NEW!!! Service Bulletin for Engine Knocking at Startup T-SB 0012-10

... and that "safety clutch" ("torque damper" is what Toyota calls it, IIRC) isn't really something that can make noise or cause knocking on its own ... all it can do is slip a little, to protect downstream components, but that's not the kind of action that makes knocking noises.

There is a case, though, where it can: the friction disc does contain some coil springs for taking up sudden shocks (in that way, it looks pretty much like normal manual-tranny clutch discs, which are also built that way). And some people have been able to pop out the little bell-housing access panel and find broken bits of those springs lying around in there.

The chicken probably precedes the egg here, and rough engine running for a while would be what caused the springs to break. But once those springs have broken, of course, the plate will have mechanical slop, and that'll make any knocking noises twice as awful.

 

No, I do not agree. I have experience the knocking sound twice, and it sounds just like all the videos that have been posted here and on youtube. And it really sounds awful. Much more than a conventional engine that misfires would sound I think.
For me the explanation that this is related to MG1 makes sense.

And if the sound goes away if one where to engage Neutral, that would be sort of proof to that theory.
I have had the issue once about 3 years ago and once this winter. Otherwise the engine works perfectly, it would not if there was damage to it.

So the conclusion is that you could get this sound from a completely new Prius/HSD, so it has nothing to do with wear and tear.

 

What do you "not agree" with?

• That the torque damper is made of a friction disc permanently gripped between a pressure plate and the flywheel?
• That the torque damper has no mechanism of engaging or disengaging?
• That a friction clutch with no means of disengaging is not by itself going to be a cause of knocking noises?
• That there are damper springs in the disc?
• That there have been times damper spring pieces have been found in the bell housing?

Several things were said in the post you "do not agree" with, so it would be clearer if you'd identify the points of disagreement.

Also, some things were not said. First, I did not question that the knocks happen, and sound really bad. They happened in my Gen 1, and sounded really bad.

While I mentioned that in some cars, bits of the damper springs have been found in the bell housing, I did not suggest that as the cause of the bad knocking. I carefully said I expect the chicken/egg goes the other way: the knocking, if it goes uncorrected too long, can break the springs. (Then, if you thought it sounded bad before, you're not going to like it any better with broken springs!)

I did not say that MG1 can't have any role in the knocking. In fact, I didn't mention MG1.

There was even a good article eight years ago that persuasively suggested there is a role played by MG1 in exacerbating the knock.

It just isn't a role played by a "safety clutch" or anything that "engages" or "disengages", because there is no such clutch.

My aim was to steer the thread away from speculating about parts that aren't there, and back toward what people really have learned about the phenomenon.

 

re: @ChapmanF

I guess it was a misunderstanding then, just wanted to make it clear that the knocking sound is really bad.

BTW, still very curious about what happens if you would switch gear into neutral, hope somebody can test this soon. Also, that could be an easy fix for Toyota, e.g. make the system auto engage neutral when the engine misfires. Especially if you have an auto handbrake, because that would need to be activated when switching from P to N.

 

Type an "@" symbol directly followed by a member's name (no space in between), and they will get an alert. Also, as soon as you type three letters there will be a pop-up window, showing members whose names begin with those letters. It's safest to just click on the right one, to avoid any misspelling. It auto-completes accordingly.

As an example:

@ChapmanF

 

There’s a fella here who uploaded a YouTube video here with engine knocks. When he puts it in reverse, knock goes away.

 

re: @Grit

Great, then I guess we can conclude it would be the same with the neutral gear.

So with P or D, the system will try to charge the hybrid battery.

With R or N, the system will NOT try to charge the hybrid battery.

 

Wow! I learn someone new every day! Thanks!

 

Great info. So how do we do a search on here so we can save on thread counts with same issues

 

B also?

 

Seriously, I find it best to just search from google home page, prefacing with "priuschat".

 

@Grit

Yes, B will behave as D, so it will charge the hybrid battery (in this scenario).

I tried this today when doing a cold start.

Even if the car is running normally you can notice there is much more load on the engine when it charges the hybrid battery. So when doing a cold start, then engine will start after a few seconds when the gear is in P. When the engine then has started and you put the gear in N or R, the load on the engine goes down. You can hear it and maybe feel it. And of course you can see it in the energy monitor (the display section of the monitor where you see the whole car, look at the arrows...).

 

I'll try tomorrow.

 

I have oil catch can installed -- knocking worse than ever.

I installed the OCC during a big overall/cleanup to try to eliminate knocking:

- Replaced plugs with the newest p/n toyota recommends
- Thoroughly cleaned original intake manifold
- cleaned the EGR cooler, pipe and EGR valve (very good)
- New PCV valve
- New intake manifold gasket
- Installed OCC

Knocks worse than ever and still throwing code.

So... that leaves ignition coils (and perhaps wire/connector) and fuel injectors.

My startup knock got progressively worse, so now I am assuming it is caused by something either:
A) Getting clogged/dirty (injector)
or
B) breaking down with age (like an ignition coil, or injector)

For Toyota to have redesigned the IM, and offer replace the EGR they seem to be aware of the problem and the IM is a relatively *BIG* fix/replacement for them to offer people. Not to get into the conspiracy side of it, but it's almost like there is a bigger issue that we're not being told about, like a major design flaw or something that might result in recall of the ICE itself. That sure would make redesign of the IM and offer free replacement seem like a better choice. Me I'm screwed since I'm at 160k miles.

 

Sorry to hear about your Prius .

Some questions:

• All connections are tight?
• Does the knock go away after driving?
• Are there only misfire codes?
• What device do you have to read codes?
• Is the engine coolant level stable?

Good luck and keep us posted .

 

I’ve done the exact same things you have, except I replaced all of my ignition coils. Still getting the knock when the car changes from battery powered to engine power, usually sitting at a stop. The only thing I can really think to do next is to replace the fuel injectors.

Also just recently noticed that my heater doesn’t work and overheats the engine if I turn it on.

I’ve pretty much maxed out my ability to do anything on the vehicle and haven’t found a mechanic that’s comfortable doing anything with it. I really don’t want to take it to the dealer, but I may have no other option

 

I think this is what I've been hearing on my 2010. But if I'm reading this correctly, I'm not covered under this? 137k miles, Texas private sale 2010 Prius

 

Sounds like a blown head gasket or bad water pump.

Pixel XL ?

 

Put it on a truck and sell it to someone in California.... quick?

 

I actually had the car at the dealership today for some recalls, and I asked them about it. They said there's something in their system that could be it. But they have to do some diagnostic test, and if it turns out that's not it, then they'll charge me a $150 diagnostic fee...