Category: Prius

My 2014 Toyota Prius uses iridium-tipped spark plugs such as the Denso SK16R11 or the NGK IFR5A11, both usually set you back around $20, but if you buy them from the official toyota dealer, they will set you back $150 ! but I have no choice, as the market is flooded with counterfeit spark plugs, and changing the spark plugs on the prius requiers the removal of the wiper area !

What about those $150 spark plugs (I will check the exact price and update this soon, so when I took them out after less than 5000 KMs and found two of them broken ! specifically the Insulator Nose (shield) around the copper core !

I had a failing head gasket, and the removal was part of fixing that, so I thought that the seeping oil or water into the piston might have been the problem, but since i maintained their order after removing them, It turns out that the one that has the inner shield fully broken was in a piston that did not suffer any head gasket leak !

Seems the Prius is known to blow head gaskets, reason being attributed to the hybrid system, the engine switches off and on so often, heating up and cooling down all the time.

I am using the official TIS repair manuals. I am warning you, this is a lengthy job, it is not something you can finish in a day.

Tools

There are plenty of tools that you will need along the way, everything from the tools needed to take out the EGR, to a triple square bit to remove the cylinder head bolts, in any case, here is a list of tools i recall needing

• A ratchet, breaker bar, and a cheater bar
• A torque wrench (I use ACDelco’s ARM302-4s)
• Oil filter removal tool
• 10mm bi-hexagon wrench (An M12 (12mm triple square) bit will do if you fail to obtain the bi-hexagon ! but you will feel a bit of wiggle in it)
• A pair of pliers
• 12mm socket (Many screws)
• 14mm socket (Many screws)
• 19mm socket (The harmonizer / crank pulley)
• Feeler gauges down to 0.004 (0.004 is the maximum acceptable engine warp)
• A super straight bar to assess the engine against (Laser cut)
• Harmonic Damper removal tool such as Schley 64300 (I made my own simple tool that works)
• A tool to take out the valve stem seals (I made my own)
• Patience

The Harmonic Damper removal tool

There are many ways to remove the pulley (Harmonic Damper), 1- the most common of which is using a torque impact drill, it just works, but my gut feeling tells me it might not be wise, if it was, Toyota would have approved it, 2- another popular way is to use a belt or strap and tie it to a strong part of the vehicle and around the pulley to use friction to hold the pulley in place, problem with this method is that if it is not 100% horizontally aligned, and the pulley is being pulled in or out, it might cause damage, 3- and there is the Toyota way, which is based on using a tool to hold the pulley in place while you loosen the screw, examples of such a tool is the Schley Products 64300, I don’t have access to such a tool, so I improvised a tool that holds the pulley against the engine mount

Parts

Distilled water

7 Liters of distilled water, You are probably going to need to use distilled water before engine coolant to flush the engine from the contaminated coolant in the car, it was contaminated because your head gasket broke, and exhaust went through that coolant.

Engine Coolant

(Applies to both Fix and repair)
If the coolant has been contaminated with engine exhaust, you will need to flush and add distilled water, then after a day (a day of light use, and zero days of the car sitting), remove as much of the water as you can and add the SLLC coolant (Do not run on distilled water for more than 1 day).

Totota’s coolant is super expensive, if you are looking for something other than the OEM, or want to understand the risks and advantages, check out my Toyota’s coolants post

The car takes 6.5 liters of coolant, every container is 2 liters !

Oil and oil filter

(Applies to both Fix and repair)

if the engine oil has been contaminated (And it has), you will need a new filter and new oils

Expected cost (35JD)

Gasket kit

PN: 04111-37316

The repair manual states that you will need a new gasket kit, the gasket kit has the following parts.

FIPG 103

PN: 00295-00103

The form in place gaskets from Toyota are best, but they are very pricey, I went with an aftermarket German brand (Victor Reinz Reinzosil) that is high quality (Used by German brands as OEM !) and have my fingers crossed, the Toyota FIPG costs around $50, the Victor Reinz Reinzosil (Universal) aftermarket brand costs less than 6 dollars

Cylinder head bolts

(90910‑02164 and later was superseded by 90910‑A2009)

Those are Torque to yield bolts, when you install them, they are stretched, and should not be used again, In my case unfortunately, Al markazeyah Toyota does not provide them, I was told today that they did have them at one point, and they cost $5 each (10 of them is $50), but they no longer carry them ! yes, I know, what the duck, as an exclusive dealer in Jordan, they absolutely should have them.

The Toyota repair manual often tells you to measure the bolts after removal, and replace them if they are out of spec — a classic sign of TTY design, even if not spelled out.

The process

Removing the spark plugs

Getting started with a big surprise !

I started by removing the spark plugs, like you normally would, and to my surprise, those brand new spark plugs (Less than 5000 KMs) are broken, and the ones that were broken are not even the ones where the head gasket leaked into ! Here is more about the failing spark plugs

The following is a result of me checking the right way to flush my engine of contaminated coolant in my 2014 prius, but it applies equally to modern Toyotas. my coolant was contaminated due to a blown head gasket !

The lowdown: fill it with distilled water, use it for a day in light traffic (Don’t let the water sit, you have to fill it and use it for a day, if the weather is hot, you should not stress it as water has less cooling capacity), then, flush as much as you can from those 6.5 liters of distilled watter, and once you have removed 5 or more liters, fill it up with SLLC (Not a drop of LLC is allowed)

The coolant from Toyota for modern cars (2004+) is super expensive ($21 for every 2L), my 2014 Prius for example has 10 liters of coolant in both engine and inverter loops, that would set me back around $100,

The coolant suitable for such new cars is called the SLLC (Super long life coolant), it comes premixed 50/50 (With distilled water)

Can i mix SLLC with the older LLC ?

You certainly can not ! they are chemically incompatible, You are not free to mix and match.

SLLC is compatible with both inverter and aluminum engine cooling systems, LLC is not, they have different chemical formulations and should not mix in any way. here is what is given by Toyota in the MSDS documents, obviously done by Toyota in a way to keep it ambiguous and keep others from copying the formulation

Long Life (LLC)	Super Long Life (SLLC)
Ethylene Glycol 107-21-1. 87% – 95%	Ethylene Glycol 107-21-1. 45% – 50%
Diethylene Glycol 111-46-6. Less than 5%
Hydrated inorganic acid, organic acid salts. Less than 5%	Hydrated inorganic acid, organic acid salts. Less than 5%
Water. Less than 5%	Water. Less than 45% – 50%
	Bittering agent (Trace amounts)
NOTES:	NOTES: This is P-OAT chemistry. OAT = Organic Acid Technology “P-OAT” or “Phosphated OAT”

So what alternative coolants can be used ?

The coolant compatible with your aluminum engine is a P-OAT, which in Toyota terms is called the super long life, if you find the brands “AISIN or Zerex”, that is the OEM for the SLLC, as for the LLC the OEM is probably castle, As they have a product that comes in an identical container, but that is not definitive proof.

Things you DON’T need to know
LLC *(The one you should not use on modern cars) is not premixed, you add 50% distilled water, but this is for older vehicles.

Attention: the stuff/information you need is at the beginning, Most of the stuff that follow the practical section you will not need (The some theory section), whatever more you see is for my reference, for the curious, and for those who are wondering why i do it this way.

The lowdown: I have successfully repaired my 2014 (3rd gen) Prius battery, despite the fact that most information on rebuilding your Prius battery online is Bull, almost as if it were engineered so that you kill the remaining good cells after a month or two.

Update Dec, 10 2024: The battery was rebuilt somewhere around the end of COVID, probably 2021 or early 2022 (Yes, i really don’t remember), it is still working perfectly on a car that commutes 200KMs per day, 5 days a week, besides its daily town use, proving beyond any doubt (in my mind) that i was right, YOU PAIR SIMILARLY HEALTHY BATTERIES AND DO NOT CONNECT WEAK BATTERIES WITH HEALTHY ONES, THE ADVICE ON THE INTERNET IS THE OPPOSITE OF WHAT YOU SHOULD DO…. Why this is follows in this post

Here are the tools you need

• An android phone (You can use Apple/iPhone with torque pro, but the instructions here are for android)
• The Torque Pro app on the phone
• Prius PIDs for torque pro (Download here)
• A compatible OBD2 adapter, I use a WiFi adapter, you can use a Bluetooth or any other that works with torque pro
• A laptop with software like excel or LibreOffice calc, A paper and pen should also work
• A charger capable of charging a battery of 6 NIMH cells (Battery means in series), I use the SKYRC imax B6 mini (I don’t, I use my own home made charger built with an arduino, a acs712 current sensor, and a screen, but for the purpose of this tutorial, we need a charger so the imax B6 mini should do the trick)
• Car headlight lamps (To drain the batteries)

Like everyone else, it all started with CHECK HYBRID SYSTEM STOP THE VEHICLE IN A SAFE PLACE getting displayed on my center “multi information display / instrument panel” or MID for short.

Connecting the OBD2 adapter resulted in fault code (P0a80) other relevant codes might display with P0a80 such as p3011, p3012, p3013 etc. which should point you to the failing module pairs that are causing the failure. in my case, I only had the P0a80.

Prius battery terminology (As per Toyota)

Hybrid battery: the whole Prius traction battery pack of 28 modules
Module Pair: the car reads voltages of modules in pairs, So voltages of the 28 modules in a Prius battery are reported to the car as 14 values, meaning every 2 modules are read together as the sum of the voltage of those 2 modules.
Battery Module: in a Prius battery, every 6 cells are enclosed in a sealed container called a module, this is why you don’t directly see the cells, a module’s nominal voltage is 7.2, which is the nominal voltage of 1 cell multiplied by 6.
Battery Cell: A 1.2V NIMH cell that you will not see because it is hidden inside a module.

So, without further ado, let us get started

Diagnosis, which modules are bad

Before we take the battery out, we can save a hell lot of time by looking at what the car has to say about it’s battery pack.

I have broken this down to steps you see below

• Install torque pro to your phone (android in my case)
• Download the Prius 3rd Gen PIDs file by clicking here
• extract the file you have just downloaded to the (/.torque/extendedpids) directory in your phone
• Open torque pro, and go to the Menu -> Settings -> Manage extra PIDs/Sensors -> Menu -> Add predefined set.
• Create an Realtime Information page in torque pro to display battery voltages in real time such as the one below, you start with an empty page, then add (tiny) displays corresponding to voltages of individual modules, I personally like to add the Min and Max voltage entries to make it easier to know when you have found what you are looking for while driving without having to scan through the batteries
• Clear the error code, switch the car off then on again, the car should now appear to be working fine as if the battery is okay, this is obviously just for the test as the car will soon find out the problem again and inform you of your problem
• Now, once connected and information is displayed, find a nice uphill climb that is not too steep, with no traffic, at the bottom of that climb, floor the break and gas pedal at the same time, this will charge the battery, then on EV, start climbing wile recording your phone screen, the battery should drain really fast and you will either hear the engine running, or the “Check hybrid system” message should appear again, either way, you now have a reading of which batteries drained very fast…
• Inspect the recorded screen recording, and figure out which modules are the ones causing the problem, please note that there may be other modules in bad shape, but for now, the worst ones are clear

Taking the battery out of the car

To be able to pull the battery out of the car, you will need to take the following steps

Some theory

The 20% to 80%

Q: Why does the car consider the battery fully charged at 80%, and depleted at 20% of the batteries actual capacity ?

A- Why the 80% cap ?

Let us start with why it caps at 80% ! (At 80 percent, 100% will display on your instrument cluster)

The most common theory (that i don’t find convincing) is that the car wants to leave headroom for regenerative breaking, if it were so, why does it start using the gas engine’s breaking at 80% ? burning fuel, and defeating the purpose of regenerative breaking ?

My own theory is that there are multiple reasons, of which the headroom theory above is not one… here are the reasons i expect the car was designed this way

1- NIMH batteries heat up once you are charging above 80%, which is wasted energy, so the car is expected to try an use up the battery back down to the happy 6/8 area.
2- Heat is bad for the module’s health, and the health of the modules around it (See 1)
3- When modules in module pairs become mismatched health wise, this 20% headroom spares the weaker cell the overcharge and the damage associated with it., illustration will be added soon.

B- And the 20% depletion mark ?
NIMH cells can be depleted to ZERO, in fact, the company that makes the enelope batteries for Panasonic calls depleting the battery to zero and then charging it again a refresh function.

The area between 0.9V and zero volts has very little energy, as most energy is delivered between 1.3 and 1 volt, but still, this area is much less than 20% ! so why 20%

1- Unlike gas cars, hybrid vehicles do not have a 12V starter motor, the gas engine in a hybrid car is started by the electric motor itself, the same one used to propel the car is used to start the engine, if the battery falls below 20%, especially as batteries start to age, there will not be enough power to start the engine, more to that, the batteries have internal resistance, so the car needs to be sure that when it is parked for a few days (or months), it will have enough traction battery power to start the gas engine.