Oil pump maintenance

[Midda Samid]

Hi, this really should be an all alfa topic rather than 116, but in the absence of an "engine" section, I'll start here..

I have a standard Alfetta 2.0L with a custom injection system(not relevant to the discussion).. If I drive my car at low to mid RPM, up to 4000-4500 when warm, I can maintain acceptable oil pressure around the 40 mark(just under) on the gauge.. warm engine idle is lower, but still on the gauge. If I ring my car to 5200-5500 a couple of times, my warm idle oil pressure (while still on the gauge) drops to what I would consider barely acceptable and the driving oil pressure is showing lower than before..

would it be safe to say without removing the oil pump to check, that it is worn so that it is less effective at moving warm(thin) oil rather than an issue with the pressure relief?

If this is the case, should I increase the viscosity of the engine oil or will this create an issue with the PRV being overactive at high rpm when I am trying to shove thick oil down a tiny hole creating a higher back pressure at same flow?

what pump relief pressure is the engine capable of handling without issue? and where is the likely failure? oil filter?

lots of questions, sorry.. morning coffee seems to be working well

[Nate Dog]

Mine does the same,
Still Carbied, drops from 40 at idle to low 10's under any load, fresh oil 10-60 dropped in last week, So doubt a more viscous oil will help.
60 weight is the heaviest oil i've ever stuck in anything i own (if its wrong blame the buggers on here! it was in their advice section)

Not sure what a fix will be but will be adopting it as soon as someone smarter than me posts it

[Anthony Miller]

I think an accurate oil pressure gauge is what is required, oem gauges are rarely accurate new let alone after 25+ years

[Midda Samid]

Hi Anthony, I trust the gauge(enough for this exercise).. I have owned the car for 11 yrs, and the readings are consistent.. may not be accurate for numbers, my concern is not numbers as much as what info it is giving me.. lower oil pressure at hotter or harder worked engine(thinner oil)..

Nate, in your case, it sounds like what I was describing in that at idle, the pump can move the thick oil at a suitable rate into the galleries.. at high rpm, the pump suffers too much back pressure and the prv opens effectively bypassing the galleries.. if the oil pressure sender was inside the pump, I think you'd find pressures that would trip the prv.. (this is obviously my theory and the reason why I started the thread).

Based on what you've written Nate, it might be worth me trying the heavier oil to see if I get the same result.. apart from the potential waste of oil and $35, it'd be an interesting test.

[Steve S]

would it be safe to say without removing the oil pump to check, that it is worn so that it is less effective at moving warm(thin) oil rather than an issue with the pressure relief?

If this is the case, should I increase the viscosity of the engine oil or will this create an issue with the PRV being overactive at high rpm when I am trying to shove thick oil down a tiny hole creating a higher back pressure at same flow?

what pump relief pressure is the engine capable of handling without issue? and where is the likely failure? oil filter?

There is no real way to tell if its the pump, PRV or the engine. Either way a pump wont have any trouble moving thin oil over thick oil. In fact the reverse is true. Higher pressure will lead to more "back pressure" on the pump creating more "leakage" past the gears.  Thinner oil will result in slightly more flow through the bearings, as much as 15% from tests data I've seen.

Low pressure at idle is not a problem per se, as as long as Alfa designed the engine correctly if you really have slightly lower than normal oil pressure at idle it can't over pressure at high RPM opening the PRV regardless of the oil grade. I would only be worried about the PRV opening at high RPM if you had high oil pressure at idle.

[Nate Dog]

Steve, Think you've missed the problem.
Oil pressure at idle appears normal, under load its dropping, right when you'd hope for peak pressure.

[Steve S]

Well that would be a problem. Oil pressure should rise about 10psi for every 1000rpm but the main point is that it keeps rising. If it stops rising with RPM it would indicate a problem, most likely the PRV is open. This should be worse when cold.

[Midda Samid]

does anyone know the design pressure for the Nord engine? 

Nate, I would drop your heavy oil and try a lighter weight.. have you been able to replicate the oil pressure issues more than a couple fo times? if it happens everytime out, then consider it the prv and it's inability to stay closed when the pump is at high rpm.

I suspect my issues are related to worn pump.. I am due for an oil change so will go up a weight(I currently am running 15/40) and see if I can't maintain better pressure at idle when hot.. I'll try a 15/50.

[Beatle]

You can 'blueprint' the pump.  If I recall there is a How-To guide in either the Jim Kartalamakis book, or The Alfa Bible, or both

Don't go too thick with the oil.  Pressure is only part of the equation.

Are you using a modern high quality synthetic?  That will likely give lower pressure readings, but ultimately better lubricity.

What oil filter are you using?   Use a high quality large filter not the smaller factory-sized jobbies.

Lastly, try temporarily installing a direct-reading mechanical pressure gauge to confirm the factory gauge is actually reading correctly throughout the range. 

Is it possible you've had an oil gallery plug drop out?

For what it's worth, I don't recall any Alfa I've owned showing a linear increase in oil pressure all the way to redline.  Invariably they max out around 4K.   

When I had the '79 in the NT I got concerned about low oil pressure at sustained high RPM in hot conditions (no speed limits!!!), but a swap to BP Corse+ put my mind at ease.  There were no readily available fully synth oils back then........   

[Midda Samid]

righto, well as per usual I have visited the forum asking for info that was partly available to me in the manual..

I am using 15/40 mineral oil.. Manual recommends 10/50.. first step, get a 10/50 or 15/50 in the car.. Repco has some cheap Valvoline at the moment.. $24 for 6L can't be sniffed at.. and before you get into me about "oils ain't oils", it must be good, it's endorsed by John Laws

Acceptable pressure levels:
at idle are 0.5-1.0 kgf/cm^2 or 7.1-14.2 lbf/in^2 (psi)
at full speed 3.5-5.0 kgf/cm^2 or 49.8-71.1 psi

My gauge reads 0 - 40 - 80 with no nominated unit of measure.. I would presume it's PSI? If it is, then I am low at full speed.. idle pressure could be argued since 7.1 on a 0-40 scale is pretty tough to estimate..

Why do the cars in the Haynes manual get a 0-55-110 gauge?

[Beatle]

Ha ha.....Midda, I'm reluctant to say it, but I've always HATED Valvoline (and Shell).  I've tried it numerous times, numerous cars, numerous versions, and never been happy with the oil pressure.  But that's a purely subjective and personal observation.

For what it's worth, I'd be trying the Penrite HPR-15 (15W60 synth) or HPR-30(20W60 mineral)

[Nate Dog]

I've got HPR30 10-60 in there now and am suffering pressure drop at anything over 3000rpm.
Don't know if that helps you...
Probably just reflects my issues not yours.

[Midda Samid]

Penrite 20/50 on the job(Repco bargain in case you guys don't get the catalogue).. peak oil pressure unchanged with needle just touching the front corner of the 4 in 40 on the gauge from about 1800rpm.. hot oil pressure at idle vaguely better than before..

Evaluation: oil pump prv is relieving a little lower than I would like.. I will check with a second gauge and then I will try a 1mm shim under the spring next time the sump is off and see what I gain.. for the low idle pressure I will blame engine and pump wear.. There is only one way to fix that.. maybe 2 ways, turn the idle up or new pump and bearings..

And to answer earlier question about oil filters, I am using a Z89A..