|
|
|
|
#1
06-13-2021, 08:22 AM
|
|||
|
|||
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] 
Last edited by Bob; 06-13-2021 at 12:53 PM. 
|
|
#2
06-13-2021, 11:12 AM
|
|||
|
|||
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 .
|
|
#3
06-13-2021, 12:50 PM
|
|||
|
|||
|
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
Last edited by Bob; 06-13-2021 at 12:58 PM.
|
|
#4
06-14-2021, 08:33 AM
|
|||
|
|||
|
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?
__________________
86 745 D24T/ZF 345k lifted 2.5" 83 764 D24T/M46 155k
|
|
#5
06-14-2021, 08:46 AM
|
|||
|
|||
|
Quote:
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
|
|
#7
06-23-2021, 08:57 AM
|
|||
|
|||
|
Quote:
__________________
86 745 D24T/ZF 345k lifted 2.5" 83 764 D24T/M46 155k
|
|
#8
08-15-2021, 11:59 AM
|
|||
|
|||
|
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
|
|
#9
08-23-2021, 08:22 PM
|
|||
|
|||
|
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. 
__________________
86 745 D24T/ZF 345k lifted 2.5" 83 764 D24T/M46 155k
|
|
#10
08-29-2021, 10:57 AM
|
|||
|
|||
|
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
|
 |
|
|
Hybrid Mode
