Intermittent heavy diesel knock

[AlanJ1901 Lurker Find all posts View Profile Close AlanJ1901]

Hi, I have searched all the threads I could find, but can't find anything similar to the noise my 2007 D4D Prado (automatic) is making, which has done 160,000km.
The problem is an intermittent heavy diesel knock when the engine is hot and cold.
Sounds something like a big end knock/rattle, or no oil in the engine, on light to medium loads at 1200 to 1500rpm and around 2000rpm.
It's most noticeable at low speeds, especially going up my driveway for example.
On a good day it will run perfectly all day, for hundreds of kms, but if I switch if off and start it again (could be 1 minute or 60 minutes) it might start knocking, or not. I guess on average it will start knocking once every 3 or 4 starts, and once it starts it will keep knocking at low revs.
To stop it, I pull over and restart the motor, and most times it will be OK from then on.
Apart from that, it has plenty of power, does not blow black smoke, no noise at higher revs, and is economical (I think) 12L per 100km towing a 1200kg camper trailer at max speed limits.
I have had the injectors scanned, but apart from a fluctuating No 1 injector which gives me a rough idle, all appears OK. And of course when I got the mechanic to look at it, the engine ran perfectly.
My thinking is it could be a faulty solenoid, sensor or check valve on the common rail, because it is either good or bad, however the knocking sound is quite slow, which makes me think it's just one cylinder, which would point to the No 1 injector? I can put up with the rough idle, but no the knocking.
Has anyone come across a similar problem? I'm tearing what is left of my hair out. Any advice would be much appreciated.

[winniliss Avid PP Poster! Find all posts View Profile Close winniliss]

Need to inspect oil pump pickup in the sump for obstruction and to check injector ranges etc for a start. There is a few threads on this, used google advance seach and use pradopoint.com for the site as an example.

Injector ranges and injector volume can change from one week to the next. PM Skywalker or the like could assist you more.

Hope this helps a little...or not

[Baileys Diesel Group Member Find all posts View Profile Close Baileys Diesel Group]

There are a few things. I'd start normally with Rail pressure, but its the most heavily 'watched' thing in the engine, and therefore if something there goes, a Code will be lodged. Id say from your notes, that this is not the case.

I "doubt" that an injector would cause this issue. Its not impossible, but its not likely. BTW, if #1 is moving that far it causes rough idle, it must be moving quite a ways? If you like, we've just added 'diagnose my rig' to our website where you can punch in the data and we can Analise it for you.

As winniliss has stated, I'd be dropping the oil, having a good look at the pick-up and in general the bottom end at the bearing shells. If this is all OK, breath a sigh of relief and be happy spending some money getting started on the fuel system. I don't think its likely its the bottom end, but better to spend an hour or two checking that before dropping $$$ on fuel system only to replace it all with a new engine later on (seen + heard this many times).

Anyway, keep us posted.

[AlanJ1901 Lurker Find all posts View Profile Close AlanJ1901]

Many thanks for your response, but if I drop the sump, what am I looking for that could cause an intermittent problem?

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

Alan this thread explains what you are looking for

http://www.pradopoint.com/showthread...ump-Oil-Pickup

And all this

http://www.pradopoint.com/showthread...e-in-D4D-Prado

If the injector seats are leaking that allows combustion gases to escape into the rocker space which burns the oil up there. This falls back into the sump and as oil is drawn to the oil pick up these burnt lumps which are very sticky bond together and block oil flow into the oil pump and engine. Starving the engine of oil can cause a bottom end knock and will kill the engine.

To inspect you need to drop the oil and put a probe in the drain hole to check the pick up. There are pics in both those threads of the pick up so you will have to look through. You could do an engine flush and drain but this won't fix the underlying problem with the injector seals if these are leaking.

If that is the case the fix is to removed the injectors and replace the seals. By the way these are called seats, seals and sheets so don't get confused by terms. Have you had the injector feedback values checked as per standard procedure? Again info in those threads.

Good luck, hopefully the sump screen and bottom end are ok. First step as Baileys said is to eliminate this.

At a guess an intermittent knock could be caused by a partially blocked sump screen with the sticky stuff falling away and reattaching blocking off oil supply.

[AlanJ1901 Lurker Find all posts View Profile Close AlanJ1901]

Just dropped the sump, all looks good, very clean and no cracks in the strainer. Is there anything else I should look at while the sump is off?

[cfryback Find all posts View Profile Close cfryback]

Well you've dodged a very big bullet there. But if you have done 160K km's on original injectors, that would be my starting point.

As others have mentioned, feedback values of the injectors will tell the true story.

A "cheap" thing you could do is have a look at the EGR and Intercooler. A mate in his '06 Hilux had his intake almost completely blocked. Dunno if he had the rattle, but total loss of power.

[winniliss Avid PP Poster! Find all posts View Profile Close winniliss]

Alan,

What is your location? Someone might have techstream software (or similar) to plug in and check injector values, injector volume, fuel rail pressure and the like. Toyota will charge you over $100 to do the same.

[AlanJ1901 Lurker Find all posts View Profile Close AlanJ1901]

I'm in Sydney, anyone you would recommend here?

[winniliss Avid PP Poster! Find all posts View Profile Close winniliss]

Sorry no, live at the other end of Australia...

[Baileys Diesel Group Member Find all posts View Profile Close Baileys Diesel Group]

Sweet Alan,
Only reason that i Stated that was we once had a car here where the bottom end bearings were GONE. Anyway, every-so-often they would align themselves back up, and the knock would go for quite some time. but then it would come back somewhat randomly... So if its not the bottom end, HAPPY DAYS!

I'd be (as a number have suggested) getting a full scan done by someone who actually knows what they are doing. we're down in wollongong which is a bit of a stretch, but if you need help we can probably help you locating someone up that way.

matt.

[cfryback Find all posts View Profile Close cfryback]

I'm in Sydney, anyone you would recommend here?

Should give these guys a go - http://www.berrimadiesel.com/home/

Wish they were closer to me....

[Baileys Diesel Group Member Find all posts View Profile Close Baileys Diesel Group]

All I would say about those blokes is that sometimes the information that they give out is a little skewed towards their intentions. Point in case, in 4WD Action magazine under their 'ask the expert' they were absolutely adamant that common rail injectors were never meant to be repaired, and that it shouldn't happen. 2 weeks later, Denso Australia launched Reman only. If its not possible, why would Denso be doing it?
At the end of the day, every one is entitled to their opinion, and they have a lot of people that sing their praise, but this was a blatant lie stated as a matter of fact, not as their opinion (never mind the editorial integrity of 4WD action to print such a thing when they take tens of thousands of our marketing money. This however is another story...)

[AJ120 Out of control poster! Find all posts View Profile Close AJ120]

(never mind the editorial integrity of 4WD action to print such a thing when they take tens of thousands of our marketing money. This however is another story...)

4wd Action and editorial integrity in the same sentence, sorry Matt but that belongs in the joke thread

Cheers Andrew

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

Alan you could do worse than give Matt a call and maybe end up spending a night in Wooloonoonoonoonoonoongonggggggg.