Technical
Knock Knock There Is A Gremlin Under My Bonnet
We get a lot of phone calls about Toyota Prado and Hilux 1KD engines, these are Common Rail injector engines. They have a couple of common issues that can cause significant engine damage if left unattended, including blowing smoke or a knocking rattling sound, that can lead to blowing up your engine.
The most common fault is diesel knock, which basically sounds like there is a little man with a hammer hitting your engine block with a hammer, some say a rattling sound under the bonnet. The knocking /rattling sound gets worse on acceleration.
This is usually caused by the spindle in the center of the injector seizing, which causes over fueling in the cylinder and when an injector starts to dump fuel in the ECU will start to try and take fuel out and lean out the engine causing a knocking sound.
A lot of companies use the electronic diagnosis of injectors to isolate which of the injectors are faulty and while this will give you a good idea it’s not necessarily 100% right.
The idea being that the fuel system can adjust the required amount of fuel the ECU thinks the engine needs to even out the idle speed and have a nice smooth idle. Most of the variance from this idle is usually caused by faulty injectors, but there are other things like cylinder compression being low, blocked intake manifolds from EGR deposits (which affect the rear 2 cylinders), engine timing being out, bad/dirty tank of fuel and lastly the suction control valves and fuel pumps.
The picture above with melted piston on the left was running with a faulty injector squirting and dripping excess fuel in the cylinder melting the piston, the cylinder beside it shows no wear at all in comparison.
We recommend servicing or replacing the injectors every 100,000km to be on the safe side, as it’s cheaper to get your injectors serviced than overhauling your engine. Not that I would complain about rebuilding your engine with our ceramic coated pistons and supped up fuel system with hydro dipping on your externals bit.
Another issue is simply worn out injectors due to the high pressure whether it is from a diesel chip or erosion itself, usually evident is large amounts of black smoke and a drop off in power, the gradual decline usually means the owner doesn’t even notice over time. This can happen anywhere from 80-100000km depending on grades of diesel fuel used and lack of fuel servicing. To get more out of your Hilux or Prado Noordeman Diesel loves remapping of an ECU over the use of the chips that are common on today’s market as they increase fuel rail pressure to a dangerous level to get the more power but at the expense of the parts themselves and the engine lifespan.
Next is a cracked 1KD piston which would have benefitted from our ceramic coating we do this to all of our pistons and valves to handle a lot more heat.
Last up we have injector failure (standard wear and tear or erosion), this is where the clearances in the injectors or the cylinder bore wear, the amount of fuel leaked into the cylinder is higher producing a less effective amount of fuel into the cylinder, meaning more fuel comes out the leak-off, rather than being put into the cylinder, which means the amount of fuel that the ECU thinks it’s injecting into the cylinder will be highly increased.
More evidence of how it can be just the one cylinder has gone, however if you look at the tip of the top one, it to was already on its last legs.
