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Mazda MX5 NB, Who Mechanics Like This?

The more I dig into the work done on this car, the more I question the sanity and abilities of anyone that has touched it in the past.

The local Mazda dealer called me the other day to let me know the valve cover gasket arrived, so it was time to pick that up and fix the oil leaks from the engine.

When I purchased the car I noticed the front of the engine was covered in oil, and there was plenty of oil down the side of the head above the exhaust manifold, so obviously the valve cover was leaking from the gasket. It’s a pretty common issue, and reasonably easy to fix (shame the gasket comes in at just under a hundred dollars though).

This is what I was dealing with

The oil leak from the front was starting quite high up, which is good, so it’s not the crank seal.

I also wanted to repaint the valve cover whilst it was off, because the paint that was on there came off in chunks every time I so much as looked at it, let alone touched it. It was also this gross glossy red.

It’s all a very straight forward job. Disconnect all spark plug leads, remove PCV valve, cam sensor, and breather hose. Remove the strut brace (and don’t forget to curse at the person that didn’t put anti-seize on the bolts last time)

And then a dozen or so bolts come out and off comes the valve cover. Easy. Looks pretty good in there. No sludge, and a nice golden sheen.

This was also a good time to inspect the cam belt, since the sticker on the valve cover was worn and you couldn’t read the date it was changed. Thankfully the belt looks good, no cracking and it’s showing about the wear you would expect for it being changed around 70,000km ago.

Can you guess where it was leaking from?

Yeah, it was leaking from almost everywhere. Obviously this had been an issue for a while, because someone had tried to fix it…. with copious amounts of sealant. I swear it was like they covered their hands in sealant and then just rubbed the gasket between their hands. It was everywhere. Note to future DIY-ers, this is not an approved solution to a leak.

It took bloody ages to get it out of the gasket recess in the valve cover, and left me with a nice pile

The gasket had also done some weird things in places. Thinking maybe it was over tightened?

A lot of the paint came off with a razor blade, but I did still need to use some paint stripper to remove some of the more stubborn bits

After MUCH scraping and cleaning, it was starting to look better already

I chose to be safe, and remove the baffle plates on the underside of the valve cover, to make sure there wasnt any paint stuck in them. The plates are held in with a bunch of screws, and stuck down with sealant. I removed them, gave the valve cover a thorough degrease and clean, and then refit them with new sealant and loctite.

Once it was clean, I gave it a good wipe down with grease and wax remover, and then masked it up. I chose to mask off a couple of little parts that the previous painter didn’t; such as the cam sensor hole and mounting surface, and the mounting faces for the coil bracket.

I chose to use wrinkle paint as from what I have seen it leaves a nice, OEM-like surface and is durable. This is the first time working with this paint, and also painting something this big. I made some mistakes, like not giving myself proper access to all angles due to where I chose to paint it, which lead to an uneven coverage of paint and some runs here and there. Thankfully the worst runs are hidden by wiring and piping when on the car.

In future I would allow more space to paint, and slightly lighter layers. I went on quite thick, and got some pooling in corners and edges. Not painting when its so cold out would be nice too.

Between coats (5 mins between each coat; three coats at different angles) I had a crack at cleaning up the strut brace since it was off the car. It was very dull and pitted.

I started off with a very fine scuffing pad, and then polished with some Autosol. I couldn’t get the pitting out on the Passengers side, I suspect the exhaust heat may have baked it on. It came up much better though.

Not bad for bugger all effort.

The valve cover did need a couple of days to cure the paint. I didn’t want to stick it in the oven as SWMBO would probably slaughter me. I used a heat gun to carefully set it initially, and start off the wrinkle process. I figure that once it’s on the car the engine heat will bake it on good and proper.

So a couple of days later, this is what I had.

OOOh. It actually came out looking damn good. I refit all the little bits like the plug wire holders and PCV gasket, and then set about fitting the gasket.

The new gasket is quite thick, and much softer than the old one. It pressed into place nicely.

Before I could refit the cover I needed to clean up the mating surface on the head. This meant scraping off the remains of old sealant, and picking it out of the gaps.

Whilst prepping the surface I noticed a lot of oil down the back of the head beneath the plug in the back of the head, where the cam angle sensor would be on older models. Since I was here, I also removed the two bolts you can see on the cap in the above photo on the RH side. The plug is also held in place with a retaining plate with a single bolt in the back of the head. I just loosened this, but didn’t remove it. The plug then pulled out. It’s a metal plug with a rubber outer. Apparently they aren’t expensive, but I didn’t know it existed until today, so I had to make do with a thorough clean and smear of sealant around the edge. I reassembled the cap and torqued the top bolts down to the recommended 55in lbs, and the rear bolt “snug”. Hopefully this fixes it or I will need to replace it.

For future reference, the ONLY sealant that should be on the valve cover gasket, is in the corners where the gasket goes over the cams (I use blue Permatex sealant, but standard high temp oil resistant RTV works).

The cover can now be carefully refitted with the new gasket in place. I tightened the bolts in a circular pattern as per the manual. I started with lightly snug by hand, and then torqued to 50 inch-lbs, and then again to the required 65 inch-lbs. The pattern and staggered torque helps to compress the gasket evenly and seal it properly.

This is the pattern

Looks pretty good if I say so myself. Red was the right choice.

I was ready to stop there, but the postie brought me a present today; a new O2 sensor from DoctorMX5 on eBay.

These are the tools needed. It’s not a very fun job on a car this low, and without a hoist. With these headers you can access the sensor from inside the wheel well. Not sure about the standard manifold.

The socket with a slot out of it is so that the wiring in the end of the sensor can come out of the slot. It’s easy to use a normal deep socket on an old O2 sensor if you cut the wiring off, but you can’t use the same socket to tighten the new sensor up, so this socket is a life-saver. You could use a spanner I guess, but the right tools are great to have.

The sensor lives here. This is with the steering on hard lock

The old sensor was super tight, so lots of penetrating fluid and elbow grease was needed. Eventually it came out, and it was well passed its best. I suspect it was the original sensor.

Refitting was easy, screw the new sensor in by hand being careful not to twist the wiring, tighten with ratchet, thread the wiring up through the engine bay away from the exhaust, and then plug in.

And that’s it. I started the car up, took it outside and degreased the engine to get rid of the old oil.

Well worth the work. If I didn’t repaint the valve cover I would have been disappointed.

A quick test drive shows the car running great with the new O2 sensor connected. It’s no longer running rich, and doesn’t overwhelm you with exhaust fumes or shoot trails of carbon out the exhaust. The engine runs smoothly through the rev range, and is a complete hoot to drive.

Now that its holding in its oil, I guess it deserves an oil change.

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