Diagnosing Cheap 3rd Gen Buys

Hi all!

New Prius owner here. Long-time reader of Grassroots Motorsports, lover of beater cars and cheap transportation. My daily driver truck is killing me with its 11MPG, and I wanted a cheap beater that was still relatively new.

You'll have to understand, I'm a big fan of cheap cars that don't turn over. It's like I've walked into the local pet adoption center filled with puppies and kittens. I just gotta take them home. I've fixed and driven many vehicles that were sold cheap cheap simply because their owners couldn't figure out why they wouldn't start. Starters, fuses, other ignition issues. With traditional engines, it's usually pretty easy to determine. I once scored an RX7 for a few hundred bucks because its owner blew a fuse while jumping it. Another time I paid a few hundred bucks for a car, brought it home, replaced a battery, found out it needed a bottom-end, sold it a few days later. You win some you lose some.

When I spotted a 2010 Prius at the local towing lot with a clear title, a set of keys, no external damage and all its fluids I got curious. It was in a No-Start No-Dash Lights No-Nothing condition. We didn't even know how many miles it had! I got it for well...really cheap.

I called the local salvage yard in advance to ask them how much they'd give me for it if I sent it to the junkyard - approximately $250. Good to know.

Brought it home, hooked it up, mystery mileage determined: 214,000. Yikes!

I've research and researched and come to this conclusion about the order of operations for determining the condition of a "dead" Prius:

1. Charge 12v Battery (mine is dead, it's from 2013, but my truck has got a strong mother-of-a-battery.)
2. Attempt to Start Car (not from running other vehicle, but a large temporary spare battery)
3a. If car starts, pay attention to noises from engine that may signify head gasket or other internal issue.
3b. If car doesn't start, could be dead traction battery.
4. Grab a PanLong Bluetooth OBDII adapter for $12 and Dr. Prius app. Test battery.

Now the question will be: if I get this far and determine the battery is bad, is it worth going any further? Is there any way of starting the motor without A) grid charging the traction battery B) reconditioning the traction battery or replacing cells or C) spending $1000?

From my research, it looks like no. It's a vicious circle, a chicken-and-egg situation of:

1. Traction battery needs engine running to charge
2. Engine Needs Traction Battery to Start
3. Can't determine engine condition without it running.
4. Can't determine worthiness of investment without good traction battery.

Could I do a compression test of the motor to determine head gasket condition?

Thanks all!

 

Well, luckily most of the mystery stuff has been resolved: I got her started with help of a strong battery and a better understanding of the power delivery.

One thing home mechanics not familiar with Priu..Priui? Priuses? Priued? Anyway, one thing I had to wrap my head around is that just sitting here in my driveway the motor isn't going to start until I press the accelerator. It's pretty easy to assume "it won't start" when your just turning the HV battery on off on off.

I figured out how to do the Maintenance Mode and that allowed it to sit there and idle.

That gave me time to pull the laundry list of codes while it sat and idled relatively quietly. Codes for EGR, Cylinder Misfire, Catalytic converter, etc. These all sound like "this car has been driven into the ground."

I've got a compression tester, I wonder if I can just check compression vs a leak down test?

Any other obvious way to determine if the head gasket is bad or going bad?

I've got a boroscope so in theory I could take a peak at the pistons and cylinder head to determine if there is any tell-tale signs there while cleaning the EGR system.

 

My main concern with driving it is that if it does have a bad head gasket, I don't want to force coolant into that cylinder and end up with a bent rod.

I'd prefer to determine head gasket condition before driving it anymore.

Would cleaning the EGR system allow for a more gradual decline of the head gasket rather than the bent rod scenario?

 

Here's my new plan:

1) Tear apart the engine bay to get easy access to the spark plugs, coils, and EGR system. This will not only allow me to clean the EGR, but also start the tear down for a head gasket if need be.
2) Do a Leak Down Test - (Anyone use the cheap $30 Harbor Freight Leak Down Tester?)
3) Get Dr. Prius and Bluetooth OBDII adapter to test traction battery. ($12 for PanLong adapter?)

My thought is, even if the traction battery is dying, it's probably still worth replacing the head gasket myself. We're talking a $90 part on a vehicle still worth $2500-$3000.

If the car somehow magically doesn't need a head gasket but the traction battery is dying, it'll totally be worth reconditioning it.

A Prius ONLY getting 30-35mpg in town is far better than my truck getting 12mpg.

 

I see that the Prius head bolts are Torque to Yield, so yea I guess head bolts are required too. Drat.

 

Which is more important or more accurate determination of head gasket condition:

Leak Down Test
Coolant System Pressurization Test

I'd prefer not to buy the tools for both. I've got a endo/boroscope already, as well as compression tester.

 

I've replaced probably 5 or so head gaskets so not super concerned with them. Did on a few motorcycles too.

Thing is, every motor is different. My old 91 Dodge Shadow was definitely much easier than the more recent dual cam motors (and Subarus, ugh).

I will say however that I've never replaced a head gasket on a vehicle that was A) as new as a Prius and B) not spewing a white cloud of coolant. I've never had to be so precise as needing a leak down tester because those head gaskets were clearly bad. It's a been bit strange to be so concerned about such a minor leak. I drove a 95 Escort for nearly 25k miles on a bad head gasket.

So if it seems like I'm asking a lot of questions its just because I want to learn the myriad of ways people approach the problem and diagnoses as sometimes the "common way" is not the best.

 

My EGR Cooler was so blocked that filling one end would result in NO water (or cleaning chemicals) flowing through. It took days of soaking and two trips the car wash for a pressure washer to clean it out. There are some still some passages on the corners that are blocked, but the majority of it is clear and I wanted the car back on the road.

Strangely enough, the head gasket appears fine. I'll need to monitor it, but I'm less afraid of hydro-locking the motor after checking the cylinder again for coolant buildup - nothing. The two center cylinders are little more oily, but no coolant.

Dr. Prius says the battery is OK. Not great (two low modules) but not dead. I'll need to run the "Personnel Subscription" tests.

I think it needs brakes. Sounds horrible when braking. Shocks too, rides like sports car.

 

Car is tagged and insured. Drove it in anger last night. Drove it to work this morning. No check engines lights.

Still needs a new 12v battery. Cheapest I've found so far is about $175. Powersports batteries are way cheaper, but will require adapters.