Miata Head Gasket – Day 1

Getting the head off proved to be a task a little bigger than I was anticipating. I went in with the mentality that it’s just a bunch of smaller tasks, which it is. It’s an oil change. It’s a radiator swap. It’s an alternator swap. It’s an intake manifold swap. It’s an exhaust manifold swap. It’s a timing belt job. Then it’s a head gasket job.

Some interesting things to note, mainly for myself:

  • N2O isn’t necessarily a good thing for your motor
  • A breaker bar with a 21mm socket and your ignition key are a damn easy way to get the front crank bolt off
  • When you pull the fuel lines on a hot day, crack the gas cap so you don’t keep getting bathed in fuel from the return line
  • Working on a dirt driveway outside slows you down
  • So does having to go to NAPA 40 miles away to get a breaker bar and a 21mm socket
  • Disconnecting either the negative or the positive terminal on a battery is electrically the same. Doing either is a good idea before trying to pull the alternator
  • Tagging your fuel send and return lines is a good idea
  • Writing down what you just did so you can reverse it is a good thing
  • Writing with ink that writes on greasy paper is smart, writing with ink that is gasoline resistant is smarter

Now some pictures of interest:

The workspace. Not much to talk about, it’s a Miata in a dirty grassy driveway. I decided to use ramps instead of stands because the ground slopes in two different directions and I didn’t want to risk the stands coming unbalanced. With some outside input I decided to pull the hood and I am glad I did. When I finished for the day I laid the hood back down on the car for some overhead (our would that be over “block”?) protection.

MMMmmmm… yummy rusty coolant. I mentioned that there was some sort of surfactant in the coolant – something that wouldn’t let the surface bubbled pop. You can see that in action in the enlarged photo. Questions arose about oil in the coolant, I presumed this would appear as black globs floating around, I don’t see any. Could it be oil that is causing the phenomenon?

Interesting – the number 4 plug wire boot is coated in oil. Usually attributed to a bad valve cover gasket. Or is it? This is a head gasket story, this could be a part of the problem. What you don’t see here is the plug socket that was completely submerged in oil when it came out of the well. Oil is not very electrically conductive – could have been causing an intermittent miss over the last couple of months.

The intake manifold is off. Not much to see here except the gooey red substance that shouldn’t be there at all. That’s the coolant passage. I don’t understand why it’s here, the intake manifold blocks it off. It may be used on a different car as the Cold Start function for the throttle body on a front wheel drive application – it’s in about the right spot.

This is the Millen 4-2-1 header I got a long time ago when another power-lister went turbo. I got it for $100 in 1999 and had it cleaned up and thermal coated. The coating is finally giving way and there are spots of rust around. It’s also leaky – looks like the welds at nearly every joint have cracked. I didn’t find this out until the gasket went and smoke started billowing from the hood. I couldn’t clear the studs without banging against the steering shaft, so out it came…

Here’s the exhaust manifold removed. More telling evidence – notice the #3 runner is wet. Felt and smelt like oil. WordPress is giving me fits on how these photos line up so I am filling in some void space to get them to stack properly here. I could probably go into HTML mode and add a bunch nbsp’s. One more line to fill it in… hopefully, maybe I’ll change the text color to white so no-one sees this.

Here’s the exhaust side of the head, again with the wet #3 exhaust port. WordPress is giving me fits on how these photos line up so I am filling in some void space to get them to stack properly here. I could probably go into HTML mode and add a bunch nbsp’s. One more line to fill it in… hopefully, maybe I’ll change the text color to white so no-one sees this.

Here’s a blurry picture of one of the head bolts with spotty surface rust on the shaft. There were two of them like this, as well as three others that were coated in oil. The rust doesn’t protrude onto the threads. I presume the head gasket leak allowed coolant (and oil) into the wells and this is the result. Or should I say I hope this is the cause. Could it also potentially mean that the block is cracked and the coolant seeped in that way? Opinions matter, there’s a message box at the bottom of the page and any input is helpful to this novice.

The head is off! The coolant you see in the photo I believe is from the heater feed line. I couldn’t reach the clamp to disconnect it from the head so instead I disconnected it at the firewall and when I pulled the head a little dribbled out. Let’s take a closer look at the cylinders…n… hopefully, maybe I’ll change the text color to white so no-one sees this.

Cylinders 1 and 2 WordPress is giving me fits on how these photos line up so I am filling in some void space to get them to stack properly here. I could probably go into HTML mode and add a bunch nbsp’s. One more line to fill it in… hopefully, maybe I’ll change the text color to white so no-one sees this.

Cylinders 3 and 4 I am guessing that the “tear” I see at the intake side had bolt passage all the way to the #3 cylinder and oil feed between 3 and 4 is what was causing the problem? Is this what a “torn” head gasket looks like? Seriously, I don’t know, is it?e photos line up so I am filling in some void space to get them to stack properly here. I could probably go into HTML mode and add a bunch nbsp’s. One more line to fill it in… hopefully, maybe I’ll change the text color to

The head. The combustion chambers are in pretty sad shape, as are the valve faces. I’m not too sure what to look at here, other than general ugliness I don’t see any signs of head gasket damage. The gasket is still on the block at this point. For orientation – #4 is on the left side of the image, #1 is on the right. Notice the flat portion of the #2 and #3 (particularly bad in #2) combustion chamber are pretty beat up. Something got in the cylinder somehow. This is the decider for me – I’m swapping int he replacement head, this thing needs some serious work. Of course it is 19 years and 220,000 miles old.

I also noticed that some of the head bolt passages on the head had a chamfer and others didn’t. Here’s a photo of one that has it. Any idea what this is for?

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3 Responses to Miata Head Gasket – Day 1

  1. rich smith says:

    How did the head gasket repair go?

    I’m attempting it next weekend.

  2. psyopper says:

    Went fine, just remember that assembly is the reverse of removal. 😉

    Pretty straight forward, though a lot more work than I had anticipated. I wound up with stitches from whacking my hand on some part of the block by mistake in the only 5 minutes I had my gloves off – replacing the front main.

  3. rich smith says:

    Glad to hear it.
    I’m going for the full head swap and exhaust as well.

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