*Knocking/rattling sound after cold startup*

It can take weeks for the coolant to drop if it is an early stage head gasket leak. They seem to seal themselves as soon as the warm up, at least at first. Plus it won't happen each cold start.

Typically people will throw money at spark plugs, coils, fuel injectors and egr cleanings and still have the issue a few weeks later, particularly if it was an occasional cold start rattle. The reason they do so is it is cheaper, they think, priuschat is full of people who think egrs cause all issues and a plug or stuck open egr might cause a similar rattle. But plug, coil, injector or egr rattles are not just on occasional cold starts.

These engines do not typically dump coolant into the oil, do not usually show combustion gasses in the coolant, may not fail leakdown tests, may never have overheated but still get slight coolant leaks into the cylinders which get worse over months. Because of the above, most mechanics have never seen a 2010-2014 Prius cold start head gasket leak. A borescope inspection can be an early indication if the cylinder looks steam cleaned.

In the US powertrain warranty would be the only possibility but a ten year old car is excluded from the five year, 60,000 mile coverage. There are no special Toyota programs for this issue.

 

It will partially clog again, likely to the same degree in the same timeframe. Primarily because gen3 egrs draw exhaust gasses before the catalytic converters clean them up. A secondary issue is 2010-2014 Prius engines have flawed piston rings that often cause excessive oil consumption that ends up in the egr cooler passages. Some early gen3s with frequent oil changes do better on oil consumption. Both issues were redesigned on gen4 engines. Most Toyota mechanics do not clean or replace egr components unless specific egr related codes are generated.

 

Looking at the invoice it does appear they were thorough, which is a little surprising. Hopefully that's the case. For more info on what's involved in the cleaning, or if you'd consider DIY to see first-hand how well it's cleaned: see the first link in my signature.

How many hours did they have the car? If only an hour or two I'd be skeptical about the efficacy of their cleaning job.

 

My guess is the egr cooler and intake manifold was not clogged but simply had normal buildup. A completely clogged egr will produce specific codes. Egrs are normally closed at startup and low speeds anyway. The earlier gen2 Prius did not have one at all.

Primarily, an egr reduces emissions slightly and leans the fuel air mixture at highway speeds to improve mpg. The fact your mechanic could do it in three hours means he was good and the egr cooler and manifold did not need major cleanup.

As far as trading it, here in the US a 60,000 mile gen3 engine like yours is usually in very good condition and is often sought after as a replacement engine for a 200,000 mile car. Change oil frequently, every 3,000 - 5,000 miles. If you have no more rattling over the next two months, you are probably good. If it does rattle, a trade might be prudent assuming you can find an affordable upgrade.

 

It's a "temporary fix", similar to every engine oil/filter change, or any other maintenance. It's steadily accumulating, constricting the flow. If you can manage an oil change, you can do the EGR. I would recommend to do it every 50K, miles or kms, take your pick.

See first link in my signature, for a fairly exhaustive list of what tools you might need, tips, links.

 

How about the updated intake manifold replacement? I'm guessing later model year gen 3s experience this clogging less? I wonder if you can read/find the intake part # without removing the manifold from the engine?

I know there was some confusion as to the correct part number. (Sigh)

REVVL V+ 5G ?

 

I think the intake manifold revision was in model year 2012? When @NutzAboutBolts did his intake manifold cleaning video, he had copious goop and carbon still. And it's (obviously) going to make no difference to the condition of the upstream cooler/valve.

Seems like Toyota dealerships were offering this revised intake when owners complained about cold start knocking (and/or had egr blockage code), then it quieted down. As in: it's not doing much, if anything.

Periodic cleaning is the cure, my 2 cents.

 

Some readers might prefer less guess-work or make-work, and gravitate to asking the car from time to time for its EGR flow test results, and letting their maintenance schedule be guided by that.

Plus periodically checking the intake manifold passages directly, because that's comparatively easy, and the built in EGR flow tests don't cover those.

 

This is the latest I have, I wonder if there is Rev 3. Since it is Google searchable AND on the NHTSA website I'll just attach... View attachment MC-10149046-9999.pdf

REVVL V+ 5G ?

 

According to the document, the intake manifold and ecu programming could be responsible for a no start below 23f, eg a cold soak. My 2012 cooler and manifold were plenty clogged several times.

 

Skip the parts cannon; just clean what you have.

 

i have 200k miles on my 2014 Prius V and have had this same issue sporadically since about 150k. Never could figure it out. I came out of a car wash recently and the engine shook violently and the check engine light came on for first time. Codes had to do with cylinder misfires and some rare downstream wiring/sensor codes. There were no other warming lights, so the advice that came up with the codes said to just ignore them and continue to drive. The engine continued to run a little rough but smoothed out eventually and the check engine light cleared. I checked out a few of the obvious things (spark plugs, coils, wiring) but everything was good.

i ran this issue by my mechanic and he thinks some water or soap from the car wash got into some wiring or sensor somewhere. At other times some condensation build up could have caused the problem. I am continuing to closely monitor the situation. I have put 4k miles on since then and I’ve only experienced some minor shaking a few times that lasts only a few seconds. The check engine light has not come back on since, and the engine runs smoothly for long distances. I not really concerned about it anymore.

i’ve read several posts about this issue. It seems to be a common issue with the Prius, but doesn’t appear to be causing anyone any serious issues. It shakes only occasionally for a few seconds, then stops and runs smoothly for hundreds of miles before happening again.

If anyone has any other suggestions as to what might be the root cause of this occasional shaking I’m willing to consider them, but right now I think it’s just water or condensation getting into some exposed wiring somewhere or onto a sensor and I’m not very concerned about it.

 

unburned hydrocarbons in the intake manifold, usuall from shutting down a cold engine.

also, egr circuit clogging can be an issue