What is the basic timing belt replacement procedure?

[volvo 4 life]

I've been reading the D24 greenbook and trying to figure out what is absolutely necessary to change the timing belt on my D24. I would like to leave the rear belt alone if possible so the pump timing doesn't change because the car runs really good right now. Is it possible to change the front timing belt by marking the pulleys and belts and then checking the injection timing afterward with the dial indicator? I was thinking I could lock the injection pump with a pump lock pin, that way the cam and injection pump won't move while changing the belt. Does this sound like a reasonable method? I would check the injection timing afterward to make sure it is within specification.

[745 TurboGreasel]

If you are checking the timing afterward, you might save 5 minutes not adjusting it, but really all you accomplish is preventing yourself from locking the cam in the right spot, but it will cost you over an hour if you have to redo it.
Yes you can shove a new belt on, and it will probably run.
The timing you are trying to preserve won't be the same after. if you like it, but don't know what it is, check it before disassembly, and set it to that when you are done.

[ngoma]

Theoretically (actually more than theoretically, I lucked out doing similar when changing the waterpump) you should be able to:

1. Check the IP timing.
2. Change the timing belt.
3. Check the IP timing. If it is the exact same as before, you are good to go. If it has changed, you must check (and probably readjust) the cam timing, which necessitates resetting the IP timing.

Supposedly there are small differences in timing belt manufacturing tolerances, and differences in waterpump tightness before & after that can introduce enough variation to throw off the cam timing, and therefore, the IP timing.

IOW, you might get lucky, but will still need: 1) The cam timing tool, and; 2) IP timing tools, and be prepared to reset the timing (both) if necessary.

[volvo 4 life]

Ok, well then I guess I will just devote a day to the project and go through the steps of locking the cam and IP so it all comes out how it should. What is good setting for timing on an NA D24 for a little more power and better cold starts? It's a bit rough right now if it's under 40 degrees and the engine is very quiet, hardly any ignition knock at all.

[sonny]

How would you place the Cam Timing Tool, which you need to Change the Main Timing belt, without removing the Camshaft sprocket, where the InjectionPump belt runs on ?

You MUST Re-Time the Pump after Changing the Front Belt .
Anything else is not goot ...

Greetings

[volvo 4 life]

I am going to remove the rear pulley on the cam and put the lock plate in so it stays at TDC. I have a new rear belt so I will just change both belts while I'm there. Tools needed would be the crank lock tool, cam lock plate, lock pin for IP, dial indicator, dial holder, and pulley holding tool right? I don't quite understand how it's possible to torque the pulleys on the cam because it isn't keyed. How do you keep the cam from moving while torquing the pulleys down? Even if you hold the pulleys with the sprocket holder it would seem the cam would still slip while trying to torque the pulleys down, especially the rear since it requires around 70 ft lbs of torque.

[ngoma]

Originally Posted by sonny

How would you place the Cam Timing Tool, which you need to Change the Main Timing belt, without removing the Camshaft sprocket, where the InjectionPump belt runs on ?

You are correct. I have modified my step 3. above.

Originally Posted by sonny

You MUST Re-Time the Pump after Changing the Front Belt . Anything else is not goot ...

If you replace only the front timing belt without disturbing the cam pulleys (front and rear), and the IP timing retains the same setting as it did before the TB replacement, then we can say the relationship between crankshaft/camshaft/IP has remained the same.

[v8volvo]

Originally Posted by volvo 4 life

How do you keep the cam from moving while torquing the pulleys down? Even if you hold the pulleys with the sprocket holder it would seem the cam would still slip while trying to torque the pulleys down, especially the rear since it requires around 70 ft lbs of torque.

The cam counterhold tool is your friend there, #9995199. This is actually the easiest one to find of all the diesel tools, you can still buy it from Volvo for around 30 bucks or used fairly frequently, because Volvo recycled it as a tool for cam pulleys on whiteblock gasser engines too and so it still has current applications. Or various members here have them available for loan, etc. It's actually pretty crucial to being able to do the job at all, let alone making it much easier. You use it for both the front and the rear pulleys, the cam doesn't move as long as you're careful.

Torquing (and loosening) the rear cam pulley bolt is also greatly aided by having the correct special offset wrench extension (can't remember the number but can look it up later...), especially in a 200 series where clearance to the firewall is even tighter, but you can survive without it as long as the last guy in there didn't go crazy tightening it.

BTW, you don't need the whole 70lbs on the rear bolt, I usually oil the threads of the bolt and underneath the head, and get the mating surfaces on the back of the cam and the inside of the pulley good and clean and dry, and go for more like 30lbs. If that pulley does slip the result is not catastrophic but I've never had one loosen up, and I like the lower torque because I want to be able to get it off again without a struggle the next time I'm in there.

By contrast, I usually prefer slightly a higher torque than spec on the front bolt, more like 45lbs rather than 33. Don't want that one to move...

[ngoma]

Originally Posted by volvo 4 life

How do you keep the cam from moving while torquing the pulleys down? Even if you hold the pulleys with the sprocket holder it would seem the cam would still slip while trying to torque the pulleys down, especially the rear since it requires around 70 ft lbs of torque.

Front pulley: Tapered fit is not apt to slip.

Rear pulley: Is a clamped fit, more apt to slip but doesn't seem to be a problem if you use this method. (v8volvo suggests cleaning up the rear pulley/camshaft mating surfaces, bolt, and washer, and lightly lubricating the bolt threads and under-bolt head contact surface [only] w/ synthetic motor oil, which permits equal [or better] clamping force with less bolt tightening torque.)

[v8volvo]

Originally Posted by ngoma

You are correct. I have modified my step 3. above.

Actually disagree with you there. The IP is driven directly off the cam alone, so as long as you don't R&R the rear belt or change its tension, the relationship between IP timing and cam timing does not change, therefore IP timing can be considered to represent cam timing exactly. If you end up with the same relationship of IP to crank after a belt change, then you've also confirmed the same relationship of cam to crank. If you really want to change the front belt without touching the rear, and you do that without removing the front cam pulley, then you can indeed get away with just confirming same IP timing afterwards, provided your goal is to have it run the same way. If the timing is close but slightly off, you can make small adjustments to it by altering front timing belt tension via moving the water pump. (Tighter = more advance, slacker = retard)

So even if your "after" timing isn't quite identical, you may still be able to get it where you need it without popping the pulleys off. As long as you're ultimately able to achieve an identical pump timing setting AND appropriate tension on the front timing belt (not too loose OR too tight), then you're good to go, you've successfully gotten away with a shortcut and you don't need to use the cam timing tool or procedure.

However, if getting the timing where you need it requires running the new belt too loose OR too tight, then you have to first set belt tension where it needs to be and then time everything according to proper procedure. So that is why you still want to be *ready* (and equipped with necessary tools) to do the full job, even if you're going to initially try to skip some steps this way.

Of course, before even attempting any of this, the thing you DO want to be 100% confident of is that the relationship of CAM to IP is perfectly correct before you start. In other words, unless you KNOW this to be the case, you're just trusting the last guy who worked on it to have gotten the cam timed to the crank correctly. Unless I have firsthand knowledge that it's right (i.e. I myself was the one who did it last or have previously verified it), I wouldn't readily make that assumption. In your case, since IIRC another forum member with D24 knowledge did the last belt change, it may be relatively safe to count on, but still you're running on faith there - up to you whether or not you're comfortable with it.

Originally Posted by ngoma

If you replace only the front timing belt without disturbing the cam pulleys (front and rear), and the IP timing retains the same setting as it did before the TB replacement, then we can say the relationship between crankshaft/camshaft/IP has remained the same.

+1