Thanks for all the responses,just seen them as I had no internet signal.
I've got an electric fan fitted,but it goes up to the end of the white on the gauge and is steady.
The bush the skew gear runs in is a good fit,there is a small ring around the vaccum pump where the o ring has been running but there is no obvious lip.
I'm struggling to find the right bearing for it,seems to be Err 528, but that's superceded by Err 928, which is the whole skew gear assembly.
 
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Thanks James, that is brilliant.
 
Just had a look,that's would have been very useful when I was rebuilding mine,shame I didn't think to look.
I'm fairly sure that the missing section of spline matched up with the counterpart in the shaft.
Looking throught the gap in the bottom of the vacuum pump,there seems to be some scoring .Doesnt seem to show that well in the picture.
Could this be dropping the pressure?
 

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That could be the end result of the low oil pressure/flow issue, same as the skew bearing, ie it is not the cause.
I feel you have to follow the advice above by @HenryB and pop a main cap off to see, that will tell you what you need to do next.

While test driving a motor last night a thought occurred to me, is there an oil flow restrictor in the cylinder head oil supply?
 
Hi,
Thanks for the all the effort that's been put into this,I really appreciate it.
I've got a new vaccum pump coming and skew gear bearing as these had to be replaced either way, once these are in I'll run it but I think your right and the engine needs to be pulled out.
I'll update once the new parts are fitted.
Thanks
 
Can't be that expensive. When we put the new engine in the aircraft after 50 hours the engine oil sample test was about £90.

90 quid got to be worth a go.
Im tight, but even I would pay that, especially if it tells me what is going on.
 
just have a look at the crank bearings,if its original vac pump its not unusual ,it just shows oil hasnt been changed as frequently as would be best
 
I reckon that it had been like it for a while, one of the spring washers on the bolts that hold the top on was missing so someone's been in there in the past.
Managed to get an old stock genuine one for much less than the £400 BritCar wanted.
 
It’s dirty oil that goes up ThereDirect from sump rather than filtered oil too
its filtered but so is all the pump fed oil ,but if you strip lots of engines youll find ones with fewer oil changes,show with worn bearings and parts like your vac pump,whereas much else shows little wear like you find in a truly old worn out unit were little looks reusable,and well serviced show good bearings
 
its filtered but so is all the pump fed oil
Looking at the diagram Above oil going to vac pump is only filtered by mesh gauze in sump and so could bring fine particles metal particles from sump Into vac pump all other oil goes into filter For bearings etc
 
Looking at the diagram Above oil going to vac pump is only filtered by mesh gauze in sump and so could bring fine particles metal particles from sump Into vac pump all other oil goes into filter For bearings etc
maybe so ,but id be checking the bearings as my above post
 
Thanks for the responses.
New vaccum pump turning up tomorrow.
As I have to pull the engine to check the bearings,I'll give it a go with the new vacuum pump,but I'll be careful.Reckon it's had at least 4 oil changes since rebuilding it so hopefully there isn't much in the sump.
For anyone interested,the skew gear bearing is a 6006 Deep groove bearing,55mm outer,30mm inner and a thickness of 13mm.
Thanks
 
Hi all,
Fitted the new vacuum pump and took it out for a run,but the pressure still dropped. I've just fitted an oil temperature gauge so will take it out again later to see how hot the oil is getting.
Going to be a couple of weeks before I can take the engine out.
Thanks
 

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