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High oil pressure

 
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RFlower
Alfa 33


Joined: 17 Feb 2004
Posts: 432
Location: S of France

PostPosted: Fri Dec 23, 2011 11:41 am    Post subject: High oil pressure Reply with quote

I fitted an electric oil pressure gauge to the Trofeo recently. It was previously on the Imola, and read just under 40 psi with the engine hot.

On the Trofeo it reads over 90 psi after starting and runs at about 60 psi even when really hot. I try to keep the revs down until it drops below 80.

As the gauge and sender are the same as were fitted on the Imola I'm pretty sure the current readings are correct, and the relief valve must be stuck closed.

The car was probably stored for some time before I bought it, as it was little used even before the owner died and his son had not driven it much. It had only done 50,000 miles or so, so I guess condensation may have accumulated in the valve and corroded it stuck.

I suppose I'll have to drop the sump and tend to it, but can anyone suggest any other way of freeing it up?
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Dick Flower, Nr. Carcassonne. '94 Trofeo 1.4 ie (F), '93 Imola 1.3/1.4 ie (now for breaking) (F), '91 1.7 ie (GB)(spare car), '86 Sprint 1.5 QV (F). '87 VW Syncro camper (F), '73 NSU Ro80 (F), '99 Fiat Seicento (F)
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JeremyC
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Joined: 06 Sep 2008
Posts: 583
Location: Petersfield, Hampshire

PostPosted: Fri Dec 23, 2011 1:58 pm    Post subject: Reply with quote

Put some sort of engine flushing oil / additive through it.

Has it been for any long runs, getting the engine thoroughly hot can often help with such things too.

If you know where the valve is you could also try some gently taps with a hammer in the vicinity.
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'93 Black 33 1.7 16v
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BigAl
P4


Joined: 06 May 2003
Posts: 2990
Location: U.K Surrey

PostPosted: Fri Dec 23, 2011 3:35 pm    Post subject: Reply with quote

the pressure release valve is in the oil pump housing at the top of the oil pick up, no access to it unless the sump is dropped off.
Could it be anything to do with the valve in the oil filter?
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pictures http://www.alfa-pages.co.uk/viewtopic.php?t=5203
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Bobkelso
Alfa Sprint


Joined: 09 Aug 2011
Posts: 190
Location: Milan - Italy

PostPosted: Fri Dec 30, 2011 12:00 am    Post subject: Reply with quote

Hi RFlower,

I just made a conversion to think about:
40 psi=2,68 atmosphere (it seams reasonable for oil in a motor)
80 psi=5,44 atmosphere (it seams quite higt but still reasonable for oil in a motor??)
At least you know the oil pump of your Trofeo is extremely efficient;
oil type and mileage are similar or different respect the previous car ?

Just to be sure that 80psi it is not a value in the normal range,
does somebody know at what pressure level the relief valve
in the pump is supposed to open in all the 8v boxers?

Ps.: I'm interested in learning a simple way
to fit an oil pressure gauge on the boxer,
in what point of the circuit it is measured
the pressure by the original probe?
You use the same point with a ramification pipe?
Do you have the possibility to post some photos
about the oil pressure probe fitted on your motor?
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RFlower
Alfa 33


Joined: 17 Feb 2004
Posts: 432
Location: S of France

PostPosted: Sat Dec 31, 2011 3:02 pm    Post subject: Reply with quote

According to my Haynes Manual for the Alfa Sud, the nominal setting of the oil pressure relief valve is 4.5 bar.

However, my (old) 33 manual says that, with the oil at 90ºC, the pressure should be between 1.18 and 2.75 bar at 800 rpm and between 4.12 and 5.69 bar at 5500 rpm. Mine is still too high, even according to those figures!

One problem with too much oil pressure is a slight possibility of erosion of the bearing surfaces by the increased flow. More important is the possibility of bursting the full flow oil filter, especially when the oil is cold and thick.

You can connect an oil pressure gauge by 1) fitting a suitable tee piece to the original pressure switch connection close to the filter 2) by fitting a combined switch/pressure sender unit in the same position, or 3) by removing the large plug in the oil gallery at the top centre of the block and fitting a separate sender unit with a suitable adapter.
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Dick Flower, Nr. Carcassonne. '94 Trofeo 1.4 ie (F), '93 Imola 1.3/1.4 ie (now for breaking) (F), '91 1.7 ie (GB)(spare car), '86 Sprint 1.5 QV (F). '87 VW Syncro camper (F), '73 NSU Ro80 (F), '99 Fiat Seicento (F)
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Oggie
Green Cloverleaf


Joined: 06 Mar 2008
Posts: 811
Location: Whitehill

PostPosted: Sun Jan 01, 2012 3:07 pm    Post subject: Reply with quote

I have always said (haven't I Al ) that any electric guage is only a rough estimate guide to what the oil pressue is, same as almost every dial in the 33. I would fit a capillary pressue unit to get an exact reading before worrying about any engine internals, can be done for under £70.
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RFlower
Alfa 33


Joined: 17 Feb 2004
Posts: 432
Location: S of France

PostPosted: Sun Jan 01, 2012 4:19 pm    Post subject: Reply with quote

Oggie wrote:
I have always said (haven't I Al ) that any electric guage is only a rough estimate guide to what the oil pressue is, same as almost every dial in the 33. I would fit a capillary pressue unit to get an exact reading before worrying about any engine internals, can be done for under £70.


I assume you mean a Bourdon Tube type gauge connected via a capilliary.
http://www.efunda.com/designstandards/sensors/bourdon_tubes/bourdon_intro.cfm

There is really no inherent reason why such a gauge should be more accurate then an "electric" gauge, just because it uses a mechanical linkage to move a needle rather than an electric signal from a strain gauge on a similar Bourdon device.

In any case, as you can see from my original posting, the gauge and sender give pressure readings of double those on the other engine, which has similar mileage.

That in itself is reason to believe the pressure is too high on this engine.
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Dick Flower, Nr. Carcassonne. '94 Trofeo 1.4 ie (F), '93 Imola 1.3/1.4 ie (now for breaking) (F), '91 1.7 ie (GB)(spare car), '86 Sprint 1.5 QV (F). '87 VW Syncro camper (F), '73 NSU Ro80 (F), '99 Fiat Seicento (F)
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Oggie
Green Cloverleaf


Joined: 06 Mar 2008
Posts: 811
Location: Whitehill

PostPosted: Tue Jan 03, 2012 9:08 pm    Post subject: Reply with quote

Does the Trofeo run a different rating of altinator to the Imola?, or a different guage of wire? my thinking is that if the altinator has been up rated to a higher output then it could be the cause of a higher reading hence the reason for you getting a direct test of the oil pressure from the block not through an electric sender (which again may not be correct as you have said it could be stuck).
A cappilary as Im sure you know has no link to the electrical system(other than dial illumination) and therefore would give you a better more accurate reading as the dial needle is moved by the engine oil itself.
Perhaps a garage could do a quick test before condeming an internal part an stripping a potentially good running motor?.
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RFlower
Alfa 33


Joined: 17 Feb 2004
Posts: 432
Location: S of France

PostPosted: Wed Jan 04, 2012 12:58 am    Post subject: Reply with quote

I have some high quality (well, quite expensive) direct reading (Bourdon tube type) pressure gauges, so I will connect one or two to the oil pressure system to check against the installed gauge when I have time.
I'll let you know the result.
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Dick Flower, Nr. Carcassonne. '94 Trofeo 1.4 ie (F), '93 Imola 1.3/1.4 ie (now for breaking) (F), '91 1.7 ie (GB)(spare car), '86 Sprint 1.5 QV (F). '87 VW Syncro camper (F), '73 NSU Ro80 (F), '99 Fiat Seicento (F)
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Brit01
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Joined: 24 May 2010
Posts: 665

PostPosted: Sat Mar 10, 2012 11:25 pm    Post subject: Reply with quote

any update on your oil pressure issue?

Wink
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RFlower
Alfa 33


Joined: 17 Feb 2004
Posts: 432
Location: S of France

PostPosted: Sun Mar 11, 2012 10:22 am    Post subject: Reply with quote

Brit01 wrote:
any update on your oil pressure issue?

Wink


I have been far too busy working on a house we have to move into next week!
However, while thinking about the issue, it occurred to me that when the relief valve opens it dumps the oil back into the sump via a fairly small passage (otherwise it could drop the pressure too much).
So, when the oil is cold and very viscous, this passage may not be large enough to allow enough flow for the pressure to drop to the nominal value of 4.5 Bar.
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Dick Flower, Nr. Carcassonne. '94 Trofeo 1.4 ie (F), '93 Imola 1.3/1.4 ie (now for breaking) (F), '91 1.7 ie (GB)(spare car), '86 Sprint 1.5 QV (F). '87 VW Syncro camper (F), '73 NSU Ro80 (F), '99 Fiat Seicento (F)
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Brit01
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Joined: 24 May 2010
Posts: 665

PostPosted: Sun Mar 11, 2012 2:23 pm    Post subject: Reply with quote

On a coolish morning I get 90 psi easily when I blip the throttle but it always stops at 90 meaning the valve is working and the oil is being dumped back into the sump.

Have to wait until it warms up to drive it above 3000 rpm. In winter will change to 10W probably.

Using 20w oil.
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Dellorto DRLA40 (32mm venturi)
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