mx5cartalk.com

Hi guys,

My car was at the tuners this week when, after a lunch break, the car started to make a very loud rattle/ticking noise. They assumed the worse and started looking into the engine shitting itself. Long story short, I get it home and use works bore scope to make sure nothing has made its way into a cylinder (which the tuners thought had happened). Happy that nothing is seriously a miss in the engine I start it up. Doesn't sound like a big end knock and the noise is definitely coming from the head. I'm guessing its the lifter. I got onto youtube and found the video's pretty well agree with me (https://www.youtube.com/watch?v=b7MgkabPfgo). I've since discovered that SE's have shim under bucket lifters, which makes the fix some what more difficult.

Now that I think about it i could hear a lifter noise a few weeks ago when driving, when the car would get past 2500rpm. The noise would happen quite suddenly. At the time I didn't realise what the noise actually was.

Can a lifter go from making a mild noise to all of a sudden sound like its about to fall apart? Will running/driving the engine cause any damage? Can anyone point me in the direction of a guide to adjusting/fixing the noise? Don't really want to have to pay for it to be fixed but if it needs special tools etc.

Thanks,

Ash.

They do not have shim under buckets. They have shim over buckets.

the tolerances between the lifter and the cams need to be checked. and if adjustment is required, then a new thicker shim will need to be fitted. it is an time consuming and expensive process.

I'd first check if one of the lifters or shims have moved before anything, especially if it was at the tuners and they were revving the nuts off it. Pull the cam cover off and have a look.

project.r.racing wrote:They do not have shim under buckets. They have shim over buckets.

the tolerances between the lifter and the cams need to be checked. and if adjustment is required, then a new thicker shim will need to be fitted. it is an time consuming and expensive process.

I'd first check if one of the lifters or shims have moved before anything, especially if it was at the tuners and they were revving the nuts off it. Pull the cam cover off and have a look.

^^^ this.

Check to see if it spat a shim.

or you could just do what my engine builder said and let it sort itself out, which would apparently take about 5,000kms. Nah, just kidding - it had to be reshimmed after 15,000kms to finally stop it sounding like a sewing machine.

Shim over buckets, yep, my mistake. Pulled the cover off and the shims all look good. All in place with no obvious cracks. Ill measure the clearances during the week. Does anyone know the tolerances? If it doesnt turn out to be the lifters, I've got no idea.

track_addict wrote:.....Ill measure the clearances during the week. Does anyone know the tolerances?

Inlet 0.21 mm (8thou) +-0.03mm
Exhaust 0.31mm (12thou) +- 0.03mm

Thanks rascal!

Given that you've already checked and found that none of the shims have been spat out I'd be looking for a broken valve spring. I'm an unfortunate expert in this field. They can be real buggers to spot. Low compression on one cylnder might give it away. Otherwise look for a slightly different lean on a spring or else use a dental mirror to check right around each spring - especially near the base. Their tendency is to break about one coil up from the bottom.

How many have you broken?! You do sound quite experienced haha. Do they just form hair line cracks or a proper split in the spring? I did have a look at them but not really close as I would of expected a broken valve spring to really go wrong and turn into many pieces.

8

They snap clean through near the bottom. Often the valve keeps working because it's only one coil shorter but you can get a lot of ticking and threshing. It's harmonic resonances not necessarily speed or stress that destroy them, so if you get a particularly "dirty" head or a set of aftermarket springs with the wrong frequencies for a BP head it becomes a bit of a pain.

Also consider the possibility of a bent or sticking valve.

So, I checked the lifter clearances. They're all good. Two exhaust valves are a bit tight (.009") but thats definitely not the cause of the noise. I spoke with my mechanic and he said I just need to start going over things to eliminate possible causes. So, this weekend I'm going to do a compression and leak down test, doubt I'll find anything but you never know. I'll also take the timing belt covers off and run it to see if theres anything happening there. He mentioned the harmonic balancer is a place to look, only caus ehe knows on some cars (commodores especially) that when they go they can make terrible knocking sounds.

My gut feeling is something in the engine has properly failed. I cant see any issues with the valve train and I'm not expecting to find anything with the timing belt but we'll see. Doing my head in!

Am I right in saying that since the lifter clearances came up ok, that rules out the possibility of a broken valve spring? I had a good look at them but it is very hard to see the entire spring with everything still installed.

I took a video on my phone which I'll post up when I can.

Please don't take offence, but you measured then all 180 degrees away from the lobes?

Haha none taken, but, yes I did measure opposite the peak of the lobe.

So if it ain't the lifters, then injectors? They make the same noise when going poo poo. And are located very close to each other.