Have a V-reg MX-5 MK2 87k miles that has started to make a rattling sound. Sound is there all the time and is more obvious when driving the car than when stationery i.e. you have to go to higher revs to hear it when stationery. Mazda dealer initially said it was likely to be water pump or cambelt tensioners. Had an ex-Mazda engineer work on it and he confirmed it was neither of those (although replaced cambelt and tensioners at same time). He says sound is coming from deeper in the engine and may be big end wear or something else. He also said that it would be costly to repair and suggested I just live with it until it becomes unbearable … which to me it already is!
Have any of you had this type or work done on your MX-5’s before e.g. new big end bearings, main bearings, etc, and if so how much roughly would I expect to pay? My old MK1 Miata manual suggests it is possible (but very tricky) to even do the big ends with the engine still in the car.
If I am to live with it I certainly need something to quieten it down … so have any of you any experience with any oil additives/treatments that can quieten down older noisy engines with wear as I have been looking at a product from Xado that seems to have good reviews. Also even considering the old Slick 50 or anything else anyone can recommend.
I think it rare for big ends or main bearing to go at this mileage ( but I am sure some will advise other wise) it is more than likely the hrydraulic tappetts you can hear. which means head off to repair possible new buckets and or a cam shaft how is the oil pressure low oil presure staves the tappets.
Haven’t noticed oil pressure being low but will check again. I believe the MK2 does not have the hydraulic tappets and has shims which is what I originally thought the problem might be. But I asked the engineer if it could be that (as he had just done the cambelt replacement) but he believed the noise was coming from deeper within the engine.
Checked oil pressure guage and it is between the second and third marker … closer to the third.
Looking at the Haines MK1 manual and a MK2 service manual it appears that the sump can be removed without removing the engine from the car. Procedure is a bit tricky but compared to removing the whole engine it would be a lot easier.
I am guessing that if I where to remove the sump and oil baffle then I could inspect the big end bearings to see if there was any play.
In addition, it looks feasible to even replace the big end bearings at this point without even removing the head. I am thinking that if I where to turn the crankshaft so a piston was at the bottom of its stroke, then the bearing cover and the bottom half of the bearing could be removed and then the piston could be pushed upwards a little so that the top half of the bearing could also be removed from the con rod. Replacing the new bearings would be the reverse … probably a bit tricky but looks like it could be done.
Anyone have any views on this e.g would there be enough room to manouver the new bearings in or has anyone ever attempted this before?
If your oil pressure is good as you say it is then it highly unlikely to be a big-end issue. Possibly if low grade petrol has been used for a prolonged period or if the ignition timing has been run too advanced then your engine may have been damaged by pinking or pre-ignition maybe? If so the damage is more likely to be in the small-end or piston end of the con-rod or ring damage or even piston damage.
If there is serious wear/damage internally then no oil-treatment additive is going to make it better, an engine change would be my course of action if it is kyboshed.
Try and get a compression test carried out on the engine to see if one or more cylinder pressures are low (175-185psi would be a good pressure)
But first of all, before you go looking for major surgery items, have a really good check to ensure all of the heat-shields and bolted exhaust brackets are fully secure and not capable of causing the noises you describe
Dont even bother looking at the oil pressure gauge it is false and will tell you nothing,it is as much use as an LED comming on when you turn on the ignition,get you head under the bonnet and check via the dip stick,
As Taff as said check the heat shields on the zorst, more the ones towards the front on the down pipe first,they can rattle it higher revs only when the tack welds give in.
Thanks for the advice, will check the heat shields, etc.
When you say check the oil pressure via the dipstick … do you mean I should use a pressure guage inserted into the dipstick holder with the engine running?
No i mean the oil pressure gauge in the roadster you own is a false gauge and is telling you nothing and doing nothing, just keep checking that the oil level is correct by the dip stick.
You can get the OE gauge working by fitting a track dog sender(moss) in place of the one already on the engine, or an after market gauge and sender on a sandwich plate with your oil filter.
Hi, Yes it is possible to renew big ends by the method you suggest, take out spark plugs first before trying to push up piston. This procedure was common practice in the trade for in-line engines. Remember to clean the crank, and clean it again before you put in the new shells. Lightly oil shells as well. Don’t go over the set torque for the big-end bolts.
I had my 1999 1.8iS serviced last autumn and the oil used was Castrol GTX mineral, (The GTX had been picked up for me by a non motoring enthusiast friend who was not aware of the difference.) then early this year I started to notice a rattle on start up which disappeared after a warm up. It was obviously valve gear noise. I decided to do an interim oil and filter change and this time used X power semi synthetic ( MG type stuff) bought from my local Mazda dealer who was doing an offer on it. After the change I was genuinely surprised to find that the noise had totally gone and has not yet reappeared. I would have thought that the Castrol would have been up to the job but obviously not.
