Changing engine coolant

Am changing both coolant loops but so far just the engine. I am using SLLC as in the new model Prius, not the original LLC. SLLC is sold pre-diluted for about $19/gallon. According to the spec, 5.2 US quarts (4.9 L) are required.

The radiator drain plug is as described in the tech manual, but the engine drain plug is not. To access that one, put the front end up on at least 4" of lift and crawl under. Between the engine and the firewall, look up for a 10 mm bolt and a metal drain tube on the engine. I'd call it about 6 " straight up from the vibration damper on the right drive shaft. Picture later.

First turn on the cabin heater and remove the radiator cap. Now drain each drain into a pan and close them. Empty the overflow reservoir as well. From all these I collected 4.1 L, not 4.9, even though the overflow was initially at the top line. Uncertain if this means an incomplete drain, or if the spec is wrong (hey it could happen).

Now drains closed, begin to add new coolant via the radiator cap hole. Initially I could only get 2.9 L in, so obviously there was air to be cleared from the system. The stated way to do this is to start the engine and run it until the radiator fan starts, then shut down. When cool enough to open the radiator cap, fill to the top and close. Repeat the heat/cool/fill cycle.

I did many repetitions, adding only small amounts of coolant each time. If you have access to Graham Davies miniscanner or similar you can watch the engine coolant temperature rise. If not, you can time how long it takes for the rad fan to kick in each time. That time increases through these cycles, which indicates that one is making progress. Adding coolant each time does, as well.

But again many repetitions are needed. I now consider this a full-day job (having started yesterday noon). It took me at least 15 reps before the cabin air 'blew hot', the first indication that air was getting displaced from the heater core.

Have now added a total of 3.45 L new coolant, including the overflow res. being filled. So I am still 0.65 L behind according to what I removed, or 1.45 L according to the spec. I reckon it is safe to drive this way, but feel better being able to monitor the coolant temp en route. Would be wise to shut down, cool, and try to add more if it gets near 100 oC. When everything is working correctly, additions can be made to the overflow tank w/o reopening the system.

The tech manual says you may need to get into 'inspection mode' to keep the engine running during the heatups, but I have not found that to be the case. Squishing the accel pedal does it for me. On some cycles I get bored, so I force-charge the HV battery.

Everyone says that the inverter coolant loop is trickier, but it has bleed valves so there is at least a mechanism to remove air. We'll see.

I had run the LLC coolant for 44k miles (spec is 30 k), but its appearance is quite good. The only particles appear to be little black bits that I attribute to erosion from the rubber hoses.

Now equipped with SLLC, my replacement cycle ought to be 50k miles. Given the time required for this process and the cleanliness of the coolant, don't be surprised if I stretch that.

Naturally after this, it is good to check for drips under the drain valves for a few days at least, and monitor the level of the overflow tank.

Toyota does not charge huge $$ for this, so maybe they have a trick. I think it might be nice to pump coolant up into the engine drain valve until the radiator wants to overflow.

if you have little black bits in the old coolant it's possible that the bleed hole in the thermostat is plugged, that would explain the sloooow refill procedure. Nomal Toyota coolant change is 3 fills and rests till the air is out of the ICE and then fire it up and let it warm to themostat opening temp then top it up. I suspect that the difference between the stated fill and what you got in is probably in the heater core and the heater coolant pump and hoses.
Edited for spelling, not my strong suit

Thanks for the interesting suggestion, Frank. I know of one other DIY who also experienced this slow bleeding sequence. If that bleed hole serves any purpose other than to assist in the refill, then I ought to put it on my list of things to consider (eventually).

To pass along a suggestion from Patrick Wong on the inverter coolant loop, do not begin the process unless you *can* open the two bleed screws.

The vinyl tubing I bought to assist in the inverter bleeding was 5/16" OD. It was just barely large enough to fit over the engine block drain tube fitting. 1/4" might have been better there.

<div class='quotetop'>QUOTE(tochatihu @ Apr 14 2007, 11:54 AM) [snapback]423298[/snapback]</div>

make sure that you hold the bleeder block with a wrench before trying to loosen the screw. Personally I'd use a socket on the bleeder to help with distributing the torque as it's hollow.

How is everyone. I have a quick question I hope someone can help me with.

Well I had my Prius in the body shop for a while because someone fell asleep on the road and hit me at an intersection. Nonetheless the body shop finished their work.

Afterwords one of the workers from the toyota body shop was putting in some coolant. though it did not seem as though he knew a whole lot about the prius. at any rate he put in coolant directly into the visible tank.. through the insert that read "coolant" rather than putting in through the radiator cap with the silver cap on it.
I think he put the coolant into what's called the resevoir tank that one can easily see when checking coolant levels in front of the air filter for the ice.

is that a bad thing? That is if my question makes sense

When refilling the engine coolant, the radiator cap should be removed and the system filled. On 2G models this requires removing the black plastic shield that runs across the front of the engine compartment area. The translucent plastic expansion reservoir tank also should be filled.

Then the engine should be run continuously by placing the Prius in inspection mode. The cabin heater should be set to max high temperature and max fan speed so that coolant will flow through the cabin heater. Continue running the engine until the engine thermostat opens. The top radiator hose will start to get hot when the thermostat is passing coolant. Then turn off the engine.

After the car cools down, check the radiator and reservoir tank and refill both as needed. Repeat running the engine, letting it cool down, and checking the levels until the fluid levels hold constant at the full mark, then you are done.

Thanks for the information.

My Prius Tech worked on my car today-- he was bleeding the coolant system (had my thermos can replaced a few days ago, because of an accident). However... when he gave me the car back today-- not even a mile from the dealership/tech garage.. lo and behold the stupid "problem" light came on with the acompanying "hot coolant temp" light on the mfd screen.

By the time I got back to the shop he was already gone, and he was the only prius tech on site today. At any rate, I left the car at the dealership so that hopefully, if he is there tommorow, he can check it out. And I presume bleed it correctly this time.. if indeed this is the problem. Does it sound like that is the case?

I too was wondering about what influence the "thermos" might have on a coolant flush/change. I am over 60K miles now, and keep putting off a coolant change because I just don't know enough about how the thermos operates.

I also want to change the inverter coolant, but since I can't even locate the bleed screws, I think I'll leave that one for a dealership.

I am about to do a search through the forums, but in the mean time, what is the name or part number of the inverter coolant?

I'm glad I found this topic.

~Andrew

Hi Andrew,

Toyota Super Long Life Coolant. It has a pink color and is premixed with distilled water so you just have to pour it in.

To find the bleed screw (only one with the 2G) for the inverter coolant, you have to remove the black plastic shield over the radiator. Before you drain the old coolant, note the sound of the inverter water pump when the car is IG-ON or READY. Also note the step in the fluid level in the inverter coolant reservoir. When you add new fluid, the challenge is to get all air out of the system so that the water pump sound is normal again and you have the step in the fluid level.

When you drain the old inverter coolant, make sure that you do not drain the transaxle ATF fluid by mistake. The coolant drain plug is at the bottom of the transaxle, between the engine and the ATF fluid drain plug.

I haven't changed the coolant in my 2004 (53K miles) yet. I plan to do this at 60K miles. My current plan is to apply 12VDC to the coolant heat recovery pump as a way to purge the air from the thermos canister and associated parts of the engine coolant loop.

so no one successfuly has DIY a engine/inverter coolant change/flush for themselfs on 2004 + priuses? It seems the classic was the easier DIYer car.

thought the toyota scantool was required just like when bleeding or changing the brake fluid on 04 + priuses

no flushes!

if stupid crap quit happening to us and people we know, we'd have done ours DIY already. it's on the list after fixing the benz, the camry, this other guy's camry, and of course DH's homework and my 75 hour workweeks.

ty galaxee, hopefully one day you guys will be free to raise a happy family because it sure robs a lot of time!

according to the bentley publishers manual.... (thanks justin fons!)

- i can bleed with the mastertech scantool EASY AS PIE

or

- use some 90 psi shop tool (looks like a bleed tool for conventional bleed braking) that hobbit mentioned if one doesn't have a scan tool.


looks like its better just to pay 100 bucks to the dealer to change it for you, well that's just engine coolant, its another 100 bucks for inverter fluid change as well...

either or no luck for the DIY at home, but guys like me who work in a INDY shop there's hope to serve those who don't like stealerships!

edit: good info below by rumpledoll about coolants

edit: looks like the inverter has a simliar procedure as well however, it looks like the inverter CAN BE CHANGED using a technique that patrick was thinking of doing ( IG power II let the coolant pumps do its thing, power off, release bleed valve, repeat ) but if one doesn't want to go through that they can use the same tool tha twas suggested with the air compressor.

Any reason not to use standard Peak or Prestone coolant? There is quite a price difference.

Yes, several reasons not to use either in your Prius. The Preston "All Colors Any Type" universal coolant appears to be identical to Preston's DexCool formulation (and everyone else's DexCool). Peak standard appears to be usual "American Green". Neither type is recommended for use in Toyota cars. The bottom line is that there is no after market coolant sold in the USA that is of the same formulation type that Toyota (or any Japanese maker) uses. Get thee to a dealer for the stuff.

Quick coolant lowdown:

The purpose of coolant is to help rid the engine of waste heat. For this purpose plain water does a great job. However, plain water has three issues in an engine, two of which are solved by the same major ingredient used in virtually all antifreezes. That ingredient is ethylene glycol*.

Issue #1 is that plain water will freeze solid in the winter, which clearly puts a major damper on winter driving. Ethylene glycol and water when mixed can have a freezing point as low as -70F/-67C at a 70/30 ethylene glycol to water ratio although -34F/-36C is more common at the standard 50/50 ethylene glycol water ratio. 100% pure ethylene glycol cannot be used in car cooling systems as it does not have the heat removal capacity of water and it freezes at a relatively high 8.8F/-12.9C.

Issue #2 is that water will boil off at 212F/100C. Ethylene glycol raises the boiling point although much of the boiling point raising is due to the 15PSI pressure that the radiator runs at (straight water at 15PSI boils at 248F/120C which is why a pressure cooker cooks so fast, a 50/50 mixture at 15PSI boils at 265F/128C).

Issue #3 is corrosion protection and this is where various antifreezes differ. More that 95% of any antifreeze is ethylene glycol so most antifreezes are at least 95% the same. An engine is made out of different materials many of which will oxidize quickly in the presence of heat oxygen and water. Additionally the different materials (such as aluminum heads and radiator and cast iron block) are subject to a galvanic reaction that will quickly eat these materials away. Antifreezes have ingredients that alter the chemistry of the mixture to suppress these corrosive effects. There are 3 main chemistries:

1) IAT - Inorganic Acid Technology. This is the oldest technology and is really fine at keeping corrosion at bay. The only issue with this technology is that the corrosion inhibitors are used up relatively quickly and the fluid must be drained/refilled generally every 2 years or 30,000 miles although some manufacturers suggest going longer. This antifreeze type is typified by standard "American Green" although Japanese and European manufacturers had different formulations in this generation. Generally the Europeans had silicates but no phosphate, the Japanese had phosphates but no silicates and the Americans had both. Europeans didn't want phosphates due to hard water compatibility issues, the Japanese didn't want silicates due to water pump issues and the Americans liked both but eventually addressed the water pump issue by have low silicates.

In order to get a longer service life the next two technologies were introduced:

2) OAT - Organic Acid Technology. GM introduced DexCool using this technology. The corrosion inhibitors last much longer (5 years/150,000 miles or more) and contain no silicates or phosphates. This formulation uses 2-ethylhexanoic acid (2-EHA) and sebacate. These inhibitors do not work as fast as the older IAT inhibitors, but they are very effective.

However, 2-EHA is a plasticizer which means it softens plastics. Ford and the Japanese manufacturers in particular want nothing to do with this in their cars and even mighty GM had problems in some of their models until they got the gasket materials right. Since our Prius does not have gaskets designed to behave in the presents of 2-EHA one would be taking a risk by using an OAT antifreeze in a Prius.

3) HOAT - Hybrid Organic Acid Technology. This is what most everyone besides GM uses now. However, the technology is different depending on the maker. Ford, Daimler and Chrysler and others have chosen an extended life HOAT antifreeze called G-05 while VW and Audi use G-11 or G-12 and possibly others. None of these G-XX use 2-EHA and none have phosphates as the European makers are still allergic to it.

The Toyotas take on an extended life coolant is a HOAT (no surprise there) and is reportedly made from sebacate (same as in DexCool, but again no 2-EHA as everyone besides GM apparently hates it) and a good dose of phosphates but no silicates as the Japanese makers are still allergic to that ingredient.

Since the Prius has a long life HOAT antifreeze and it is difficult to do a complete flush, I would *only* use the Toyota sourced silicate free antifreeze in the Prius. I would also not worry about it until the recommended interval as getting a long life was the whole point of replacing the earlier IAT technologies.

Rumple

*The alternative to ethylene glycol is propylene glycol. Propylene glycol isn't quite as good as ethylene glycol as an antifreeze but it has a far lower toxicity.

WOW!! Thanks to Rumpledol for that fantastic explanation.

I had scowered the forums trying to find information regarding the differences between all of the coolants and that explains it perfectly.

Seems interesting to me that Prestone is willing to post on their website that their extended life coolant is fully compatibitle with "ANY" other coolant.

Only Toyota coolant for me!!

You are welcome. I got curious about antifreeze and spent a few days researching it.

Prestone was taking before the National Advertising Review Board for the claim of the "all makes, all models" antifreeze and the board ruled against Prestone. However, it appears the boards decisions are non-binding and Prestone continues to advertise this deception. See here.

Gee, I wonder why it could be that our mechanisms against deceptive advertising is toothless? I suppose we just just shut up and buy more product. :yell:

Rumple

so no one successfuly has DIY a engine/inverter coolant change/flush for themselfs on 2004 + priuses?

I changed my electric inverter pump last month, and so had to change the inverter fluid (110 K). Reading up the the subject, some shop had this vacuum contraption on top of the inverter reservoir ,to help get the air out of the system. When I had the bleed valve hooked up, the tube going back into the reservoir, no coolant would flow at first, and I could tell that the inverter pump wasn't pumping fluid by squeezing on the hose. Lacking any device, I made a seal with one hand on top of the reservoir, (there is an overflow on the rear), and blew in a few puffs of air,while the inverter pump was running. I was trying to make a pressure difference inside, to remove the air pockets, and it worked (I could tell the inverter pump sound got deeper, and started the coolant flow through the tube, and I had to had more coolant ). I may have used air from a compressor, but I didn't have one. Sounds a little strange I realize , but it got the job done fast. Seriously, within 10 minutes I think in all. I probably did add some more coolant after the first test drive. Note I did have the large plastic cowl that holds the wipers off the car. Someone using air from a compressor probably wouldn't have to remove that. Also note, the bleed screw should be watched, mine still has a very slow leak, I've tightened as hard as I dare, I'll probably add a thread sealant to stop it's very small leakage.

Now to the engine coolant , which I haven't done yet. The arrangement seems complicated, and I don't have the scan tools to control the electric motors. I've read about the dangers of air pockets, and this doesn't make sense to me, doesn't the car create huge air pocket when the hot coolant is pumped into the storage tank? I suppose one 'danger' is having an air pocket in the line for the electric motor that controls the storage tank. I'm considering just removing the rubber hoses from the electric motors to help drain the coolant especially from the heater core part. Guess I'll report back results when I get around to it.

Thanks for the tip regarding refilling the inverter coolant. I've done that change a couple of times on my 2001 but not on my 2004 yet.

Regarding the need to refill the CHRS canister, my plan is to remove the relay that controls the electric pump to the CHRS (located in the relay box mounted to the cowl.) Then connect a wire across the appropriate relay socket terminals to activate the pump for 30 second intervals, to refill the canister.

When the car is in operation there should be no air pockets because no air should be in the system. As hot coolant is pumped into the canister, colder coolant from the canister is moving back into the cooling system.

A further consideration is the valve that routes coolant flow from the engine either to the cabin heater OR to the CHRS canister (or to both simultaneously). After studying the repair manual, I believe that this valve will remain in the position allowing flow to the CHRS canister when the car is IG-OFF. So if true, this is good news because if the car is off and you bypass the CHRS relay terminals (the socket has 12V available even when the car is off) to run the pump, the canister should fill up nicely with fluid.

Then, once the CHRS canister is full, you can top off the coolant, start the engine, and coolant should flow into the cabin heater core if you have the heater controls set to produce max cabin temp.

Anyway this is my theory, and I may have a chance to test it this weekend. I'll post my results when available.

well, our plans to do this are shot.

we were going to do this as soon as DH finished his summer finals next week, because the last of the laundry list of other stuff is getting taken care of today. however, his departure was unexpectedly changed from mid august up to, uh, tuesday. we will not have time between the other half a million things we need to do before he leaves.