EGR Replacement Test

How many miles on the car?

Have you checked the level of the engine coolant.? Is it low?

 

Good probability that there is a problem with the head gasket.

How long has it been since you first noticed the cold start rattle?

 

I was similar startup issue got three different valves none of them have made a difference One of the valves is the latest and the latest software is applied to the car already there are no other updates for this unit and still didn't do it I'm at a loss too but some of these things these guys get to work Not sure how but I guess some work some don't oh well.

 

In my opinion the easiest way to get a 100% confirmation would be to purchase a borescope (~$30 should do it) and look down cylinder #1 with it. You'll see coolant and/or a super clean piston top compared to the others. You'll know for sure and you'll have a nice useful tool for future use.

You could also examine the spark plugs you replaced for clues (post pics if you have them), or you could possibly even tell by removing and examining the new cylinder #1 spark plug you just put in, looking for wetness or just general darkness. The idea you mentioned could also work. I'd personally just want to look in the cylinder myself.

I wouldn't go to the dealership for anything except to purchase parts. $500 diagnosis is crazy talk,

 

Stay away from the dealerships. If you hear a knock when starting up, it's possible that you have coolant leaking into the cylinders. A symptom known as hydro Lock. Indicating that you need to replace the head gasket.

 

There are other places that specialize in gen 3 Prius repairs other than the dealerships.

 

There's a guy out in the Midwest that if you make an appointment with him you can drive out there from North Carolina and have your engine changed in 6 hours with a 1 hour running procedure I think $2,800 something like that bunch of places have sprouted up

 

EGR ever been cleaned?

Better deal with the head gasket failure first. If you get through that:

Then clean the EGR system, including the intake manifold. The EGR “cooler” (colloquial name for the first component, at exhaust manifold) may be clogged beyond redemption, but give it a try.

The EGR valve may have incurred damage internally: a plastic ramp can develop a rut, disrupting its action. Accordingly, you’ll need to clean it and inspect it’s internals.

The pipe between EGR valve and intake manifold is very straightforward to clean.

With the intake manifold there’s a large diameter EGR passage, and small diameter passages branching off at each cylinder. All of it requires clean out.

This also a good time to clean the throttle body. For the PCV valve, either clean or replace.

With the intake manifold off you have access to the intake ports in the head; they’ll need cleaning as well.

Again, all of this should be addressed after you’ve dealt with the head gasket. That’s if you don’t just swap the engine, or sell it as-is.

What you’re doing with that terminology is skirting a basic understanding, of what’s actually happening. The time to start dealing with the EGR was about 150k back. That ship has sailed. Sort out the failed head gasket first.

more info in my signature, for EGR and head gasket. Last link is the full engine section of Repair Manual. (On a phone turn it landscape to see signatures.)

 

^^^^ This seems to be one of the best checks suggested here. A borescope that has a second, side camera can be best (they don't all have those; mine has a funky side-view-mirror attachment but it's pretty much useless). You can pump the cooling system up to operating pressure and use the side camera to watch for drops forming around the top edge of the cylinder at the head.

Leakdown tests and chemicals to detect exhaust in the coolant are two other common tests for head gasket problems, but might not detect a failure as early as you could by seeing drips with a borescope.

Until you've done such checks, if you read a post telling you what to do about "the" failed head gasket it assumes you have, you can kind of smile and remember where the post was, and come back to it later if you've checked and that has turned out to be what your issue is.