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cambelt query
hi guys
i hope someone can help me, i have recently bought a volvo 740 estate with a d24tic engine. (it had a swap from the later variant so the mk2). i got it running and decided to do the cambelt as it had been off the road for 12 years. anyway after 3 months trying to source one and too many missing parcels later i bought it in parts. i got gates belts, febi idler, qh tensioner, FAI water pump. anyway here's the problem. im getting it done ive got it timed up and locked the crank to 600nm (as i don't have the crank extension too) but i noticed that the idler pulley doesn't sit quite square in the hole, in other words the hole isn't center of the idler causing it to pull sideways when tight and to add to this the threads seem to be stripped but there are a few at the back so i can get it tight enough. i have managed to square it up as much as i can by removing a burr from where the old idler was mounted, it looks as if the old one has heated up and possibly span causing the surface to wear unevenly. now the other concern the belt rides off the water pump slightly by a couple of mm which is an improvent from when i first mounted the idler. this happens slowly if i rotate the engine 10 revs or so. everything seems relatively true now as per pictures but im not sure if this overhang of the belt is acceptable. perhaps the water pump isnt quite correct or the idler mounting is causing issues. in addition what do you suggest i seal the idler bolt with. ptfe, loctite thread lock or a loctite thread sealant. i just dont want to do anything silly so i thought id get in touch with the specialists who may know better[IMG]https://ibb.co/khTbC36 https://ibb.co/8jRCLdH https://ibb.co/885gzzp https://ibb.co/WK7w4rD https://ibb.co/qJf17gG https://ibb.co/FqYcvqL https://ibb.co/7jBb99X https://ibb.co/pvG4fQ5 https://ibb.co/tM0zpvr https://ibb.co/nB7BkqG https://ibb.co/2yYFVXT https://ibb.co/JFFdtw5[/IMG] ;) |
940 tic auto 1995
hi i have the later version of your cam belt set up with tensioner too . post 1993
the cam belt to me should be just a milimeter back from outside face ,as mine is ,why it wants to ride so close to the back face is beyond me ,the idler i have never seen mine is just in centre of idler ,but the tensioner has a off set centre im sure, some one here will know whats the cause of your problem im sure . |
hi thanks for your feedback. slightly less concerned now cheers. when you say 1 mm back from the outside face does that mean it overhangs on the engine side of the waterpump by 1mm or is it 1mm until it reaches the back edge of the waterpump, or the belt is 1 mm back from the front sprocket/ wp
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Good eye on catching the idler not sitting square, that is important.
The idler needs to be seated into its recess by tapping it in with a mallet. Pulling it in with only the bolt is not enough to get it all the way in, and can lead to it going in crooked as well. I have experienced this too. Have you tried seating it that way? |
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thankyou for your reply. yes i have tried tapping it in gently however the hole seems off center when the idler is tapped in square as you may be able to tell from the photos. i thought perhaps the idler hole itself is not completely central and thus you have to put the idler in a certain way to match the block. but if not i cant understand why the hole is not center. the only way the hole is centre is when the idler is placed on the piss if you like and obviously if you tightened it at that it would pull the idler even further out of alignment. I'm not going to lock it up until i know its all correct as we dont want another broken d24. thanks again for your reply. bob |
940 tic auto 1995
hi bob
my belt sits just back for the front face of the cam sprocket only about a millimetre don't want it over lapping that sprocket if you get what i mean . regards jim |
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hi, i have improved it by centralizing the idler to the pump with a Dremel and the idler now seems square as i have measured it with a straight edge, how accurate this is i am not sure so i couldn't guarantee it isn't still causing the issue. I'm pretty sure the oil pump is still at fault. id like to fit a new one however apparently the tic pumps are slightly different. I can find lt35 ones on ebay but they have a flat face whereas like mine and yours there is a recessed bore for the idler. i may end up taking the pump to a machine shop and getting them to square the bore and dti the outer edge of the idler to ensure its true to the pump. I may have to ally weld it first as you can only remove material. the only other potential cause i can think of is the tensioner as if it is not tight the belt runs true and sits nicely on the cam sprocket. i have a quinten hazel tensioner however i fitted the old litens one and it does the same so im doubtfull its a quality issue. judging by the wear marks/ polished areas on the cam sprocket it seems to have been running slightly off for some time. im planning on firing it up at the weekend and keeping an eye on the belt with someone in the car ready to switch off. if it throws a wobbly ill be on the lookout for a new pump and oem tensioner. FINGERS CROSSED
regards bob |
940 tic auto 1995
hi just looking at photo number 7 your car must be different set up as my idler roller is in the centre of roller
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UPDATE. no further forward...
regretfully after further work conducted to the engine i still have not managed to prevent the cambelt walk. the work completed or parts tried and installed would include the following
1. 1x Quinten hazel tensioner 1x febi tensioner ( febi one had significantly less preload on the belt tension). 2. febi idler pulley 3. FAI water pump 4. new crank and cam drive sprockets 5. gates belts 6. oil pump idler mounting machined and sleeved with a steel insert. The reason i replaced the drive gears was because i noticed they were visibly worn at the back from where the belt had been previously riding and i figured that the combination of both top and bottom worn gears could encourage the belt to ride back however the new gears did not solve my issue. the oil pump was machined by a friend of mine as the hole was not central when the idler was inserted for some reason. so he bored it out square and machined a steel insert for the idler to ride in to keep the original measurements the same. this was a good time to change the sump gasket. (what a game) not something i enjoyed in the driveway in the rain.however that didn't solve my issue. i am beginning to come to the end of my tether with this fault as no matter what i try and ultimately spend does not fix my issue despite my best intentions. so, i was thinking i noticed that the older waterpumps have two flanges either side of the gear. this would help the belt to stay on course in the event of the belt walking i thought and i was wondering if anyone knows if i could fit an older flanged gear onto my pump to limit the belts movements. i would buy one second hand if possible from a forum member. also when i removed the rear cam cap to time the cam i noticed there was significant float probably a few mm but once the rear cap is installed it seems to locate the cam in a fixed position. that's the situation for anyone following, open to ideas from anyone who has had a similar issue. ta |
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. :) |
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 |
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. :p 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. :cool: |
further work required
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 |
TB position on camshaft pulley
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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. |
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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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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/ |
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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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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:
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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