Technical Tips > Post 84

AIR Pump prototype(s)

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Stingraynut:
I’ve had another drama with my re-engineered AIR Pump – Previously I had new bearings put in and the fins removed, making it a freewheeler to support the belt. The pulley fell off after only 20 minutes driving. I sent it back and it was recently returned with a grub screw inserted to hold the pulley on. I re-fitted it last Thursday.

On Monday the guy that recommended the engineering firm in Brisbane for my AIR pump job, had his pump pulley fall off – with a different problem to mine.  I was immediately worried.
He had done 600kms with his, so I was hoping that they'd find the problem then I'd get mine fixed before it happened to me. Murphy decided that would be far too easy and struck ruthlessly.
On Tuesday morning, driving slowly at 45kph my   #$%^&^ AIR PUMP PULLEY FELL OFF !!!! - AGAIN !!!!AAAAAARRRGGGGHHH - It's becoming a familiar noise.

I rang John, (JOH Engineering Brisbane) he didn’t seem to want to take ownership of the problem, just advised me how to fix it, but actually had no idea why it happened.
.
The shaft was very tight and I couldn't spin it by fingers only with multi grips – there was a rough bumpy feel as if each roller bearing was going over bumps. I’ve travelled at most maybe 50kms. No bearing should go that quickly but it sure feels as if it has. It looks like the pump shaft bearing partially seized and the pulley was dragged off, the grub screw has broken off in the shaft and the part in the pulley has left a 1/4 turn spiral groove in the shaft.

Bending over the car by the side of the road, refitting my loaned pump in the blazing sun was no fun. I really didn't need this (who does ? )

I took the pump apart and found that the front bearing had almost seized, it was tight on the shaft and I couldn’t get it off . There appears to be a hard green substance, which I think is some kind of loctite all around the join of the shaft to the front of the bearing. I also found some wet green paste on the end of the shaft where there is no contact. Maybe the loctite has seeped into the bearing.

I took it to an engineering shop I've used before. There is still some unset green loctite about, and a strong possibility that some loctite strayed into the bearing causing the problem. The other alternative suggested by the engineer is that the shaft is too thick for the bearing and has caused the inner ball race to be too close to the outer - I don't think so, but he's going to check - it won't come off with a hammer but that could be the loctite that has oozed everywhere.

Because my pulley has come off twice, the aperture in the pulley that the shaft fits into is now not parallel - sort of opened out at the back end due to running half on/off just before falling off completely. I think the excess loctite was squirted in to fix this problem, as I think the pulley would have been loose on the shaft on the second re-fit.

I'm sure that John copied the original but the engineer here says there's not enough shaft protruding forwards to ensure a good fit. The front end of my shaft is a bit buggered due to the pulley being keelhauled off, so I'm getting a new shaft made, the benefit being that the hole in the pulley can be lathed back to parallel and the shaft can be lathed to fit that hole, which will be a couple of mm more than original. Rather than fitting another grub screw, he's planning to put a bolt through the centre from the front, which will ensure that it won't fall off completely again.
 
Thanks once more to vette obsessed who loaned me a pump, at least I can keep driving.

I can feel some more dollars anxious to leave my pocket

S’nut

david_moore:
Sorry to hear about the air pump S'nut, it has been for quite some time you have been wrestling with that murderous thing. I was going to do the same on my recently aquired '91 but will certainly leave it until you have had some success. Good luck with it mate I expect you will win in the end!!

Stingraynut:
Hi David - thanks for the good thoughts - yes, I feel like I've arrived on the set of 'Groundhog Day', catching taxi's home twice to collect my loaned pump and socket set etc and exchanging pumps on the roadside.

I have several other issues I want to deal with. JOH engineering is very lucky I don't live locally. I;m normally very calm....but....

I really wish I had used my local engineer, I'm sure I would have had the job done right first time. How hard is it to turn the pump into a freewheeler ? I'm not asking for rocket science here.

Have you posted any pics of yours yet ? I seem to remember it's a 91 . Any problems ?

As part of this issue I've been wondering what I would do if I had a breakdown that wasn't immediately fixable - I have RACQ insurance so would get a trailer tow although they have a very short distance limit.

As far as I can see, it wouldn't be possible to use a tow rope because of the low front .

Does anyone reading this have a simple solution ?

S'nut

77CVT:

--- Quote ---Originally posted by StingraynutDoes anyone reading this have a simple solution ?
--- End quote ---


Flat bed is the only way to go unless you want to take the front clip off.

Stingraynut:
Hi 77CVT - thanks for the reply, does that mean that a 'trailer' tow when they put the front wheels on a jockey trailer will be no good because of the rear low ground clearance ?

How's your C4 going ? I read your post about the dyno results before/after removing rear MAF screen - very interesting - have you cracked 300hp yet ?

S'nut

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