still confused

[ianmaxtec]

In a previous post I spoke about my ongoing oil leak (that was coming from a 14mm core plug on the fly wheel end)…………..after replacing the plug the leak eventually came back, so I did what I should have done long ago and tested the oil pressure (at the oil cooler). When I started the car from cold the pressure was hovering around 100 psi, and when you blipped the throttle it was off the scale !!!!! I know that the pressure is much higher when the oil is cold, but surely 100 psi is far too high…..I am now thinking that the pressure relief valve (in the oil pump) might be stuck….this would certainly explain why I cant seem to stop the oil leek……(I should explain the the engine has had a complete rebuild, pump, tappets, oil seals core plugs etc..1.8gti ev engine)

[Wayne]

Yes oil pump would be my guess as well.

However why did you not fit a new one when you rebuilt the engine or is it new???

[ianmaxtec]

new pump fitted when rebuilt (along with tappets, valves, seals gaskets etc...)

[ianmaxtec]

What I really need to know is what the (oil) pressure should be when the engine is stone cold. I am getting all sorts of figures from different people, some say a BAR, and some say 6 BAR (there is a massive difference between the two), I am getting around 120 psi when the engine is cold, at app 1000 rpm

[Ben Lessani]

At idle:

Cold: 4.5 Bar
Up to Temp: 0.8 Bar

At 2k RPM:

Cold: 4.5+ Bar (my gauges are only 0-5)
Up to Temp: 3 Bar

After *just* starting, the oil will be relatively thick - as a result, oil pressure will be unnaturally high until it begins to flow and thin down. Although multi-grade oils are meant to be the same viscosity whatever - it doesn't exactly work in practice.

The above results are from the pressure measured at the head.

[ianmaxtec]

Thanks for that Ben,  I'll get cracking taking the box out, fixing (replacing) the plug, and I'll put 2 guages on the engine at the same time, block and head, and see where I go from there....I'll post the results, and hopefully will not need to take to box agian (until I need a clutch) !!

[ianmaxtec]

only now got around to checking the oil pressure (thanks Ben Lessani), and here are the results (still thing there is a problem with the oil pump)

From cold (on the block)  tick over 80 psi, rev above 1000rpm pressure 120+psi
80C at 2000 rpm (on the block) 65 psi
80C at 4000 rpm (on the block) 80 psi
idle while hot (on the block) 40 psi

-----------------------------------------

on the head:

cold at idle 55 psi
cold at 2000 rpm 60 psi
80C at 2000 rpm 35 psi



Not a million miles off Bens figures, but I suspect it is too high !!!
New pump tomorrow..