Coolant Pressure Test for Toyota Prius Gen 3

Correct procedure, but where did you find a cap adapter that fits the Gen 3 Prius Reservoir?

Also, you don't necessarily need to top off the coolant in the tank. Having some air in there could throw off the pressure a little, but once you pressurize the system to ~16psi, you should be able to find your leak regardless. Also, you may want to do this test cold and warm as certain leaks may only be leaking when cold or warm (expansion of metal/seals).

BTW, I may be jumping the gun since you're new here, but why are you doing this test? Coolant going down without an obvious source of leakage?

 

How many miles on the Prius? Have you looked at the oil to see the condition?

 

Raytheeagle, funny how we're all jumping to assist someone and immediately pointing to the head gasket issue in gen 3's without even knowing why he's doing this pressure test. I'm hoping for his sake that it's not the case, but yeah, why else would he be doing this (on a Prius)?

 

The fact that the head gaskets are gone is probably your best bet of where you should start to diagnose the issues. Since you have so many of these cars, your first step should be to mark off the hot and cold marks of the coolant in each car. Maybe use a color code marker system and just have every car topped off to start at an even level. From there, have them monitored for coolant loss. If any are losing coolant, you can do a coolant combustion gas leak test. That will confirm if the head gasket is leaking into the coolant chambers. You can also do a compression or leak down cylinder test, but that's a lot more effort, especially when you are talking about the scale you're talking about.

Combustion gas tester:

You can buy refill bottles that'll cost less than $1 an ounce (1 ounce per test if I read the instructions correctly).

The sad part is that there is no low coolant light in the Prius. That would help you at least identify when the issue is at the early stages, but at the end of the day, you're going to have to pull the head and replace the gasket anyways.

BTW, how long is it taking your shop to replace head gaskets from start to finish (excluding machining of the head)? U.S. shop hours look like 18.8 hours according to AllData. Very long considering most 4 cyl engines can be done in under 12 hours, including bleeding the air out of the coolant.

Also, what are you using to test the pressure? How are you locking onto the coolant tank? Have a specific model or kit you're using?

 

It's suitable for all cars. There's other brands that may be cheaper or more expensive. Read reviews on Amazon for real world opinions.

As for how to suck the air out, yes, the coolant reservoir is the place to do it from as that's the only place that you can get a sample.

BTW, can you let us know what specific adapter you are using to do the coolant pressure test?

 

Where did you get that adapter to fit the cooling bottle or what brand and model is it? I can't find one anywhere...

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If you look at the pressure cap on that bottle, you may see a rating, like 108 kPa, on the label.

108 kPa is slightly under 16 psi (around 15.7). 16 psi is probably ok for testing. (If you were testing with the factory cap in place, it might vent slightly at 16 psi. But that won't be an issue when your test cap replaces the factory cap.)

 

From the short amount of looking these adapters on Amazon appear to be what is needed if you have a gen 3 engine.