HLA rattle (Video...)

Hi guys,

Hope you can help me here…


Mx5, Mk1, 1.8 s-special

Oil used:

Mobil Super 2000 - 10w 40 last changed about a month ago.


I have tappet noise after a motorway drive. Sustained 4,500/5000rpm (70/80mph)

I do not get tappet noise on start up, or if i do it quickly goes away.

I read it may be low oil, but its definitely not that (checked).

I have changed the CAS O ring, as there was oil behind the engine. The
old O ring was so brittle! I assumed that would cure the issue… wrong!

I have no idea what to do next. normal town driving, and anything under
50mph tends to keep her purring. But as soon as i hit higher mpg/rpm it
will chatter like mad. Once i slow it back down and drive at below 50mph
for a few minutes, the chattering tappets stop!

I’ve uploaded a video to show the problem i’m getting… is this just one noisy tappet or oil or worse?

Please advice me if you have heard of this before/had this before.

Many thanks,


Vid here: http://www.youtube.c…h?v=Nwqc3UnHn6Y it’s 4 mins from start to finish, but the main bit (after motorway driving) is at 2.00 mins.

G’day mate Welcome to the forum–

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Forum Technical Index

HLA rattle is normally caused by the oilways getting clogged up, they fail on very few occasions.

Try giving the engine a dose of Wynns, this stuff   follow the instructions exactly and see how it goes. New oil and filter needed also, the oil you are using looks like good stuff, I’m also a fan of Mobil oils

id go with what geoff is suggesting,it does sound like its being starved of oil at high revs you could try and flush it with an oil additive,or what i use is about half a pint of deisel added to the oil give it a good blast for ten minutes then empty the sump and add new oil with a fresh filter should do the trick


In the situation described you need to use better oil; something that stays in grade when it’s hot.  Unfortunately MX-5s tend to cook their oil on motorway runs, especially if you drive a bit too fast.  The 1.8 has an oil cooler under the filter but it’s tiny.

A shot of Wynn’s Hydraulic Lifter Treatment (use half a bottle) a hundred miles before the oil change wouldn’t go amiss.  It’s one of those rare products that actually works.

 I’ve used the diesel in the oil trick before with my old rover T16 engines-they suffered with sticky valves. I put in about 1/2 a litre of diesel. Take it for a quick italian tune up once warm, then drain, flush using flushing oil and refill + new oil filter. Should work well.

 Blimey that does sound nasty.  I use Mobil rally1 in mine and have never had any problems.  Maybe as suggested, you need to give the engine a flush and then an oil change.

Hi guys,

Thank you for all your help. Many people post on here and never explain what fixed the problem… Well here is what fixed mine:

Wynns Engine flush for 20mins at 3,000rpm

Drop the oil straight away (when its very very hot = get rid of everything)

Genuine Mazda filter

Mobil 1 0w40


Result??? -  Not a tick in ear shot!

 agree, but not a 0w-40


better a 10w-40 or 10w-50

There’s nothing wrong with 0W40 except the price.  It’s exactly the same as 10W40 when hot, but flows a little better when cold.  It is still thicker when cold than when it’s hot!