Strange noise from 328 engine.

Hopefully you have some ideas what this strange noise is, coming from the engine. It appears upon a cold start, almost every time. Sounds like small fire crackers. The sound dissapears after around a minute. Engine seems to be running fine. Of course while at workshop, they didn’t hear it when starting 4 times over the course of a week, so they couldn’t help and didn’t find anything. Recent service with belts. Please check a video I uploaded to YouTube.
https://youtube.com/shorts/iCm6VIM-w28?feature=share

 

Is the sound from the right hand side of the engine as you look in from the back. All the fan and cam belts are on that side. A/C , water pump and alternator. They would have been off when cam belts done. Might need adjusting if it is them.

 

Sounds like HT leads may be arcing somewhere. Could be the spark plug extenders.

 

Thanks. Yes, the sound is on the right hand side. At the workshop they also suspected something like this and checked the tension on all these belts. So that's probably not it.

 

Hi,
maybe one of the exhaust manifold gaskets. Or some screws there loose.
Paul

 

Start it up and engage the ac, that will turn the compressor- see what that does to the noise. Normally this belt turns the pulley but no tension as comp clutch disengaged. With ac on the belt will be under tension, see if any thing changes

 

Thanks. Exactly, it sounds like sparks. I replaced all extenders and leads, but the noise was still there. The coils were replaced with new ones last year.
To describe how it started: I had a service done a couple of months ago. The very next time I started, it ran badly and made rattling noise. When I looked under the hood I saw sparks where the lead is connected to the coil. It turned out to be a bit loose. After pushing it back, it ran better, but there were still occasional sparking sounds when cold. So this is when I decided to replace extenders and leads, thinking this would solve it, but it didn't...

 

I assume it is the snapping noise. My 328 began making a snapping noise a number of years ago. Turned out it was an exhaust sampling tube that connected to the front header. It had failed due to corrosion right where it attaches to the header. Rather than replacing the set I plugged the four holes after drilling out the threaded portions and rethreading. Front header removal was lots of fun.

 

I would lean towards this myself. You could try pulling the cable off the plug to test, but this can be tricky on the forward side.

 

Thanks, I will try that. The ac has never worked, despite some attempts in the past. During the service they had a look but we decided to leave it. This could explain why the noise started after the service.

 

Years ago a small crack in a manifold was fixed. At the workshop they also noticed that there was a small leak. But would it make this sparking noise, it is the combustion that you hear?

 

Thanks, helpful to know that this made a similar noise. Not sure which parts you mean, the manifold or further down?

 

If the leak is near the head -> yes
Far away -> no

 

That's worth a check, maybe go for a new manifold while at it, if it's not 100%. I am seeing varying prices, 1777 pounds (2450 $) at ferrariparts.co.uk but only 495 pounds (680 $) at superformance.co.uk. (And at Tubi a set of manifolds around 2500 euros, 2960 $). Any idea why the difference and where best to get it?
By the way it's a german car, I live in Spain.

 

...slow down....first find the problem.

 

Assuming the compressor will turn, if the system has no gas the clutch for the compressor will not engage. To prove the belt noise you can try shorting the 2 wires on the pressure switch on top of the filter drier in the front boot. This will fool the compressor in thinking it has gas, but only do this for short time.
Look up P D Gough in Nottingham uk for exhaust manifolds, they make them and a lot cheaper than superperformance etc. The manifolds are not an easy item to change, especially the rear one

 

Did you use the ferrari bits when you changed the extenders and leads ?

 

Oh, that sounds complicated, but I will try to translate that into spanish an pass it on to someone who can check that for me. Will check out PD Gough, thanks for the tip. I expected the front manifold to be more complicated to change.

 

Ordered from superformance.co.uk, it did not seem original Ferrari parts.

 

Sounds like belts noise to me. The AC or alternator belt lashing against one of the pulleys. When is the last time these were changed?

 

Before you do anything, I would remove one belt at a time and see if the noise goes away.

 

My '85 has a bit of snapping at cold startup - maybe the first minute or so. On mine, it's definitely the AC belt. Very regular pattern, almost in time with the engine rotation sounds. Not a huge problem for me; I'll deal with it at some point.

 

I think you have to tip the engine to change it

 

Other comments also point toward the ac belt. Would it hurt removing the belt and drive, firstly to see if the noise is gone, secondly just leave it off because I don't use the ac anyway? Or does it drive something else as well, or maybe disturb a certain balance?

 

Sounds similar, hope that's it, not much to worry about. How did you find out it's the AC belt?