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Z31 Timing Belt Change
http://forums.ctzcc.com/viewtopic.php?f=4&t=7387		 Page 2 of 4
Author:  Filipe [ Thu Mar 21, 2013 7:29 pm ]
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This is the best I've found for Z31.

http://www.youtube.com/watch?v=zD3G50oufM4
Author:  ZCARNUT [ Thu Mar 21, 2013 10:02 pm ]
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It's great to work on your Z, that's part of the joy of owning one. But, IMO, if there is one job that you should pay a professional to do, that would be timing belt replacement. Too much at stake and too much that can go wrong. The Z31 is not as complex as the Z32 but it is labor, and knowledge, intensive just the same. The valve train is not something you want to take chances with.

And you need the Nissan FACTORY SERVICE MANUAL,not a Clymer, not a Haynes. The FSM is the size of a big phonebook and year/model specific. You can fi.d them o. Ebay for $50-$75.

My 2 cents..... :D
Author:  Filipe [ Thu Mar 21, 2013 10:31 pm ]
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Thanks John, appreciate the feedback. I read a lot in the FSM today regarding the TB, water pump and a few other odds and ends. Was a good starting point. I'll call in to RDZ tomorrow, see what they can quote me.

Only thing now is, it's a hr + drive down to Danbury; on a Z that needs a TB change.

For FSMs: http://www.xenonz31.com/reference.html
Author:  jtang [ Thu Mar 21, 2013 10:33 pm ]
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Both the FSM and Haynes are available through xenonz31.com as mentioned. It's a good idea to print both of them out in their entirety and stuff them into a binder for the garage.

I was able to get through the timing belt (and all associated service) on my own as a first-timer. The only special tool I needed was a bolt puller (pulley puller would work too) to pull the crankshaft pulley off. Torque wrench is good too. As long as you're careful you will be okay.

Things I changed (and will recommend changing even if you don't 'need' it):
Timing Belt
Timing Belt Tensioner (many people recommend changing the stud too, but I didn't)
Water Pump
Thermostat
Coolant bypass hose
Coolant Head Temperature Sensor (CHTS.... buy Nissan OEM) + Subharness (also get from Nissan)

I know people on z31p are telling you to change oil seals and all this junk. For me, I pulled the timing covers and everything was perfectly dry. I opted to not change any of the oil seals because of this. If you pull the timing covers and find everything is wet with oil, then you should change the seals. This is just my opinion.

I pretty much followed the Haynes manual to the letter except the part where they tell you to unbolt the rocker covers (valvecovers). It's not really necessary. Everything else was spot on if I recall correctly. I'll double check for you soon-ish.

As far as I know none of the instructions are year-specific. I know the accessory belt routing is different for turbo and non-turbo but that should be it.

Also, 40 teeth separate the left and right camgear (between the timing marks) and 43 teeth separate the crank pulley timing mark to the right camgear. Count it after you put the belt on. As long as your engine is still at top dead center and the teeth count are correct then your engine will not blow up. Also set the tension correctly.
Author:  Filipe [ Thu Mar 21, 2013 10:49 pm ]
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Thanks Justin, appreciate the input as always. What's the reason that you took off the crankshaft pulley?

Does "timing belt covers"="timing belt plates"?

I agree about the rocker covers. I feel that if the car had been driven longer, it would be different, but it seems like it's just a way to verify TDC.

Can you clarify this for me? Thanks!

Quote:
Also, 40 teeth separate the left and right camgear (between the timing marks) and 43 teeth separate the crank pulley timing mark to the right camgear. Count it after you put the belt on. As long as your engine is still at top dead center and the teeth count are correct then your engine will not blow up.
Author:  jtang [ Thu Mar 21, 2013 11:01 pm ]
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You have to pull the crankshaft pulley to remove the lower timing cover (which you need to remove in order to change the belt).

Image

By timing belt cover (upper and lower) I am referring to the "front upper belt cover" and "front lower belt cover".

The rocker cover loosening is there to make turning over the engine smoother or something like that, but you can do it with a ratchet with no problems.

The teeth count is a final check to make sure your belt is on correctly. There's a dot on both cam gears and a dot on the crank sprocket. The timing belt you will buy will have 3 white lines which are supposed to line up with these dots. In addition to lining up the dots, I also like to actually count the teeth between the dots on the camgear+crank sprocket to make absolute sure that the belt is on correctly.

The reason why your motor will die due to timing belt failure is a de-synchronization of the valves and the cam. As long as both cam gears and the crank rotate together then they won't crash into each other and your engine will be happy. Counting the teeth and lining up the marks right is absolutely critical to make sure you are lining up these components right.
Author:  jtang [ Thu Mar 21, 2013 11:10 pm ]
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For reference.... timing marks:

Image

Image

Image
Author:  Filipe [ Thu Mar 21, 2013 11:26 pm ]
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Ah ok. Didn't realize the crankshaft pulley was on the outside of the TB covers. That makes sense now. :wink:

I'm familiar with the TDC process from the FSM, and until about .43 seconds ago, I didn't understand what you meant by "difference". You mean total teeth on the camshaft pulley minus the camshaft timing pulley, correct?
Author:  jtang [ Thu Mar 21, 2013 11:28 pm ]
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I mean counting the teeth on the actual belt between the timing marks.
Author:  Filipe [ Thu Mar 21, 2013 11:30 pm ]
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LOL. It just clicked.

I was counting the wrong teeth..


:roll:
Author:  Frank T [ Fri Mar 22, 2013 7:00 am ]
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A lot of engines today are what some people call "intrusive" and others call "invasive" ~ it means that two moving parts often share a common space inside the engine, but obviously not at the same time.

In this case, the valves and pistons pop in/out of the same space inside the cylinder. If everything works as planned, one enters as the other leaves. We roughly refer to this plan as 'timing'.

As long as everybody stays in step, the engine runs many thousands of happy miles. If anything causes the cadence to change (like a slipped timing belt), everything tries to occupy the same space at the same time, and Sir Isaac Newton gets all upset.

John's gentle caution sounds pretty sage. I personally salute you for your willingness to tackle your own mechanical repairs and learn your Z at the expense of your own skinned knuckles, but if you screw up even ONE THING on this job, you'll be paying for a ZXT which sits in your driveway until you can afford a total rebuild.

Your dad sounds pretty intelligent ~ why not pop a beer with him and zee what he thinks?


:wink:
Author:  Gregmatic [ Fri Mar 22, 2013 8:14 am ]
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Congrats on the Z31! I know you had been looking for a long time. Let me add mt .02 in here:

1) be sure you change the timing belt, water pump, timing belt tensioner & stud, CHTS & subharness, coolant bypass hose cam and crank seals too....
don't skip anything, these motors are 25+ years old and even if it hasn't failed yet it will eventually

2) usual problems encountered out of the ordinary are: can't get crank pulley off, can't get timing gear off, CHTS breaks off in head. Be prepared for these things with the appropriate amount of time and tools, you will likely encounter some form of obstacle

3) you do not need to remove the valve covers to do this, regardless of what the FSM and a Chilton/Haynes tells you. Also note that the gears on the timing pulleys have a little tiny dot stamped into them, these are your timing marks NOT the marks on the cover. The tming marks on the cover are just sort of a "close enough" reference if you are timing this motor from scratch and not to be used as an exact reference.

4) everybody has their own method of tensioning. I have done dozens of these motors and the way I do it is to twist the belt dead center between the two cam gears. You should just about be able to turn it 90 degrees, a tad on loose side is preferable to a too tight. Considering you are new to this, I would follow the FSM or Haynes/Chilton procedure.

5) 40 teeth between the cam pulleys, 43 between the driver side cam and the crank pulley. triple check it, turn motor over by hand, check it again

6) lots of people F@#$ up replacing the guide discs on the timing gear, they either put them on backwards or forget them altogether. Don't be one of these guys:

)#(


^that is what it should look like. Concave outward to "guide" and center the belt on the gear. It'll make sense once you see it...

****Nissan OEM parts only for the CHTS & subharness, tensioner stud & crank/cam seals. Aftermarket is fine for the T-belt, WP and hoses....



Good luck! I kind of retired form the repair business this last year, or else I would have offered to give you a quote on the job. But if you have any questions you PM me on here and I'll help as best I can...
Author:  Frank T [ Fri Mar 22, 2013 8:29 am ]
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What a great Club.
Author:  phil280zxt [ Fri Mar 22, 2013 8:31 am ]
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... also known as interference motors....
Author:  Paul [ Fri Mar 22, 2013 9:28 am ]
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Secret for crankshaft bolt: Put breaker bar with socket on bolt, lay the breaker bar on the ground, and crank the engine for a few seconds. Works all the time, especially if you don't have an air gun or can fit one in the space. Can't do this on Hondas or any other engine that runs counterclockwise. I have never counted the teeth, just make shure timing marks are dead on and not one tooth off. Turn engine over a few times by hand, and always recheck timing marks. This is the most crucial part. The only way to learn is doing it yourself. You could pay someone, but that would probably cost more than you paid for the car. Get a Haynes Manual. :D
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