1hz Timing Belt Change

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Jul 10, 2006
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Bowen Basin, QLD Australia
Gday
I thought Id do a write up on a 1HZ timing belt change. I did a search and didnt see 1, and thought it may help someone.


I start by pulling the bolts (3) from the P/steer resivior, to let it flop around a bit.
Then remove the 3 bolts (10mm head) and 4 clips from the plastic timing belt cover. I use a 3/8 drive ratchet and a short 2.5" extension to get these bolts.
Next, I turn over the engine, using the bolt on the injector pump pully (19mm), to line up the timing marks to Bottom Dead Center. You may need a 1/2" drive breaker bar for this.
Here is a pic with the cover off.
I high lighted the timing marks on the pulleys with a white pen on this engine.
Also note the mud on the tensioner spring.
pic 1.jpg
 
Joined
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Bowen Basin, QLD Australia
This is a 1993 engine and has the spring tensioner - not the hydraulic 1. I miss the spring, myself - spring =early , hydraulic = late.
Next, flip the tensioner spring off its lower mount with a flat screwdriver and remove the bolt from the center of the tensioner idler. It comes out with a spring and washer all attached.
Now slip the belt off, and inspect the spring for length (if you want) and inspect the idler. Give it a spin and feel for a wobble in it. Ideally, youd change it every time, but....whatever.
Slip the new belt on. I start at the injector pump making sure all the teeth are seated, then slip the belt onto the cam - going anti-clockwise to keep all the slack out.
Now you flip the spring on. I use a #3 phillips screw driver for this. I slide the spring down the phillips with the flat screwdriver used earlier.
pic 2.jpg
 
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Joined
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Reinstall the bolt+spring in the tensioner idler.
Now I like to turn the engine over by hand, just to check the timing marks still line up. It will run fine 1 tooth out either way, but will be gutless and a little smoky.
Now its time to fire 'er up, and have a #6, - unless your at work.
You may see the injector pump pully running a little eccentricly, causing the tensioner idler to move around a bit. This is standard.
Refit the cover (dont be tempted to leave out the bottom bolt) and the p/steer res. and your good as done.
On an 80srs, reset the light on the dash by pushing the reset button in the speedo with a scriber or similar.
On a 79 or 100, you hold in the odometer button while tuning on the ignition, then hold for 5 seconds. Then push it again, and get it to reset through there.
I can book about 30 minutes to this.

Hope this helps someone, sometime
Regards

Matt
 
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Ron R

Drive a Landruiser, enjoy life
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Matt,
nice write-up.
May I add a few lines?
I do not align the timing marks. This saves me having to turn the engine by hand and through the timing belt (puts enormeous strain on the belt).
I just mark the pulleys and the timing belt in one go in a convenient spot. This way the marking on the pulley and timingbelt are aligned. I do this on the camshaft pulley and the injectorpump-pulley.
Mind, I use a marker that 'sticks' very well.
Then after getting the belt off I transfer the position of the markers on the old belt to the new belt. (side by side)
Then put on the new belt that way that the markers line up with those on the pulleys.
This saves you turning the engine by hand and it shows clearly that the timing belt is exactly on the spot and not a tooth off.
 
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On related note: I have a 1998 HJ70 with a 1HZ motor. The manuals are in Japanese and everyday I look at a dashboard LED marked "Timing belt". It hasn't gone on yet. When should I expect it to?

The odometer reads less than 60,000 km (35K miles)

Cheers,
Dennis
 
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Ballarat, Victoria, Australia
100k.

It goes on every 100k

To clear it, you take the plastic cover off on the dash (gently, it'll break!)... it's near the one you push in to clear the odo to 000. Then stick a pen in there, push the button and you're done.
 

Ron R

Drive a Landruiser, enjoy life
Joined
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Messages
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The Netherlands
On related note: I have a 1998 HJ70 with a 1HZ motor. The manuals are in Japanese and everyday I look at a dashboard LED marked "Timing belt". It hasn't gone on yet. When should I expect it to?

The odometer reads less than 60,000 km (35K miles)

Cheers,
Dennis
As Entaran discribes, it's easy to solve your light-problem.
But be aware the light is not there just for fun.
I agree on Entaran saying it should come on at 100.000 km indicating the belt is due for replacement.
Are you sure the engine has not run more than 65k km? Nobody tinkered with the odometer?
In that case add an other 35k km and replace the belt then. But if not a 100% sure I would replace the belt because if it tears it's a costly thing, could ruin your engine almost completely.
At the moment you replace the belt you also should reset the light, being it on or not. Then, a 100k km later it will come on again, warning it's time to replace.
 

roscoFJ73

 
 
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At the moment you replace the belt you also should reset the light, being it on or not. Then, a 100k km later it will come on again, warning it's time to replace.
Are you sure? I was under the impression it was mechanically fixed to come on every 100000klms regardless of whether you have reset it early.
 

Ron R

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Are you sure? I was under the impression it was mechanically fixed to come on every 100000klms regardless of whether you have reset it early.
To my best knowledge: Yes.
It's just a small counter, driven by the odometer.
If you reset it (and that's possible any moment) it just starts counting from zero.
So if you accidentally reset it before you reach the 100.000km mark you won't get a warning at 100.000 but at 100.000 plus the k's you had at the moment of resetting.
If, for example you reset at 55.000 k the light will be there when you hit the 155.000 km mark.
AFAIK the light stays on untill reset.

Note: There even is a procedure in the manual to set the timingbelt counter gear in case the odometer has to be replaced.
 
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Thank you to all who have PMed me regarding this thread.
Ron, If you are worried about the enormeous strain you put on the timing belt, when you turn the engine by hand, I suggest that this may not be a job for you.

Matt
 
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Ron R

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Thank you to all who have PMed me regarding this thread.
Ron, If you are worried about the enormeous strain you put on the timing belt, when you turn the engine by hand, I suggest that this may not be a job for you.

Matt
Hmmm, guess I expressed myself wrong here, rereading my posting.
It's a matter of having certain thoughts, typing and leaving things out.
I've seen people turning the crank not by turning at the crank itself but at the nut/bolt of the camshaft. And that was where I was referring to.
I think the belt was not designed for that....

So called mechanics doing that would not be allowed near my rig...
 
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So these are interference engines? And I thought it was gear driven like the 3FE. Is that the 1HD-T maybe? Sorry, but I am in the U.S so not too many diesels and all. Thanks.
 

Ron R

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So these are interference engines?
Yep.

And I thought it was gear driven like the 3FE. Is that the 1HD-T maybe? Sorry, but I am in the U.S so not too many diesels and all. Thanks.
Yes, they are and no, they are not. It's a combination.:)
The Injectionpump is gear driven by the crank. On the pump gear is an extra pulley for a toothed timingbelt which drives the camshaft.
In the drawing below the two pulleys are indicated by a yellow marker. The crankdriven gear is marked with a red arrow.
From the drawing you cannot see it, but in fact the lower pulley is sitting at the front of the crankdriven gear.
timingbelt.GIF
 

mac

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So these are interference engines? And I thought it was gear driven like the 3FE. Is that the 1HD-T maybe? Sorry, but I am in the U.S so not too many diesels and all. Thanks.
You'll find all diesels to be interference engines due to the height that the piston rises in the cylinder to achieve high compression.
 
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Toronto, NSW, Australia
There are two versions of the timing belt tensioner spring - one slightly longer than the other. Is it critical to use the right one, or did the later version simply replace the earlier one for all tbelt renewals after a review by Toyota of the design?

Also, I'm told that in earlier 1HZ's (probably mine, being in a 3/1992 build 80 with over 600 k km's on the clock), there are some dowels associated with fitting the tensioner?

While I'm at it, do most people renew the water pump at the same time as renewing the timing belt? What about doing the valve shims (if you have the right tool)?
 

roscoFJ73

 
 
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Around 1999 the 1HZ gained another tooth on the timing belt. It maybe when the spring got longer. No need to do the water pump when you do the timing belt unless it needs it.
Water pumps die slowly on these , mine has been leaking when cold around the shaft for 2-3 years. I have to do something soon but they give you a lot of warning.
 
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Gday, I don't know if there's many active users but I could use a bit of advice.

My timing belt recently went in my 75 series (1HZ) and when i'm trying to get the 2 pulleys aligned there's tension like the valves are hitting on the pistons and I can't turn them any further. What is the best way to turn the cam and injector pulleys so they dont get stuck?

Thanks in advance.
 
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So your timing belt failed? Broke while running?

If so, have you had the head off and inspected for damage?

IMO, damage to valves is almost a certainty.
I would start with pulling the head and seeing if you have any damage.
The fact that your pulley's match marks aren't aligned suggests bad things are waiting for you under the head.
If you have damage valves, fitting a new belt and running the engine may just increase the damage, and the repair bill.
 
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I think, you could remove the cam shaft, align crankshaft with the timing marks, and realign the cam and pulley, check your pulleys are aligned with the timing marks then refit a timing belt and slowly turn the engine over by hand.
Removing for plugs will make it a lot easier to rotate the engine gently.
If there is any suggestion of interference, your back at pulling the head.
You'll never be certain of damage without pulling the head.
 

Locked79

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As above, remove the cam, put #1 piston on TDC, install camshaft with cam lobes pointing up (at this point all timing marks should align) and turn over by hand. If nothing binds, fire up the engine. Any rough running, misses or ticks will mean you have damage valves. Since the 1hz is an interference engine, there's a 99% chance its damaged
 
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