No Oil Pressure - AJP8 Auxiliary Drive Shaft Failure

No Oil Pressure - AJP8 Auxiliary Drive Shaft Failure

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ukkid35

Original Poster:

6,138 posts

172 months

Tuesday 13th August 2019
quotequote all
A few weeks ago the oil pump drive failed on engine start

This was obvious because I lost power steering and oil pressure at the same time

Although I am nowhere near removing the timing cover, I have now received a new uprated Auxiliary Drive Shaft from TVR-Parts



I was warned by another PHer that the only difference was that the PS Woodruff Key has been changed from 3mm to 4mm width, and in all other respects it remains the same

The failure of the PS Woodruff key is relatively trivial, it can be replaced within a couple of hours, and you can drive the car without power steering in an emergency

If the PS Woodruff key fails, it acts a bit like a fuse, in that it protects the rest of the pump assembly (h/t TwinKam for the fuse metaphor)

So uprating the PS key seems like a poor idea to me, especially as the PS coupling is exposed to foreign debris, as both TwinKam and I have found out

Mine ended up with kitty litter in it after going off the track at Zolder



TwinKam had a bolt from the airbox find it's way in IIRC

Although the PS key is now 4mm, the Oil Pump Woodruff key remains 3mm (long)



As does the sprocket key which is 3mm (short) and hence tiny



This key is just a spare and is most likely too large, despite being the right 3mm width



The Water Pump impellers are a push fit without keys

My engine failure is due to the sprocket key failing, perhaps because the nut securing the sprocket has become lose, perhaps because something has partially jammed the pumps - I have yet to find out

I have never touched the oil pump drive on the several occasions that I had the timing cover off, I think that was a mistake

I probably should have removed the nut/sprocket/key and checked for wear, and retorqued using threadlock - hindsight is a wonderful thing

There was a warning before it failed, the previous couple of times that I started the engine there was a brief squeal which disappeared within a second or two

I guessed this could be an alternator bearing or clutch release bearing complaining, but since the squeal was so brief I assumed investigations could wait until returning from the trip

How wrong could I be!

Edited by ukkid35 on Tuesday 13th August 21:45

Chimp871

837 posts

116 months

Tuesday 13th August 2019
quotequote all
Feel for you but at least this time it's a final fix.

Personally I like the idea of a slightly thicker PAS key, when I took mine out it was severely cut into so an extra mil may extend life. Makes me wonder if the 2nd grub screw I had tapped in to the adaptor has actually made a difference.

Happy to assist it dismantling the pump, I've now got a press to press off/on the impellers. Tvr parts sell all required sundries including the ceramic seals.

Picture below shows the wear on the PAS slot.


ukkid35

Original Poster:

6,138 posts

172 months

Wednesday 14th August 2019
quotequote all
Chimp871 said:
Feel for you but at least this time it's a final fix.
Sadly not, in fact I would much rather use the original shaft, but I am sure it will have suffered severe corrosion just as your did, so I will have to use the uprated shaft which I believe increases the risk of oil pump failure, even if it decreases the risk of PS failure which is a trivial issue

Fortunately now that I have a PS coupling shield (thanks to TwinKam) the extra risk due to the uprated PS key should be minimised

I would strongly advise anyone fitting an uprated shaft to ensure they use similar protection



I have found your thread and the contributions from Rufus Roughcut absolutely invaluable - thank you

Was there evidence of threadlock on the sprocket nut?

https://www.pistonheads.com/gassing/topic.asp?h=0&...


Rufus Roughcut

532 posts

174 months

Wednesday 14th August 2019
quotequote all
No evidence of threadloc on the nut I took off.

They are a strange looking thing, K-Nuts I believe they're called, they look like they have been squashed.

On rebuilding mine i did use a drop or two of threadloc.

On a side note the new power steering coupling was a really tight fit on the shaft, I didn't use all of my 20 tonne press but you get a feeling for how much you are using, very important to support the shaft at the other end.

I was thinking if at some time you may have hammered the coupling on you could have damaged the bearings or maybe pushed the shaft through the impellers? The pumps are built from a centre, any tapping on one end without supporting the other could damage it.

Rufus Roughcut

532 posts

174 months

Wednesday 14th August 2019
quotequote all
My cars done 48K miles, the old power steering woodruff key and slot was pristine. There again the coupling was on really tight and took some doing to pull it off.





ukkid35

Original Poster:

6,138 posts

172 months

Wednesday 14th August 2019
quotequote all
Rufus Roughcut said:
I was thinking if at some time you may have hammered the coupling on you could have damaged the bearings or maybe pushed the shaft through the impellers? The pumps are built from a centre, any tapping on one end without supporting the other could damage it.
On mine the coupling is not a press fit, which is why it could be done easily in situ

The small grub screw in line with the key is to stop the coupling moving up the shaft and releasing from the the PS 'dog clutch' - guess how I found out

Rufus Roughcut

532 posts

174 months

Wednesday 14th August 2019
quotequote all
Fashioned a cover for the pump, great idea, thanks for sharing.




Jhonno

5,762 posts

140 months

Wednesday 14th August 2019
quotequote all
Rufus Roughcut said:
My cars done 48K miles, the old power steering woodruff key and slot was pristine. There again the coupling was on really tight and took some doing to pull it off.




Pulled my coupling off by hand..

Chimp871

837 posts

116 months

Wednesday 14th August 2019
quotequote all
My pump is still unassembled, let me know if you need any measurements or photos.


Chimp871

837 posts

116 months

Wednesday 14th August 2019
quotequote all
Rufus Roughcut said:
No evidence of threadloc on the nut I took off.

They are a strange looking thing, K-Nuts I believe they're called, they look like they have been squashed.

On rebuilding mine i did use a drop or two of threadloc.

On a side note the new power steering coupling was a really tight fit on the shaft, I didn't use all of my 20 tonne press but you get a feeling for how much you are using, very important to support the shaft at the other end.

I was thinking if at some time you may have hammered the coupling on you could have damaged the bearings or maybe pushed the shaft through the impellers? The pumps are built from a centre, any tapping on one end without supporting the other could damage it.
On mine it needed some force to shift the impellers, whether it's threadlock or a newer design shaft I don't know. But a hammer knock on the shaft end wouldn't have done much in my case

Edited by Chimp871 on Wednesday 14th August 20:36

ukkid35

Original Poster:

6,138 posts

172 months

Tuesday 19th November 2019
quotequote all
The Woodruff key is no more, the gear can turn relatively freely, and it appears to have welded itself to the shaft that also turns

However neither the water pump impellers nor the PS pump moves at all

How can that possibly happen?

More importantly how can I remove the gear, so as to remove the pump assembly?

The gear is being significantly distorted by the remover, which I am struggling to tighten further

Any ideas?






TwinKam

2,937 posts

94 months

Wednesday 20th November 2019
quotequote all
Paul, if the gear and (nose of) the shaft turn freely as one, but do not turn the water pump impellers, then the shaft must be broken just behind the front bearing.
Try not to damage that gear ..they are nla new. Progressively heat the hub with a blowtorch whilst applying pressure with the puller.
On mine, the shaft snapped in front of the bearing and was therefore loose in the timing case, and the nose of the shaft remains in the pulley to this day... Martin at TVR Parts kindly sourced a secondhand one for me.
Good luck!
Rik

ukkid35

Original Poster:

6,138 posts

172 months

Wednesday 20th November 2019
quotequote all
TwinKam said:
Paul, if the gear and (nose of) the shaft turn freely as one, but do not turn the water pump impellers, then the shaft must be broken just behind the front bearing.
Try not to damage that gear ..they are nla new.
Many thanks for the warning

I have not budged the sprocket at all yet, although I haven't tried heat so far

If the shaft is broken before the wp impellers, might it be easier to pull the shaft out of the bearing, than pull the welded sprocket off the shaft?

Assuming it really has broken, then it would be most likely to happen at the diameter change, so what could be keeping it in place?


TwinKam

2,937 posts

94 months

Wednesday 20th November 2019
quotequote all
...try a pair of opposed levers behind the gear, or tug it with a slide hammer... it should only be the interference fit of the shaft in the bearing holding it IF it has broken at that first diameter change. Take precautions to avoid chipping the teeth of the gear.

ukkid35

Original Poster:

6,138 posts

172 months

Wednesday 20th November 2019
quotequote all
Perhaps I can find some way to attach a slide hammer to the bearing puller...

Thanks for that idea

TwinKam

2,937 posts

94 months

Wednesday 20th November 2019
quotequote all
If you don't have suficient inward pressure on the legs for the puller to grip the gear, try a large 'Jubilee' clip (or several smaller ones joined end-to-end) around them, but I would recommend making an adapter for the slide hammer by welding two nuts back-to-back (one to fit the slide hammer thread, the other the aux shaft thread), this will give you a direct linear tug on the shaft without further damaging the gear
Be gentle though, the shaft may be wrecked, and possibly the pulley too, but you don't want to end up damaging the 'wing' of the block by pulling that bearing through it!
Once the gear is off, you may be able to press the nose of the shaft out on an hydraulic bench press, this will give you better opportunity to support the hub of the gear to avoid distorting it further.

ukkid35

Original Poster:

6,138 posts

172 months

Wednesday 20th November 2019
quotequote all
Once again, thanks for the warning, cracking the block would probably ruin my day

ukkid35

Original Poster:

6,138 posts

172 months

Wednesday 20th November 2019
quotequote all
There are no obvious signs of oil starvation damage so far, although the lifters look a bit weird, as if they've been etched



There's no sign of anything similar on any other parts, and all the cam caps look fine

I will be removing one of the main bearing caps soon, which one is most vulnerable to starvation?

Presumably the one closest to the oil feed? If so which is that?

CerbWill

670 posts

117 months

Wednesday 20th November 2019
quotequote all
The cams should be fine as they sit in a bath of oil. If your oil pump stopped it just means fresh oil wont be added to the bath and old oil spilled down the drains front and rear back to the sump.

On the crankshaft side of life I'd look at the thrust bearing as lack of oil pressure probably drastically affects flow to the thrust face.

If you're removing the sump you might as well remove and check each bearing one at a time. It's an opportunity to plastigauge them to assess wear vs the as new limits in the build manual too.

ukkid35

Original Poster:

6,138 posts

172 months

Wednesday 20th November 2019
quotequote all
CerbWill said:
If you're removing the sump you might as well remove and check each bearing one at a time. It's an opportunity to plastigauge them to assess wear vs the as new limits in the build manual too.
I'm assuming that it would be worth replacing mains and big ends as a matter of course

I can't be sure no one has been there before, so how will I be able to tell whether mains are standard or oversize?