It doesn't spin freely by hand though, it turns without much resistance but will not spin if you stop turning, is this normal? Anyway it will be changed as well. ![]() The water pump bearing feels OK, no noticeable play in it. The idler wheel is a bit rattly when spun by hand, this was changed on the first rebuild so not sure if that could be a contibuting factor or not. I suspect as stated in a previous post that when valves met piston this would cause extra tension on the belt so bending the locating tab. The tensioner locating peg is bent but was planning on replacing anyway. Well spent yesterday morning getting engine dismantled and the head off.Īll pulleys are tight and none have slipped. A sudden increase in belt tension like metal ring under belt or valve hitting piston will whip the tensioner to full and bend it sideways. Make sure it hasn't twisted over to one side. Next to the locating tang might be another tang bent towards the bearing. Presume you would fit a new tensioner but if not, check the back of it. It's even possible that belt manufacturers have increased the width of the belt slightly over the years which would cause ring rub. If one side has shiny teeth and the other has dull teeth, it has run against the guide ring. If someone has a used belt lying around, take a look at the teeth on the sides of the belt. Have included a picture of my Scenic belt. The belt may gently run against the guide plate otherwise it's pretty unnecessary. ( I know I pointed to the head you got from ebay so I do feel a bit guilty). Once the ring snaps, the belt will push it off where it can catch the cover and either rip the whole thing off or break off a piece and it ends up being thrown under the belt.Īll that metal flying and the belt riding off the edge of one pulley put's pressure on the other and will easily detach the other ring if it's welds are weak.Ģnd hand pulleys,especially in a rusty state are just as likely to break up as your original pair. If you find any it could have been a weak point that may have caused the ring to break up.īoth the pulleys look very rusty which will be a factor. If the weld was good, the rest of the edge should be clean and fairly bright. Look at the remaining edge of the welds where the ring has detached. Take a close look at the spot welds around the 2 cam pulleys.Ī tiny part of the guide ring may still be attached to the weld. If you don't find any play in the pump or idler wheel. Worn bearing is more likely.Ĭan't really fit a crank pulley or cam pulley wrongly or it would slip. If you kept any of the old parts, you should see the same markings.ĭoubtful on a loose idler unless you forgot to tighten it. ![]() If you look at the wear marks left by the belt on all the wheels, you should see it's natural running line. PS How do I measure crankshaft end float, need to read up on what that is as well, I presume its allowed movement at the end of the crank but lateral along the axis of crank rotation or perpendicular to crank rotation? Another complete cylinder head may be the easiet option plus gaskets, stretch bolts and belt kit.Īlternatively a box of matches is looking tempting! ![]() I have not yet pulled the engine all the way apart but I can see that the inlet cam is out of phase so I know that I am looking at at least some inlet valves, gaskets, stretch bolts, new belt and camshaft pulleys. I am loathe to throw good money after bad with another rebuild unless I can positively identify the source problem. I had assumed that the guide plate was the cause of the initial problem but now I am reaching the conclusion that the guide plates are a symptom of something else. I changed the tensioner and idler wheel as part of the belt change following the first blowup so I know they are OK but I am now suspicious of the water pump as it is the only part of the belt run that hasn't been changed. One question I have is could a failing water pump bearing cause this, I checked the water pump during the first rebuild and it seemed to be OK and I had been told it had only been changed 40k km before by the previous owner when he had a belt change done. When I rebuilt the top end both times I made sure the belt was well seated and away from the guide plates. Thanks for all the replies so far and the useful pictures, although I am seeing the belt run for this particular engine in my sleep now!
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