Folks,
1999 Mazda MX5 MK2.
As a follow-up to my previous post about a rattling noise that appeared
at about 3000RPM I thought I should post a follow-up of how I got on to
help anyone else with a similar problem.
As well as applying to replacing the big-end bearings the work equally
applies to anyone who just needs to remove the sump e.g. to replace the
gasket … hence the subject of this post to aid people searching.
Forum moderator … feel free to post this in the FAQs if you wish.
So after much research, and failing to cure the problem with a new cam
belt kit, the problem was not due to cam belt tensioners or to a worn
water pump … it cost me £200 to find that out.
I decided that it was either the big-end bearings or possibly the main
bearings that were the problem and set out on a course to replace the
big end bearings with the engine still in the car and hope that turned
out to be the problem.
So the next part was to source the parts and get on with the job.
For parts, I found the following:
Sump Gaskets - Front: B6F4-10-427, Rear: B6F4-10-428.
Big-End (Conrod) Bearings - Standard: B6Y2-11-SEOA.
For the big end bearings alternatives that I had confirmed by the manufacturers
where: ACL: 4B8351 , BECK/ARNLEY: 014-6384.
Re prices, for the Mazda bearings I was quoted £78 + VAT, and the ACL
bearings where about £72 incl P&P from eBay. The cheapest UK gaskets
where £23 for the pair.
I shopped around and got lucky getting a one-off set of ACL bearings from
a US based eBay seller that only cost me £23 incl P&P! I got the gaskets
from a US auto parts store on the web and they cost me only £9 incl P&P.
It helps having part numbers when you shop around as you can search
eBay, Google, etc, with them and deals tend to turn up.
So onto the job. I would say allow 3 days in total to cover things going
wrong, etc. If your MX5 is your daily commute then plan the job for a
bank holiday weekend … if it goes well you get the Monday off to drive
around in your repaired MX5 … if it does not go well you get the extra
time to try and finish the job!
What you need is some form of engine support, a standard metric socket set,
a torque wrench, a decent jack, a pair of axle stands, fresh oil, plenty
of penetrating fluid, a number of good light sources / torches, new big end
bearings, new sump end gaskets, lots of small plastic bags, paper and a pencil
and some RTV silicon gasket - top tip: for the silicon gasket, the motor factor
offered me a canister version (similar to kitchen sealant, etc, that you apply
with a gun) I declined and asked for a small tube … big mistake … there is
a lot to apply and the tubes are not very good for running continuous beads all
the way around a sump! If you can get your hands on the Haines manual then that
helps with pictures, torque settings, etc.
Some advice before starting - as you remove each component, put all the
nuts/bolts/washers into its own plastic bag and write on a piece of paper
what part they are from and anything to note when re-installing (as it may
be a couple of days before you come to use them again) put the paper also
into the bag and seal with a knot or a tie. I kept all of these little bags
in a single bucket so they did not go missing around the garage which ended
up looking like a war zone in the end!
In addition, before you start removing things try to plan ahead and spray
penetrating fluid on the nuts/bolts and give it time to work as some of
the nuts/bolts you will be removing have probably never been touched since
the car came out of the factory!
So onto the steps …
1. Remove bonnet, first mark the position of the bonnet to its brackets to
make it easier when re-installing it … I just used some tippex.
2. Remove spark plugs to make it easier to turn the crankshaft later on.
3. Loosen front wheel bolts and jack the car up and support at each front
side on axle stands, use the side chassis support areas for the axle
stands so that all of the front underneath of the car is accessible.
Important: Centre the steering wheel and remove key to engage steering
lock … when you disengage steering column later it is very important
that you do not turn the steering wheel whilst it is disconnected.
-
Remove the front wheels and drain the engine oil.
5. Fit a support (e.g. chain hoist) to the 2 lifting eyes on the engine and
tighten up so engine is supported. I made a big mistake here in trusting
this part of the job to an old hoist that I thought was up to the job. On
tightening it up it broke and I wasted a whole hour trying to fix it with
no success (this is why you allow 3 days!). I eventually had to support the
engine using thick strong nylon rope over a main joist in the garage and
connected to the lifting eyes … I jacked up the engine briefly from below
the sump and tightened the rope (which I had doubled up as a failsafe) using
a crowbar as a tourniquet! This was because all the hire shops were closed
by the time my hoist broke!
Now we get to the part where you drop the structural sub-frame so that you
can get free access to the sump …
6. Remove the engine splash cover (beware, at least 4 of the small bolts just
sheared off on mine) and also remove the heatshield that is just a little
further back underneath the car.
7. Undo the 2 engine mounting nuts on each side of the engine that are inside
a sort of cup within the subframe … make a note of the position of the
passenger side bolt as that side only has an upper or lower position whereas
the driver side can be slid up and down in its slot.
8. Undo the 4 mounting nuts that hold the suspension struts in place under
the bonnet.
9. Undo the 4 nuts that hold the steering stabiliser bar by its U-shaped lugs
to the front of the car close to the bottom of the radiator so that it and
the drop-ends that attach to it can move freely.
10. Remove the small pinch bolt that holds the splined steering column to the
steering gear and mark the position of where the splined end of the column
enters the pinch bolt joint with tippex.
10a.If car has ABS brakes, on each side undo the 2 small clamps that hold the
ABS sensor cable in place to give it a bit more freedom to move. Caution: I
followed the manual and tried to remove the ABS sensor itself from the back
of the brake disk … with lots of penetrating fluid beforehand the bolt still
sheared off with very little force being used!
11. Place your jack under the subframe and support its weight.
12. Remove the nuts and bolts that hold the sub-frame to the chassis. There are
4 nuts (2 pairs each side) that are close to wheel area, and then another 4
bolts that are further towards the back underneath the car. These are very
tough and I needed a tubular steel bar to extend my socket wrench to crack
them initially.
13. Begin to lower the jack supporting the subframe. You may have to wiggle it
a bit to get it all the way down … and keep a close watch on anything such
as pipes, etc, so that they don’t get over-stretched. Important: when you are
lowering the subframe the steering column will eventually work free from the
pinch bolt connection (10 above) … this is good, but keep a watch on it too.
I eventually got the subframe so that its backend (the bit furthest under the
car) was sitting on the garage floor … and the sump was clearly visible and
accessible … hurrah!
14. You can now remove the sump. First start on the bolts that hold the transmission
to the upper back part of the sump. I recall there was about 5 of these and that
they were very tough to crack. On the passenger side the top most one (which was
also a little longer that the others) was very hard to get at. Finally, remove the
sump rim bolts starting on the middle bolts and working out in a spiral cracking
each one to reduce any strains on the engine block.
15. With all the bolts removed the sump will not just drop off as the old silicon will
be holding it to the engine block and in some areas to the oil baffle. There are
2 areas on either side of the sump at the back where you can pop a screw driver in
and prise the sump away … be patient and persevere it will eventually work free
as long as you have definitely removed all of those sump to transmission bolts!
16. When the sump does prise free, it will likely drop only a small distance and appear
to be stuck. This is due to the oil baffle as it is fixed to the oil pickup and also
silicon fixed to the sump. It is quite thin and when covered with lots of silicon is
hard to spot but runs most of the long length of the sump on each side so you will
need to gently pry it off the sump on both sides all along its length … I used an
old blunt butter knife that I worked under one end then slid along to free it.
17. Finally the sump should come free. The oil baffle is only held to the oil pickup by
a small nut so can be separated, you will need to remove the oil pickup too which is
2 small nuts and be careful not to damage the oil pickup gasket if you haven’t got a
new one like me!
18. OK, for me, by this time is was Sunday lunchtime! I had started Saturday morning and
it had took me 1.5 days to get the sump off. Granted, they were not early starts or
late finishes … but with time wasted on the engine support, and some very inaccessible
and/or tough nuts and bolts that ate up time … that is how long it took. -
So onto the big end bearings themselves … what a breeze to replace! This was the nicest
part of the job. I just worked from the front of the engine to the back turning the crank
until each piston was at its lowest point. Remove the bottom conrod cap (may need a tap
with a wooden handle to free it but be gentle) and the lower bearing shell … they can
cling to the crankshaft but come away easily. Now very carefully push the conrod upwards
until the 2 conrod bolts clear the top of the crankshaft and then move them over to the
left or right and you will be able to pull them downwards past the crankshaft until you
have plenty of access to the upper bearing which you can remove … it may too not be there
because it has clung to the crankshaft, so just slide it around and remove it. Clean everything
spotless and take the new upper bearing shell and click it into place in the conrod (there
is a groove on one side of the conrod and a ridge on the bearing so it is hard to go wrong.
Oil the inner face of the new top bearing (i.e. the side that contacts the crankshaft) then
carefully push the conrod back upwards until its bolts clear the crankshaft, move back over
to centre and pull down so its sits snugly on the crankshaft. Clean the conrod cap and new
bottom bearing shell spotless and click the bottom bearing shell into place in conrod cap
aligning groove and ridge again. Oil the face of the bottom bearing shell and push conrod
cap onto the conrod bolts until it is snug with the crankshaft and replace nuts ensuring that
you tighten up in stages to the correct final torque. Repeat for each conrod, turning the crank
until it is at its lowest, etc … just do one at a time. This part of the job probably took me
only 30 minutes in total! -
Once bearings are replaced, clean all old silicon gasket off the engine block, sump and
oil baffle. Take your time and be meticulous … make sure it is very clean and do not
scratch the engine block or sump rim. Also clean any old sealant off the sump bolts.
21. Top tip: before starting to apply any new silicon gasket, dry fit the oil baffle and oil
pickup to make sure everything is straight. I found that the when the oil pickup was
tightened up … as it had the oil baffle bolted to its stem … it pulled the oil baffle
away from the engine block. I found this out the hard way with my freshly siliconed oil
baffle pulling away from the block and making a mess! So straighten everything up whilst
dry before moving on!
22. The manual says to apply silicon to the upper edges of the oil baffle and end gaskets and
then fix them to the engine block … if I where to do this job again I would apply the
silicon directly to the engine block instead as it is easier, then just push the 2 new end
gaskets into place (they are different sizes and have little tabs on them so it is not hard
to get them in the right place and carefully press the oil baffle into place aligning with
the bolt holes in the block … the rim of the engine block has a slight dip where the oil
baffle goes which helps.
23. Replace the oil pickup and connect the oil baffle to oil pickup bracket.
24. Finally apply bead of silicon all around sump lip when passing bolt holes always pass the
silicon bead around the inside of the hole (same for engine block / baffle).
25. Carefully press sump into place and first replace sump rim bolts again tightening them up
to final torque in stages working from centre outwards in a spiral. Then replace the sump
to transmission bolts and tighten these up to torque.
At this point it was about 9pm Sunday. I knew I was not going to finish the job and anyway I
realised that I needed to wait about 12-to-24 hours for the silicone to set. I did not want
to replace anything else until I new the sump was leak free, so I left it overnight, went to
work on the Monday and returned Monday evening after work.
26. Refill with oil and replace spark plugs. Fire up engine and check for leaks … oh … and
rattling noises! At this stage I was certain problem was solved … so I got a second wind!
Important: Make sure you do not move the steering wheel at all whilst you are testing for leaks.
Once you have finished, remove key again and engage steering lock so that steering wheel is in
exact position as before.
27. If all OK, get your jack back under the subframe and start to raise it up. VERY IMPORTANT: As
you do this you need to watch for the point that the steering column becomes close enough to
its pinch bolt connector so that you can align the tippex marks you made and ease it into place
whilst raising the subframe. I first reconnected the suspension strut nuts (not fully tightened
but just about on) which took some of the weight and allowed me to rock sub-frame when needed
(without jack) when trying to align it with its mountings. I next worked the subframe upwards
to the point that I could work it onto the 2 engine mounting bolts … again I loosely connected
the engine mounting nuts to help overall alignment. Next I jacked the subframe up further until
I could loosely replace the 2 pairs of subframe mounting nuts close to the wheel area. Finally I
replaced the other subframe mounting bolts and slowly tightened everything up including the engine
mounting bolts and suspension struts. The 2 subframe tails furthest under the car had to be jacked
up to get them onto the chassis to be bolted. Ensure you replace the steering column pinch bolt when
everything is in place and tightened up. Also replace the steering stabiliser bar.
28. And that’s about it. Replace the wheels, remove engine support, replace bonnet and get the car back
onto solid ground! You should have no little plastic bags with nuts/bolts left!
Overall, with all the odds and ends purchased for the job it still cost me well under £100 … from research
it was looking like a grand upwards to get someone else to pull the engine out and do it for me.
Time wise it took a weekend and 3 evenings … but that was without the hindsight I’m giving you now
and I did replace the brake pads and the transmission oil also in that time and did a fair bit of
rust prevention, cleaning, etc.
For me it was worth it. The big-end bearings were the problem and the engine sounds great now with no rattling.
The car is old and has 90K miles so probably was not worth spending a grand on … plus you can never
guarantee that someone won’t hike the price up further when they have your car with its guts out!
Hope this helps someone who may be stuck like I was and willing to have a go themselves. None of it is
rocket science … just nuts and bolts, sweat, a few cuts and bruises and taking your time to do the job.
Ziggy
… I figured that with all the oil being delivered to that area they would get oiled anyway so I would get them started … hmmmm … if you think this would cause problems let me know and I will edit original post so that anyone else reading those instructions won’t do the same.