Evening…can anybody shed some light on this. I have a 1995 mk1 1800 uk mx-5. She’s done 78k, i do 6k a year in her. On start up it had the usual HPA rattle that subsides after about 5 seconds. What I then get when the engine is warm is a rattling noise, very similar to the HPA noise. I’ve been told it could be a sticky tappet, and might need a possible top end rebuild. Recently, I changed the oil and flushed through some winns engine flush and used 10-40w castrol magnatec. Doesn’t seam to have helped. Also tried a noisy tappet additive which you add to the oil. Again, no joy. Any ideas would be greatly appreciated?
Hi, the top end of an engine is usually referring to the head assembly of valves and springs, and in this case cams and followers/tappets. They would remove the head and dismantle it to clean the tappets which may have desposits on them causing them to stick instead of following the cam movement. When they stick it causes a larger gap than should be and a rattling sound. These gaps are also the reason an engine may rattle briefly on start up untill the oil has filled the gaps and the tappet then follows the cam movement without rattle. (Sometimes a top end rattle may be referring to piston slap or little end wear but that would involve a bottom end strip to fix.)
So, what you’ve done so far is good. It’s your choice whether to have it stripped just yet but I would try one more time, getting it good and hot, doing a Wynns flush, then refilling with a high detergency oil such as Mobil 0W40 fully synthetic. Then give it some good long motorway runs.
When we got ours it had only been doing 3K miles a year and had a ticking tappet. I changed the oil to Mobil 5W30 fully synthetic and after about 3 longish days out (where we tend to do about 200 miles a time often on faster roads to various shows) I was genuinely surprised at how the tapping had completely disappeared and the engine runs much smoother. So, just gummed up I think. I’ve also noticed now, having changed the oil at just 3K miles, that the oil came out surprisingly dark so I think it is cleaning the muck out and will be interested to see if at the next change it is cleaner.
I agree with rich, assuming it is a sticking HLA I would try another flush as he has suggested. A head rebuild may be the only answer, but it will cost a few quid, so worth exhausting all other avenues first.
Thanks so much for taking the time to post your replies. I will try another flush and some mobil 0-40. Will keep you posted on how I get on, I am hoping that this fixes the problem as I don’t fancy an expensive engine repair at the moment.
Finally got around to the flush and oil change after the snow and a holiday…Thats sorted it, i think the 0-40 mobile is making a big difference…of course after my tinkering session (new headlight bulbs, topped up everthing, flushed oil, filter change, new oil), got the car off the ramps and it wouldn’t start…Battery must have been on the way out and leaving courtesy lights on for a few hours knackered it!
This has highlighted my next job to me, the non-standard battery has been quietly rusting the whole battery compartment as it was not vented and was a poor fit…stripping it down at the weekend to mend damage and new Genuine Mazda battery going in…