Technical 1.3 Multijet Loud Knocking or Tapping

[NZFIAT]

Hello all,
My wife rang me on her way home from a long trip, the car had developed a tapping/knocking noise. I thought it might have just been the exhaust running so she carried on 200km to the next town. I went and met her but the noise is definitely engine related so have left the car there in the interum.

The noise seems to be coming from the upper engine N.o 1 Cylinder area. It's audible at idle but becomes very loud with revs and load. Aside from the noise the engine seems to be running fine with no loss of power or smoke etc. The noise is a crisp but loud tap, not a dull knock, and is consistently in time with engine revs.

The car has 140'000km on the clock and is running good quality fresh diesel, has had a recent fuel filter and is running the proper selenia oil etc.

Any ideas? Should I stump up the money and get it towed the last 100km or drive it?

I did wonder if it was a crook injector but not sure what they sound like. Any thoughts/ideas would be MUCH appreciated. Wishing I had recorded the noise before I came home now too.

 

[Humour]

Hello NZ,

its obviously very hard to diagnose not being able to hear it but the area that you are describing sounds like your camshaft chain tensioner is on its way out, which would be consistent with the engine still being driveable. If it was a Cam or the Big ends, I would be guessing that 200Kms later it will start binding and seizing the engine.

Anyway, I WOULDNT drive the car at all because if the chain fails you are talking open heart surgery to your engine with the head off, valves replaced and a whole load of pain for your wallet, and at worst case a new engine if the pistons rods and shells transfer interference energy into the crank when it happens.

I would suggest get it towed to a garage you trust and allow them to diagnose with a specific request to heck the cam chain tensioner condition.

If the car has always had the correct oil grade in it at the correct level and the oil change intervals have been shorter than the recommended 18,000 miles, then I wouldn't expect the tensioner is likely to fail, but of course no guarantees despite this engine being built to live to 250K miles +

Humour

 

[Markt8]

Did you find out what caused this?


Mark

 

[NZFIAT]

Hi,

Yes I did track it down in the end, here is the long story in the hope it might help someone. Probably not what you want to hear though.

I did a lot of diagnosis on the car when I got it home. Looking at multiecuscan, listening with a stethescope, putting it on my oscilloscope (have an exhaust pressure sensor etc). In the end I concluded it was a badly leaking injector as an injector balance test pointed right to the injector that was where the loudest noise was and an injector leak down test pointed to that being a problem injector.

However, I was wrong. A new injector did not fix the problem. In the end I was super busy so sold the car and actually got really good money for it as is, with the problem explained as best I could.

The new owner contacted me and according to his mechanic, the problem turned out to be a bottom end bearing. Which is interesting because I was quite convinced the problem was at the top of the motor.

In retrospect, there was a big clue that it wasn't the injector. That is multiecuscan was showing perfect contribution from all cylinders. This should have tipped me off as to it not being an injector, but because it was a completely perfect reading I discounted it as being incorrect or a non applicable test for that engine.

Thinking about it, I bought the car originally at auction. Despite the km's the timing chain was super quiet. I think what may have happened is it may have had a stretched chain which was repaired, but perhaps the debris from the old chain damage got down in to the sump. They probably saw it wasn't pretty and sold it. It's the best theory I have as I was super meticulous with servicing and using the right fluids. My only other thought was I did have a coolant pipe come adrift at one point (my own fault missing a hidden hose clip) this did cause the engine to get pretty warm before I stopped. I didn't change the oil after this as I normally would as I had only just done it.

Sorry that may not be of much help but at least you have the story and can draw your own conclusions. All the best with your one, if I can provide any further info/help please ask.

Alex

 

[NZFIAT]

Just another quick couple of thoughts. If I was faced with the problem again given what I now know. I would whip the injectors out where the noise is loudest and rig up a dial indicator to the top of the piston. Then mark the flywheel carefully and see if I could detect a difference in movement from one piston as it rocks over TDC. Not sure if this is a legitimate test, but it makes sense to me. If that looked OK I wouldn't rule out a bearing issue but if there was a noticeable difference then I think you could consider that to be the issue fairly safely.

Incidentally, the injectors can leak and get stuck on this engine. Try soaking them in "easy off bam" (might be called something else in your country). It's actually in the Suzuki workshop manual apparently to do exactly this when removing injectors from this engine.

Remember the noise really didn't sound like it was coming from the bottom end, and I did lots of checking with a stethoscope so it could be a bit of a trap. I also had a more experienced mechanic take a listen and they agreed with me. (I am only a serious enthusiast not a paid mechanic)