2000 miles from home with rough startup knock

Sorry to hear your in for $1800 worth of parts cannon with no results except a broken windshield. Unfortunately too many shops get fooled by a gen3 Prius.

Pretty close but it's more likely the head gasket leaking while shutdown but with coolant pressure. Sometimes warped heads happen due to overheating but I doubt your there yet.

The heat recirculation system is not causing a start up rattle. It's not a stuck open egr either; egrs will cause a stumble or stall at worse.

I suspect the borescope test was not done properly under coolant pressure. The quality of the borescope is important as well.

The following video was done by one of the best mechanics around and he is 75 minutes away from you.

This was done on a Honda with a bigger leak but you will get the idea
South Main Auto
Excellent Borescope Footage at 6:50

Assuming you have a leaking head gasket, you could limp along by relieving the coolant pressure by slightly loosening the passenger side reservoir cap.

Assuming it is a head gasket (I would give it 95% likelihood) the question is how to proceed. A JDM would be the lowest cost solution but it would have to be shipped in from a bigger city and you would have to trust a local shop to change it. A head gasket job with a rebuilt head might be a good option if the engine does not burn oil and you do it fairly quick.

I would consider taking it to South Main Auto if you can get in and let him diagnose and repair.

South Main Auto LLC, 47 S Main St, Avoca, NY. Eric O

 

IMHO; if it's in the early stages of HG failure; you may be able to limp it back home. You'll have to monitor your ECT to make sure you don't push it too hard on the way back. The BIG assumption is that the mechanic tested the car correctly and the leak closes up when the aluminum heats up.
I'm not a big fan of JDM motors because your putting in another motor with a know defect. If the car is in good shape and your planning on keeping her - I'd probably look into a rebuilt motor with all the updates that negate the gen3 motors' deficiencies. In other words, JDM motors are a "crap-shoot", no telling how long they may or may not last.
Whatever repairs you decide to do; you may want to preemptively replace that electronic ICE water pump. They tend to get lazy, especially if you don't change your coolant per OEM recommendations. Coolant goes acidic, quietly eating away at your engine internals - you've got a lot of plastic and electronics for the coolant to "chew on".

Well; that's my rant for this thread - good luck....

 

Not all JDMs have the same issues as a 2010 through early 2014 Prius. Used in Japan gen3 JDMs can be as recent as a 2021 as the Prius v/+ was still sold there until then. However there is no US vin plate to id the year so it's possible any 2010-2021 JDM could be in the crate you receive.

Since you have a 2014 v, there is a good chance you have the revised pistons and rings. Verify by vin.


Take your vin and determine which plant (3 or J) it was built in and then determine if your last six digits are higher than that plant's production change sequence number.

An early head gasket job with existing revised pistons and rings will include an improved head gasket from Toyota or Felpro. A rebuilt head cleans things up in the valve train. Have the shop update the ecu software to 34751200.

End result is you have a head gasket job with the same updates as a good gen3 rebuild. Assuming you have a first class shop do it.

You could spend $225 more and include the latest intake manifold as described in the attached tsb. An improvement you don't get with most rebuilt engines.

 

Eric will diagnose, but I don’t think he’ll take on head gaskets, hopefully can refer you to someone competent. In a recent video* he mentioned his go-to machine shop shut down.

make sure EGR system and intake manifold is thoroughly cleaned.

* he has YouTube channel South Main Auto

 

Sorry you had a poor outcome with the shop.
My opinion is you are in early or not so early stage of HG failure.
Now some will say NG to my suggestion but having experienced HG failure in my V and my sons CT200H As well as a few other motors over my 50+ years of driving and wrenching this often works to delay changing HG.
The longer you delay HG repair obviously greater risk of Bending connecting rods, scoring cylinder walls.

Take cap off the coolant overflow tank. Remove and save the Oring that pressure seals the cap.
Unpressurized a lot less coolant leaks into the cylinders. To make the trip back top off coolant. Carry plenty of extra coolant.
Use power mode so ICE and stays on as much as possible. During startup is when the coolant has to be expelled from the cylinders and caused the knocking.
I actually drove from Salt Lake City to Maine in April with a HG leak on a 2015 V that I bought with 251K on it. (SLC = No rust!)
Used blue tooth ODBII dongle and the Prius App on my phone to constantly monitor coolant temp. Going up mountains had to turn heat on high to keep from exceeding 210F.
Added a Overflow to the coolant tank to capture coolant so I could just pour it back into expansion tank after car cooled down.
I should make a Post/Thread how to that.

I'm actually debating btw a JDM long block and a Brand new short block for my V as the cylinder walls show signs of abuse.

How Toyota thinks its OK to not have a temp gauge is beyond me.
LOL. Too many service requests for temp over 180-195 I guess.

Side note:
Saab 95 the gauge goes to middle and stays there whether temp is 180-220F . To avoid service requests I suppose.
Different engineering idea!

Pete

 

He still does head gaskets but he will tell you if it's worth it or not.

When I suggested relieving the pressure to limp it along I did not mean so you could drive it 2000 miles. You will wreck the engine which has a fighting chance now if it has the revised pistons and rings.

 

Yeah see now he has done a few. Agree, a Signiant part of his work is answering the "should it be done".

One recent video, he was lamenting the close of his go-to machine shop. The guy retired, nobody want to step in, it's a fully equiped shop, getting dusty.

 

Yes that is a plus especially if it has not been burning oil.

 

Looking forward to the SMA episode:

“…It’s the Prius v, got the big 1.8, money-light’s on…”.

 

IMHO; this is the simplest and cheapest way to monitor actual ECT. At least this will give you an early indication to back-off or slow down; before you can potentially damage your engine.

These Prius only has a simple dummy lamp that triggers at around 245F. Normal operating temps is around 190-210; so you could be running hot and damaging your head-gasket without knowing it.
Note of caution; there has been some complaints of some of these unit causing a parasitic battery drain. Don't know if it's wired wrong or some cheap component within failed.

Hope this helps...