Identifying a rogue absentee

MattSnap

MattSnap

Member
Help Please,
can anyone identify what this part is?
It’s clearly splined and must have been held on by a bolt of some kind.
It came off my Tdi 90 on Sunday, from the Off Side Front, fortunately at low/walking speed.
There is some rubber inside which makes me think a mount or something which rotates given the spline. I haven’t had the opportunity to put the car on ramps yet.
The car sounds different now and I don’t want to use it until I can identify the issue.
Any help gratefully received from those more knowledgeable than I.
 

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Yeah tbinknits the over run plate o the altenator or ac compressor, have a good check as it's important don't drive car until you check that area properly.
 
Here's a shot of the ac compressor, you can see the cap, from ebay there's lots of images. The rubber is part of the over run softening system when engine tries to bully the units, preventing damage.

Screenshot_20231017_072736_eBay.jpg
 
Thank you @CrispyEdd, it was indeed the air con compressor balance end cover.

Jacked up OSF and within 20mins (10 spent finding the right sized bolt and spring washer) it was back together.

No damage to splines or rubber surprisingly but all from low speed pootleing on Essex’s notoriously crater like roads.

You wouldn’t realise what a difference it makes to the harmonics and vibration- such a small cover but clearly heavy and vital.

I know it’s my DMF on its way out that has made me lose the original bolt.

Time to bite the bullet and do the clutch change- it’s not like I don’t have the parts, suppose I need to buy an MYP or PTW box and do the 6 speed conversion whilst I’m there…..

Thanks again Edd,
Matt
 
This is the "one time clutch" on the AC compressor/ pump. Your AC will no longer work. The rubber/plastic inside is moulded to the same shape on the outside of the AC pulley. The pulley is attached to this "one time clutch" plate which is in turn connected to the AC pump. ie the pulley is not connected directly to the AC pump. The idea is that this device fails in the event that the pump seizes so that the AC pulley can still spin freely and not mince the auxiliary belt.

There should be no problem with continuing to run the car except the AC won't work, however It in inadvisable to simply replace the part without addressing the very likely seized AC pump.
 
TAABVW said:
This is the "one time clutch" on the AC compressor/ pump. Your AC will no longer work. The rubber/plastic inside is moulded to the same shape on the outside of the AC pulley. The pulley is attached to this "one time clutch" plate which is in turn connected to the AC pump. ie the pulley is not connected directly to the AC pump. The idea is that this device fails in the event that the pump seizes so that the AC pulley can still spin freely and not mince the auxiliary belt.

There should be no problem with continuing to run the car except the AC won't work, however It in inadvisable to simply replace the part without addressing the very likely seized AC pump.
Click to expand...
Thanks for this info.

The bolt was missing. The cover fell off. Splines all ok, no bolt retention through shearing.

Need to check if AC is not working.
Maybe time for a new ac compressor.

Will report back if the ac is not working.

Thank you for your advice @TAABVW
 
I have done some threads on ATL AC replacment, I ended up 2nd hand (polo) compressor (buy 2 just in case), new condensor and the more vital part new accumulator dryer. Take bumper off and intercooler and away you go, oh and good luck as its fairly tricky! Especially the dryer, but remmeber that bit as its a service item, AC was so cold after that really was awesome like 4/5 deg c

If you do the accumulator do some checks as there are two type of bolt hole fittings on them and you need a certain type or the bolts wont align on the new dryer...Ill see if I did a thread..
 
Side note on the gearbox comment that may help - Six speed gearbox codes that work:

MYP, NTG, PTU: standard gearing through gears 1-5 with an “overdrive 6th” in addition.

PTW: Longer gears, especially 1-4, 30 mph is 1800rpm in 3rd instead of 2000rpm for instance. Sixth is ever so slightly taller (70mph is just under 1950rpm instead of 2000rpm).

I prefer the latter on my mapped 90, many prefer the former.
 
CrispyEdd said:
I have done some threads on ATL AC replacment, I ended up 2nd hand (polo) compressor (buy 2 just in case), new condensor and the more vital part new accumulator dryer. Take bumper off and intercooler and away you go, oh and good luck as its fairly tricky! Especially the dryer, but remmeber that bit as its a service item, AC was so cold after that really was awesome like 4/5 deg c

If you do the accumulator do some checks as there are two type of bolt hole fittings on them and you need a certain type or the bolts wont align on the new dryer...Ill see if I did a thread..
Click to expand...
I'd be interested in that thread Edd. I have Replace AC radiator and have working AC pump and "one time clutch" is intact. However after refilling it loses all its AC fluid in a couple of days. the fluid has the UV dye in but there is no sign anywhere that it is leaking.

Any Ideas??
 
Interesting - I have never notice any meaningful / measurable difference in consumption between A/C on or off...
 
dj_efk said:
Interesting - I have never notice any meaningful / measurable difference in consumption between A/C on or off...
Click to expand...
I found in summer when on cold like 19 deg etc it was very noticable on the DIS screen info, I used to amuse myself on cruise on my boring commute swithcing it off for as long as I could cope with. Nowadays I roll on poverty spec..tough gig for a few weeks a year.
 
dj_efk said:
Interesting - I have never notice any meaningful / measurable difference in consumption between A/C on or off...
Click to expand...
The AC in the A2 is quite clever, it, (the compressor), runs all the time, via aux belt, but the flow, (via variable swash plates in the compressor), and hence mechanical load, is also modulated to match demand. More usually, the compressor is switched on and off, when on, the mechanical load is high.
In the A2 even with AC off, it is still rotating, and circulating, albeit, at about 5%, I think. So on days when the ambient temp is not extreme, the flow will be low, so effect on mpg will be low too.
Mac.
 
So I checked, with a photographic alcohol thermometer and dialled the ac down. It’s still working cooling. The metal cover originally pictured seems to have vibrated loose rather than the ac compressor clutch breaking. Next spring I may we’ll overhaul the ac to your guidelines @CrispyEdd but it’s functional right now.
 
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