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  #11  
Old 08-23-2021, 08:22 PM
v8volvo v8volvo is offline
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Interesting and strange problem.

It seems like you have already done a great deal of smart work to it. Most of the first guesses I would be thinking about you have now addressed. Good idea on the replacement of all the sprockets and the work to ensure the idler sits straight.

The machining of the oil pump must have been quite a job! I assume you had to take the whole pump assy off the engine first?

Correct that the original type water pumps had flanges to guide the belt. In fact the pumps available here in the US continue to have those, so they are still possible to obtain. However, I don't think they alone would correct the issue you are having, since the belt should ride square on the sprockets even without them. To my recollection there are guide flanges on the crankshaft sprocket anyway.

I would be happy to send you one of the water pumps with guide flanges on the pulley if you would like -- I have a few NOS -- but again I'm not sure it would make a difference. Even so, perhaps worth trying.

The rear cam cap does have the thrust surfaces for the cam so I think your observations about axial play in the cam with that cap removed makes sense.

I am looking back through the earlier discussion now on this and I realize there is an important question that I don't think has been asked yet: do you remember if this problem existed already when you got the car, when it had the belt it came with? Or did the belt riding off kilter only begin after you did the timing belt replacement?

That may tell us something about my final guess. If the previous belt rode square but this belt now is riding offset, then it means the phenomenon must be caused by something in the timing belt components, as you have pursued so far. BUT if the other, old belt was already riding off kilter, then it could be due to the installed position of the cylinder head.

I have seen it be the case that after a cyl head R&R on these engines, the timing belt's position on the sprockets can change. There is just enough free movement possible in the headbolt holes in the head that the head can be not perfectly parallel to the block and I believe that causes this to occur, since the cam sprocket is not sitting square to the rest of the components.

That may be the only explanation left given all you have checked out so far. If that is indeed the cause, then the only solution might be to R&R the head, but that's honestly quite a bit easier than the oil pan job you already did.
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  #12  
Old 08-29-2021, 10:57 AM
Bob Bob is offline
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hi
thankyou for your in-depth reply

firstly, yes i had to remove the whole oil pump assembly in order for the machining to take place. as far as i am aware the machinist then lay the pump on two parallels either side of the drive tangs/ pump gear and bored it out square in relation to the mating surface of the pump and then made a sleeve. i may of not had to remove the sump if the gasket was not disturbed in the process of removing the pump. however as i was in there i thought just go the whole way and do the sump gasket plus crank seal other applicable gaskets.

yes you are correct the crank gear does have a rear flange to prevent the belt walking and the front will meet the pulley. however the width of the belt is significantly less than the gear so it can walk back quite a way before it hits the flange. by this time the belt is a few mm off the back the the water pump idler and cam gear.

now, before your most recent reply i noticed while looking for a flanged pump that the older style pumps (flanged) have 20teeth. i thought this may be an issue with my setup as the pitch may differ slightly and could be part of the reason for the older belts to have 1 less tooth or this may be due to the adjustment that can be made on the water pump mounts.because of this i had doubts about fitting the older gear to my newer pump. anyway this is where it got interesting as i noticed that although my water pump was not flanged, it had 20teeth much like the older flanged style gears. i had not noticed anyone else's later style engine with a water pump that had 20 teeth and a fixed position. so i began looking for a 18 tooth pump with a fixed mounting position much like all the others for sale and that can be seen pictured on the internet. this time i bagged a hepu pump with 18teeth and no flanges. when comparing the hepu pump to the fai pump installed the fai pump gear was larger and with more teeth. i roughly worked out the pitch to be around 2.8 on the hepu gear and 2.9 on the fai gear. so although the gear had a bigger size it seemed similar in pitch.

when testing the new hepu pump the cambelt seemed well where it should be however when the engine was running it tracked back towards the engine just like before. i made tweaks to the tensioner just to see what would happen i even contemplated and then acted upon the fact that the angle of the engine was so sever due to being on an incline and with the front on axle stands that the belt may be wandering back ever so slighlty. i corrected the engines angle. if i gave the belt more tension the process of belt walk slowed somewhat. the process was taking about 20 seconds of normal cold engine tickover. it was noticed that the belt was wandering slightly left to right on the idler on the way up to the tensioner while running. this was why i thought to increase the tensioner preload for testing purposes.

the idler was checked for squareness in relation to the water pump as the belt was wandering most visibly in this location. by eye the idler seemed to lead slighlty inwards away from the turbo side of the engine ever so slightly. in other words if you put a straight edge on the idler and waterpump the gap on the right hand side of the waterpump gear seemed more on the right than the left.however after loosening and turning the idler it really looked dead square to the water pump. this could have been caused if the boring process of the pump or sleeve was not quite correct although the idler seems dead on square by eye now.

so i started the engine again and the belt remained in the centre of all gears apart from the idler as for some reason it is 2mm proud of the water pump. in other words much like before if you use a straight edge from the idler to the water pump a gap of 2mm is between the rule and the water pump. I'm not sure if this is normal??. the belt remained centred for at least a minute which seemed to be an advancement. however i began to rev the engine quite high every second or so and watched the cambelts movements. it then tracked back quickly to the back of the engine. this test was repeated and the same results occurred each time.

when the belt runs correctly it is always near the edge of the idler. perhaps when i rev it up and its wandering increases on the idler as previously mentioned, once the belt meets the edge of the idler it pulls it the rest of the way and the belt then subsequently walks back on all gears and tensioners. this is why i would like to know if the idler should be flush with the waterpump or perfectly inline.

it seems as though any tweaks of adjustments i make alter the initial characteristics of the walking however the outcome always remains the same. i am looking at getting 2mm turned off the idler so that it sits inline with the waterpump. worth a try i think.

it seems that unfortunately the car had this problem when i purchased it however the position of the belt was not so extreme as it is now. the belt has always been on the back of the cam gear.

what you have mentioned about the cylinder head makes sense i hope this is not my issue but it could well be.

image of the idler and waterpump with a straight edge
https://ibb.co/NxFhFSB
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  #13  
Old 09-06-2021, 09:43 PM
v8volvo v8volvo is offline
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I just spent some time searching for a VW/Audi TSB that I know I have found before but cannot seem to track down right now. However this thread makes mention of it. https://forums.tdiclub.com/index.php...ng-off.373906/

I went through something like this on a TDI engine once a couple of years ago. Per the instructions in the TSB (which are summarized in the thread above in the link), I had to remove the injection pump and reposition its bracket. The way it had to be repositioned seemed counterintuitive for the direction I wanted the belt tracking to move. But it worked.

I'm going to keep looking for the TSB but you get the idea. Of course in the case of the Volvo D24TIC engine, where the IP is driven off the rear belt not the front, this exact procedure is not relevant. But the general principle is that even just one component that is very slightly out of parallel can have the effect of changing the belt's position. (And can lead to damage of course as happened to the fellow in the thread above)

One thing I have realized in reading your last post is that you have a late style D24TIC engine with a dedicated tensioner for the front timing belt and a fixed position water pump. Thus, my earlier comments about the availability of pumps with flanged pulleys are irrelevant I now see, since those are the old style pumps with slotted mounting holes -- not what you need.

I'm not sure on your question of whether the back of the idler roller should be flush with the water pump pulley and in any case I am not sure my examples would be the same as yours, given that they use the old style system with slotted WP. However I don't see how making that pulley narrower will make any helpful difference with the belt's position.

THE GOOD NEWS, despite all of that, IMO, is that this is a pretty simple system. If my understanding of the late style system is correct, there still are only a total of 5 components the belt touches: crankshaft, camshaft, water pump, idler roller, and tensioner roller.

1. OK, so based on your update, we now know that this problem persists with two different water pumps with different pulley sizes. That rules out a problem with the WP, I think, unless it is something really sneaky like the face of the block where the WP mounts being worn somehow to where it is not square. Highly unlikely.

2. You had the idler recess sleeved already and set right square to the pump mating surface. That probably rules the idler out as a possible cause. Probably.

3. The tensioner roller -- have you replaced the stud that it rides on ? Any chance that stud could be bent?

4. Crankshaft. This of course is the one part that cannot move. We'll assume the problem is not here especially since you replaced the crankshaft gear.

5. Camshaft. This itself cannot move, but the cylinder head could be positioned imperfectly on the block. As I mentioned before, this is my #1 hunch cause. The reason I think so is that I have personally seen the effect where a timing belt rides in a different location on the pulleys after a headgasket replacement job. In the cases I have seen, it was not far enough of a change to result in the belt riding off the pulleys or to cause any serious problem. It was just different but still an acceptable position. However, I think a more extreme version of this could cause what you have seen.

Don't give up now after putting in all the effort you have done -- no doubt there is a solution. I would probably try replacing that tensioner stud first, see what that does, and if no luck there, I would pull the head and see if you can get it lined up better. A fresh headgasket and opportunity for a valve job is a nice side benefit.
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  #14  
Old 09-28-2021, 12:06 PM
Bob Bob is offline
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hi

when i mentioned the idler i was referring to moving it further into the oil pump by machining the custom sleeve that had been made not decreasing its diameter. this action would bring the face of the idler inline with the waterpump and all other pulleys as i thought if the belt caught the edge of the idler it could encourage its deflection off course further. i have since tried this and it has not corrected my issue although i think its an improvement on the setup.

yes there are only a few components on the cambelt assembly which have all been changed at least once. i was considering buying a new belt on the off chance it was a dud however i have tried it in both directions so my thoughts of there being a tight braided strand are unlikely. But what's 20 quid for a new belt going to do after going this far...

my only other thought before doing the headgasket at the moment would be if the tensioner stud was bent or worn. you may not know due to you having the older variant but the tensioner assembly is loose (in my case) on the stud/shaft but has a flat face which sits on the head. so even if the shaft was worn the nut securing the tensioner should pull it flat face to face which is what is occurring. i cant remember if someone else on the forum mentioned this but someone said the tensioner wasn't sqaure and leads off from factory. how true this is i don't know. another unlikely cause.

now the headgasket topic. this would be a good time to bulletproof the engine with the mls gasket and hts head studs, not that im looking to push serious power but i like the idea of having the option there. how can i tell what notch headgasket i have or do i have to measure the thickness of the gasket when the head is removed( i doubt it as it would be compressed). I'm sure there is an indication of the thickness prior to removal that i am not aware of. i understand i can order the same thickness//notch as what is fitted or less if i measure the clearance between the pistons. the process seems simple in theory considering i have timed the engine a silly amount of times trying to fix the walking belt. is the head on dowels? if so surely you couldn't move the head.. or is it literally floating on the head studs? i have a general idea of what angle i want to push it in considering the general dynamic of where the belt is tracking and the rotation of the engine. i just hope it gets bolted down in a better position.(seems very hit and miss).

the annoying thing is since messing about with the setup as per my previous message the cambelt will run forever in a day on track until you increase the revs to say 2500-3500. i have shown this in a video which i have uploaded to YouTube. the first clip is the cambelt on course and the second section shows the belt after it has tracked. it does not move further but it does not return to its original position.

that's my thoughts at the moment. looking like the head is going to be coming off at some point, just need to source some ht head studs/bolts and a new gasket. i sure hope that will fix my problem or im going to break down

youtube link for my video
https://www.youtube.com/watch?v=grUQbxMhMmY

just noticed this guy examining his on YouTube and seems to be in the position i dont want mine!!!
https://www.youtube.com/watch?v=LzVw4H10zm0

regards
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  #15  
Old 09-28-2021, 01:28 PM
RedArrow RedArrow is offline
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Default TB position on camshaft pulley

Quote:
Originally Posted by Bob View Post
just noticed this guy examining his on YouTube and seems to be in the position i dont want mine!!!
https://www.youtube.com/watch?v=LzVw4H10zm0

regards
Your thread is about a very interesting topic. I hope someone will be helping you with good advice.

My timing belt appears to be in that very same position since at least 9 years ago (the belt runs in a `rearmost position` on the very back of the camshaft front pulley). It worried me first but then I was told it would be okay. AND, I do know that the belt was installed by a real professional who is also an extremely knowledgeable d24 enthusiast.
As far as I know, the head never came off on this engine but maybe I am wrong about that. I think it has the 3-notch fiber one.

Last edited by RedArrow; 09-28-2021 at 01:32 PM.
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  #16  
Old 09-29-2021, 11:39 AM
ngoma ngoma is offline
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Quote:
Originally Posted by Bob View Post
how can i tell what notch headgasket i have or do i have to measure the thickness of the gasket when the head is removed( i doubt it as it would be compressed). I'm sure there is an indication of the thickness prior to removal that i am not aware of. i understand i can order the same thickness//notch as what is fitted or less if i measure the clearance between the pistons.
Should be able to see the notches (sometimes holes) on the protruding section of the headgasket near under the radiator hose flange. But you can't count on that being the correct thickness for your engine. Even the factory didn't always use the best one. Oftentimes during headgasket R/R the tech would just select the 3-notch to save time but this might give up easy starting, performance, and economy. Better to measure the piston protrusion (above the block deck) as per the greenbook. Tom Bryant likes to run on the edge, even removing layers of a MLS gasket to get it as tight as possible.


Quote:
Originally Posted by Bob View Post
is the head on dowels? if so surely you couldn't move the head.. or is it literally floating on the head studs?
There is quite a bit of slop and moveability side-to-side, front-to-back and rotatability. We make our own locating posts by cutting the heads off a couple of old head bolts and cutting a flathead groove in the top to allow removal with a screwdriver after setting the head.
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  #17  
Old 09-30-2021, 10:11 AM
Bob Bob is offline
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thanks for the feedback.

how do you go about "setting the head" when there is so much slop. when you say setting the head do you mean just centralizing all the bolt holes that go thorough the head-gasket-block by installing like you said the modified bolts and then removing them for the new bolts/studs. that way everything is mostly where it needs to be and all bolts are aligned correctly? i assume in the factory they must have had a jig so that this could not be done incorrectly.

If i remove the head i will measure the clearance and order an appropriate gasket to suit.
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  #18  
Old 09-30-2021, 12:47 PM
RedArrow RedArrow is offline
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Yes Bob,
Volvo in fact had a tool for this, 9995235 (21)
or you could use modded headbolts. The four pins may have their own part number as 9995234 but I`m not sure at the very moment.

The four white little plastic pins/plugs have their outer ends threaded to go into the head smoothly (for fitment see illustration)... and the other end of the plastic pin is hollow and threaded inside as well, it is left-threaded BTW (to accept the `picker tool` then you can pull them out safely). Picture 4 shows this.

There are (at least,?) two kinds of headbolts used in the d24 family of engines, thinner ones are visible on left, the thicker 12mm ones are on the right. Their heads have been shaved/removed to properly fit `through`. There is still some thickness left of the top to use the headbolt-tool to install/remove these home-made `alignment pins`.


A 'Snap-on 12' tool is also pictured (used to handle the thicker later years headbolts) /right side, 5th picture/
Attached Images
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File Type: jpg Screenshot_20210930-165524.jpg (6.5 KB, 4 views)
File Type: jpg Screenshot_20210930-165856.jpg (25.3 KB, 3 views)

Last edited by RedArrow; 09-30-2021 at 01:12 PM.
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  #19  
Old 09-30-2021, 01:19 PM
RedArrow RedArrow is offline
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A little off-topic but for the piston protrusion they also had a Volvo tool made, 9995192 (21)
Works with the dial caliper the typical way, has its own 'clamp-bolt' on top.
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File Type: jpg Screenshot_20210930-171811.jpg (17.9 KB, 5 views)
File Type: jpg Screenshot_20210930-171818.jpg (23.7 KB, 5 views)
File Type: jpg Screenshot_20210930-171828.jpg (21.9 KB, 4 views)

Last edited by RedArrow; 09-30-2021 at 01:23 PM.
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  #20  
Old 10-01-2021, 10:55 AM
ngoma ngoma is offline
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Quote:
Originally Posted by Bob View Post
how do you go about "setting the head" when there is so much slop. when you say setting the head do you mean just centralizing all the bolt holes that go thorough the head-gasket-block by installing like you said the modified bolts and then removing them for the new bolts/studs. that way everything is mostly where it needs to be and all bolts are aligned correctly?
Yes centralizing the holes on the (ground down used headbolts used as) locating pins. Two are sufficient. Although in your case you may end up with the headbolt holes not centralized but rather up against the edges, in an effort to get the cam sprocket positioned where you want it.

IMHO there is some slop there yes, but not enough that it would impact the coolant or oil passageways if the head was not exactly centralized.

Quote:
Originally Posted by Bob View Post
If i remove the head i will measure the clearance and order an appropriate gasket to suit.
A good short straightedge and feeler gauges works. Measure along the piston wrist pin axis, both sides F/R of each piston.

More reading material for you, courtesy of Tom Bryant https://thosbryant.wordpress.com/201...-pump-re-seal/ :

"Tom Bryant says:
April 29, 2016 at 10:42 pm

Jeremiah,

Headgaskets make a significant difference to winter starting, but glow plugs and general engine condition are much more important. Thinner headgaskets also make a dramatic improvement to horsepower and performance. If you do decide to replace your headgasket, you should try for the thinnest one you can get away with. That means that you really must use an MLS headgasket, as you cannot readily predict, or control, just how thick a composition headgasket will be.

Volvo’s original “Green Book” specifications, when boiled down to their basics, call for a piston to cylinder head clearance in the range of 0.58-0.73mm (0.0228-0.0287″). That is an overly-conservative specification. And to make matters worse, engines often left the factory with piston to head clearances well in excess of the maximum specification. I have seen situations where a 3-notch gasket was used when the clearance specifications should have dictated a 1-notch gasket.

Then, to make matters much, much, worse, aftermarket replacement pistons are often about 0.25mm (0.01″) shorter than the OEM pistons, so if they’re used with the original head gasket thickness, the situation goes from bad to intolerable.

The cure is to install the thinnest MLS head gasket you can. I have experimented with many, many, such thinner head gaskets to find out just how small a piston to head clearance I can get away with. The answer is just about 0.014″ (0.356mm). I have had several successful engines with that low of a calculated clearance. And, I’ve also had a few failures with that same calculated clearance. To be safe, I don’t really recommend trying to go below a minimum piston to head clearance of 0.017″ (0.432mm).

To achieve such low clearances, it is generally necessary to remove layers from an MLS head gasket. Such gaskets have 4 layers. You can get away with removing any of those 4 layers *except* for the top layer. You can also get away with using a bottom layer in place of the top layer, but you have to put a sealant on the bare metal side of that layer, which would then face upward toward the cylinder head. I recommend Volvo’s “High Temperature Chemical Gasket” Part Number 1161059-9 for that purpose.

If you decide to go with one of these radically thinner head gaskets, you must measure your piston deck heights very accurately, and you must make sure the piston top is square across (or level). And, you will have to measure the thicknesses of each layer of your MLS head gasket very carefully.

For reference purposes, here are the layer thicknesses that I have measured on Volvo’s MLS head gaskets (which, unfortunately, are no longer available):
Top layer: 0.23mm
2nd layer: 0.87, 0.92, 0.97mm (1, 2, & 3 notch gaskets, respectively)
3rd layer: 0.12mm
Bot layer: 0.23mm

As just one example of how a person can mix and match head gasket layers to obtain a desired thickness, here’s what I used for my latest head gasket replacement: One top layer, and 4 bottom layers. That’s right, I didn’t use the thick “notched” layer at all. The piston deck heights maxed out at 0.030″ (0.762mm), and I needed a thin head gasket, so I used only the corrugated “top” and “bottom” layers. I had several brand new bottom layers that had been removed from previously-installed gaskets. So, I combined four of those bottom layers with one previously-used top layer that had lost its rubber coating. I applied a bit of that special Volvo anerobic gasket maker to both sides of that top layer. The calculated piston to head clearance of this gasket is 0.0153″. It was installed in the engine on 6/24/2015, and to this date (4/30/2016) has accumulated over 7600 trouble-free miles.

Be extremely careful with your measurements, and don’t push the envelope too far until you’re really sure of yourself.

If you do this, and depending on just how thick your old gasket was, you may notice a dramatic improvement in horsepower and performance.

Tom"
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