More BSA oil pressure problems. A real puzzle

[Jeremy]

Great post Orabanda!



Just to clarify, was anything done to the engine between when it had higher oil pressure and now, or did it just happen one day?

Yes - due to being mislead by a faulty gauge I swapped then swapped back the oil pump, then later changed the oil pump gasket.  I also swapped around with different  PRVs and replaced the filter element.  I also had the timing cover off and on a good few times and have replaced the quill seal. which goies into an ally block with oilways drilled into it.  some where in all this I introduced a fault but now cannot eliminate it.. the more I think about the more I think its the fit of the prv.  Especially if this fault is one that is known. 

[orabanda]

Jeremy,
Unlikely to be the PRV if you can get the pressure when cold.

i would have a very close look at the quill seal.

Regards,
Richard

[Jeremy]

its a possible leakage round th threads as in a10boys post.  You can feel the threads deeper into the crankcase are loose as you wind it it.  Quill seal was changed with no change in symptoms

[orabanda]

Possible, but they would have to be REALLY loose threads; ie. tapped significantly oversize.

When you tighten the PRV up, against the fibre / sealing washer on the outside, the  thread form on the prv is pulled up against one side of the thread form in the crankcase, which improves the sealing significantly.

Regards,
richard

[A10Boy]

I'm not saying this is the cause, but it was raised in the original post. But, I've seen as much as 28thou between the OD of a PRV and the ID of the case threads!

[chaterlea25]

HI All,
Jeremy, There are two "O" rings fitted to the hollow dowel that transfers the oil to the outer timing cover block on either side of the inner timing case on my SRM engines, are these in place? or is your set up different?
Is the seal in the case face correctly?
Another possibliity (remote) could be that the timing side needle roller bearing is loose in the crankcase
as I believe this blocks off the old feed to the original bush ???

Richards explanations are valid but ignore one vital element, centrifugal force !!!
The spinning of the crank actually sucks in oil to the bigends
Another reason that baffles people with oil pressure gauges fitted as they watch the pressure drop as the revs rise unless the system is bleeding off through the PRV

A symptom of change over time without milage can also be due to the detioration of the mazak of the pump body
causing leakage through the body and at the end plates
I would send the pump to SRM for testing on their rig to eliminate this from the possibilities

HTH
John

[Jeremy]

O rings in place and renewed, quill seal replaced, symptoms persist with a different oil pump ( I have 3)

this is wy I am baffled. 

I don't want to have to do a full engine strip but its looking likely right now.  Today I shall try the prv see if I can ensure it is sealing properly.

[Jeremy]

What I am thinking of doing is puttin fibre washers under the prv so that it bottoms onto those before it is fully threaded in - then I will know that the prv is sealed at the bottom to the crankcase.  I can't see any issue with doing this other than it might leak oil around the threads at the top of the thread.

[alanp]

Ok, I'll throw this in since after a winter's lay up I gawped at my oil pressure gauge's low pressure reading once under way in amazement for a while and checked and changed things until I was blue in the face until one day I decided to concentrate on the suction side of the oil system. I found accumulated oil gunge at the bottom of the tank which I cleaned out, blew through the internal pipe inside the tank and changed the oil feed hose for one from SRM and .......65'ish psi at start up, consistent 55psi hot on the road, 30'ish psi at idle. Happy bunny time!!!!
P.S. The engine is in good nick, uses an SRM end feed, PRV and oil pump, 40 grade oil and oil cooler and filter on the return side.
It worked for me.

[Jeremy]

alanp - was your engine giving full pressure when cold before cleaning the sludge out?  Or where the pressures low consistently?  This is what baffles me as its fine until it gets hot then the pressure dissappers

[Jeremy]

Keep the ideas coming tho chaps - it all helps - ta

[orabanda]

Jeremy,

The zero pressure is a result of the leakage path(s) within the engine being great enough that all of the oil the pump is capable of producing when the engine is hot, is leaking away into the sump.

There might be only one significant leakage point, or it might be a culmination os seval factors which include:

 - Oil type (viscosity too light)
 -worn big ends and or journals
 - worn oil pump
- leaking past the quill
 - leaking past the quill seal
 - leaking past any of the other flow paths that were added when the engine was converted the needle roller bearing, including the o-rings arond the dowel, and the alloy black which houses the quill oil seal
 - potential issues with the quill oil seal (see below):
       Has the recess for the quill seal been machined in line with the quill? (is the seal concentric)?

        Is the internal lip of the quill seal engaging on the quill? Is the seal installed to the correct position (depth) in the machined recess?

        What is the ID of the quill seal?

        What is the OD of the quill?

 - leaking around the OD of the timing side bearing

- PRV jammed open (unlikely as you can reach 50 psi when cold). I doubt that there will be sufficient leakage around the threads of the PRV.

keep your chin up, and keep looking!

[Jeremy]

Hi

thanks for that.  the quill seal is new and is a tight fit on the quill - much tighter than the old one.  I can check the depth of it but I am sure it is engaging properly.  I will check tho.

I ran it on multigrade for many years and multigade is only thinner when cold - not when hot compared to straight oils.  Running on 50 straight oil made no difference apart from higher pressures when cold.

the PRV is working properly - you can see it open as it hits 50 psi - ie pressure rises with revs when cold until it hits 50 psi  fault exists with different prvs installed

Fault exists with different oil pumps installed and with or without the ball and spring

As said - it used to run fine, I had a oil pressure gauge fault ( reading low at both cold and hot) which fooled me and led me to replace all components in the system and then I realised the gauge was at fault so put a new gauge on to find this fault which I presumably introduced when replacing pump and PRV and so on. 

I have no reason to suspect the big ends - check by srm not many miles ago,no nasty noises, crank holds pressure when pumped full of oil from an oil can

I do wonder if when taking the PRV in and out too many times I damaged the thread or it became worn past a tipping point.

Having checked / replaced / substituted every thing I can thank of bar the big ends I am left with a conundrum.

Ho canI check if the PRV is bypassing along its threads? 

[muskrat]

"Ho canI check if the PRV is bypassing along its threads?" 
As I suggested a O ring would work better than fiber washers, or you could try teflon tape just on the first part of thread on the PRV.
What type of bearing is it? The INA NKIB5906 that was in mine had an oil hole in the outer that needed to be blocked or oil pressure would be lost.
It's gotta be something silly. Were the o rings you replaced exactly the right size? Too big will be as bad as too small. A metric one will look the same as a imperial one but the very slight difference could do it.
We can't see the forest for the trees.
Cheers
ps SR500's have a problem in that the seal only just engages the quill.

[chaterlea25]

HI

Alan, where did all that sludge come from ???
I now remember something similar happening on a Triumph  brought to me some years ago

Jeremy,
A collapsing oil pipe when it gets hot on the suction side is worth a thought????

On the other hand
Why not set up a reverse flow into the engine???
Weird ???
Ok add a T into the feed line to the oil pressure gauge, a pipe from the tee to a pressurised oil feed
maybe one of those pressureised brake bleeding bottles??? or similar
block off the feed from the oil tank
remove the timing cover and block the feed to the block in the outer case, since the crank is holding pressure
remove the ball from behind the oil pump to allow the pump to be pressurised, refit pump
remove sumpplate
pressurise the system
You can pressurise the timing cover block separately if needed

now you can watch where the oil pees out, 


HTH
John