.

I'm assuming you would not use a cheap aftermarket coolant like Prestone, Peak, etc. in your Prius.

 

Ed's suggestion was just to drain the radiator and leave the engine block and coolant heat recovery storage tank drains untouched. He further suggested flushing the system with distilled water. His reason for suggesting that was to reduce the chance of introducing air into the system. However, as we've discussed, the disadvantage of using distilled water for flushing is that you will end up diluting the final SLLC coolant added to the system.

If you open up all three drains: radiator, engine block, and coolant heat recovery storage (CHRS) tank - then you will have done a comprehensive job and should not have to worry about residual fluid in the system. Further, my recommendation is that flushing with water is unnecessary if the drained coolant does not have sediment within.

If you open up all three drains, then you will be faced with the issue of purging air out of the system, especially the CHRS canister and plumbing. Ed recommended the MityVac tools for this purpose. I haven't done this job yet, so I don't know how tough it is going to be. My idea is to provide 12VDC to the CHRS pump as a way to fill up the canister and purge air in that part of the system...

If you decide to proceed with this work, I suggest that you take some photos, especially of the CHRS system, so that other owners can see how easy or hard the job will be.

Yes, I suggest that you change the thermostat while you are at it, and inspect the radiator hoses. Don't forget to get a new O-ring for the thermostat housing.

Good luck...

 

After replacing coolant, wouldn't a prolonged engine run-up with radiator cap off cause the trapped air bubbles to float to the top?

 

Hi Andy,

Not necessarily, since the Prius engine coolant system is more complex than most. You will need to run the heater at max temp for an extended period, to get air out of the heater core. It should be possible to hear air bubbling around in the heater core, so this will allow you to determine when the air is gone.

The coolant heat recovery pump only runs for a few seconds upon engine startup and shutdown, so it is unlikely that air will get purged out of that part of the system unless you take active measures.

 

Always, reliable answers, Thanks Pat

 

The thermostat is hiding behind the water inlet housing. One of the radiator hoses leads to the water inlet housing, and the engine oil dipstick is nearby.

The water inlet housing is attached to the engine block with two nuts and the tightening torque is 80 in.-lb. When installing the new thermostat, the jiggle valve should be at the top. Don't forget to install a new O-ring gasket.

 

This is a little unclear to me.

I let my dealer "flush" the coolant at 30,000 miles. (It's a long story. In summary, I (stupidly) let them sell me a super service. On the plus side, when I complained to the service manager, he gave me $250 credit toward future service, which they have honored without complaint.)

Anyway, does your 100k then 50k statement mean that once it's changed, it should be done every 50k after that? I'm inclined not to do it again until at least 100k (70k after the first flush at 30k).

Bob