Knocking noise on startup

[rob-mu]

When starting my motor up cold it has developed a bit of a knock for 30seconds,Got told it is probley the glow plugs? Could this be true?
And is it ok to use for another week until i replace them
Rob

[pouw]

I always thought knackered glow plugs would make it hard to start, but not result in a knocking sound?

[oldblue]

What motor ?

[Jungle]

Sounds more like a poor spray pattern from an injector. Our new work hilux's developed a bit of a knock when cold and under load. We had the injectors replaced with a fancy tipped one. Something to do with the NZ diesel stuffing up the nozzle.

Is it smoking on start up too?

G

[nachi]

Weird.. I've just had the same thing.. last couple of tanks.. am more worried that it might be something worse.. motor was rebuilt 40k ago.. so I'm told.. will keep an eye on this thread.

[sibainmud]

Hi Guys,
Not trying to be a smart arse here, but you need to be more descrip with the term "knocking".
There can be any number of causes why a diesel motor will knock when cold
You can break them up into a couple of possibilities.

Harsh Diesel Knock,
Can last up to a few minutes after cold start, but not so present on hot starts.
Causes for this can range from injectors, rings, valves or glow plugs.
This can be attributed to lack of compression, incomplete burn, or low combustion temps (glow plugs)
Some diesel engines not only use glow plugs to help them start but can also have an after-glow function and/or manifold heaters that get the combustion temps up as soon as possible.
Most of these causes also have a fair bit of smoke coming from the exhaust as a symptom as well.

Metallic Knock,
Worn internal engine components.
These sounds can quieten down after just a few seconds when the oil pressure reaches the worn parts.
The indicators for this kind of problem can be lower than normal oil pressure and if ignored can be fatal.


So, some more description would help a lot. And don't forget observation too, like colour of exhaust smoke, any other unusual symptoms or behaviours.

Hope this helps.
Cheers,
Simon.

[rob-mu]

Hi
Motor is a 2.8l 3l hilux
Sounds more like Diesel knock but there is no smoke on start up
sound has developed since i put in a new fuel filter ( i did add injector cleaner straight into the filter) and replaced the filter housing gasket
Cheers
Rob

[rob-mu]

Also does not do it all the time maybe 1 out of 5 starts regardless of temp
Rob

[sibainmud]

Boy does that shed some light on it

Here goes a bit of a prattle.
Injector cleaner should only be added to the tank...for starters.
It relies on being diluted by the contents of the tank.
It is real harsh shyt.
To give you some back ground,
When doing a service on a marine engine, I never prefill a filter as you are adding unfiltered diesel to both sides of the media in the filter. i always prime the fuel using the starter or the manual pump on the engine (or both).
Injector cleaner is only a "band aid" and should be used with caution. With some new engines, the warranty is void if the cleaner is added to the fuel.
So, if I were you this is what I would do, get the injectors cleaned and set, replace the glow plugs asap.
Diesels can run 1/2 a million litres of clean fuel through them with no issues, but can only handle a tablespoon of contaminate or harsh chemicals and the injectors will be affected.

I know this sounds anal, but spend the dollars and the problem will go away.

Good information gets good advice

[mud_slinger]

why did you pour injector cleaner into the filter?
that stuff is harsh odd's are you may have damaged somethin

[rob-mu]

Thanks for the advice,Will get them sorted
Btw not sure how this thread ended up in Drivetrain / Suspension

Cheers,Rob

[rob-mu]

What sort of $ am I looking at to get injectors done?
Cheers
Rob

[crazyclark31]

maybe 3-500 bucks. depends were you go.

[rob-mu]

Still had the originial glow plugs in it.So put in a set of new genuine ones in and sounds alot healthier
I had a set of new Ngk ones but rather the genuine

Still will get injectors done though
Cheers
Rob

[nachi]

..my knocking noise turned out to be a stuffed key on the lower drive pulley.. every revolution it would knock.. to an untrained ear it sounded worse than it was.. (thank fcuk) .. it had slogged out the pulley but not the crank key-way.. not a common one apparently, but there ya have it.. phew