Broken crankshaft key leads to tear down and timing service

Also I ended up going with the national seal for the record…

 

You're a rebel... Look at me, I am Toyota parts snob who replaced his own head gaskets and used all Toyota parts except for the head bolts. I'm in no position to judge.

All seriously now, we are 10 pages in on this thread, let's get this repair going so we can see some progress on this thing...

 

Still waiting for the water pump and harmonic balancer in the mail. I’ve got everything stripped down ready to take off valve covers and timing cover but just want to wait till I have the parts so my engine isn’t open and exposed to the elements(it’s parked outside in my dirt driveway because I don’t have a garage). Believe me, y’all will get a full update when the repair is complete this week hopefully

 

Here is a pic to tide you over. I put the covers back on with two bolts each just to keep it all clean.

 

hood closed should keep rain out.
If you want might be possible to drape a cover over anything open

to speed up the job allowing to get started on any cleaning and prep involved in components that might get re used

such as covers. Like cleaning, degreaser, scraping, etc.

Wish I painted my valve covers back when I released them rather than just fast gasket renew job.

drawback is having to remember what goes where and laying things out in an organized matter or labeling, pics, etc

 

Ok well here is where I’m at. I got the timing cover off and when setting to Tdc I noticed that I am missing a mark down near the crankshaft gear. The mark on the block is lined up with the gear mark that corresponds with the key, however the gear mark that is supposed to line up with the crank sprocket mark seems to be non existent. After rotating multiple times I can’t find more than one mark so I’m beginning to think it wore off somehow? I should be at Tdc tho. Chain seems to have some slack so the marks on the cam sprockets are a little off but they are at the approximate position they should be at when at Tdc. My lobes seem to show Tdc as well.

 

If I’m correct there should be another mark right here

 

18 yrs of age

 

This type problem was common on early Miatas, called 'short nose crank' in that case.

Google short nose crank Miata lance schall and see if that on vehicle repair procedure will work for you.

It's based on very specific Locktite products

Or poke around on Miata.net

No, it's not the same root cause situation, but I'm thinking the repair could work

 

No, there is no mark there. There is only the mark on the cylinder block that aligns with the key on the crank. That is TDC. You will use the dot on sprocket to install the chain after removing it. That dot will appear to be approximately in the 9 o'clock position.

From your pictures, it looks like you are at TDC. Your main chain does not line up but it will if you continue to turn over the motor. You do not need to do this, but if you are looking to prove it to yourself you could continue to do so.

 

What about this mark here(picture pulled off YouTube). I don’t see it on mine. But I agree either way I believe I’m at Tdc right now

 

Here was mine.

 

Here's a kind of odd/cheesy video, but good for a reference. Your first pic shows the crank in the right position, and the other sprockets appear to be lined up.

 

That makes me feel better. Weird that there are marks there for some but not all. Could just be worn down I guess?

 

My FSM does not talk about another mark there. I'm not sure what you are referring to.

 

Yes I don’t believe I ever saw it in the fsm. I guess I’ve just seen it on the videos I’ve been watching such as in the picture I uploaded above. As long as I have the key and that one mark lined up to the timing mark on the block I should be good and ready to take everything off though

 

You can move forward with confidence. Things may move a bit with the chain off. You can always fall back to the position of the gears relative to the bearing caps. The camshaft lobes are helpful as you mentioned. Remember some of the valves are open so you will need a crescent wrench (on the flats of the cams) to reinstall the main chain since the valve springs will want to close the currently open valves.

 

Once the main chain is off I have to adjust the cam shafts with the crescent wrench correct? So the marks line up to the bearing caps?

 

In a perfect world, let's assume you have everything at TDC currently and the crankshaft bolt is loose. Meaning, you can loosen it by hand without affecting the position of the crank. Once you remove the chain, following the FSM, the crank and bank 1 should remain in their current position. Notice the lobes on the intake cam on bank 2, you can see that the valves are slightly open currently. Once you remove the main chain, the bank 2 cams will move. During installation, you will need to slightly turn the cams on bank 2 in order to align the marks on the caps and gears like they currently are. You will use your large crescent wrench on one of the cams in bank 2 in order to do so.

Hopefully that makes sense.

 

I believe it does