Ahh yeah what is that racket at startup

[Rhys123]

Hey guys

Quick question I have purchased a 2007 STX with 100K on the clock. I have noticed over the last week or so it has developed a loud knock on cold start up (morning going to work afternoon coming back from work) under acceleration which dissipates once the engine warms up (though if you listen carefully there is an underlying tick when acceleration very faint).

Now I am a diesel mechanic BUT the engines I work on are quiet a bit larger (3600 Cat Marine and Power Generation) and I have never really been exposed to diesel engines this small or in a automotive application so any suggestions would be appreciated.

The car is under a 3 month used car warranty.

Cheers

 

[Old.Tony]

Check the air box. If the side of the airbox facing the engine has come loose it will make a very loud ticking sound under a light load (under moderate or higher loads, the suction holds the side closed).

If you have a listen to the front of the engine block you'll hear if it's the timing chains.

 

[Rhys123]

Cheers Tony

Mmmm timing chains that can't be a good thing (why the hell chains and not gears).

Would the knock settle once up to temp if it was the chain.

Of course your mind goes to worst case scenario one would hope it is only a adjustment if it is the chains..

 

[Old.Tony]

If it's the chains you'll hear them rattle and yes when hot they could easily sound differently, but I wouldn't think they'd "knock".

I wonder if the glow plugs are working properly? Diesel will still combust when cold but it just won't do it as well.

 

[Rhys123]

Yeah it is definitely a knock you can here it as you accelerate it reminds me of the old Perkins engines that I used to work on as an apprentice.

Might take it over to Nissan to get them to have a look at (though I don't have a lot of faith in dealerships).

If it is the chains how likely is it that it will need a replacement versus adjustment. Are these engines known to chew chains?

Well on a positive note sticking my head into the engine bay the noise seems to be coming from the back top quadrant of the engine maybe a lifter.

Shrug the joys of purchasing a second hand car.

 

[ST-R]

These common rail engines are noisy cold..My d22 is the same. The noise I am thinking of is the different fuel map during warm up. If the chain/tensioner/guides/rails are worn the same noise will occur hot or cold.

Regards

Greg

 

[Rhys123]

Yeah it has a bit of injector noise but it is not to bad.