Engine Noise

Technical Area Engine, Transmission, Exhaust etc
2

 

I wonder if anyone can help me, I’ve always fancied having an MX-5, and a colleague at work has decided to sell her 1991 Mk1 Eunos 1.6 (Japanese import) it has around 90K miles on the clock.

However, after having looked at the car, the only real problem would appear to be a continuous tapping when the engine is running, from idle through to when being revved, the engine was left to idle for 10 minutes and the noise continued.

I’m suspecting that it may be the hydraulic tappets and as the car hasn’t been used regularly and am guessing the oil has drained from the tappets.

The oil in the sump is relatively new oil, although I’m not sure which grade/weight .

My concern is that the tapping noise should have subsided when the oil had circulated around the engine but after 10 minutes of idling the noise was still present.

Is there any way of understanding if this is a purchase worth pursuing with this problem, should I:

  • Leave the engine to idle and see how long it takes for the noise to subside – if so what is a reasonable length of time in which to expect to see the situation improve.
  • Take it for a test drive to circulate the oil and see if this helps the issue
  • Buy the car as the remedy is relatively inexpensive – what is the remedy?
  • Stay well clear as replacing the tappets is a complex/costly job – if so how much should I expect to pay?
 

Any advise is thankfully received

 

3

I’d check oil level first, then idle it for a good 10 mins or so, take it for a run, then see if noise is any different.

You could poss. fix it with simple dose of Wynn HLA treatment (or similar), and an oil & filter change.

Big question - are you sure it’s the tappets?

 

Mine is due an oil change soon, and tappet/HLA noise is there for about 10 seconds - but mine’s used daily 35 miles/day.

I’m sure there’s a “Buyers Guide” somewhere on here for you to go through to help.

[:D]

4

Replacing the tappets (actually HLAs - hydraulic lash adjusters) is indeed expensive as they’re not cheap things and you need 16, but they can be easily cleaned once removed. Removal involves taking off the camshafts, so not too hard but not something you can do as a first job. Low usage and irregular oil changes seem to result in them getting gummed up with old oil. So long as they’re not worn they should be cleanable. IIRC oild changes should be every 3000 miles or so, or whenever the HLAs start to get noisy again.

Some details on cleaning here:  http://www.miata.net/garage/hla/cleaning.html

 Normally an oil change should quieten them down, I’m using 5W40 fully-synthetic and my HLAs only give about 1/2 second of rattle at cold startup as they fill with oil. You can also try an additive into the oil - look in Halfords for some Wynns HLA treatment, it might help.

TBH though if you’re happy to do mechanical stuff then the condition of the body is more important than the engine - a recon engine is about £350, one from a breakers or Ebay is about £200. I swapped a recon engine into my Eunos and it took about half a day to do with just basic tools and an engine hoist. Much more important that the sills are solid etc… as a rusted body can instantly make the car worthless.

5

Thanks for the quick response.

In answer to the big question - No I’m not sure. I’ve visited several forums and the issue with noisy tappets seems prevalent, so I guess I’m making a risky assumption!!!

Have you any experience of what this may be?

6

G’day mate, Welcome to the Forum

If your oil pressure is good, and the rattle rises and falls with the engine speed, then it’s almost certainly HLA noise.

Buy a can of Wynns engine flush, the one that you add to the oil, and do exactly what it says on the tin [that sounds familiar, dont use Ronseal[;)]]

Fresh sump of oil, either fully synthetic or semi synthetic for everyday use is fine, I use fully synth Mobil 1 5W50 and have had no HLA noise since changing to it. You may need to repeat the procedure a couple of times to get a complete fix.

HTH

7

 I’ve Googled for the instructions of the use of the Wynns Hydraulic Valve Lifter treatment but can’t find any… do they advise using it just before an oil change?, or can it be used day-to-day without oil change?

I’d like to put some in mine, but I’ve only just done oil & filter…

8

http://www.wynns.uk.com/sheets/58.pdf 

 

9

 Ta GW.

Read that later last night - so am I to believe it’s ok to dose the oil after an oil & filter change and leave it in until the next oil change in 5000 miles time?

My HLAs are only audible for a few seconds after starting (i.e. no real prob), but have noticed a slight ticking after a sustained 5000rpm run ~ this does go away after a few minutes.
So I was wondering whether to treat no as a bit of preventive maintenance, or wait until just before next oil change?

10

I saw a number of fairly scientific tests back when I was in the engineering business, and Wynns products, along with a Lube/penetrating oil called SFR were the only products that came out with any credibility at all. We changed from being big WD40 users to using SFR pretty exclusively. The Wynns engineering products were used on a variety of fork trucks etc and the vehicle fleet. I was convinced. As for the stuff in question, it says to leave it in so why not…just don’t blame me if it all goes horribly wrong, it’s all just IMHO

11

 I agree with most of the answers on here, but listen up, HLA clatter is easy to quieten.

I bought a low mileage Eunos Roadster (fresh import with no issues except this noise on start up). However after gettin her warm after a run, when i pulled up at lights etc, it started again as if the top end was being starved of oil (which indeed it was).

It had been freshly serviced prior to my ownership so this suprised me.

As others have said, use Wynn’s engine flush. Add it to your existing oil, and fast idle (2000rpm) for approx 15 mins. Drop and replenish with any synthetic, or semi synthetic of 5W-30, or above spec. Oil filter too!

This will sort this out period. However the issue regarding HLA clatter when warm, turned out to be the engine sensor that operates the rad fan. It was getting too hot due to not working. It doesn’t read any differant on the dashboard because its 2 differant sensors. This 1 at fault is underneath the CAS at the rear of the engine, and is a pig to get to. You must remove the leads, coils, dis connect some wiring harness etc, but can be done in an hour.

There is a test to find out if this sensor, (or its relay) is at fault. In the diagnostics box, arc out 10 and GND, turn the ignition light on (dont start the engine), depress the accelerator fully. If the engine fan does NOT kick in, either the relay, or sensor has failed, and needs to be replaced.

Please note my NA 1 roadster has air-con so has 2 rad fans, the 1 to note if working or not is the right hand side fan, if looking under ther bonnet stood in front of the car.(passenger side i should say).

This is a tried and trusted solution.

Mazda mechanic “The Drifter”

Eunos Roadster Mk 1, 50K, Rust and rot free, mint original example apart from Il motorstort cat back, de-cat from differant source, style bars, wind jammer, 1 off Mazdasport alloys.

12

You’re saying your tappets lost their oil pressure because the cooling fan wasn’t turning on?

I’m not sure there is a direct causal link there.

13

Mr Muppet agreed…

 

Mr Drifter…

 

???please explain a bit deeper{#emotions_dlg.confused}???

This is a new one on me?

Regards

14

I’d be more worried about noise due to pre-ignition/detonation rather than the oil going out of grade if the engine is overheating.

 

15

 

 

Hi, Sorry if it seems a little confusing, The first part of my problem was similar to all the others on this post. All was fully sorted after the flush and re-plenish of oil.(No noise on first start up). However my car still made this noise when the engine got really hot,(on idle), after a good run say. The new oil got that hot in the engine because the fan didn’t work, and was draining away from the HLA holes, so the oil must have been thin due to the heat in the engine. After proving the sensor was at fault, and was replaced, the problem completely disappeared. P.s Re- pre ignition, i’ve altered the timing when i first got the car (it makes a differance to the performance), but was not the cause of this problem. My car was running ok for a good while before the HLA clatter developed, apart from a little clatter on first start up. The sensor must have failed at a similar time, by coincidance .Hope this reads a little clearer. Thanks  

16

Interesting. What brand & grade of engine oil were you using at the time that you had the failed thermoswitch/overheating problem?

17

 It was 5W-30, semi synthetic. It got too thin and with getting hot, run from the tappets causing the lash noise. I suppose i was lucky the headgasket didn’t give up.

Capt’n Muppet, Please read the whole article. Thanks. Its self explanitory.

18

IMHO 5W-30 is too thin for a Mk1 engine, moreso for summer use especially if they have a few miles under their belt.

10W-40 would probably be better for summer use and then maybe 5W-40 or 0W-40 if HLA noise is a problem on cold winter mornings.