x98boardwell

So, I am in the middle of an engine oil leak clean up along with re-doing a few parts while I am in there to ensure I have a sunny future. My questions are as follows.

1) I cannot use the flywheel lock (the standard one which bolts in the cover access hole) since the motor is on an engine stand. I am curious when removing the timing belt how I should do it....? One of the write ups that I had seen stated to turn the crank past TDC to the 4/5 mark (1 and 3/4 turns past TDC) and then I would ensure there would be no interference of the valves with the pistons.
... The reason I ask is when I removed the belt the first time the cam pulleys/gears moved slightly and I was hoping to keep everything still while I'm in there. The other reason is that I need to replace the gears and fix and oil leak behind one of them while I'm there so I am trying to ensure I put everything back on correctly and doesn't move once I remove the belt.
--- What is the best way to remove the belt and keep everything in place and is there another way to "lock" the crank if needed at all once at the 4/5 position?

2) I had another one but can't remember now... TBC

Thanks for the help in advance!!

Cheers,
Bryan

Bmw635

I would do the PKtensioner now since its right there. The oil tensioner leaked end up allowing the lose belt to flap, wearing out the cam pulley when the timing belt is fairly new in my recently acquired car.

James Bailey

I do not doubt that your cam gear is worn but the cause is at best a theory...Kibort I believe has raced his car for years with a dry tensioner not that I recommend it. The oil has NOTHING to do with setting or holding tension other than transferring heat to the bimetallic washers. The basic design is it is a detensioner and relaxes as the engine expands and never ever tightens beyond where you set it or sees any pressure.

x98boardwell

Still looking for answer on original question, how to remove belt with least possible movement of pulleys when I can't use flywheel lock, looking for direction on this and alternative "best practice" options.

On a side note, thanks for the info on the tensioner.

James Bailey

figure out how to insert bolts into the fly wheel and wedge and clamp it to the engine stand use some flat steel stock.....

dr bob

^^ What Jim Said. I'll warn you now that even with a strap on the drive end of the crank and a big bar helping it, getting the bolt out of the crank snout will take at least two people. Torque you apply at the crank nose will try and tip your engine stand over. Adding length to the bar at the front end requires similar length bar at the other end, and even then it takes some careful coordination to get the bolt loose without dropping the engine onto the floor.

I visited a local owner who was in the same situation you find yourself. We ended up with his floorjack handle wedged through the arms of the stand at the flywheel end, with my 5' long 3/4-drive bar at the front of the crank. With carefully coordinated pressure applied, we kept the engine and stand upright.



I seldom recommend using an impact wrench on the crank nose bolt, but this is the perfect time to do so. You have easy access to the front nut. It will take a pretty big impact to do the job. I use a 3/4" drive IR fed by a 1/2" hose, but the home compressor only makes 120 PSI best. It took more than a few seconds before the bolt started to move.

On trying to keep the cams indexed to the crank: Waste no time worrying about this. When the belt is off, the cams will rotate on their own slightly as the valve springs push back on the cams. You'll be pulling and pushing on wrenches as you remove the bolts that hold the gears on and the drive spiders, on your way to replacing the cam seals. You'll also have the covers off for the cam end plugs and oil galley pins, and the can chain tensioner pads if they haven't already been replaced. The cams are going to move. Get used to the idea and it will save you the anguish later as you watch them snap a few degrees left or right as you slide the belt off. Trust me on this.

mark kibort

as Jim and Bob say above ^^^^^^ And yes, I don't worry about the oil in the tensioner. haven had oil in there for many years now. however, its not dry, just not full. lest just say its oily and there is no more leaks, because most of the oil has leaked out. (never could fix that darn seal on the front of the tensioner) since the oil is only for lubrication and heat transfer, It just takes longer for the heat to hit the tensioner discs to adjust tension for block expansion, but there's enough oil in there to keep things from rusting.

and more than likely, the pulleys are worn due to over tension, not too loose of a timing belt and "flapping" you have skipped teeth before you ever get the belt to "flap"

dr bob

Mark, Mark, Mark....

You seem to take tremendous pride when you share your "mine is undermaintained and doesn't work correctly, and the car still seems to run OK so far" experiences. PLEASE don't suggest to others that they should test the limits of their own systems unnecessarily. Do you run Carrol Shelby's recommended oil additive, drain the oil out as he did in his commercials, then drive the car around with no oil just to show that you can do it? So why suggest to others that it's OK to ignore the oil in the tensioner?


The oil provides dampening for the tensioner piston, working with the o-ring seal and that little check-valve in the bottom to offer differing rates extending or compressing. If the factory just needed to move the heat through, why would they bother with oil? Why not a solid aluminum damper casting, with heat-sink compound instead of a gasket? Turns out that PRIMARY funtion is to make the dampening directional, plus it lubricates the piston on the bore.

Does oil pour out of your tensioner? Why not figure out why, and FIX THE LEAK?



[/soapbox mode]

mark kibort

Its a weak design, at best. its fixed. the thing doesn't move as that spring is incredibly tight. yes, I think the oil is for quicker heat distribution to the washers that expand and contract to keep the tension. there needs to be some movement based on the expansion and contraction of the plunger, so there needs to be oil lubricant. just enough to keep things moving and from corroding. to really think that the pin hole and the seal creates enough damping for the micro-movement is very optimistic. its an argumement that neither one of us can proably prove, BUT, I have used it without oil and raced this thing for 15 years with no issues . and then again, what issues would you expect to have?? we are talking such a small amount of movement, that on a belt with so much length, I doubt you or anyone could tell the difference between a welded shut tensioner designed for operating temp vs stock or even a porken tensioner.

there is a reason why manufacturers race test their designs.... to see if they work. it seems to have worked in my use, but I also maintain the correct tension..... in fact there is a huge discrepancy between even tension measuring techniques and values, that far outweigh any possible movement or damping the oil system could provide.

Now, if you want to post some superhigh speed video of with oil vs without, and show that the system is solving a problem that actually exists at operating temp.... lets see it... but until then, its all guess work on our part.
And, you will find me lap after lap, redline after redline using the wrong belt, no oil in the tensioner.

As far as the piston goes, it might just be a bleeder port so that the piston can move and the oil doesn't pressurize, so it CAN move.

as far as the leak goes.... trust me, with the new engine, I was all fired up that I finally fixed the leak with some new parts in the seal area... uggg, still poored out the front. because I have other things that im chasing, im just trying to fix the other more pressing issues these days. (i.e. shock revalving, CF intake)

docmirror

Maybe because the leak failure is about a 99% rate, and a failure of the fluid in the tensioner is not fatal, nor really even contributory to belt/tension/gear/idler failure.

I would wager that there are thousands of 928s out in the field with little to no oil in the tensioner and they are running fine. Is it optimal? - Nope, wouldn't say that, but the cost to repair again, and again, and again are significant - and the consequence of leaving it fairly dry are nil.

x98boardwell

Guys, I loosened the bolt with the flywheel lock tool before i removed the engine so no worries there.

My question was if he motor was at 45 degrees and I removed the belt would the cam gears move or be loaded with tension. The answer is no as I did it this evening and no movement. Motor is at 45 degrees and progress continues.

Cheers,
Bryan

docmirror

The right side cam will prolly go 'sproing' before you are done and move a few teeth. Mark the cam gears before it goes 'sproing'.

PorKen

In theory, the bi-metal Bellville washers could also flex the other way depending on what the 'shop temperature' was when set, but the movement would be negligible.

On a 32V, belt tension has to be so high with the stock tension based (pre-stretch) system - just to stop the belt light from triggering - that the washers are going to be pretty squished after 100K miles, though.

GregBBRD

More fear marketing.

I'd love to see the vehicles/tensioners that you base your claims on.....

must be a difference in how the latitude in this country affects the cam belt and tensioner.

I've literally "resealed" probably a thousand stock tensioners. I've seen a total of three with bad Bellville washers....and those were all super early cars that had zero oil in the tensioner. And they wore out the hole in the center, not the actual curve in the Bellville washer.

I've never seem a flattened Bellville tensioner washer. Have you? Got a picture?

One other point....you seem anxious to tell stories about what happens to a stock tensioner after 100,000 miles. Do you have a vehicle with one of your tensioners in it that has actually gone 100,000 miles? Multiple vehicles?

Comparisons depend on having data to compare.....

PorKen

Now that PKTs have gone 50K, 70K - the '*****-make-it' test is 100K miles, now?


Speaking of data. How far do the Bellville bi-metal stacks, as arranged in the 928 tensioner, flex, from hot to cold, for a range of how many MMs? What is the dampening range, in MMs? You should know, right?