rexpontius

Dear all,

I am posting this question also here because there are so many technically skilled people here, and I am trying to acquire as much knowledge as possible before possibly pulling the engine .....
So any feedback is much appreciated.

Now here is the issue:

About 1,5 years ago I rebuilt the engine of my Alfa Romeo 164 3.0 V6 24v, replacing all bearings (crank and big end) gaskets etc. Off course I used plastigauge to determine the correct bearing sizes.

The engine has run approx 5.000 miles since and still runs great, lots of power no clattering noises.

However since the rebuild the oil pressure with really warm oil (spirited drive or crawling in city traffic) falls below 0.3 bar at idle tripping the warning light.

I ran 10w40 full synthetic and replaced the oil once after the rebuild.

The problem did not worsen, but I am still curious what causes this problem and what I can do to solve it?

The engine runs great and I really don't want to pull it out again.
Last week I tried swapping the oil with thicker 10w60 oil (recommended by Alfa for 'enthusiastic' drivers), but the problem still occurs after driving in slow traffic with engine at idle.

The car has both a pressure gauge as well as a warning light, which use separate circuits/sensors so the chances that both sensors have failed seems very minimal.

So my plan for this weekend is to check the pressure with a mechanical gauge, and replace the pressure relief valve which is located near the oil filter (ball/springloaded type). Also I could change the oil filter (did not do that when switching to 10W60 oil because the filter is a real PITA to replace)

Have you guys got any more ideas?

Many many thanks

cheers
Michel

Dave928S

That's the first thing I'd do with a known accurate gauge, to determine what the pressure really is, then go from there. You don't really know that you actually have a problem at all, until you do that check.

928Shane

I am curious, what were your bearing clearances?

rexpontius

Well guys, I just swapped the oilfilter and cut open the old filter.

I was shocked to see how black and clogged the thing looked, after just 5000 miles ?!

Check this link for a picture: http://imageshack.com/i/nacecbj

I mounted the new filter and instantly the pressure was PERFECT! 5 bar with cold engine, perfectly withing factory spec!

I am the happiest man alive this evening!!!

I learned two very important lessons:
A. It is possible to remove the oil filter without changing the oil :-)
B. The filter is very important.

Despite the fact that I changed the oil a few times, the filter was apparently clogged up enough to cause problems.

There was fortunately not a lot of glitter or shiny debris in the oil from the old filter, so I think the engine is OK.

Is is normal for a rebuilt engine (that is new bigend and main crank bearings) to need a new oil filte after only 5000 miles?


Many thanks for you input!

Cheers
Michel

Mrmerlin

normally on an engine rebuild you would be looking for metal after the rebuild,
I would swap out the filter after the first 50 miles .
Then an oil and filter change at 500 miles.

It would be normal to see some small metal bits,
but this should reduce after the first oil change unless the engine was making metal.

With the filter you have,
might you care to share the maker of the filters you had,
and and have now?..

Also what is the temp range the engine is operated at and what does the owners manual suggest for oil viscosity?

Did you use Dino oil for engine break in?

rexpontius

the filter was an original Alfa Romeo filter.
I replaced it today with a bosch filter.

I checked the oil regularly for shiny particles, but fortunately never found any.

But I really did not think that the filter could get so clogged after such a low number of miles and at least 3 oil changes. The engine performance is now exactly according to factory spec, so I hope it did not occur any damage because of my ignorance.

I will surely replace the oil filters very frequenly on all my cars, and especially the 928 :-)

cheers

rexpontius

With regard to break in, i used Kroon Oil specially for break in the first 150 mls and replaced it with Kroon Oil 10w40.

I live in The Netherlands which is a pretty mild climate. But Alfa recommends 10w60 for spirited drivers, so that is what i am using now :-)

Cheers