505 Fan Coupling issue

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baldrick56

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Hi All,
the legend of cooling system issues with my series 2 505 GTi over the last few years has reached the proportions of one of the Norse Sagas. Won't go into the whole tale now but the initiation was fitting a new waterpump (the old one was squealing intermittently). When it was all put back together a squealing noise was still there - worse at idle either disappeared or drowned out at higher revs. Worse than that an occasional bout of overheating still happened. Eventually after eliminating other things the viscous coupling to the fan was the last suspect standing & a replacement (pre-loved) one cured the overheating - but the squeal was still there. Discovered that if I sprayed an absolute shit-ton of belt-dressing the squeal died down, but would always reappear. Getting the car ready for its Rego yesterday I discovered the waterpump pulley was 'wobbling' as it turned - must have been doing this from the beginning but muggins was the second of the not-so-wise monkeys it seems. Couldn't see the same eccentricity happening with the fan - that seemed to be turning smoothly. Reasoning that there must be a locating pin or dog that I hadn't properly engaged when changing the fan over I set about undoing same - first bolt sheared off instantly, as did its opposing neighbour a minute later. At this point decided fronting up for the Rego check was more important than belt squeals so left it & drove gingerly to & from mechanics keeping revs down.

Today I tackled removing the fan & pulley - predictably the other two bolts sheared as well, then there was a horror story when it all came off. The pulley holes have enlarged themselves from round to oval (photo). Also noticed the pulley central hole is a loose fit on the boss of the waterpump - unlike the central hole of the fan coupling which is very tight. I'm guessing a new pulley will be a minimum requirement - not sure any "repair's" going to be successful here. Any tips as to how I can stop this happening again?

Thanks, Rob
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hi rob,I would say it looks like the four bolts were not tight enough to hold/sandwich the fan flange and belt pulley to water pump flange.could have been caused by tightness of fan flange hole on water pump shaft giving a false sense of tightness when bolts tightened.were the bolts tightened evenly,say half a turn at a time when fitting.I would clean out hole in fan flange and trial fit on pump shaft so to be a slide fit by hand.the fan flange would need to be machined or filed flat to remove any high spots before refitting.also the washers behind the heads of the bolts would need to be reasonably thick say 2mm at least and once tightened check that all flanges/pulleys are seated,a thin feeler gauge could be used to check for full contact….jim
 
Thanks Jim and Mark,
Originally the bolts were tightened evenly - opposing pairs, it's a bit of a fiddle because the pump flange wants to spin as you try & tighten & the only way I found of locking it is to jam a large screwdriver against the spindle & the head of a bolt your not tightening - so whatever force goes to the spanner, same must go to the screwdriver, all within inches of the fragile matrix of the rad in the firing line if you slip with either - could be they didn't end up mega-tight last time. But yes, dressing the pump boss & fan recess with emery cloth will be a precursor next time.

Electric fan idea's tempting in its own way - but I've still got to fix the pulley to allow pump & alternator to rotate.
Regards,
Rob
 
Hi.

I wonder if the four bolts were thread bound? Was there any shank between the thread and the undersinde of the hex head? If so, and the shank was longer than the assembled length of the fan coupling and pulley this could explain the lack of clamping of the pulley flange?

I know you mentioned that the water pump shaft was a tight fit into the hole in spigot of the fan flange. But I wonder looking at the image whether this is in fact the case??

Yes you need to get the pulley fixed, I would be tempted to drill new holes for the bolts midway between the elongated holes in the pulley flange. H'mm would be nice to have the shaft and hole fitting correctly and working as a spigot to center the pulley on the pump shaft. As others have mentioned ensure that all mating faces have no high points. I tend to agree with the fitting of electric fan(s), but I suppose that a viscous coupling that functions correctly won't sap much power from the engine.

Cheers.
 
Whippet said:
Hi.

I wonder if the four bolts were thread bound? Was there any shank between the thread and the undersinde of the hex head? If so, and the shank was longer than the assembled length of the fan coupling and pulley this could explain the lack of clamping of the pulley flange?

I know you mentioned that the water pump shaft was a tight fit into the hole in spigot of the fan flange. But I wonder looking at the image whether this is in fact the case??

Yes you need to get the pulley fixed, I would be tempted to drill new holes for the bolts midway between the elongated holes in the pulley flange. H'mm would be nice to have the shaft and hole fitting correctly and working as a spigot to center the pulley on the pump shaft. As others have mentioned ensure that all mating faces have no high points. I tend to agree with the fitting of electric fan(s), but I suppose that a viscous coupling that functions correctly won't sap much power from the engine.

Cheers.
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Hi Whippet,

yes the "bolts" were technically "machine screws" so threaded all the way to the head. I’m reasonably confident that Jim is on the money above - that the bolts weren’t tight enough due to the fan coupling being very tight on the boss of the pump shaft. So the bolts were “tight” while the fan flange wasn’t fully “home." The squealing (which was there from the moment I changed the original viscous fan to the replacement) was because the pulley could wander or ‘chatter’ as it rotated. Given the rounding out of the bolt holes in the pulley there must have been resultant wear on the bolts which I think is why they’ve all sheared in the attempt to undo them (I did use thread lock liquid when they went in :eek: ) - Not looking forward to getting the broken bits out of the flange much, the Rad. (+AC rad) might have to come out to get the space to attack the thing. If a new pulley's impossible to get I'd go for the redrilling in the gaps, but it'd have to be very accurately done as the central hole's a sloppy fit on the pump shaft - not sure my 'Aldi' drill press (or its operator) is up to the superhuman tolerances needed and I'd end up with a wobbly pulley all over again.
Cheers,
Rob
 
baldrick56 said:
Hi Whippet,

yes the "bolts" were technically "machine screws" so threaded all the way to the head. I’m reasonably confident that Jim is on the money above - that the bolts weren’t tight enough due to the fan coupling being very tight on the boss of the pump shaft. So the bolts were “tight” while the fan flange wasn’t fully “home." The squealing (which was there from the moment I changed the original viscous fan to the replacement) was because the pulley could wander or ‘chatter’ as it rotated. Given the rounding out of the bolt holes in the pulley there must have been resultant wear on the bolts which I think is why they’ve all sheared in the attempt to undo them (I did use thread lock liquid when they went in :eek: ) - Not looking forward to getting the broken bits out of the flange much, the Rad. (+AC rad) might have to come out to get the space to attack the thing. If a new pulley's impossible to get I'd go for the redrilling in the gaps, but it'd have to be very accurately done as the central hole's a sloppy fit on the pump shaft - not sure my 'Aldi' drill press (or its operator) is up to the superhuman tolerances needed and I'd end up with a wobbly pulley all over again.
Cheers,
Rob
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Hi.

You could heat the flange where the bolts threads are broken off, and allow the smoke to escape thus in-activating the thread locking compound. You might be lucky and be able to use multigrips to grasp the remaining threads and unscrew them?

I agree you need to get the spigot repaired for the pulley. A suggestion:
  1. Mount the pulley in a lathe chuck and check for center relative to the OD. Then machine out the spigot hole in the pulley flange to true it up and maybe 5mm larger diameter than the Dia of the water pump shaft.
  2. While it is there scribe a line on the PCD of the bolt holes. Then you can mark out the centres of the four holes with a divider. Providing steps 3 & 4 below is done, the bolt hole could be a clearance to the bolts, so accuracey is not that important as the bolts will only be clamping and the spigot spacer will be centering.
  3. Turn up a spigot spacer with the ID clearance on the pump shaft, the OD neat sliding fit in the new hole in the pulley, Maybe 3 mm longer than the width of the pulley flange.
  4. You would need to counterbore the ID of the viscous fan drive hub by the length you used in (3) above. to allow the spigot spacer to enter into it.
  5. Make sure everything is flat and clean, and reassemble. As others have said ensure that everything is seated.
All the best

Cheers.
 
Hi.

Upon reflection, I would do step 3 first, that will make easier to get the hole diameter a neat fit in step 1 above.
 
Beano said:
If it was mine, I'd just fit an electric fan and be done with it....
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If you want an electric fan I have a brand new one i bought from repco [14 inch] for about 100 dollars . I wanted to fit it to my 504 cab to replace the original fan which is locked on permanently but it wouldnt fit behind the rad without interfearing with the pulley .I tried to fit in to fit it in front but gave up due to the sloping bonnet line and 504 rad width and went back to the fixed fan. repco would/nt give a refund because it had been opened . It may be suitable for a 505 rad being wider . If you are interested i could sell it for $40 or any offer . Julian 0401 382 454 or pm me
 
Workable suggestions:
Spot weld short, but strong[ish], rods to bolt stubs so as to unscrew them.
Obtain new/secondhand pulley
Mount to flange using high tensile bolts or setscrews.
Tighten to 9 ft/lbs [factory workshop manual]
Revolve pulley and check for trueness.
If OK remove and refit bolts using loctite.

Do not overtension drivebelt. Factory manual states:
New belt: 50-58 SEEM units.
Used belt: 40-48 SEEM units.
[If anyone knows what a SEEM unit is; I'd be happy to know.]

As an aside; I've fitted a 16inch electric fan controlled via an adjustable temperature capillary switch. There is just enough room to fit the radiator/fan assembly in place in my GTi ZDJ 505.

Pavel
 
julian c b said:
If you want an electric fan I have a brand new one i bought from repco [14 inch] for about 100 dollars . I wanted to fit it to my 504 cab to replace the original fan which is locked on permanently but it wouldnt fit behind the rad without interfearing with the pulley .I tried to fit in to fit it in front but gave up due to the sloping bonnet line and 504 rad width and went back to the fixed fan. repco would/nt give a refund because it had been opened . It may be suitable for a 505 rad being wider . If you are interested i could sell it for $40 or any offer . Julian 0401 382 454 or pm me
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Good news for me. I had another try with repco to get a refund and this time they accepted it for return and i got a full refund.
 
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